United States Environmental Research April 1993
Environmental Protection Laboratory - Corvallis
Agency Corvallis, OR 97333 *'
Research Plan
f/EPA Effects of C02
and Climate Change
on Forest Trees
CฐJ
-------
Research Plan
Effects of C02 and Climate
Change on Forest Trees
Global Processes and Effects Program
Environmental Research Laboratory - CorvaUis
United States Environmental Protection Agency
CorvaUis, OR 97333
For additional information contact:
Dr. David T.Tingey
Program Leader
ERl^Corvaliis
(503)754-4621
-------
EJJtctt of CO3 and ClimaJt Chang* on Forest Trtts
DISCLAIMER
The research described in this report has been funded
by the U.S. Environmental Protection Agency. It has
been subjected to the Agency's peer and administra-
tive review and it has been approved for publication
as an EPA document. Mention of trade names or
commercial products does not constitute endorse-
ment or recommendation for use.
Carmttit Emrbrnwuntnl Ramrtk Laboratory
-------
Effttis of CO j v>d CUmat* Chang* onFcrtst Trta
ACKNOWLEDGMENT
This research plan was prepared through the consci-
entious work of the following researchers at the U.S.
EPAEnvironmental Research Laboratory-Corvallis:
David M. Olszyk, Paul T. Rygiewicz, and David T.
Tingey of the U.S. EPA, Bruce D. McVeety of
Battelle-Pacific Northwest Laboratories (1AG
#DW89934110), and Mark G.Johnson of ManTech
Environmental (Contract #68-C8-0006). The plan
also includes important contributions from Don
Phillips and Jim Weber of the U.S. EPA, George
King of ManTech Environmental (Contract #68-
C6-0006), and Danny Marks of the U.S.Geological
Services.
The authors graciously thank the members of the
peer review panel: Kermit Cromack, Jr. of Oregon
State University, James R. Ehleringer (Chairman) of
the University of Utah, Alex L Friend of Mississippi
State University, Boyd R. Strain of Duke University,
and Robert J. Zasoski of University of California at
Davis. Their careful review and consideration of our
research plan and thoughtful input proved invalu-
able to raising the overall quality of this document
The authors of this plan would also like to thank Jutta
Richter of ManTech Environmental (Contract #68-
C8-0006) for her technical assistance in producing
this document Jutta's careful note taking during
planning meetings, artistic input into the develop-
ment of illustrations, and mastery of desktop
publishing helped compile our thoughts and ideas
into a polished presentation.
The research described in this report has been funded
by the U.S. Environmental Protection Agency. This
document has been prepared at the US EPA Envi-
ronmental Research Laboratory in Corvallis, Oregon,
by the individuals acknowledged above. It has been
subjected to the Agency's peer and administrative
review, and it has been approved for publication.
Mention of trade names or commercial products
does not constitute endorsementorrecommendation
for use.
fmg* ti CanaHii Emrinmmuntal Rttmrck Laboratory
-------
JUftctt 0/ C0} and Climmt Chongt m Forts Tr*u
TABLE OF CONTENTS
ACKNOWLEDGMENT
TABLE OF CONTENTS
~Ui
LIST OF FIGURES viii
LIST OF TABLES.
EXECUTIVE SUMMARY.
-ES-1
INTRODUCnON .. ES-1
GENERAL APPROACH ..ES-1
SCOPING STUDIES ES-1
C02 and Climate Analysis ES-1
Species Selection ES-2
EXPERIMENTAL DESIGN ES-3
EXPERIMENTAL TASKS ES-4
Task 1 Shoot Carbon and Water Fluxes ES-4
Task 2 - Shoot Growth, Morphology, Allometry, Phenology, and Carbon Partitioning ..ES-5
Task 3 - System Nutrients.
...ES-6
Task 4 - System Water ES-7
Task 5 - Litter Layer ES-8
Task 6 - Root Growth, Morphology, Phenology, and Carbon Partitioning ES-8
Task 7-Soil Biology ES-9
MODELING TASKS...... ES-10
INTEGRATION AND INFERENCE ES-10
L INTRODUCTION,
CLIMATE CHANGE
EFFECTS OF ELEVATED CO, ON TREES
Photosynthesis
Respiration
Stomatal Conductance/Transpiration...
Growth and Carbon Allocation
EFFECTS OF TEMPERATURE ON TREES
Photosynthesis and Respiration
Phenology
Carbon Allocation
EFFECT OF WATER ON PLANTS
Stomatal Control, Photosynthesis and Respiration
.1
2
Phenology Ml
...... 4
....6
....6
..7
.8
8
.10
Carbon Allocation and Nutrient Uptake.................................. 10
EFFECTS OF ELEVATED CO, AND CUMATE CHANGE ON SOILS....... 11
-------
Efftets of COj and Climate Changt m Forest Trta
SENSITIVITY OF PACIFIC NORTHWEST FORESTS TO CURRENT AND FUTURE
CLIMATE ........... 13
Current Climate 13
Adaptation of Forests to Current Climate 13
Sensitivity to Future Climate Change 13
Vegetation Modeling - Local Climate-Forest Zone Correlations 14
Vegetation Modeling - Holdridge life-Zone Classification 15
Simulation of Current Vegetation 15
Estimated Vegetation Change 16
Expert Judgement - Effects of Climate Change on Forest Disturbances 17
SUMMARY 17
n. POLICY ISSUES 19
m. GENERAL APPROACH 20
SCOPING STUDIES 20
EXPERIMENTAL TASKS 21
MODELING TASKS 21
INTEGRATION AND INFERENCE 21
IV. SCOPING STUDIES,
COj AND CLIMATE ANALYSIS
22
22
CO j Concentrations and Projected Trends 22
Role of COa in Radiative Forcing 23
Temperature and Precipitation Current and Projected Treads 24
EXPERIMENTAL DESIGN 29
Experimental Facilities 29
Selection of Plant Material 32
Duration of Experiment
Planting Design.
34
....34
Experimental Treatments ........ ............... 35
Soil Selection 39
Utter Studies
Soil Fauna Collection and Inoculations
MNIMmflMIMMtlCMtltllMMMMItltMtMtMMCtWiMfmttfltMimil****!
SUPPORTING STUDIES.
Pot Studies ~
Large Lysimeters.
Field Studies
.41
.42
.42
.43
.43
43
TREE GROWTH MODEL SIMULATIONS TO PROJECT EXPERIMENTAL OUTCOME .43
V. EXPERIMENTAL TASKS.
INTRODUCTION
TASK 1: SHOOT CARBON AND WATER FLUXES.
Introduction.
Objectives...
Approach
Task Outputs,
Model Inputs.
MtMMtMtfllHMMtlMMMMMMMW
.46
.46
.48
.48
...48
49
52
52
Jhagปh
CormiUt Eavfromauiual Rtnorek Laboratory
-------
Efftcts of COj and Climate Chang t on Forts* Trta
TASK 2: SHOOT GROWTH, MORPHOLOGY, ALLOMETRY, PHENOLOGY, AND
CARBON PARTITIONING . 53
Introduction 53
Task Outputs 56
Model Inputs ....56
TASK 3: SYSTEM NUTRIENTS 57
Introduction 57
Objectives 57
Approach 57
Task Outputs 61
Model Inputs 61
TASK 4: SYSTEM WATER 62
Introduction 62
Objectives 62
Approach 63
Task Outputs 64
Model Inputs 64
TASKS: UTTER LAYER 65
Introduction .................a.........ป.**.***..* ...** 65
Approach 65
Task Outputs ....68
Model Inputs 68
TASK 6: ROOT GROWTH, PHENOLOGY, AND CARBON PARTITIONING 69
Introduction 69
Objectives 70
Approach 70
Tft$k C^u^puts *#~**#~*####ป*#ซซ##ป#ป*#~*#ป***ปป##ซป**ป####~ซป**~**~*##*~##***ป~*#ป#ป~~ป 72
Model Inputs 72
TASK 7: SOIL BIOLOGY 73
Introduction 73
Objectives 74
Approach 74
Task Outputs......... 76
VL MODELING TASK,.,, ฆฆฆ,,ฆ 77
MODEL SELECTION 77
TREGRO FEATURES 77
RESEARCH T<^^SKS ........ 79
Model Development 79
Model Parameterization 79
Model Calibration/Verification 80
Model Validation ..80
Model Outputs 80
Canm lUi Ewrtrommattai Matarck Laboratory
-------
Effects of C03 and CUmatt Cknng* on Forta Trtts
VII. INTEGRATION AND INFERENCE 81
OBJECTIVES 81
INTEGRATION 81
INFERENCE 81
OUTPUTS 82
Vm. PROGRAM MANAGEMENT 83
COMMUNICATIONS...... . 83
PROJECT RESPONSIBILITIES . 83
IX. QUALITY ASSURANCE STATEMENT 85
X. OTHER RELEVANT RESEARCH PROGRAMS 86
U.S. ENVIRONMENTAL PROTECTION AGENCY - ERL CORVALUS 86
Vegetation Modeling Work 86
Spatial Analysis of Water, Energy and Biogeochemical Processes 86
Tropospheric Ozone: Forest Impact 87
Study at Harvard Research Forest, Petersham, MA 87
Carbon-Nitrogen Interaction in Brazilian Forest Species 87
U.S. ENVIRONMENTAL PROTECTION AGENCY - ERL ATHENS 88
Earth Systems Model (ESM) 88
U.S. DEPARTMENT OF AGRICULTURE/AGRICULTURAL RESEARCH SERVICE........88
Temperature and COa Interactions on Rice Growth and Yield 88
ELECTRIC POWER RESEARCH INSTITUTE (EPRI) 89
Forest Response to COa 89
U.S. DEPARTMENT OF ENERGY 90
Tall Grass Prairie Elevated C02 Experiment.... ........... 90
MICHIGAN STATE UNIVERSITY 90
Hardwood Root Dynamics and Root Image Analysis 90
XL REFERENCES . _...91
Xn. APPENDIX A A-l
SPA'S TERRESTRIAL ECOPHYSIOLOGICAL RESEARCH AREA (TERA) FOR
CLIMATE CHANGE RESEARCH A-l
INTRODUCTION
TERA PHYSICAL DESCRIPTIONS
TERA Site
TCRA Physical Plant
TERRACOSM DESIGN AND SENSOR LAYOUT ... A-4
Teiracosm Enclosure
Aboveground Sensors .. A-5
Belowground Sensors....................ซ A-6
Jfeftrf
-------
Efftcts of COt and Climatt Clumgt m Fortst Trtts
TERRACOSM C02 AMD CLIMATE CONTROL A-10
Computer Data Acquisition/Process Control A-10
Host Analytical System A-12
Tenacosm Site Meteorological Station A-14
ERL-C LABORATORY CAPABILITIES A-14
Gas Exchange Laboratory A-14
Video Analysis Laboratory A-15
Nutrient/Elemental Analysis Laboratory A-15
Soil Microbiology Laboratory A-16
MOLECULAR BIOLOGY EQUIPMENT ...A-16
REFERENCES A-16
Xm. APPENDIX B B4
IMAGE ANALYSIS B-l
INTRODUCTION B-l
APPROACH B-1
Aboveground B-l
Belowground B-l
REFERENCE B-2
Pm&rli
-------
Effects of CO2 and Climate Change on Fann Tna i^
LIST OF FIGURES
Figure 1,
Figure 2.
Figure 3.
Figure 1-1.
Figure 1-2.
Figure 1.3.
Figure 3-1.
Figure 4-1.
Figure 4-2.
Figure 4-3.
Figure 4-4.
Figure 4-5.
Fipre 4-6.
Figure 4-7.
Figure 4-8.
Figure 4-9.
Figure 4-10.
Figure 4-11.
Figure 4-12.
Figure 4-13.
General research approach and relationship among the various tasks.,
..ES-2
Side view of terracosm chamber showing details of soil horizons, minirhizotron root
observation tubes, data acquisition packages, dew point hygrometer, and CO,
sampling port ES-3
Research tasks for the experiment .. ES-4
The influence of C02 concentrations on photosynthesis (PN), transpiration (E) and
leaf conductance (CS) in Populus deltodies (Kramer and Sionit, 1987). 5
Growth of Douglas fir seedlings varies with day and soil temperatures ....8
Projected changes in various forest types of the west side of the Cascades, assuming
various temperature changes that may occur with projected climate change 15
Genera] research approach and relationship among the various tasks 20
Monthly average C02 concentration observed at Mauna Loa, Hawaii (Keeling et al.,
1989) .....22
The association between the annual cycles of C02 and photosynthetically active
vegetation 22
Projected changes In atmospheric C02 concentrations, given several scenarios ...23
Predicted global warming from a "doubling" of atmospheric C02 and associated
percent change in global-annually averaged precipitation (Houghton et al., 1990) ...25
Illustration of typical grid cell sizes used in various general circulation models 26
Long-term mean and predicted future mean monthly temperatures for three sites in
the Pacific Northwest (NOAA, 1989a, b). ..... ......28
Long-term mean and future mean monthly precipitation for three sites in the Pacific
Northwest (NOAA, 1989a, b). 28
Layout of the Terrestrial Ecophysiological Research Area (TERA), drawn to scale. 30
Side view of terracosm chamber showing details of soil horizons, minirhizotron root
observation tubes, data acquisition packages, dew point hygrometer, and C02
sampling port 31
The current regional distribution of Douglas fir (Little, 1971). ........ 33
The map illustrates the geographic location from which die seeds for the study were
collected. ซ<ปป#. ฆฆ<ฆฆฆฆฆฆ >33
Planting design showing rear and top view of terracosm 34
The experimental design is a complete randomized block, with three replications of
each treatment ......35
Figure 4-14. Comparison of monthly mean temperatures for die lira experimental regimes 35
FagtwiS CermBisE*virxMM*iua!Rts* arcklAberctcry
-------
EJJicts of CO2 and Climatt Chang* on Forts: Trtts <
Figure 4-15. Trend of warmer night (minimum) temperatures and relatively constant day
(maximum) temperatures for the United States (Kerr, 1992) 36
Figure 4-16. Monthly precipitation and potential evaporation for Corvallis, OR 38
Figure 4-17. The annual watering schedule will have two distinct periods; soil moisture content at
field capacity and below field capacity 38
Figure 4-18. Volumetric soil moisture versus tension curves for the three horizons of the terracosm
soil 38
Figure 4-19. TREGRO simulations of the effects of C03 and temperature on tree photosynthesis
and respiration over a 2-year period 44
Figure 4-20. TREGRO simulations of the effects of COa and temperature on tree growth over a 2-
year period 45
Figure 5-1.
Figure 5-2.
Figure 5-3.
Figure 5-4.
Figure 5-5.
Figure 5-6.
Figure 5-7.
Figure 5-8.
Figure 6-1.
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Research tasks for the experiment 46
Physiological-based schedule of above- and belowground sample oollection timing
and frequency 47
Carbon balance in chamber, showing input and output rates 49
Samples collected in Tasks 2,5, and 6 will be analyzed in this task with the chemical
analysis reported back 58
Location of TDR probes, neutron probe access tube and tension soil lysimeters 60
Cross section and top view of soil chamber giving details of plant spacing, soil
horizons, and sample locations 67
Location of minirhizotron access tubes 71
Location of soil thermistors and soil gas samplers. 75
Row diagram showing the major compartments and their interactions in TREGRO,
the physiology based process model used to simulate tree growth 78
Layout of the Terrestrial Ecophysiological Research Area (TERA), drawn to
scale - A-2
Side view of terracosm chamber showing details of soil horizons, minirhizotron root
observation tubes, data acquisition packages, dew point hygrometer, and C02
sampling port A-4
Location of Soil Thermistors and Soil Gas Samplers. In this example, sensor
locations are shown for a terracosm with sensors concentrated in the NW
quadrant
Location of minirhizotron/neutron probe access tubes. A-8
Location of TDR probes and tension soil lysimeters..............~~.............~..... A-9
Flow diagram of data acquisition/systems control strategy for the terracosm field
^^*l l
fmgtix Certain* Enrirommtntal Rttmrtk laboratory
-------
Efftca of COj end Climatt Ckmgt em Form Trtts ฆ
LIST OF TABLES
Comparative drought resistance of Pacific Northwest tree species compiled by Lassoie
et al. (1985) 9
Comparative stomata] sensitivity of Pacific Northwest tree species as compiled by
Lassoie et al. (1985). 10
Table 1-1.
Table 1-2.
Table 1-3. Projected changes in the area of various life forms, assuming various climate change
Table 4-1.
Table 4-2.
Table 4-3.
Table 4-4.
Table 4-5.
Table 4-6.
Table 5-1.
Table 5-2.
Table 5-3.
Table 5-4.
Table 5-5.
Table 5-6.
Table 8-1.
SCCQSflOSi *aซป a*ป#ฆ>>**ซปซปaซ**a*ป*ป* 16
Current radiative forcing from C02 24
Suggested Climate Change Scenarios from the USEPA/OPPE Workshop (ICF, 1989)25
Comparison of the impact of climate change on mean annual temperature and mean
annual growing degree-days for the Pacific Northwest 27
Comparison of the impacts of climate change on annual precipitation and annual
potential evapotranspiration (PET) 27
Chemical and physical characterization of forest soil selected for the experiment.......41
Critical invertebrates introduced into the terracosms 42
Measurements required to determine photosynthesis and respiration parameters for
TREGRO model ..52
Measurements of morphology, shoot biomass, and phenology for the TREGRO
model
56
....61
Measurements of nutrient concentrations and CVN ratios for use in TREGRO.
Measurements of volumetric soil water content and water flux by soil horizon for input
in the TREGRO model 64
Measurements of seedling characteristics and selected processes for input in the
K U model. 68
Measurements of root parameters for input in the TREGRO model 72
Program Management 84
fugtx CormBit Emrirommfnta! Rtsmxrck Laboratory
-------
Effects of CO2 mkJ ClinuUt Chang* on Forts Ttra
EXECUTIVE SUMMARY
INTRODUCTION
Concentrations of carbon dioxide (OOj) and other
trace gases such as methane are increasing in the
atmosphere due to human activities. Evidence sug-
gests that increased levels of these gases will produce
increases in global temperatures and associated
changes in precipitation patterns and amount, cloudi-
ness, and other atmospheric factors which are
collectively known as "climate change."
The U.S. Environmental Protection Agency (EPA)
has created the Global Climate Research Program
(GCRP) to provide integrated research on all aspects
of the trace gases and climate change. An important
focus of the GCRP at the EPA's Environmental
Research Laboratory in Corvaliis, Oregon (ERL-C),
is to understand how CO, and climate change will
affect vegetation in North America. A crucial goal
of this research is to provide information to policy
makers who must make decisions about forest re-
sources. Answers are needed for these key policy
issues:
What are the effects of elevated C03 and
climate change on thegrowth andproductiv-
ity of forest trees?
Will elevated C02 and climate change alter
the caibon sequestration potential of forest
trees?
What is the magnitude of elevated C02 and
climate change impacts on forest trees and
will the impacts be widely distributed?
Existing data are not adequate to provide defensible
scientific answers to the above policy issues, at either
the level of an individual tree or a forest stand. Thus,
ERL-C has begun the study called Effects of C02
and Clima te Change on Forest Trees, to help deter-
mine bow trees are influenced by elevated C02 and
climate change. The focus will be on Douglas fir, a
key Pacific Northwest forest species, which is eoo-
logically and economically important and adapted to
the current local climate conditions.
GENERAL APPROACH
To evaluate the qualitative and quantitative ef-
fects of climate change on forest trees, four
separate but interacting research activities will be
undertaken; scoping studies, experimental tasks,
modeling tasks, and integration and inference
activities (Figure 1).
SCOPING STUDIES
COj and Climate Analysis
To establish experimental conditions, C02, tem-
perature, and moisture records were examined for
past and present trends. It was established that in
1990the atmospheric concentration of002was 353
ppm, or 25% higher than in pre-industrial times. At
a moderate rate of increase, the C02 concentration in
the atmosphere may double to about 700ppm by the
year2059. However, other trace gases are increasing
along with COp and will contribute to global warm-
ing over this same period of time. Thus, realistically
concentrations of 00a alone will be in the range of
only 450-500 ppm When global temperatures in-
crease to a level equivalent to that associated with a
doubling of CO, concentrations.
To predict the impacts of increased C02 levels on
future temperatures in the Pacific Northwest, we
reviewed the output of four atmosphere/climate
models. The models projected a significant wann-
ing and drying of the dimate in the Pacific Northwest
using a scenario which included a doubling of atmo-
spheric COj concentrations. For example, in die
Willamette Valley temperatures could increase for
all months resulting in a mean from 23 to 5.1'C,
depending on the model used. Also, growing de-
gree-days are projected to increase significantly by
27% to 171% from current conditions, with greater
percentage increases ingrowing-degree days a: higher
elevations.
ES-1 CorveJUt EnvbvMunlal Ktrtarch Laboratory
-------
Efftcts of CO} ซwf CUmatt Chang* m Forta IHa
General Approach
Scoping Studies
OOydimalt Scenarios
Species Selection
a
Experimental Design
*
Experimental Tasks
SbootGufeonA Water Flu
Shoot Growth & Phenology
System Nutrients
System Water
Utter Layer
Root Growth & Phenology
Soil Biology
Integration & Inference
Gsncepftial Summaries of Experimental Results
System Budgets (C, HjO, Nutrients)
Model Application Assess Effects of 002 and
Jdintte on Trees
Modeling Tasks
Model Selection
Parameterization
Figure 1. General research approach and relationship among the various tasks. The dotted lines indicate
information flow, and the solid lines indicate data flow.
The model -based projections for precipitation under
double 00, concentrations did not show die same
ooDsisteot trend as temperature. Model outputs
tanged from essentially no change to 27% increase
in annual precipitation. All models projected that the
current seasonal pattern of relatively dry summers
and wet winters will persist, but the proportion of
rain vs. snow from current conditions may change
because of the increase in temperature.
Overall, the future climates projected from the cli-
mate models represent a significant change from
present conditions. When viewed in a south-to-
sorth transect, the projected temperature changes
were equivalent to shifting current climates from
200 to 500 km north, ie., moving the dimate of
northern California intonorthemOregon. However,
strict geographical analogues of future dimate were
difficult to define since projected precipitation may
remain unchanged. Similarly, from an elevational
perspective, the dimate projections suggested b 500
to 1000 m upward movement of temperature re-
gimes.
Species Selection
Douglas fir (Pseudotsuga memiesii ), currently the
most important timber speries in the Pacific North-
west, was selected as the experimentalplant material.
Douglas fir is widely distributed, growing under a
variety of dimaticconditions. Seedlingswere grown
from "woods run" seed lots, rather than half-sib or
full-sibseedlots,toensurethattfaeseedling'sgenetic
variability reflects thai of the natural forest. Seed lots
were selected from five low-elevation seed zones
-------
Effects of COj and CUmate Chang* on Fortst Trtes
(<600 m) on the western side of the Oregon Cascade
Mountains in the Willamette Valley. Seedlings were
provided by the Weyerhaeuser Company as 1+1's,
Le., grown for one year in a seed bed, then one year
inanursery bed, and thentransplanted into tenacosms
as bare-root, 2-year-old stock.
EXPERIMENTAL DESIGN
Experimental Facilities; The study uses twelve 1.0
x 2.0meter surface area and
12 x 13 meter high "terra-
the tenacosms and trees growing under native con-
ditions.
Experimental Treatments: Hie experimental design
is a 2 x 2 factorial with two 002 treatments, two
temperature treatments, and three replicate tenacosms
per treatment combination. The two 002 levels are
ambient and ambient plus 200 ppm (a possible C02
increase in approximately 50 years). The two tem-
perature levels are ambient and ambient plus 4eC (a
predicted temperature over die same period of time).
cosms" built at ERL-C
(Figure 2). Tenacosms are
closed systems including a
sun-lit upper chamber where
atmospheric and climate
conditions are controlled
and measured, and a lower
soil lysimeter where soil
water content is controlled
and soil parameters are
monitored. The terraoosms
alJowresearchers to achieve
control of the environment
and provide a mechanistic
understanding of the effects
of elevated COr tempera-
ture and drought on above-
and belowground tree and
soil processes.
While the overall study will
focus on die long-term ef-
fects of increasing C02 and
climate change on Douglas
fir seedlings growing in the
tenaoosms, supporting ex-
periments also will be
conducted in pots, large soil
tysimeters, and at field sites.
These studies will provide
additional data necessary for
modeling activities and for
comparison between re-
sponses of trees grown in
Side View of Terracosm
Dew Point Hygrometer
Hot and Cold Water
Beat Exchangers
Hoct/Chanber COj
Sampling Ports
Data Acquisition/
System Control
\
TDR Probe
Multiplexer
\ \
L5Mซten
Utter Layer
Hortioa
[Otacrratloa
Tuba
1 Meter'
Figure 2. Side view ef terracosm dumber shaving details of soil
horizons, minirhizotrcn rootobservation tubes, data acquisition pack-
ages, dew point hygrometer, and COJ sampling port
FiagiBSJ Carmllis EinrbtmmtKUil Ratarck Laboratory
-------
Efftca of CO) mdCUmait Chang* on Factst Trret
The increased C02and increased temperature treat-
ments are added continuously to the current ambient
levels to preserve natural diurnal, seasonal and yearly
variability. Ambient conditions are based on con-
tinuous measurements from a meteorological tower
at the research site.
Sofl Selection: Douglas fir is found primarily on two
kinds of soils in the Cascade Mounta ins of Oregon.
Roughly 30% grows in high-elevation sandy loam
derived from volcanic ejecta and glacial till. The
other 70% grows in a heavy-textured soil derived
from colluvium and residuum. The sandy loam soil
was chosen for use in the tenaoosms because of the
ease with which it could be exca-
vated and reconstituted and its
resiliency to disturbance. Hie
soil was collected by horizon from
the perimeter of a 500-600 year-
oldDouglasfirstandinthe Oregon
Cascade Mountains and then re-
constructed by horizon in the
terracosms (Figure 2). Sensors,
samplers and minirhizotrop tubes
were placed in the soil during the
reconstruction process.
EXPERIMENTAL TASKS
Seven research tasks were cho-
sen to answer fundamental sdence
questions of this project (Figure
3). For each task specific objec-
tives and experimental
approaches were identified. Out-
puts will be in the form of data to
address the scienoequestions, and
as specific inputs for a physi-
ological process-based tree
growth model.
Task 1 Shoot Carbon and Water Fluxes
Science Questions:
* Will the net carbon flux for plants change in
response to elevated COiand climate
change?
Will plant water-use efficiency (WUE) in-
crease in response to devoted C02 and
climate change, and will this WUE increase
occur on a vegetated area basis as well as on
a single plant basis?
Experimental Research Tasks
rซt;
Shoot Cartwa aod
Water Fluxes
rซu
Sboot Growth and
rbcDOtogy
rซป j
ftntan Nutrients
ISmM
GMem Water
Ftaal Notmnta
riant Water
# Am 3
Utter Layer
Tukf
Root Growth and
Phenology
1
Biology
<ฆ.,,,ySVV,
ftifxi
Figurt3. Research taste for the experiment.
H&BS-4 CmaSisEmfrmamtalKmmrtkiMbormaj
-------
EJJtcts of CO; *nd Climate Change on Forest Trees
Objectives;
To measure at the whole plant canopy level
photosynthetic, respiration, and transpira-
tion rates in response to the individual and
combined effects of increased C02 and in-
creased temperature.
To measure at the needle/branch level pho-
tosynthetic, respiration and transpiration
rates, and stomatal conductance changes in
response to elevated 0O2and climate change.
These measurements will be made with
different photosyntheticalJy active radiation
(PAR) levels, temperatures, and C02 con-
centrations, and will be made for different
needle age classes and leaf nitrogen levels.
To measure at the canopy and needle/branch
levels, diet and seasonal patterns in photo-
synthetic, respiration, and transpiration rates,
and stomatal conductance in response to
elevated C02 and climate change.
To measure at the needle/branch and whole
plant level the influence of leaf water poten-
tial (WP), and aii vapor pressure deficit
(VPD) on stomatal conductance and tran-
spiration. These measurements will be made
with different photosynthetically active ra-
diation (PAR) levels, temperatures, and 002
concentrations; and for different needle age
classes and leaf nitrogen levels.
To derive photosynthesis, respiration and
stomatal conductance input variables for the
TREGRO model based on the above mea-
surements and literature values.
Approach; Photosynthesis will be measured at two
scales; 1) total plant canopy using the terraoosm
upper chamber, and 2) needle^ranch using a por-
table gas-exchange system. Measurements may
also be made on a whole plant level to assist in
scaling from the needleAjranch to canopy levels.
Ctaopy level measurements will be made in the
terracosms and needle/branch (and possibly whole
plant) measurements will be made primarily in sup-
porting studies. A limited number of needle/branch
measurements will be made in the terraoosms to
determine bow the OOaand temperature treatments
affect the shoot responses characterized in the sup-
porting studies. Respiration rates will be measured
throughout the duration of the experiment to quan-
tify net carbon flux to characterize metabolic rates
and energy consumption. Respiration will be mea-
sured on the needle/branch and canopy scale, using
a darkened chamber during the day, and/or under
natural darkness at night, as neoessaiy, to obtain
accurate measurements. Respiration will be parti-
tioned, as feasible, between growth and maintenance
components. Transpiration will be measured at the
following three scales: 1) plant canopy in the
terracosms, 2) whole plant in the terraoosms, and 3)
needle/branch in supporting experiments. Stomatal
conductance will be derived from transpiration and
leaf temperature measurements on both the needle/
branch and whole plant scale.
Qytpwts;
Characterization of net caibonfluxforDoug-
las fir shoots in response to elevated C02and
climate change.
Characterization of WUE for Douglas fir
shoots in response to elevated C02 and cli-
mate change.
Characterization of diel and seasonal pat-
terns of carbon and water fluxes for Douglas
fir shoots in response to elevated 002 and
climate change.
Characterization of relationships among
photosynthesis, respiration, tissue C/N ra-
tios, and total nonstructural carbohydrates
CINQ.
Evaluation of potential for changes in plant
canopy temperature induced by transpira-
tion inductions.
Ifesk 2 Shoot Growth, Morphology, Allom-
dry, Phenology, and Carbon Partitioning
Will shoot growth change in response to
devoted C02and climate change?
Will shoot morphology and alkmetric rela-
tionships change in response to elevated
C01andclimate change?
Will shoot phenology change in response to
elevated C02and climate change?
*tpES-5
-------
Effects of CO2 tmiCtimat e Change on Forest Trees
Will the biochemical partitioning of C in
shoots change in response to devoted C03
and climate change ?
Objectives:
To measure, at the individual plant level,
effects of elevated C02 and climate change
on shoot biomass (dry weight) by age class
of the main stem, blanches, needles, and
buds.
To measure, at die individual plant level,
effects of elevated C02 and climate change
on shoot allometric parameters, i.e^ stem
diameter, height, and needle elongation.
To measure, at the individual plant level,
effects of elevated C02 and climate change
on shoot morphology and allometric rela-
tionships including numbers, rank, and
weights of branches, needles, and buds for
all age classes of tissue. Needle areas will be
taken to determine specific needle weights.
To measure, at the individual plant level,
effects of elevated C02 and climate change
on shoot phenology. Tbedatesofkey events,
such as onset of bud break, secondary bud
break, and first frost will be carefully noted.
To quantify the changes in the biochemical
partitioning of C between structural and
nonstructural compounds in the various shoot
fractions in response to elevated C02 and
climate change.
Approach; He study will focus on the long-term
effects of increasing C02 and climate change on
Douglas fir seedlings growing in the tenacosms.
Baseline measurements will be takes at bo initial
destructive harvest of 50 bare-root seedlings. Inter-
mediate measurements will be taken to follow the
course of tree growth over time; they mil be nonde-
structive in die tenacosms but destructive in die
supporting experiments. Final destructive measure-
ments will be made to look at the cumulative effects
of the treatments and experimental conditions on
overall tree growth.
Qptpufc;
Characterization of shoot growth of Doug-
las fir in response toelevated 002and climate
change.
Characterization of shoot morphology and
allometric relationships of Douglas fir in
response toelevatedC02and climate change.
Characterization of shoot phenology of
Douglas fir in response to elevated 002 and
dimate change.
Characterization ofchanges in the biochemi-
cal partitioning of C between structural and
nonstructural compounds in the various shoot
fractions hi response to elevated 002 and
dimate change.
Evaluation ofthepetfonnance of the CERES
device for continuous analysis of seedling
growth through stem diametermeasurement.
Task 3 - System Nutrients
Scfc m Owatons
Will elevated C02and climate change affect
plant nutrient balance?
Will the response afforest trees to elevated
C02and climate change alter plant and soil
nutrient pools?
Objectives;
To monitor changes in inorganic nutrient
concentrations in above- and belowground
plant tissues, liner material, soils and soil
solutions as a function of C02 and dimate
change.
To evaluate the effects of elevated C02 and
dimate change on inorganic nutrient bal-
ance in Douglas fir seedlings.
To evaluate the physiological significance
of nutrient availability in respect to the ob-
served responses toelevated C02and climate
change.
To measure C, N, S, and INC concentra-
tions in above-and belowgroundplanttissue,
litter material, soil, and soil solutions.
HgtES-6 *~UhE*HHmmmtalMซmi*ki*bot*ov
-------
ซTซ* of COt Climatt Chang* om Fortsi Trtts mm
Approach: Chemical analysis will be conducted on
plant tissues, litter material, soil samples, and soil
solutions to 1} determine C and nutrient concentra-
tions, 2) quantify C and nutrient pools, and 3)
monitor changes in these pools over time. Samples
will be from Tasks 2,5, and 6 focused on above- and
belowground responses, with theresultsof the analy-
ses evaluated within die task where the samples
originate. Questions on die whole plant and soil
nutrient status will be addressed within this task.
Analyses will indude OH/N/S, inorganic nutrients,
mdTNC.
fiutetitu
Characterization of complete soil macro-
and micronutrient composition at the begin-
ning and end of the experiment both in the
individual terracosms and at the field soil
collection site.
Evaluation of changes in plant nutrient con-
centration, composition, and relative nutrient
ratios to assess differences between experi-
mental treatments.
Characterization of changes in plant avail-
able soil nutrient levels over the period of the
study.
Evaluation of the dynamic relationships be-
tween plantand soil nutrientpools as affected
by elevated CO} and climate change.
Analysis of ON and lignin/N ratios in plant
tissues (needles and roots), total CandNin
soil, and net C and N storage.
Task 4 - System Water
Scfcnre Owstfons;
Will elevated C02and climate change affect
plant water balance?
Will elevated C01 and climate change sig-
nificantly change the driving farces and
resistances that determine water flow in the
soQ-pknt-atmosphere continuum ?
Objectives:
To measure the effects of elevated 00, and
climate change on die relationship between
plant and soQ water potential.
To measure the effects of elevated (DO, and
climate change on the overall system water
balance.
* To measure and monitor volumetric water
content in each soil horizon. These data will
be used to regulate irrigation scheduling and
for calculating system water budgets.
Approach: Plant water potential will be measured at
the needle level four times a year using destructive
sampling and thermocouple psychrometry. Efforts
will be made early in the experiment to develop and
apply a method for continuous and nondestructive
measurement of water status on a whole plant basis.
This techniquewill be based on the application of the
CERES Device. Because regular collection and
drying of soil samples, to determine soil water, is not
practical due to die number of samples and time
required to process them, two non-destructive tech-
nologies were selected to provide measures of soil
water. The first is a relatively new technology called
time-domain reflectometry (TDR), and the second is
die neutron moisture probe.
Outputs:
* Characterization of the independent and in-
teractive effects of elevated00,and climate
change on plant water balance and soil water
status.
Qiaracterization of relationship between
short-term seedling stem diameter changes
and plant and soil water status.
Evaluation of die potential for die continu-
ous nondestructive measurement of plant
water status and plant water flux through the
combined use of the CERES device and
stem sap flow gauges.
* Daily characterization of volumetric soil
water content by soQ horizon and rooting
volume to determine seasonal irrigation
scheduling.
#hf*ฃS-7
Cormllis E*vbxmmtntaJ tlcf*ardi laboratory
-------
Eff*rtsofCO) and Climate Chongt am Fortst Tftts
Task I-Litter Layer
Science Questions:
Will the rate oflitter decomposition change
in response to elevated C02 and climate
change?
Will nutrient cycling through the litter layer
change in response to elevated C02 and
climate change?
Objectives:
To measure changes in the rate of litter
decomposition with elevated C02 and cli-
mate change.
To determine how elevated C02 and climate
change affect nutrient cycling in the forest
floor litter layer.
To measure changes in litter layer quality
(C/N ratio, lignin/N ratio, etc.) throughout
the study.
To determine the effects of elevated C03 and
climate change on the net storage of caibon
in the forest floor litter layer.
Approach: This task focuses on the long-term
effects of elevated C02 and climate change on
decomposition and nutrient cycling in the forest
floor of the terracosms. Weight loss and changes in
mineral nutrient and organic chemistry of the litter
layer will be used as integrative measures of litter
processing and carbon storage. Rates of litter layer
' decomposition and changes in chemistry will be
monitored using litter contained in inert mesh bags
and needle packs.
Qytppts;
Characterization of litter layer decomposi-
tion rates, and caibon and nutrient cycling of
Douglas fir litter under elevated C02 and
climate change.
Characterization of changes in litter quality
while undergoing decomposition under el-
evated C02 and climate change.
Characterization of net storage of carbon in
the litter layer tinder elevated GO, and cli-
mate change.
Task 6 Root Growth, Morphology,
Phenology, and Carbon Partitioning
Science Questions:
Will root growth change in response to
devoted C02and climate change?
Will elevated C02 and climate change affect
the allometric relationships among coarse
roots, fine roots, andmycorrhkae?
Will root phenology be altered by elevated
C02and climate change?
Will the biochemical partitioning of root C
and N be affected by elevated C03 and
climate change?
PWfgtjvss;
To quantify root growth with numbers of
roots produced, their distribution and turn-
over, and the total weight of the standing
stock of roots under elevated 002 and cli-
mate change.
To quantify dynamics of root production,
development, and mortality under elevated
C02 and climate change, and to determine
the effects on root allometries, i.e., distribu-
tion of biomass among coarse roots,
nonmycorrhizal fine roots, andmycorrhizae.
To characterize effects of elevated C02 and
climate change on root phenology.
To quantify biochemical partitioning of C
between structural and nonstructural com-
pounds in the various root fractions.
Approach: Roots will be assessed by two methods,
one destructive (cores-to-depth) and one nonde-
structive (minirhizotrons). Destructive sampling
will be limited in the terracosms to avoid destruction
of the biological and physical integrity of the
belowground component, recognizing that infre-
quent destructive sampling may be insufficient to
characterize toot biomass with a high degree of
accuracy. Two soil cores (5 cm i.d.x 95 cm) will be
collected twioe a year and separated into ID-cm
segments by depth. Samples will be sorted into four
fractions: live coarse roots (> 2 mm), live fine roots
(< 2 mm) and myconhizae, dead coarse roots, and
dead fine roots and myoonhizae. Besidesdry weights,
the separated soil and root fractions will be analyzed
f*gtE$-ง Cermtlb Emtinmmutual Rtuttrck Lebomoty
-------
Effects of CO2 end Climate Change on Forest Trees
for C fractions and nutrients. Total C and N will be
measured in the root "cellulose", "extractives", and
"lignin" fractions. Minirhizotrons will be used with
miniature video camera system to provide a nonde-
structive measure of root production and dynamics.
Outputs:
Characterization of the effects of elevated
COa and climate change on root growth.
Characterization of changes in root phenol-
ogy caused by elevated C02 and climate
change.
Characterization of changes in die distribu-
tionofQnutrients, "cellulose","extractives",
and "lignin" in the belowground standing
stocks of coarse roots, nonmycorrhizal fine
roots and mycorrhizae.
Characterizationofchangesinthebiochemi-
cal partitioning of C between structural and
nonstructural compounds in the various root
fractions.
Task 7 Soil Biology
Science Questions:
ฆ Will bacterial and fungal populations, soil
fauna, nematode community structure, and
the colonization of tree roots by mycorrhizal
fungi, be affected by elevated C02 and cli-
mate change?
Will soil greenhouse gas production, pro-
cessing, and emissions be affected by
elevated C02and climate change?
Objectives:
To quantify the effects of elevated C02 and
dimate change on total and active soil mi-
crobial populations (bacteria and fungi),
nematode community structure, and soQ
fauna populations.
To characterize the carbon transformation
rates of the bulk soQ microbial population
under elevated C02 and climate change as
indicated by the activities of enzymes pro-
cessing organic compounds.
To quantify the effects of elevated C02 and
dimate change on the colonization of roots
by mycorrhizal fungi and on the diversity of
mycorrhizal fungi colonizing roots.
To measure trace gas production and loss
within the soil profile and the physical, chemi-
cal, and environmental factors affecting their
production and loss.
Approach: Measures of soil bacteria, fungi, myoor-
rhizae, nematodes and soil enzymes will be
determined using samples from the cores-to-depth
collected twice a year. Soil fauna populations will be
assessed using separate litter and soil samples col-
lected at the same biennial samplings. Bacterial and
fungal total biomass estimates will be performed by
direct microscopy on hyphae and bacterial cells.
Bacteria] and fungal active biomass will be deter-
mined by fluorescein diacetate staining followed by
direct microscopy. Soil microbial activity will be
determined by measuring activity of enzymes such
as 6-glucosidase, peroxidase, phenoloxidase, phos-
phatase, and proteinase. Mycorrhizal fungi
colonization will be determined by microscopy.
Mycorrhizal fungi diversity will be determined on a
limited basis by assessment of nudeic add "finger-
prints" of myconhizal fungi. The fate of key soil
fauna species, induding earthworms, spiders, milli-
pedes, and centipedes, will be assessed by direct
observation of litter and soil samples.
Two kinds of soQ gas samples will be oollected and
analyzed for COr CH4, N20, and 02. Soil gas
samplers have been placed at five depths in the
terraoosm soil. Headspace chambers will be used to
measure soil surface emission (litter layer-air inter-
face). Both kinds of samples will be analyzed using
gas chromatography.
Qu&Uls;
Estimates of total and active bacterial and
fungal biomass, nematode community struc-
ture, and soil faunal populations under
elevated C02 and dimate change.
Estimates of soil microbial activity as af-
fected by elevated C02 and dimate change.
Estimates of root colonization by mycor-
rhizal fungi under elevated C02 and dimate
HgeES-9
ConoUit Emrtnmwuntal Ramrdt Laboratory
-------
Effects of C02 end Climait Change on Forttt Tnts
Characterization of the effects of elevated
C02and climate change on differentiation of
the mycorrhizal fungi community on roots.
Estimates of annual emissions of green-
house gases from terracosm soils.
Characterization of greenhouse gas produc-
tion and processing in terracosm soils.
MODELING TASKS
Hie primary goal of these tasks is to parameterize a
process-based tree growth model to study the re-
sponses of trees to elevated C02 and climate change.
The TREGRO model was selected because it simu-
lates the growth of both above- and belowground
plant components and incorporates fundamental
processes likely to be affected by elevated C02 and
climate change. Hie model is currently operational
and providesa reasonable simulation of plant growth.
Parameterization of the TREGRO model will occur
using data from the experimental research tasks from
this project, with additional data from the initial
biomass values for our population of Douglas fir
trees, published literature, and the Ozone and Forest
Response Program at ERL-C. The parameterized
model will be used to test our conceptual understand-
ing of how Douglas fir responds to elevated CO, and
climate change by comparing experimental results
to model predictions in an iterative fashion. The
output from the modeling tasks will be a parameter-
ized and calibrated version ofTREGRO for Douglas
fir, useful for studying the effects of elevated C02
and climate change.
INTEGRATION AND INFERENCE
Hiis study will support policy objectives of the U.S.
Interagency Committee on Earth and Environmen-
tal Sciences (CEES), particularly in die areas of
effects of global climate on ecosystems and influ-
ences (feedbacks) of ecosystems on atmospheric
C02 concentrations and climate change processes.
The support will be in the form of providing: 1) an
integration of the experimental results into a cohe-
sive understanding of the effects of elevated C02and
climate change on forest trees and soils, and 2)
inference of these effects across time and spaoe
through the application of a tree growth model.
-------
EfftettofCOj andClimoitChmgtmPortaTrtts
L INTRODUCTION
A focus of the U.S. Environmental Protection
Agency's Global Change Research Program is to
derive a better understanding of the interrelation-
ships between atmospheric carbon dioxide
concentrations, global climate and the terrestrial
biosphere. This research planning document de-
scribes a project being developed to provide a
scientific understanding of CO^climate/biospheric
interactions necessary to make some of the difficult
policy decisions facing the U.S. Government. This
project is focused specifically on Investigating the
eoophysiologf cal responses of forest trees to changes
in atmospheric carbon dioxide (CO^ and climate.
This research plan provides the reader a brief expla-
nation of the physicochemistry of the greenhouse
effect and climate change issues, followed by a
review of the current understanding of the effects of
COy temperature and water stress on tree physiol-
ogy. Next, a discussion of the important role soils
play in the forest ecosystem is presented, with a focus
on how climate change may affect soil processes.
The introduction ends with an analysis of the pro-
jected effects of climate change on the forests of the
Pacific Northwest, to provide an example of poten-
tial climate change impacts on vegetation.
The introduction section is followed by a brief
description of the policy issues addressed by this
research project, These issues cover the scale of the
response of the individual tree to larger scale issues
at the watershed level. The remaining portions of the
plan provide an overview of die general research
approach, details of the scoping studies used to
establish the experimental design, details of experi-
mental studies on a specific task-by-task basis, details
of modeling studies, and an overview of integration
and inference activities. The plan is completed with
a review of the planned research outputs and a
discussion of related research projects being carried
out by this and other agencies.
CLIMATE CHANGE
Sinoe the beginning of the industrial revolution, the
composition of the atmosphere has been altered by
increasing concentrations of atmospheric trace gases,
such as carbon dioxide (COJ and methane (CHJ
(Houghton et al., 1990). These and other atmo-
spheric trace gases play a lay role in the energy
balance of earth by trapping a portion of the earth's
Infrared radiation leading to a warming of the planet.
Solar radiation is our primary energy source and the
sun can be thought of as a blade body radiation
source with a surface temperature of6000% emit-
ting a broad electromagnetic spectrum (Mitchell,
1989). The longer wave emissions have a relatively
normal distribution of energies, centered about a
mean wavelength of -550 nm and within the range
of 150 to 5000 nm. The surface of the earth absorbs
a portion of this spectrum that passes through the
stratospheric ozone layer and overly ing cloud layers,
resulting in surfaoe warming to a temperature of
-255ฐK (-18ฐQ, Life on earth would not be as we
know it today if this were the earth's average surface
temperature.
The earth also behaves as a black body radiation
source reemitting some of the energy absorbed from
the sun's rays as electromagnetic radiation, with a
spectrum normally distributed about a mean of
-14,000nm and within the range of4000to 100,000
nm [infrared (IR) region of the electromagnetic
spectrum]. 1>ace gases in the earth's atmosphere
absorb some ofthisreemitted energy, causing earth's
biosphere to warm up an additional 33ฐKto approxi-
mately 288ฐK(15eQ (Houghton et al, 1990). This
trapping of energy, commonly referred to as the
greenhouse effect, is what makes life possible on
earth.
There aie several gases in die atmosphere that are
Important to die greenhouse effect; die most notable
Is HjO. But other gases [CO,, CH4, NaO, O, and
CFCs (chloro-fluorocaitjons)], which are found at
mudi lower concentrations than Hp, are also im-
portant These gasesaretennedradiatively important
trace gases (RTTOs). RJTGs are the trace gases
found in the atmosphere that have significant IR
-------
Effects of CO j and Climate Change on Fortst Trees
absorbtivities at wavelengths that align with the
black body IR emissions from earth.
Based on the careful examination of gases entrapped
in glacial ice, it appears that the concentrations of
RITGs in the free troposphere have been relatively
constant throughout the most recent geological his-
tory (Mitchell, 1989; Khalil and Rasmussen, 1987;
Ramanathan et al., 1985). However, over the last
several hundred years there has been a notable, and
in some cases a very rapid, increase in the concentra-
tions of all RITGs. The recognition of this rapid
increase has caused concern among the international
scientificcommunity and world governments. While
it is realistic to assume, on the basis of atmospheric
radiative transferproperties, that continued increases
in RITGs concentration will have a measurable
effect on climate; our limited understanding of the
processes controlling global climate allows us to
only speculate on the possible magnitude or timing
of the changes.
EFFECTS OF ELEVATED CO, ON TREES
Hie potential effects of elevated 00, concentrations
on forested ecosystems are uncertain. Many assess-
ments of impacts of climate change on forests have
focused on direct effects of increased temperature
and drought on trees, but have not quantified poten-
tial impacts of elevated C02 in combination with
these other environmental stresses on forests.
Hie physiological response of plants (Oechel and
Strain.1985; Allen, 1990) and more specifically
forests (Kramer and Sionit, 1987; Jarvis, 1989) to
elevated 00, has been reviewed by several authors.
The observed increase in biomass resulting from
seedlings and other plants grown under elevated C02
levels has been termed the C02 fertilization effect
Sionit and Kramer (1984) summarized results of 15
short-term experiments (several months to 2^ years)
using elevated 00, on woody plants and provided
the following generalized conclusions:
-------
J$ffteec/COj and Climalt Ckangt on Fortst Tr*a
concentration-based competition between 02 and
CO, for RuBP, photorespiiation decreases with in-
creasing C02 concentrations and net photosynthetic
rates increase. At 600 ppm C02, pbotorespiration
rates drop by as much as 50% compared to rates at
current ambient levels (Oechel and Strain, 1985).
While there is general agreement that elevated C02
causes increased photosynthetic rates in most spe-
cies, it is largely unknown if these increases will
persist as plants acclimate to elevated C02. In-
creased photosynthetic rates may be largely a
short-term response of plants grown under condi-
tions where photosynthetic rates are limited by a
number of factors. However, measurabl e C02 fertili-
zation effects have been reported to occur in some
woody plants under light, water, or nutrient deficien-
cies (Tolley and Strain, 1984a; 1984b; Kramer and
Sionit, 1987).
A decrease in the increased photosynthetic rates
ฆ under elevated CO} has been observed in longer-
term experiments,butmechanismsforthe reductions
are cot understood. Current research focuses on the
ability of plants to use an increased supply of photo-
synthate. Evidence suggests that increased rates of
C02 assimilation can be maintained only if growth,
.-environmental conditions and nutrient availability
i permit oontinued development of sinks to aocom-
vmodate higher photosynthetic rates (Oechel and
Strain, 1985; Thomas and Strain, 1991). If excess
photosynthetic products are produced, end-product
inhibition or insufficient substrate availability may
limit potential COt-induced increases in photosyn-
thetic rates.
Respiration
While there is general acceptance that C3 plants
respond to elevated 00, through increased photo-
synthesis, substantially less is known about die
effect of elevated C02on plant respiration. In terms
of net primary productivity,any potential increase in
carbon sequestration could be offset by increased
respiration. However, if plant respiration remains
the same or decreases under conditions of elevated
COr the increase in net primary production could
lead to increased carbon sequestration in the bio-
sphere.
Recent studies suggest that there may be decreased
foliar respiration in plants exposed to elevated C02.
Wullschleger et al. (1992) reported decreased leaf
level respiration in shorter-term (24 weeks) C02
exposure studies conducted on yellow-poplar and
white-oak. They measured 37% and 52% reductions
in respiration rates on a per leaf area basis, respect-
fully. Hie authors suggested that these results may
be associated with the observed reduced nocturnal
carbon export and higher carbohydrate concentra-
tion in leaves exposed to C02-enriched air. Hendrix
and Grange (1991) recently provided evidence that
carbon export and the subsequent leaf level carbohy-
drate depletion were positively correlated with dark
respiration.
In longer term studies, Noiby et al. (1992) found that
yellow-poplar trees exposed to elevated C02 over
three growing seasons showed a 30% decrease in
dark respiration. While no mechanism was postu-
lated for this observation, die combined effect of
increased leaf-level photosynthesis and decreased
dark respiration did not result in significant changes
in whole plant cartwn storage. Noiby et al. (1992)
explained the results through the observed shifts in
carbon allocation from aboveground (leaf-produc-
tion) to belowground (fine-root production)
processes.
Ryan (1991) discussed the theoretical potential for
climate change affecting plant respiration. Mainte-
nance respiration and tissue nitrogen concentration
are strongly correlated and show a positive relation-
ship to each other. This relationship exists because
most of the organic nitrogen in plants is in protein
and roughly 60% of maintenance respiration sup-
ports protein repair and replacement (Ryan, 1991;
Penning de Vries, 1975). Based on this relationship,
the increased C/N ratios observed in plant tissue
developed with enhanced photosynthetic rates un-
der elevated C02 conditions, could be expected to
result in decreased maintenance respiration.
t*g*3 Cerretiit EarirtmMtminl Rtttarch Labomorj
-------
EJJtcts of CO2 Climalt Changt on Fortst Trtes
Baker et al. (1992) observed a positive correlation
between specific dark respiration rates and nitrogen
content for rice plants grown under subambient,
ambient and superambient C02 conditions. For all
treatments plant nitrogen levels decreased with plant
age, as did the specific respiration rates. Plants
grown under elevated C02 levels showed decreased
nitrogen content and dark respiration rates in all age
groups as oompared with the ambient and subambient
COj treatments, consistent with the discussion of-
fered by Ryan (1991). Changes in tissue C7N ratios
were not reported by Norby et al. (1992) or
Wullschleger et al. (1992).
Stomatal Conductance/Transpiration
Regulation of stomatal aperture in response to atmo-
spheric C02 concentrations has been studied for
some time. Reviews by Raschke (1979) and Zeiger
(1983) provide detailed discussions. While a gen-
eral mechanism, underlying the response, has yet to
be identified (Morison, 1985), of greater interest to
this discussion is the physiological significance of
COj-induced stomatal regulation and its effect on
leaf gas exchange.
A complex relationship exists between stomatal
conductance, rate of C02 uptake and transpiration.
The influx of C02 and efflux of HjO through the
stomata are diffusion-based processes, so that rates
of movement are affected similarly by size of the
stomatal aperture. However, the uptake of C02 into
chloroplasts also is limited by various other bio-
chemical and diffusional processes, which are
collectively termed as the mesophyll resistance.
Thus, while resistance of HjO efflux is primarily
dependent on size of the stomatal aperture, resis-
tance to C02 influx is die sum of die mesophyll
resistance and conductance resistance. As meso-
phyll resistance for C02 is similar to, or larger than,
the stomatal diffusion resistances for C02 and HjO,
reduction in conductance due to a decrease in sto-
matal aperture is more significant for HjO than C02.
A paradoxical condition exists where it is possible
for photosynthesis to increase as stomatal conduc-
tance and transpiration decrease (Kramer and Sionit,
1987). If the long-term response of trees to elevated
C02 is to reduce stomatal opening, the loss of water
(per unit land surface area) during C02 uptake may
be reduced, consequently, forests may endure peri-
ods of drought with greater water use efficiency.
The inverse relationship between photosynthesis
and transpiration/conductance is illustrated in Fig-
ure 1-1 for Populus deltoides. The difference in
conductance should lead to a more efGcient use of
water, (i.e., less water will transpire during photo-
synthesis). The ratio of002fixed toHjO transpired
is termed the plant water use efficiency (WUE).
Experiments have shown that increased C02 con-
centrations cause partial closure of stomata,
simultaneously decreasing conductance of C02 and
water vapor (Morison, 1985). Rogers et al. (1983a)
reported a 40% decrease in conductance for sweetgum
grown outdoors in open-top chambers at doubled
C02 concentrations. Tolley (1982) reported a 50%
decrease in stomatal conductance in sweetgum by
increasing the C02 concentration from 350 to 675
ppm, but found no difference in conductance for
loblolly pine exposed to the two C02concentrations.
In long-term exposure studies (2 J years) on Pinus
ponderosa seedlings, Surano et al. (1986) found
small differences in conductance between the treat-
ments and controls during early morning hours, but
a significant decrease in conductance in seedlings
exposed to elevated C02by mid-moming. At noon
differences between controls and treatments were
again insignificant, but by mid-afternoon the
seedlings exposed to elevated C02 showed a 50%
decrease in conductance. After two growing sea-
sons, trees exposed to elevated C02 showed signs of
stress (needle abscission, chlorosis, an apparent al-
teration ofheat tolerance) that may be due to increased
foliar temperatures resuJ ting from red uced transpire -
tional cooling of need! es because of the CO, induced
stomatal closure.
It has been suggested that increasing C02 levels may
increase leaf area index and WUE simultaneously.
Hiese two changes, combined with increased leaf
temperature, may not result in net changes in water
use per unit land area (Allen 1990). Key unanswered
questions remain:
Page 4 CamlUsEwrtrtMwunulktuarekLaboratorj
-------
Effnets of CO2 ซjuf Climait Chang* on Forest Trtts
Popufus deltoldes
-iปo
0.80
_j_ _ _ _g rooo
COa Concentration
(Ml I1)
Figure 1 -1. The influence ofC03concentrations on photosyn-
thesis (PJ, transpiration (E) and leaf conductance (CJ in
PoduIus del todies (Kramer and Sionit, 1987).
Will increased WUE, due to decreased sto-
matal conductance, persist as treesacdimate
to elevated C02?
Will decreased conductance negatively af-
fect needle physiology because of decreased
transpirations! cooling?
Will decreased stomatal conductance effect
overall tree response to 002 and climate
change?
Growth and Carbon Allocation
Growth effects of increased photosynthesis in tree
seedlings stimulated by C02 enrichment have been
evaluated by many research groups. A general
growth response usually is measured in seedlings
exposed to elevated 00y but there are dearly differ-
ential responses among species. Jarvis (1989)
summarized studies of increased 00, concentration
on the growth of young conifers and broadleaf trees
as showing that "young trees growing larger more
quickly and that the majority of the changes ob-
served are normal, ontogenetic changes associated
with growth and development"
Eamus and Jarvis (1989) reported on effects of
doubled atmospheric C02 on growth of young coni-
fers and broadleaf trees conducted in controlled or
partly-controlled environments. The trees were
grown in pots and the experiments were generally
short in duration (a few weeks to 25 years), In all
cases rates of dry matter production were increased
between 20 to 120% at elevated 00, concentrations,
with a median increase of about 40%. Dry leaf mass
increased in most experiments as a result of in-
creased number, area, or thickness. Coarse and fine
toot production also increased, with increased root/
shoot ratios more notable in seedlings grown in
nutrient-limited conditions.
Sionit et al. (1985) found increased stem growth and
brandling in loblolly pine (Pirns taeda L) and
sweetgum (Liquidambar styradflua) exposed to
elevated CO^, but no significant change in root/shoot
ratios in the pine and decreased ratios in sweet gum.
Tolley and Strain (1984a) used the same species to
look at the combined affect of002 enrichment and
variations in irradiance levels. They found that
although reduced irradiance did not predude the
growth enhancement from elevated COj, the magni-
tude of die fertilization effect was diminished. The
largest C02 effects were shown by sweetgum grown
-------
Effects of CO2 end Ciimai* Change on Forest Trees ,
a! high inadiance (1000 |xmol mJ s'1) and high C03
(675 ppm); height, basal stem diameter and leaf area
increased by 31, 20 and 44%, respectively, com-
pared with seedlings grown at the same inadiance
and 350 ppm C02. Increased leaf area was associ-
ated with increases in leaf number rather than area
per leaf, indicating an effect of C02on leaf initiation
(Tolley and Strain, 1984a). They concluded that for
both species elevated atmospheric C02 concentra-
tions had a greater affect on dry matter production
than onheight, basal stem diameter,leaf area, orroot/
shoot ratios.
Water stress has been shown to create shifts in the
root/shoot ratios of seedlings grown under elevated
C02(Tolley and Strain, 1984b;sweetgumand loblolly
pine). Increased root/shoot ratios in drought-stressed
seedlings were most significant in sweetgum, show-
ing an increase of 29% with seedlings grown at
elevated C02 compared to those grown under ambi-
ent COj concentrations. This response has important
implications for seedlings experiencing water stress,
as the increased root/shoot ratios indicate increased
root surface area for absorption of available water.
EFFECTS OF TEMPERATURE ON TREES
Photosynthesis and Respiration
Gross photosynthesis increases as temperature in-
creases to about20-25ฐC Respiration also increases
as temperature increases to a critical level above
which respiration declines with further increases in
temperature. However, the rate of increase of respi-
ration at lower temperatures is less than the rate of
increase for gross photosynthesis. Starting at ap-
proximately 10-15#C, respiration begins to increase
faster than gross photosynthesis. In general then, net
photosynthesis rapidly increases up to about 10 to
15ฐC, above which it rapidly drops due to increases
in respiration. At about35-40ฐC net photosynthesis
falls to zero (Kozlowski et aln 1991).
Hie temperature optimum for photosynthesis in
conifers varies (Dougherty and Morikowa, 1980;
Leverenz, 198laฃ) and is associated with genetics
(Sorensen and FerreD, 1973), seasonal adjustments,
light (Brix, 1967; Lassoie, 1982; Webb, 1971) and
vapor pressure (Leverenz, 1981b). Net photosyn-
thesis response curves for Douglas fir are fairly flat
between 2 and 25ฐC with an optimum at 10ฐC (Sab,
1974); above 25ฐC, Douglas fir photosynthesis de-
creases significantly. Needle conductance ofDouglas
fir generally is highest between 5 and 20ฐCand drops
rapidly as temperature increases (Lassoie, 1982;
Neilson and Jaivis, 1975).
Between -5ฐC and 45ฐC, C02 and temperature are
mutually compensating factors for photosynthesis
of trees (Leverenz and Lev, 1987). Increased C02
compensates for temperatures above and below the
optimum and temperatures near optimum compen-
sate for low atmospheric COa. There is greater C02
compensation for superoptimal than for suboptimal
temperatures. Generally, the optimum shifts up-
ward by 5-10ฐC as C02 increases to a concentration
of600ppm. In summary forphotosynthesis, doubled
atmospheric C02 more than compensates for tem-
perature increases of up to 10ฐC Leverenz and Lev
(1987) oonclude that despite large increases in pho-
tosynthetic efficiency as C03 doubles, C02 effects
on relative carbon uptake and loss will diminish due
to respiration responding to temperature.
In general, as temperature increases carbon con-
sumption for all tissues increases. Root respiration
increases with increased root temperature and growth
respiration comprises nearly a constant fraction of
total root respiration as temperature increases
(Lawrence and Oechel, 1983a,b); dark respiration
also increases as air temperature increases (Lassoie
etal., 1985).
Phenology
Temperature directly affects all metabolicprocesses
and hence may have a great influence on the size and
form of trees. Past and current temperature affects
shoot growth, expansion of internodes and leaves
and induction of bud dormancy (Kramer and
Kozlowski, 1979; Kozlowski, 1983). Chilling re-
quirements for release of dormant buds vary with
genotype and location ofbuds on the tree (Kozlowski
et aln 1991)and photoperiod (Wareing, 1953; 1956;
Campbell, 1978; Lavender, 1981). Tlie most effec-
tive temperature for release of dormancy in those
plants requiring a cold treatment is near 5ฐC
fmf* 6
ConaUis Emrtrommtnlcl Ktfartk Laboratory
-------
Effects of COj and Climate Change on Forest Trtes
(Nood^n and Weber, 1978). Copes (1983) reported
failure of grafted Douglas fir due to insufficient
chilling when mean monthly temperatures did not
drop below 93ฐC Wommack (1964) found 5ฐC
optimal for breaking dormancy of Douglas fir and
more efficient than either 0 or 10ฐC Wells (1979)
reported a 17-week chilling period (s 5ฐQ is needed
for Rocky Mountain sources of Douglas fir seed-
lings to break dormancy. Van den Driessche (1975)
also found that increasing the number of hours of
chilling produced more rapid flushing. Once die
chilling requirement is met, bud sprouting may be
controlled entirely by temperature (Lavender and
Hermann, 1970).
Seed germination, as with shoot growth, is affected
by mutually compensating factors, e.g., wanner
spring temperatures can compensate for warm win-
ter temperatures and increased winter dulling can
compensate for cool spring temperatures (Lavender,
1981). Chilling requirements for seed germination
of Douglas fir genotypes growing in areasof wanner
winters (coastal) are greater than for mountain and
interior genotypes (900to 1300m; Lavender, 1978).
For coastal Douglas fir, where stratification require-
ments are longest, warmer winter temperatures are
more likely to be insufficient for proper timing of
seedgermination. Asfew data are available, Leverenz
and Lev (1987) suggest using a 9ฐC threshold (as-
sumed for shoot growth) for seed germination; it is
possible that the threshold for chilling of seeds and
buds of western coniferous species may be as low as
rc
Carbon Allocation
Most of the information on temperature effects on
physiological processes in shoots concerns whole
plants that are exposed to a single temperature. This
simplifies experimentation but doesnotmimic natu-
ral temperature variation. For example, allocation
patterns between shoots and roots are affected by the
temperature of each organ. Problems arise from
growing plants at the same root and shoot tempera-
ture. Such procedures do not account for normal
diurnal and seasonal variation Id absolute and AT
(difference in temperature between roots and shoots)
and do not account for the greater variation in shoot
temperature than root temperature.
A general failure to recognize normal variations in
temperature and AT makes it difficult to evaluate
root and shoot temperature stress on whole-plant C
allocation. However, the importance of temperature
on C allocation and utilization processes in plants is
dear, e.g., Q10 - 2. In general, carbon allocation,
organ dry weight and terminal bud formation are all
influenced by day and night temperatures (Hellmers
et al., 1970). Whole-plant allocation patterns change
as whole-plant temperature increases. Soybean (Gly-
cine max (L) Merrill) kept at root and shoot
temperatures of 18/12 (day/night), 22/16 or26/20eC
grew taller and had a greater number of branches as
temperature increased. Root/shoot ratio decreased
with increased temperature, indicating a reduction in
relative biomass allocation to roots (Sionit et al.,
1987). Differences between shoot and root tempera-
tures (AT) influence biomass allocation. Loffroyet
al. (1983) exposed cotton shoots and roots to a set of
four constant day/night temperature regimens with
varying AT values: a) both shoots and roots at a
constant 17ฐC (17:17); b) shoots and roots at a
constant 2TC (27:27); c) a shoot temperature of
27ฐC with roots at 17ฎC (27:17); and d) a shoot
temperature of 17*C with a root temperature of 27ฎC
(17:27). When die temperature of the entire plant
was increased (17:17 versus 27:27) root/shoot ratios
decreased. When only the temperature of the shoots
was increased (27:17) the greatest decrease in root/
shoot ratio occurred. When only the root tempera-
ture ^was increased (1727)tootishoot ratios decreased
but to a lesser extent compared with die changes for
die other temperature regimens.
The various allocation patterns were the result of not
only a general increase in total dry matter production
as temperature increased, but also a greater increase
In shoot dry matter production (ten-fold increase)
compared with increases in production of roots(two-
fold). Tomatoes Qjycopersicvn lycopersicum Kaisl)
and lettuce ('fjatuca sp.) were grown at constant day
air temperature (20ฐC) and root temperatures that
were either 20ฐC or higher (Moorby and Graves,
1980). In another study, tomatoes were grown at
Hgt7 CenmUbEMrbrmmruttil Rtstardi Labontorj
-------
Etficts of C0} and CUmattChmgt on FertaTrtts
elevated root temperatures (10 to 38ฐQ while air
temperature was maintained at 22ฐC (Hurewitz and
Janes, 1983). In both experiments, a broad growth
response curve to temperature occurred with an
optimum at 25-30eC, based on dry matter produc-
tion and leaf area data. Furthermore, root length
increased but not necessarily with a correspondingly
greater root dry weight (Mooiby and Graves, 1980).
The increased growth at wanner root temperatures
may have resulted from higher C exchange rates in
leaves (Hurewitz and Janes, 1983). Moreover, in-
creased root zone temperature may have increased
the translocation rate to the roots.
We are not aware of comparable data for many
coniferous species. However, some data exist on the
net production of Douglas fir seedlings grown under
different combinations of air and soil temperatures
(Figure 1-2). The results indicate that different
combinations of these temperatures yielded dif-
ferent dry weights (Cleary and Waring, 1969).
However, night air temperature had little effect on
growth (Lavender and Overton, 1972). These re-
sults may be important because it is hypothesized
that most warming under altered climates will occur
at night (Karl et a., 1991; Figure 4-13).
EFFECTS OF WATER ON PLANTS
Stomatal Control, Photosynthesis and Respira-
tion
Water stress elicits many responses in plants, e.g.,
stomatal closure, osmotic adjustment and altered
carbon allocation and partitioning. Availability of
water depends on the water-storage opacity of the
site, the timing and types of moisture inputs and the
plant's ability to reach and extract the water. Mois-
ture demand is imposed by the seedling itself,
competing vegetation and the atmosphere. Evapo-
ration from the soil and transpiration from the plant
exert a demand for the water held in plants and soil.
Moderate to severe water deficits can affect tree
growth directly by reducing turgor pressures in
meristematic tissues (Vaadia et al., 1961) and indi-
rectly by promoting stomatal dosure which decreases
C02 uptake and photosynthesis (Beadle et al., 1976;
1979). Some of the reduction in photosynthesis
during drought results from increased resistance to
diffusion of C02 to the chloroplasts and some is
caused by a reduction inphotosyntheticcapacity. As
a drought develops, photosynthesis is reduced early
by stomatal closure and as leaves become more
severely dehydrated the photosynthetic process is
eventually intubited (Luukkanen, 1978; Kozlowski,
1982). In long-term water stress, total photosynthe-
sis is also reduced by reductions in new leaf area
(Kramer and Kozlowski, 1979).
Dark respiration of leaves and root respiration de-
crease in many deciduous hardwood species as leaf
water potential decreases (Jarvis and Jams, 1965;
Bunce and Miller, 1976; Brandle et al., 1977). In
f
eo
eo
OT
60 ฃ
SO
ML TKMPCIIKriMC.KOC
Figure 1-2. Growth of Douglas-fir seedlings
varies with day and soil temperatures. Con-
toured lines represent equal fractions of
optimum growth observed (optimum growth
equals 1.0). The effect of different night tem-
peratures is slight and has been averaged out
(Cleary and Waring,1969). FromGreaveset
aL,1978.
PugtB Corwaflu Enrbrmmtmlal Rtttartk Labcmay
-------
Effects of CO2 end Climate Chang* on Forest Trtts
addition, pbotorespiration often decreases with in-
creased water deficits in mesic species and increases
with water deficits in xeric species (Bunce and
Miller, 1976). As leaves reach critical (and irrevers-
ible) water potential values both light and dark
respiration increase dramatically (Levitt, 1972). Stem
respiration in hardwood trees decreases during the
day, even though temperature conditions are more
favorable than during the night (Edwards and
McLaughlin, 1978). This may be related to changes
m stem water potential and concentration of reduc-
ing sugars in the phloem and reflected in changes in
stem cambial growth. When leaves are present,
higher rates of stem cambial growth occur during the
night than during the day, which also happens when
greater turgor pressures occur (Fritts, 1958; Hinckley
et al., 1976). When leaves of deciduous trees are not
present, cambial growth is not limited by water
deficits and occurs in short surges during the day.
Most of the research on drought tolerance of Pacific
Northwest forest species has focused on stomatal
behavior and osmotic adjustment Osmotic poten-
tials vary with tissue age in coniferous species
indicating a progressive adjustment with tissue de-
velopment (Jackson and Spomer, 1979; Teskey,
1982). Ability to maintain leaf waterpotential above
the turgor loss point can be used as a measure of
drought avoidance by plants, involving active (regu-
lation) of water loss through stomata. In general,
species that dose stomata at relatively high thresh-
olds should avoid water stress-related physiological
problems. Douglas fir is ranked slightly better than
average in comparative drought tolerance of Pacific
Northwest tree species (Table 1-1; Franklin and
Dyraess, 1973; Lopushinsky, 1975; Minore, 1979;
Wambolt, 1973; Aussenac and Granier, 1978).
Specific control of stomatal activity by water is
important in determining distribution of forest tree
species as it arises as a normal consequence of
environmental conditions that promote low water
uptake relative to loss. Stomatal response is complex
and is affected by light, leaf and soil water potentials,
leaf-to-air vapor-pressure differences, leaf tempera-
tures, abscisic acid levels and internal CO,
concentrations (LassoieetaL, 1985). More impor-
Table 1-1. Comparative drought resistance of
Pacific Northwest tree species compiled by
Lassoie et aL (1985). Rankings are based only
on responses to soil drought and not to winter
desiccation.
Resistance
# Species
High
Quercus garryana
Quercus kelloggii
Pinus jeffreyi
Libocedrus decurrens
Arbutus metmesii
Pseudatsuea mennesii
Pinus contorta
Picea engelmannii
Abies grandis
Pinus lambertiana
Larix occidentals
Abies lasiocarpa
Thuja plicala
Pinus monticola
Abies concolor
Picea breweriana
Chamaecyparis lawsoniana
Abies procera
Tsuga heterophylla
Picea sitchensis
Abies amabilis
Low
Abies magnifica
Tsuga mertensiana
tantly, the environmental factors controlling sto-
matal activity rarely act independently. During the
day stomata will open photoactively and remain
open unless a threshold of leaf water potential is
reached (barring low light or high vapor-pressure
differences; Hinckley et al., 1978; Lassoie, 1982).
Hie threshold for Douglas fir seedlings is approxi-
mately -2.0 MPa as such deficits have been observed
to induce abrupt midday stomata] dosure in the field
(Running, 1976; Tan et al., 1977). In contrast, old-
growth Douglas fir has a threshold of -22 MPA
(Waring and Running, 1978) while initial stomatal
dosure occurs near -1.7 MPa in seedlings (Waring
and Running, 1978; Drew and Ferrell, 1979). Sto-
mata are sensitive to high rates of water loss due to
Pat* 9 ConcUs Etrrirommrntal Rtttarck Laboratory
-------
Efftas of COj attd CUmalt Change on Forta Trta
atmosphericconditions. A ranking of Pacific North-
west species was compiled by Lassoie et al. (1985)
from most to least sensitive to high evaporative
demand (using data of Barker, 1973; Running, 1976;
Rutter, 1977) (Table 1-2).
ฆ
Table 1-2. Comparative stomatal sensitivity of
Pacific Northwest tree species as compiled by
Lassoie etaL (1985).
Sensitivitv
Species
Most
Picea engelmannii b P.
sitchensis = Pinus contorta
P. ponderosa = Pseudotsuea
meniiesii = Tsupa heterophvlla
Least
Abies concolor.
Leaf conductances decrease rapidly as needle-to-air
vapor-pressure differences increase from about 03
kPA in Douglas fir (Leverenz, 1981c; Running,
1976). The vapor-pressure differences will have
indirect effects on net photosynthesic response to
light via direct effects on stomatal conductance
(Jarvis, 1981).
Some conifers may adapt to atmospheric evapora-
tive demand by modifying stomatal conductance to
prevent low water potentials in shoots when water
flux across roots is reduced. Maximal stomatal
conductance during the day is closely correlated
with predawn xylem pressure potential and/or va-
por-pressure differences between needles and air
formed during the day (Running, 1976). For Dou-
glas fir, Tan et al. (1977) found that stomata will
remain relatively dosed on days when atmospheric
evaporative demands are high even though soil
moisture levels are high, Le, high predawn soil
moisture potentials. During severe drought when
predawn xylem pressure potentials are very low
(-1.6 MPa in large, field-grown Douglas fir) stomata
are essentially dosed all day as hydraulic factors
override the photoactive response (Hinckley et al.,
1978; Lassoie, 1982).
Phenology
Water deficits inhibit both leaf growth and internode
expansion. Water deficits reduce leaf area by inhib-
iting initiation of leaves as well as their subsequent
enlargement (Kozlowski, 1982). As water stress
intensifies, rates of cell enlargement decrease rap-
idly at first and then more gradually. In many species
leaf enlargement is so sensitive to water deficit that
leaves may enlarge only during the night (Boyer,
1968). Whereas, normal diurnal changes in leaf
dehydration do not greatly affect final leaf size,
desiccation of long periods results in smaller leaves
(Boyer, 1976a,b). Water deficits affect height growth
and elongation of internodes of lateral shoots differ-
ently than they doleaf expansion. Asummer drought
may or may not influence current-year height growth
depending on when the drought occurs and on the
inherent pattern of shoot elongation of the species.
Late summer droughts usually influence subsequent
year height growth in spedes of fixed growth
(Kozlowski, 1982). As seeds must imbibe water
amounting to 2 to 3 times their dry weight to initiate
germination, germination capacity generally de-
creases rapidly as soils dry (Kaufmann and Eckhard,
1977).
Carbon Allocation and Nutrient Uptake
Water stress affects development of roots, as well as
myconhizal roots but only has a secondary effect on
overall root growth (FeQetal., 1988). Waterdefirits
in roots can reduce the rate of root elongation, root
brandling, cambial growth, increase root/shoot ra-
tios and increase the proportion of suberized root tips
leading to decreased water absorption. High branch-
ing density of very fine roots ofPicea sitchensis is the
result of reduced elongation rates and a simultaneous
increase in lateral root development (optimal for
myconhizal development) and can be caused by
drought (Feil et al., 1988). High brandling density
caused by drought is probably an adaptation to water
stress, leading to enhanced uptake of water from dry
ฆoils (especially by myconhizal roots; Feil et al.,
1988).
Yearly dynamics of drought influences die develop-
ment of roots (and seasonality of myconhizal
colonization). For example, if alternating periods of
10 CermlUt EMvbxmmrrttnl Ktstarck Laboratory
-------
Effects of COj and Climait Change oa Fortst Trta
drought (causing increased branching density) and
rewetting (stimulating root elongation) are repeated
frequently, mycorrhizal colonization will be high
and shoot growth may be reduced due to competition
between aboveground and belowground sinks for
carbon assimilates (Kottke and Agerer, 1983). If the
drought/rewetting cycle is infrequent, e.g., once per
year, less densely-branched roots develop with lower
myoonhizal colonization. A continuous water sup-
ply results in increased root elongation and
mycorahizal root systems which are regu] arly but not
densely branched (Kottke and Agerer, 1983). Low
water poten tials in the root environment decrease ion
uptake and transport to shoots (Greenway et al.,
1969; Cole and Alston, 1974; Pitman, 1981) due to
impaired absorption processes in the root and de-
creased water and ion mobility in soil (Russell, 1973;
Dunham and Nye, 1976). Low uptake rates in dry
conditions quickly return to pre-drought conditions
upon watering and may be due to alterations in
carbon partitioning to belowground components for
- the production of new nodal roots (Shone and Flood,
. 1983). Altered carbon pools of plants under water
stress have been demonstrated for cotton (Anderson,
1981; Oosterhuis and Wullschleger, 1987; Miller et
al., 1989),sorghum and sunflower(JonesandTumer,
1980).
EFFECTS OF ELEVATED CO, AND
* CLIMATE CHANGE ON SOILS
The response of forested systems to climate change
will not be limited to direct effects on vegetation
alone. Other components of these systems will be
affected that may Intensify the vegetation response.
Soil is one component thai will be crucial since it is
the source of plant nutrients and water, and it is also
a considerable reservoir of organic matter that, under
certain conditions, can be converted into additional
greenhouse gases, i-e., COp CH4 and N,0. Soil
mediated effects of climate change oould magnify or
buffer the plant response. Under elevated COa and
droughty conditions some plants will have increased
water and nutrient use efficiencies, but eventually
plant growth could be limited by water or nutrients.
Forest systems may be particularly vulnerable be-
cause they rely on a relatively tight nutrient cycle.
Alterations in this cycle could limit plant growth
because nutrient supply cannot meet demand or
because die timing of nutrient availability and plant
need become decoupled. Hie influence of climate
change driven but soil mediated effects on plant
response will depend upon climatic and soil condi-
tions in specific regions.
In general, the forested soils of the Pacific Northwest
formed in volcanic, intrusive igneous, sedimentary
and metamoiphic parent materials (Lassoie et al.,
1985). In higher elevations of the Cascade Moun-
tains many soils have formed in glacial til] derived
form andesite and basalt mixed with volcanic ash
(Patching, 1987). Vulcanism, glaciation and alluvial
processes have shaped much of the landscape.
From the Cascade Mountains westward and in the
higher elevations to the east, two moisture regimes,
xeric and udic, have prevailed in the recent post-
glacial period that affect soQ development and
vegetation distribution in die region. In the lower
elevations east of die Cascade Mountains the aridic
moisture regime has been dominate. The xeric
regime is typified in Mediterranean climates, where
summers are warm and dry and winters are cool and
moist with total annual precipitation less than about
ISO cm. The udic moisture regime is characterized
by a similar rainfall pattern but with more total
annual precipitation (greater than 150 an) and Mils
that do not dry out for any extended period of time
during the summer. During die periods without
rainfall, many ofthesoilson the western slopes of the
Coast Range receive precipitation in the form of
coastal or local fog (Norse, 1990). Hie udic soils at
higher elevations are kept moist for longer periods
because of melting soow. They lose less water
became of shorter growing seasons (lower overall
transpiration) and lower temperatures (lower PET).
Hie dominant forest communities is die xeric mois-
ture regime include the keteraphylla (western
hemlock) community and the mixed conifer and
mixed evergreen forests (Franklin and Dymess,
1988). In die odic moisture regime die dominant
forest communities include the Picea sitchensis
-------
Efftets of CO2 and Ciimait Chang* on Fonst Trta
(Sitka spruce) community in the coastal areas and
Abies grandis (grand fir) and Pseudotsuga menziesii
(Douglas fir) communities and the subalpine forests
[including Abies amabilis (Pacific silver Gi), Abies
lasiocarpa (subalpine fii)^\bies magnificashasterisis
(Shasta red fir) and Tsuga mertensiana (mountain
hemlock)] (Franklin and Dyrness, 1988).
Forested soils in the xeric regime tend to have a
somewhat greater base status than soils of the udic
zone because oflower precipitation, i.e, lower leach-
ing rates and because of the annual return of deciduous
vegetation leaf litter to the soil surface. In general,
there is a large amount of organic matter accumula-
tion in the upper horizons of these soils. In the udic
regime, greater leaching rates and conifer vegetation
have lead to lower base status soils than soils in the
xeric regime but with greater organic matter accu-
mulation. On older land surfaoes in the udic regime,
the combination of low base status, presence of
organics and high leaching rates creates zones of
eluviation (leaching zone) and illuviation (accumu-
lation zone). At higher elevations soO temperatures
can limit the extent of biological activities.
The distribution of vegetation is determined largely
by climate, i.e., temperature and moisture (Stevenson,
1986). Similarly, these factors influence mineral
weathering and organicmatterdecomposition, which
also influence vegetation distribution. Climate change
may affect soils in a number of ways but these effects
will be driven largely by changes in temperature and
moisture (Brinkman, 1990). It is unlikely that el-
evated canopy CO, will have a direct effect on soil
processes since soil 00, is usually a! super-ambient
concentrations (Fernandez and Kosian, 1987; van
Veen et al., 1991). Temperature will affect the rate
at which biological and non-biological reactions
proceed, with faster rates being associated with
higher temperatures. Similarly, soil moisture levels
also influence soil processes. Hie combined effects
of wanning and increased or decreased soil moisture
may have complicated effects on forest systems. It
is hypothesized that increased temperature alone
will accelerate decomposition and result in net efflux
of caibon out of soil to the atmosphere (Jenkinson et
al., 1991), thereby adding to radiative climate forc-
ing.
If elevated C02 is accompanied by warming, as
indicated in Houghton et al. (1990), then changes in
precipitation, amount and timing, will be a large
uncertainty in predicting the effects of dim ate change.
Within the Pacific Northwest, drying alone, i.e., udic
and xeric moisture regimes becoming dryer, would
result in a transition from current forest species to
those tolerant of dryer conditions. In the soil these
changes would be accompanied by loss of organic
matter and a vertical restratification of soil nutrients.
The forests west of die Cascade Mountains could
become more like those currently on the east, e.g.,
Pinus ponderosa (ponderosa pine). If the region
becomes wetter, i.e., xeric moisture regime becom-
ing udic, the opposite shifts would probably occur.
The effects of warming without a change in moisture
are less certain.
Indirect or secondary effects of elevated C02 and
climate change on soils will be mediated by plant
responses to climate change. Elevated C02 and
dimate change will affect the amount and quality of
plant litter and the amount of soil water and nutrients
removed by plants (van Veen et al., 1991). Plant
growth can be limited by lack of nitrogen and other
nutrients which influence the response of photosyn-
thesis to elevated C02 (Wong, 1979). Nitrogen is
particularly important since linkages between the
caibon and nitrogen cycles regulate the distribution,
quantity and to a large extent the quality of organic
matter in many ecosystems (Agren et al., 1991). In
soils the caibon to nitrogen (C/N) ratio of organic
matter substrates can constrain or aooelerate decom-
position since the C/N ratio of plant litter governs to
a large extent litter quality and consequently decom-
position (Melillo etal.,1982; Melilloet al., 1989; and
Aber et al., 1990). Nutrients other than N may play
a significant role in the forest system response to
dimate change by limiting microbial metabolism
(van Veen et al, 1991).
With warming, mineral weathering and riemmposi-
tion (turnover) will increase nutrient availability. If
the availability of these nutrients is synchronized
fmgt 12 ComUit Emrtommmnl Rcuarck Laboratory
-------
Efftcts of C0} and Climait Changt on Fortst Trttt
with plant growth periods, primary production will
increase. Otherwise excess nutrients could be lost
from the system. Nitrogen could be lost in soil
leacheates as NO,' or as gaseous N20 following
denitrifi cation. Base cations would also be leached
from the system.
Plant response to climate change will be coupled to
soil processes. To understand the response of forest
trees to climate change requires that we know how
the observed plant response is coupled to soil pro-
cesses, and which component of the response is due
to plants and which part is due to soils.
SENSITIVITY OF PACIFIC NORTHWEST
FORESTS TO CURRENT AND FUTURE
CLIMATE
Current Climate
"Climatically the (Pacific Northwest) region exped-
iences wet mild winters and wann dry summers. The
dormant season (for aboveground processes), when
shoot growth is inactive, is characterized by heavy
precipitation with daytime temperatures usually
above freezing. Away from the coast, the growing
season is characterized by warm temperatures, clear
days and little precipitation. Water storage in snow-
pack, soils and vegetation - as well as pulses of fog,
clouds, or cool maritime air which reduce evapo-
transpiration - obviously are more important during
a summer drought" (Waring and Franklin, 1979).
The forests in this region grow under a wide range of
temperature and moisture regimes. Mean annual
temperature is about 5ฐC in western Oregon and
Washington. Seasonal variation in temperature is
greater in the forested regions of Idaho. Annual
precipitation varies from 40-60 cm on the east slope
of the Cascades to about 300 cm in the coast ranges
of Oregon and Washington [Water Information
Center (WIC), 1974; Gholz, 1982; ftanklin et al.,
1991]. In Idaho forests annual precipitation ranges
from about 60-150cm (WIC, 1974). Depending on
die temperature and elevation, winter precipitation
falls as either rain or snow, significant snow pack
occurs at higher elevations. Orographic and
elevational influences on precipitation are stronger
than the latitudinal influence. Rain shadow effects
are particularly evident east of the crest of the
Olympic Mountains and Cascade Mountains (Dolph
etal., 1992).
Adaptation of Forests to Current Climate
Distinctive seasonality of precipitation in the North-
west is a strong determinant of regional vegetation
patterns. Evergreen conifers are well-adapted to this
climatic regime compared with hardwood species.
These adaptations, summarized by Waring and
Franklin (1979), include:
ability to photosynthesize under cool winter
temperatures;
needle-shaped leaves which red uceleaf tem-
perature and respiration during the warm dry
summer,
a large volume of sapwood that stores water
which can be utilized during dry summer
days;
ability to reestablish broken vascular water
columns during evaporative stress (many
hardwood species can not; Sucoff, 1969;
Burke et al., 1976; Sakai, 1983).
Within the region, lower elevational ecotones are
controlled primarily by soQ moisture, whereas upper
elevational zones are controlled either by air tem-
perature, soQ temperature (Teskey, 1982), snowpack
(Scott, 1980) or by competition with higher
elevational species (Daubenmire, 1943; Zobel et al.,
1976; Franklin, 1988).
Sensitivity to Future Climate Change
Climate change of a sufficient magnitude will affect
regional vegetation. A key question is: How much
can climate change before significant vegetation
redistribution takes plaoe? One way to answer this
is to analyze the response of vegetation to past
dimate variation. Forest growth is higher in years
with wanner winters and cooler summers (Peterson
and Heath, 1990). Within the historical record, short-
Pmfi 13 CcncUis EmriromMMaJ Kttmrtk Laboratory
-------
ESJtm o/C02 and Ctimatt Ckangt on Fermi Trtts
teim droughts had little impact on vegetation
(Graumlich, 1981). Since 1675 droughts similar to
those of the 192% and 1930s occurred at least once
every century as determined by tiee ring analysis
(Graumlich, 1987). This variation affected tree
growth but did not change vegetation patterns.
In the longer term, temperatures were about 2*C
warmer during the early Holocene (10,000 - 7,000
years before present) when the vegetation was much
different from today's (Brubaker, 1988). Douglas fix
wasmore prominent than today in western Washing-
ton, and oak savanna extended north of its present
limit in the Willamette Valley to the southern part of
the Puget Trough (Bamosky et al., 1987). TTius, it
appears that a warming of even 2ฐC will likely have
significant impact on regional vegetation patterns.
A complicating factor in assessing forest response to
climate change is the long life spans of trees in the
Northwest (500 to 1000+ years; Brubaker, 1986;
Franklin, 1988; Franklin et al., 1991). Adverse
climate conditions may eliminate seedling establish-
ment and sexual reproduction while mature trees
may survive for several centuries. Under these
conditions, current vegetation is "out of equilib-
rium" with the new climatic regime, since
climatically-favored succession would lead to a
different vegetation type. Adistuibance such as fire
would speed the conversion to the new vegetation
type favored by the new climatic conditions. Other-
wise, vegetation change would be slower and
dependent on senescence of mature trees. Hie
ability of the major Northwest tree species to repro-
duce asexually (e.g., by sprouting from root stocks)
islimitedandthusasexual reproduction is not impor-
tant in influencing the response of PaoficNoithwea
forests to climate change.
Vegetation Modeling - Local Climate-Forest
Zone Correlations
Franklin et al. (1991) coRelated climate and forest
zonation in the central Oregon Cascades to estimate
changes in area! extent of forest communities in
response to either > 25 or 5*C wanning scenario.
Current relationships between temperature and for-
est zones were used to define new elevational bands
the forest zones would occupy. Then the areal extent
of forest zones at new elevations was determined
using an elevation model relating area with a given
elevational band. Mean annual temperatures of
adjacent vegetation zones in the region differ by
about 15 to 2.0ฐC at Mount Rainier, WA (Franklin,
1988) and 2-5ฐC in southwestern Oregon (Atzet and
Wheeler, 1984; Franklin et al., 1991). Uius, a 2ฐC
warming would completely shift a forest type one
zone upward; a 4ฐC warming would shift them two
zones upward (Franklin et al., 1991).
More specifically,on the west slope of the Cascades,
the dry Douglas fir series would increase from 8% of
current forested land to 39% or 27% (Figure 1-3)
using current climatetforest correlations (Franklin et
al., 1991). Moister western hemlock - Douglas fir
forests would decrease in areal extent, as would
subalpine and alpine forests. Reduced area of upper
elevational forests is a function of decreased area
occupying each successive elevational band up a
mountain. Subalpine and alpine vegetation could be
eliminated locally if new elevation limits art above
local mountain crests. For Douglas fir, Leverenz and
Lev (1987) project that either lower range limits will
remain the same (due to compensation of C02effects
on temperature) while the upper limits move up-
ward, or entire ranges move upward because chill ing
requirements are not met.
In terms of modeling assumptions and limitations,
the Franklin et al. (1991) correlational approach has
die same limitati ons as does die Holdridge approach
(below), except that taxonomic resolution is finer.
Also, Franklin et al. (1991) assume that current
forest zones will not significantly change in compo-
sition. However,paleoeoological datadeariy indicale
that this is incorrect Species moved independently
in response to wanning after degladation and at
times framed assemblages without modem ana-
logues (Davis, 1981; Webb, 1986). Each species has
Its own set of climate limits. Thus future vegetation
change will be more complex than suggested beie.
P*g*14 CarvalUtEKrinmMunialRntarckLabcntoij
-------
Effects ofC03 end Ciimait Chang* on Farwf Trta
IU
CURRENT
+2.5 C
+5.0 C
S lซ
OREGON
WHITE OAK
MOUNTAIN
HEMLOCK
~
DOUGLAS
FIR
ALPINE
WESTERN
HEMLOCK
PACIFIC
SILVER FIR
Figure 13, Projected changes in various forest types of the west side of the Cascades, assuming various
temperature changes that may occur with projected climate change.
Vegetation Modeling Holdridge life-Zone
Classification
Hie Holdridge Life-Zone classification system
(Holdridge, 1947; 1967) has been used to simulate
the effect of climate change oa global vegetation
patterns (Emanuel et al1985a,b; Prentice and Fung,
1990; Leemans, 1990; Smith et al., 1991). Summa-
rized are the results of Leemans (1990) and Smith et
al. (1991) for the Pacific Northwest Although they
appUed the dassification system at arelatively coarse
resolution (05 x 0.5 degrees) considering the size of
the region* the Holdridge results are the only pub-
lished data.
Hie Holdridge system relates major vegetation for-
mations with mean annual biotemperature,
precipitation and the ratio of potential evapotranspi-
ration (PET) to mean annual temperature.
. Biotemperature is an index of the growing season.
PET (Holdridge, 1967) is a linear function of
biotemperature and is not an independent variable.
Holdridge created a triangular axis system relating
climate and vegetation. Leemans (1990) and Smith
et al. (1991) applied the Holdridge classification
system to a gridded (05 x 03 degrees), global
database of mean monthly temperature and mean
annual precipitation (Leemans and Cramer, 1990)
for current climate and created future climate sce-
narios .
Simulation of Current Vegetation
The Holdridge classification presentsa much coarser
taxonomic resolution of vegetation in the Northwest
than summarized in Franklin and Dymess (1988).
Nevertheless, the Holdridge system does a good job
of separating current forest from non-forest land;
estimate of forest land in the region (318,000 km3)
reasonably approximates the Forest Service esti-
mate (290,000 km*; USD A, 1990). Main forest
types simulated under current conditions are temper-
ate and boreal forests whereas the Society of American
Foresters (SAF) classification has eight major forest
tat* IS CarmlUt EmvtimmmUil Ktttarek Laboratory
-------
EJJtcts oj COj and CUmait Change on Fortst Trtts -
Overall, 26% (OSU) to 90% (UKMO) of the tri-state
region will change from one Holdridge vegetation
class to another (Table 1-3). Total forested area
decreases under all scenarios from 5% (OSU) to
25% (GFDL). Boreal (subalpine) forests decrease
by at least 50%, while temperate forests generally
contract (except for OSU in which these forests
increase by 20%). Temperate forests remain or
expandathigher elevations in the region. In contrast,
warm temperate forests expand greatly.
In terms of model assumptions and limitations, the
Holdridge system is assumed to adequately define
current vegetation in the region and that current
dimate-vegetation correlations are unchanged in the
future. Although the Holdridge system correctly
dassifies only 40% of the globe's vegetation
(Prentice, 1990), the model does a reasonable job of
separating forest and non-forest vegetation in the
Northwest. The Holdridge system cannot simulate
dynamics of vegetation
change (e.g., tree establish-
ment, migration, or
succession). Climate change
results must be viewed as a
snapshot of future patterns
after vegetation has re-
sponded to a double CO,
dimale. Lagsofunmanaged
vegetation response to cli-
mate change could be
significant over a decadal to
century time scale (Davis
1989). The model simulates
only natural vegetation, land
use is not considered. Hie
influence of soils on vegeta-
tion is not addressed, nor are
direct effects of higher CO,
concentrations on plant
growth. Because of model
limitations, the 2 x C02 sce-
narios presented here should
be interpreted as relative
changes in species composi-
tion rather than as specific
changes in individual spe-
cies.
fag* 16 CenaBis EmrbmmnHil Rntarek laboratory
types (USDA, 1970). All the forests west of the
Cascade crest are considered to be temperate while
subalpine forests are simulated for parts of the Cas-
cade crest and portions of the Northern Rocky
Mountains in Idaho. Hie Holdridge model does not
depict the heterogeneity of forest vegetation in cen-
tral Idaho.
Estimated Vegetation Change
Major shifts in vegetation occur in the Northwest
under four dimate change scenarios (developed
from output of General Circulation Models - GCM),
according to the Holdridge system (Smith et al.,
1991). In this evaluation, 4 GCMs were used:
[Oregon State University (OSU; Schlesinger and
Zhao, 1989), Goddard Institute for Space Studies
(G1SS; Hansen et al.t 1983), Geophysical Fluid
Dynamics Laboratory (GFDL; Manabe and
Wetherald, 1987) and United Kingdom Meteoro-
logical Office (UKMO; Wilson and Mitchell,1987)].
Table 1-3. Projected changes in the area of various life forms, assuming
various climate change scenarios. The Holdridge vegetation mode! was
used to project the changes in life form area. Area (thousands of km') and
percent change (in parentheses) from current conditions are given for each
life zone category.
ArM PrvdtcM toป Cadi
CSnat* 2am
Wi|i>>
Cwrwit
CSmaU
MU
Icwrio
OB8
tcamria
tm
IciMrio
UKMO
Itanmlo
CoUDaMrt
77
m
(10)
8
("681
60
M7)
2
("67)
Hot DซMrt
0
4
23
15
St*p*
218
aas
185
t14)
170
(-21)
111
(49)
Chapparml
4
87
(767)
144
{3182)
148
(M01)
255
(5760)
SotmJ (Watpbw) Fawn
130
aa
ซn
28
M0)
16
Hป)
0
(100)
TmpOTti Pofwti
186
223
OOJ
171
Wi
142
KMl
89
(-60)
wvnn 1 vn^wi rwi
a
16
(B711
96
1*810)
78
0621)
110
(4968)
Ttaptnl tomhMtf fowl
0
0
a
B
80
Tfrofiltil Pond
0
0
0
0
18
Trapfe* Dry Fcrwt
0
0
0
>
4
neWFereetA*
910
am
K)
SB2
*8)
fป)
254
<-ป)
-------
Effects of CO2 ond CUmait Change on Forest Trees
Expert Judgement Effects of Climate Change
on Forest Disturbances
Although not quantitatively modeled for the North-
west, effectsof climate change on forest composition
and structure could be indicated initially through
altered disturbance regimes (Cvvynar, 1987;Neilson
et al., 1989; Graham et al., 1990; Overpeck et al.,
1990; Franklin et al., 1991). Disturbances reduce
resilience of existing forests and are events that
hasten adjustment of forest vegetation to new cli-
mate conditions. Brubaker (1986) notes disturbances
should decrease the time lag in vegetation response
imposed by "long tree life spans by accelerating rates
of population decline when climate change makes
conditions unfavorable for seedling establishment"
For example, postglacial increases in Douglas fir
and declines in western hemlock were caused by a
climatically induced change in fire frequency
(Cwynar, 1987).
Disturbances could create more severe conditions
for forest reestablishment under changing climates
(Franklin et al., 1991). Transitions in vegetation
types could be slowed as forest loss due to fire may
occur faster than forest reestablishment Changes in
soil conditions due to loss of forest cover could slow
forest reestablishment (Perry et al., 1990). Conse-
quently, there could be a shift in area from forest to
non-forest vegetation (Franklin et al., 1991). Fire
frequencies are likely to increase in the region given
increased temperatures, unchanged precipitation and
higher potential evapotranspiration (Clark, 1988).
The key factor in fire frequencies will be die number
of ignition events. How these will change is un-
known, although wannersummer temperatures may
increase convective storms and lightning (Overpeck
etal., 1990).
New or more severe insect problems also are prob-
able. A more favorable environment for insects, or
greater susceptibility of trees may be a consequence
ofdimate-change stress in trees (Mattson and Haack,
1987; Graham etal., 1990). For example, the balsam
woolly aphid (Adelgespiceae), is an introduced pest
that can be a problem in Pacific silver fir and low-
elevation subalpine fir (Mitchell, 1966; Franklin and
Mitchell, 1967; Franklin et al, 1991). Currently, the
aphid is restricted to low and middle elevations by
temperature. During summer the second generation
must read) the first ins tar stage to survive the winter.
Higher subalpine zones of the costal and Cascade
mountains rarely experience sufficient heat for the
second generation to develop sufGdently to over-
winter, hence too few aphids attain the critical stage
(Mitchell, 1966; Franklin et al., 1991). However,
with increases in growing degree/days and mean
temperature increases of 2 to 5ฐC, it would be
possible for the aphid to successfully reproduce and
spread at the higher elevations (Franklin etal., 1991).
Timber harvesting could also speed the response of
forest vegetation to climate change. Shorter rota-
tions, preferential cutting of declining forests and
planting of seedlings better adapted to die new
dimate would speed the response of regional forests
to climate change. Intensively managed forests may
have the potential to be less sensitive to dimate
change than unmanaged forest ecosystems (Davis,
1989). However, current forest management may
complicate the response of forests to dimate change.
Elimination of shrubs from plantations may elimi-
nate mycorrhizae and thus reduce forest growth after
fire (Amaranthus and Perry, 1987; Franklin et al,
1991). Elimination of shrub and hardwood nitrogen
fixers may reduce soO fertility and affect response of
forests to dimate change (Perry and Maghembe,
1989). Also, young forest plantations may be more
susceptible to fire than older forests (Perry, 1988).
Maintaining forest biodiversity with climate change
may be more difficult in a heavily managed land-
scape because of fragmented ecosystems.
SUMMARY
Despite the limitations of the expert judgement and
models, some overall oondusions can be made.
Foremost is that the distribution and composition of
forests in Washington and Oregon could change
substantially. The Holdridge, dimate and forest
correlations, all forecast shifts to forests better
adapted to wanner and drier conditions. Temper-
ate forests in the Holdridge scenarios are generally
restricted to upper elevations and total forest acreage
tag* 17 Ccnattb Emrtxmmental Research laboratory
-------
Effects of CO2 end Climate Charge on Forest Trees
decreases by 5% to 25% depending on the climate
scenario used. In central Oregon, total forested area
is projected to decrease by almost half under a SฐC
wanning. Forest zones could move up one complete
elevation band under the same degree of warming.
Oak woodlands and dry Douglas fir dominated
forests are likely to increase in areal extent, while the
more productive western hemlock/Douglas fir for-
ests will undergo significant contraction. Subalpine
and alpine vegetation are likely to be reduced sub-
stantially.
Pag* 18 Corrollij Emirom mnUoUi tfterck Laboratory
-------
$ff*cu of CO) mtd Climate Ctongtm Fort* JHa
II POLICY ISSUES
The project"Effects of C03 and Climate Change on What are the impacts of elevated C02 and
Forest Trees" was designed to address several criti- climate change on forest ecosystems and
cal issues for policy makers. The principle policy their associatedphysical(energy,water,etc.)
issues that were integrated in the project design are: properties?
1. What are the effects of elevated C02 and
climate changeon thegrowth and productiv-
ity of forest trees?
What are the potential impacts of elevated
will influence vegetation distribution?
CX)2and climate changeonforest trees which
Z Will elevated C02 and climate change alter
the carbon sequestration potential of forest
trees?
What is thesignificanoe of feedbacks (physi
cal and biologies]) from the terrestrial
biosphere to climate change processes?
3. What is the magnitude of elevated COa Existing data are not adequate to provide defensible
and climate change impacts on forest trees scientific answers to the above Policy Issues at
and will the impacts be widely distributed? either, the level of the tree or the forest stand, nor to
assess the impact of elevated 00}and climate change
In addition to directly responding to the above policy to forest trees. Consequently, a research program
issues, the Research Project will provide supporting was developed to contribute relevant information
data to other research programs at ERL-Corvallis toward the Policy Issues,
which are addressing related policy issues:
FmtilS
-------
Effects of CO2 and Climate Change on Forest Trees <
ffl. GENERAL APPROACH
To evaluate the qualitative and quantitative na-
ture of the effects of climate change on forest
trees will require a number of integrated experi-
mental and modeling tasks, rigorous data quality
control, and coordination of research activities
among tasks. The research will proceed along
four separate but interacting avenues (Figure 3-1)
including:
Scoping studies;
Experimental tasks;
Modeling tasks; and
Integration and Inference activities.
Information obtained from each of these areas
will provide valuable insight to the response of
forest trees to elevated C02 and climate change.
The integration of the results from these four
avenues will yield data that can be used to: 1)
make a regional-scale assessment of climate
change impacts on trees, and 2) provide data to
support other on-going climate change/vegeta-
tion studies at ERL-Corvallis.
SCOPING STUDIES
Scoping Studies will provide a critical review of pre-
dicted 002and dimale change and includesregionalized
climate scenarios as forecasted by several general circu-
lation models (GCM's). Ibis section also describes the
species selection process and defines the experimental
design-
General Approach
1
Scoping Studies
COyaimate Scenarios
Species Selection
Experimental Design
ExperimentalTasks
Shoot Carbon & Water Flu*
Shoot Growth & Phenology
System Nutrients
System Water
Litter Layer
Root Growth & Phenology
Soil Biology
Modeling Tasks
Model Selection
Parameterization
Test Understanding
Integration & Inference
Conceptual Summaries of Experimental Results
System Budgets (C, HjO, Nutrients)
Model Application - Assess Effects of OOj and
Climate on Trees
Figure 3-1. General research approach and relationship among the various tasks. The dotted lines
indicate information flow, and the solid lines indicate data flow.
Page 20 Ccrvailis Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
EXPERIMENTAL TASKS
These tasks will be conducted to provide a mecha-
nistic understanding of the effects of climate change
(elevated C02, temperature and drought) on tree
processes (both above- and belowground). Data
from these tasks will provide input to process-based
tree growth models. Additional experimental tasks
will focus on the effects of climate change on soil
biological and chemical processes.
MODELING TASKS
These tasks will provide the basis to:
identify essential areas where research
should be concentrated,
parameterize a tree growth simulation model,
and
test the correctness of our understanding of
the mechanistic processes.
INTEGRATION AND INFERENCE
The results of the experimental and modeling tasks
will provide data to make an assessment of the
impacts of elevated C02 and climate change on tree
growth. Two main activities will be conducted in
this area;
the integration of the experimental results
into a cohesive integration and interpreta-
tion of the effects of elevated C02and climate
change on forest trees and soils, and
the application of a tree growth model, to test
our understanding of the effects of elevated
C02 and climate change on forest trees aid
soils, and to project these effects across time
and space.
Page 21 CorvaUis Environmental Research Laboratory
-------
Effects of CO2 ond Climate Change on Forest Trees
IV. SCOPING STUDIES
CO, AND CLIMATE ANALYSIS
A key element to insure that the experimental
design yields information useful to policy
makers is to insure that experimental condi-
tionsare realistic, e.g.,dotheynowoccurorcan
they be expected to occur within the time
relevant to a policy decision. To meet this
objective, a series of C02 and climate change
analyses were conducted to establish the cur-
rent status and trends of key variables that
control or are associated with vegetation re-
sponse to elevated C02 and climate change.
56 60 63 64 66 66 70 72 74 76 78 60 82 84 86 68
Year
Figure 4-1. Monthly average C02 concentration
observedatMaunaLoa, Hawaii (Keeling et aL, 1989).
C02 Concentrations and
Projected Trends
The mean annual concentra-
tion of C02 is relatively
homogenous throughout the
troposphere because it is well-
mixed on the time scale of
approximately 1 year. In 1990,
the atmospheric concentration
of C02 was about 353 ppm,
25% higher than in pre-indus-
trial times (1750-1800) when
the concentration was approxi-
mately 280 ppm (Houghton et
al., 1990). The current con-
centration is higher than at any
time in the last 160,000 years.
Continuous monitoring of at-
mospheric CO% at a growing
number of locations, has estab-
lished that the atmospheric
concentration is increasing an-
nually (Figure 4-1).
A seasonal cycle is superim-
posed on the increasing
concentration trend (Figure 4-1,
4-2). The annual amplitude of this seasonal cycle
varies with latitude, ranging from about 15 ppm C02
at Point Barrow, Alaska, to approximately 6 ppm at
w tM
Figure 4-2. The association between the annual cycles of C02and
photosynthetically active vegetation. A: The variation in global
atmospheric C02 with time of year and latitude. B: The variation in
weighted normalized differential vegetation index (NDVI) as a func-
tion of season of year and latitude (Tucker et aL, 1986).
Mauna Loa, Hawaii, and 1 to 2 ppm in the Southern
Hemisphere (Tucker et al., 1986). This seasonal
cycle is primarily due to the seasonal exchange of
Page 22 Corvallls Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees <
C02 with terrestrial vegetation. In the Northern
Hemisphere the annual maximum occurs in the late
spring to early summer with the minimum occurring
in the fall.
Due to anthropogenic emissions, the atmospheric
concentration of C02 is increasing at the rate of about
1.8 ppm/year (0.5%/year) (Houghton et al., 1990).
Using a linear rate of C02 increase (1.8 ppm/year)
and several multiplicative rates we have projected
the increase in atmospheric C02 concentrations over
time (Figure 4-3).
At the current linear and multiplicative (05%) rates
of C02 increase, the atmospheric concentration will
double by the year2183 and 2128, respectively. The
"business-as-usual" scenario in the IPCC report
(Houghton etal., 1990) used a growth rate for C02of
2%/year which would double current C02 concen-
tration by the year 2025, while a more moderate
growth rate of 1 %/year would project a doubling by
the year2059. To maintain the atmospheric concen-
tration at the present level, C02 emissions would
need to be reduced immediately by at least 70%
(Houghton et al., 1990). This magnitude of reduc-
tion is unlikely in the short-term, consequently, we
can expect the atmospheric concentration of C02 to
increase. However, the magnitude of the expected
increase is dependent on various policy options.
Role of C02 in Radiative Forcing
Carbon dioxide contributes between 50 and 60% of
the radiative forcing in the atmosphere (Houghton et
al, 1990), the remainder is from other RITGs, such
as, N20, CH4, CFCs. Consequently, the current
radiative forcing of the atmosphere will double well
S
a
o.
c
o
900.0
800.0
700.0
5 600.0
C
u
g 500.0
u
ง 400.0
300.0-
Projected Changes of C02 Concentrations with
Various Scenarios
/
/
1990 2015 2040 2065 2090 2115 2140 2165 2190 2215
Time (Years)
ฆ C02 (1.8 ppm/year)
C02 (0.5%/year)
C02 (1%/year)
C02 (2%/year)
Figure 4-3. Projected changes in atmospheric CO} concentrations, given
several scenarios.
Page 23
CorvaJlis Environmental Research Laboratoi
-------
Effects of COj and Climate Change on Forest Trees
before the ambient C02 doubles (see text box be-
low). Given the current emission rates of greenhouse
gases, vegetation will experience the climatic stresses
associated with double-radiative forcing while the
C02 levels are still relatively low (450 to 500 ppm).
Consequently, realistic simulations of climate change
conditions should use moderate C02 concentrations
(450 to 500 ppm) so that plants are exposed to
reasonable C02 levels when they experience the
thermal stress associated with double-radiative forc-
ing. The use of the lower C02concentrations (450 to
500 ppm) has an additional advantage that these
concentrations will be reached within a reasonably
short time (assuming current emission rates) render-
ing them more relevant to the policy maker than
higher levels.
The following procedure (Table 4-1) was used to
calculate the C02 concentration associated with a
doubling of the current radiative forcing. Once the
C02 concentration associated with "double" radia-
tive forcing was determined, the time to reach double
forcing was calculated assuming various C02 sce-
narios.
Temperature and Precipitation Current and
Projected Trends
The evaluation of current and projected temperature
and precipitation trends considered both expert j udge-
ment and analyses based on the output of General
Circulation Models (GCMs). To assist in the analy-
ses of the potential effects of climate change the
EPA's Office of Policy, Planning and Evaluation
(OPPE) convened a workshop to provide guidance
on the creation and use of climate change scenarios
(ICF, 1989). The Workshop concluded that a num-
ber of approaches should be used to develop climate
change scenarios including: General Circulation
Models (GCMs); paleoclimate data, instrumental
data and arbitrary scenarios. The Workshop recom-
mended that the scenarios:
consider spatial and temporal variability
within a GCM grid cell;
be relatively easy to produce; and
be well-documented.
The Workshop made no recommendations on the
C02 levels to be used in conjunction with the tem-
perature and precipitation scenarios. However, there
was the implicit assumption that a "doubling" of the
current ambient C02 concentration would be used
because that is the level used in generating the
climate change forecasts from the GCM output.
Arbitrary Scenarios: Although not based on ac-
tual data or model results arbitrary scenarios
provide a useful tool for sensitivity analysis, par-
ticularly for defining sensitive boundaries of natural
systems. The OPPE Workshop (ICF,1989) rec-
ommended that one of the following two sets of
climate scenarios be chosen for sensitivity analy-
ses (Table 4-2).
General Circulation Models: The output from a
number (16) of GCMs all show (Figure 4-4) a
significant increase in the equilibrium global av-
erage surface temperature generally ranging from
1.9 to 5.2ฐC for a doubling of the current radiative
forcing, (doubling of radiative forcing simulated
by doubling of the atmospheric C02 concentra-
tion) (Houghton et al., 1990). More typically, the
GCM's project a global average temperature in
Table 4-1. Current radiative forcing from CO2
Current radiative forcing from CO} (Houghten et al., 1990):
AF = 1.46 W/m2
If CO2 contributes 50% of the radiative forcing then double
forcing due to CO2 will be:
AF = 2.92 W/m2
To derive the concentration of CO2 associated with double
forcing (Houghton et al., 1990):
C double s e(AF/6J + In Ci)
CI = 280 ppm in 1750 to 1800
C current (1990) = 353 ppm
The CO2 concentration at double forcing is:
445 ppm
Scenario
CX>2 Doubling
Double Radiative
to 700 (Year)
Forcing (Year)
CO2 (1.8 ppm/yr
2183
2041
CO2 (0.5%/yr)
2128
2037
CO2 (1%/yr)
2059
2013
CO2 (2%/yr)
2025
2002
Page 24 CorvoUis Environmental Research Laboratory
-------
Effects of CO j and Climate Change on Forest Trees
16.0
Y = -3.269 ~ 3.127X
14.0-
12.0-
10.0-
8.0-
ฃ 6.0-
4.0-
2.0-
0.0
5.0
6.0
3.0
4.0
1.0
2.0
Global Mean Warming (C)
Figure 4-4. Predicted global warming from a
"doubling" of atmospheric C03 and associ-
ated percent change in global-annually
averagedprecipitation (Houghton et al, 1990)
Table4'2.SuggestedClimateChangeScenarios
from the USEPA/OPPE Workshop (ICF, 1989)
1
Scenario
Temperature
Precipitation
1
+ 2 C
+ 20%
1
+ 2 C
+ 10%
1
+ 2 C
+ 0%
1
+ 2 C
- 10%
1
+ 2 C
- 20%
1
+ 4C
+ 20%
1
+ 4 C
+ 10%
1
+ 4C
+ 0%
1
+ 4 C
- 10%
1
_+4 C
- 20%
2
+ 4C
+ 20%
2
+ 4 C
+ 0%
2
+ 4 C
- 20%
die range of 35 to 4.5ฐC. Most models forecast
global precipitation to increase, with average in-
crease projected to be 8.4% (ฑ 3.4%).
Development of Climate Scenarios for the Pacific
Northwest from GCM Output: We used the output
from 4 GCMs [Oregon State University (OSU;
Schlesinger and Zhao 1989), Goddard Institute for
Space Studies (GISS; Hansen et al. 1983), Geo-
physical Fluid Dynamics Laboratory (GFDL;
Manabe and Wetherald 1987), and United Kingdom
Meteorological Office (UKMO; Wilson and Mitchell
1987)] to project future climate conditions associ-
ated with a double-radiative forcing in the Pacific
Northwest Because the grid cell sizes of the models
(typically 4 degrees latitude by 5 degrees longitude,
or larger) are large relative to the area of the Pacific
Northwest (Figure 4-5), the models can not be
expected to exactly reproduce the current or pro-
jected climate. They can, however, provide insight
into the potential climate change over broad regions
caused by increases in the atmospheric C02 concen-
tration (Jenne, 1988).
To derive climate change scenarios, assuming a
doubling of radiative forcing, GCM simulations
were performed using both current (lxCOj) and
"double" (2xCOj) atmospheric C02 concentrations.
For each climate variable, the ratio of the 2xC02 and
lxC02 GCM outputs for the grid cells of interest
were determined. Temperatures were first converted
to ฐK before deriving the ratios. Historic climate
data, from sites within each GCM grid cell, were
multiplied by the appropriate ratio (2xCOJlxCO^)
for that grid cell, to estimate future climate condi-
tions (Parry et al., 1987; Smith and Tirpak, 1989).
Potential Temperature and Precipitation Changes in
the Pacific Northwest; The GCMs project a signifi-
cant wanning of the climate in the Pacific Northwest
under double C02 conditions (Table 4-3). As an
example of the magnitude of regional changes in
climate, annual mean temperatures in the Willamette
Valley (HJ. Andrews, OR) are projected to increase
from 23 to S.1ฐC Current seasonal pattern for
temperature is projected to persist under climate
warming, with all months showing an increase in
Page 25 CarvalUs Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
Figure 4-5. Illustration of typical
grid cell sizes used in various general
circulation models. The map illus-
trates the sizes and locations of the
cells used in the OSU-GCM. The as-
sociated table contains the grid cell
sizes for several common GCMs.
GCM
Latitude
Longitude
(d*grซM)
(dig"")
OSU
4.00
8.00
GISS
7.83
10.00
GFDL
4.40
7.50
UKMO
5.00
7.50
temperature (Figure 4-6). There will be fewer months
with mean temperatures below 5ฐC at Rainier/Para-
dise and H J. Andrews Forest. Also, growing degree
days are projected to increase significantly. The
OSU GCM projects a 27 to 72% increase in growing
degree days while the GISS model projects signifi-
cantly more warming (76 to 171%). Percentage
increases in growing degree days are greatest at
higher elevations.
The GCM projections for precipitation under double
002conditions in the Pacific Northwest do not show
die same consistent trend as temperature (Table 4-
4). The OSU GCM predicts that annual precipitation
, will be essentially unchanged, while the GISS GCM
predicts a 22 to 27% increase in annual precipitation.
Despite the differences in projected annual precipi-
tation, both GCMs project that the current seasonal
pattern of relatively dry summers and wet winters
will persist (Figure 4-7). However, the proportion of
rain and snow may change from current conditions
because of the increase in temperatures.
In terms of the impact on vegetation, changes in soil
moisture are of greater interest than changes in
precipitation alone. Changes in soil moisture de-
pend in a large part on potential evapotranspiration
(PET), estimates of which are listed in Table 4-4.
The OSU GCM projects a 7 to 16% increase in PET
while the GISS model projects a greater increase in
PET(15 to 36%). However,for eitherprojection, the
increase in PET is greater than the increase in annual
precipitation. A regional water balance model for the
Columbia River Basin (Dolph et al.,
1992)was developed to integrate changes
in temperature, precipitation and PET.
Application of their model, for the Co-
lumbia River Basin with various climate
change scenarios, suggests that soil mois-
ture (on an annual basis) could decrease
by more than 50%.
The future climates projected from the
GCMs represent a significant change
from present conditions. When viewed
in a south to north transect, the projected
temperature changes are equivalent to
shifting current climates from 200 to 500 km north,
i.e., moving the climate of northern California into
northern Oregon (Franklin et al., 1991). However,
strict geographic analogues of future climate are
difficult to define since projected precipitation may
remain unchanged. Thus it is more precise to say that
the temperature regime of northern California will
be imposed on the precipitation regime of northern
Oregon. Similarly, from an elevational perspective,
the climate projections suggest a 500 to 1000 m
upward movement of temperature regimes (Franklin
et al., 1991).
Page 26 Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
Table 4-3. Comparison ofthe impact of climate change on mean annual temperature and mean annual growing degree-
days for the Pacific Northwest The temperature data are from historical records (NOAA J989a,b) or from 2 x C02
climate scenarios generated by the OSU and G1SS GCMs. The 2 x C0} temperature scenarios were generated by
multiplying the historical monthly mean temperature by the ratio of the GCM-simulated 2 x CO} monthly mean
temperature to the GCM-simulated 1 x C02 monthly mean temperature. Mean annual growing degree days were
calculatedfrom the WEA THR routine in the ZEL1G simulation model (Urban 1990). The length ofthe historical record
from which the mean temperatures were calculated is given in parentheses.
LocsSm
Curent <
Twp.fC)
OSU
2XC02
Tarnxft}
CSS
2xC02
TerBP.ro
Girrt
Degrae-Days
OSU
2xC02
OwtfrOayi
OSS
2x002
DsptfrDays
Forte, WA
9.7 (68)
11.8
13.6
1636
2317
2926
Rainier, WA
11 (ซ)
5.4
8
502
865
1360
Longview.WA
10J (65)
13
15.9
2013
2741
3790
Astoria, OR
10.4 (36)
115
15.4
1793
2548
3606
HJ, Andrews, OR
9.8 (13)
12.1
14.9
1779
2501
3413
Crater Lake, OR
12 (57)
5J
&1
604
963
1454
Gold Beach, OR
11.6 (60)
13.6
16.7
2234
2922
4076
Ashland. OR
11.1 (104)
13.1
16*
2208
2809
0000
Table 4-4. Comparison of the impacts of climate change on annual precipitation and annual potential evapotrans-
piration (PET). The current precipitation data are from historical records (NOAA 1989a,b) from the OSU and GJSS
GCMs, while current PET was calculated from the WEATHR routine in the ZELIG simulation model (Urban 1990,
Urbanetal 1990) using the Thornthwaite method The ratios for precipitation and PET are (2x COfiCMprediction)!
(1 x C0} GCM prediction). See text for discussion ofhow 2 xCO}precipitation scenarios were created The length
of the historical record in years from which the mean annual precipitation was calculated is given in parentheses.
location
CwrertPree.
fern)
OSUPrec.
Mi
GSSPre.
'< v Ratio
CwtwIPET
(era)
OSU PET ,
m
OBSSPET
...';Raflo
Forks, WA
902 (79)
1.01
1.27
62J0
w
1.15
Rainier,WA
289 (53)
m
12
4150
1.16
1.34
Longview,WA
117 (65)
1.01
12
66.00
1J9
1J4
Astoria, OR
177 (36)
1.00
1.23
63J0
1j08
12
HI Andrews, OR
142 (13)
MB
12
6180
1.10
12
Crate Lake, OR
170 (61)
1.00
1J4
4140
1.16
1.36
Gold Beach, OR
210(69)
W
12
6540
1i)7
12
Ashland, OR
48(111)
1.01
12
67.00
1.09
12
Page 27
Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forea Trees
Rainier/Paradise, WA
"30.0
|25.0
| 20.0
1 15.0
H
flO.O
S.0
o 9-ฐ
Jซ.
J Current
~ OSU
~ GISS
r
i
i
c
1 1
I
i
j
1 jpw- FW
| r P F
2345(789 10 11 12
H J. Andrews Forest, OR
H 15.0
= 10.0
i 0.0
^30.0
I 25.0
120.0
115.0
1 2 3 4 5 6 7 S 9 10 U 12
Gold Beach, OR
110.0 4-:
S 5.0
J 0.0
:U0
ji
1
1 23436719 10 11 12
Moolb
Figure 4-6. Long-term mean and pre-
dictedfuture mean monthly temperatures
for three sites in the Pacific Northwest
(NOAA, 1989a, b). Scenarios of the
future temperature regimes were gener-
ated usingoutput from the OSUandGISS
climate simulations of double C02 cli-
mate conditions.
S <0.0
jso.0
f.40.0
ฃ 30.0
1*20.0
2 10.0
I ซ
Rainier/Paradise, WA
~ GISS
1 2345(789 10 11 12
HJ. Andrews Forest, OR
1 2 3 4 5 ( 7 8 9 10 11 12
Gold Beach, OR
1
12345(789 10 11 12
Month
Figure 4-7. Long-term mean and future
mean monthly precipitation for three sites
in the Pacific Northwest (NOAA, 1989a,
b). Scenarios of future precipitation re-
gimes were generated using output from
the OSU and GISS climate simulations of
double CO j climate conditions.
Pag* 28 CorvaiUs Environmental Research Laboratory
-------
Effects of CO3 and Climate Change on Forest Trees
EXPERIMENTAL DESIGN
The selection of the experimental design was gov-
erned by the need to meet both the scientific and
policy needs. Although there are a number of
possible experiments that could be run, we decided
that the following experiment meets both types of
needs and will yield timely data that supports EPA
policy actions.
Experimental Facilities
Innovative research facilities are required to assess
C02 and climate change effects on vegetation (Drake
et al., 1985: Allen, 1990). The three major types of
outdoor facilities used for elevated CX>2 exposure
studies include: outdoor open-top chambers (Rogers
et al., 1983b); free-air C02 enrichment systems
(Allen et al., 1985; US DOE, 1987; Hendrey et al.,
1988); and closed-circulation, sunlit,computer-man-
aged, controlled environment plant growth chambers
(Soil-Plant-Atmosphere Research (SPAR) unit). The
SPAR units are unique to the field of plant exposure
facilities because they have not only the capability to
precisely control gas concentrations, but also dry
bulb temperature, dew point temperature, and root-
ing zone conditions (Jones et al., 1984a, b, 1985;
Baker et al., 1990). This gives SPAR units an
advantage for measuring the interacting effects of
rising C02 and climatic change factors on vegetation
photosynthesis, transpiration, other gaseous ex-
changes, growth, and yield. Furthermore, because
these chambers use solar irradiance rather than arti-
ficial light they provide a more natural radiance
regime than that used by indoor growth chambers.
The Global Change Research Program at ERL-
Corvallis constructed the Terrestrial Ecophysiological
Research Area (TERA) to provide a state-of-the-
science research capability to investigate the effects
of elevated C02 and climate change on plants. This
facility is unique compared to others because it is
designed to accurately measure and track ambient
C02, temperature and dew point while operating
continuously for several years.
The layout of the TERA facility is given in Figure 4-
8 (oompass orientation of facility is indicated on
figure). The central component of this facility is 12
SPAR units, called terracosms, that are capable of
providing complete climate control of an enclosed
plant/soil system. Each row of 7 terracosms is
separated by 4.9 m, and each chamber in a row is
separated by 3.4 m. Chambers 1 and 8 (chamberless
controls) differ from the 12 terracosms in that the soil
units were constructed, instrumented, filled, and will
be planted as the terracosms, but they will not have
an enclosure over the trees. A comparison of these
controls with ambient environment chambers will
provide a measure of the terracosra effects on seed-
ling growth.
The intended C02 and climate treatment scheduled
for each terracosm is also given in Figure 4-8.
Ambient conditions are indicated by the capital letter
A and elevated conditions are indicated by the arrow
pointing upwards. For instance, the treatment as-
signed to chamber 5 (COjA, T t) is ambient C02
and elevated temperature (+4ฐC). The four treat-
ments have been randomized in each of three blocks
of chambers: block 1 - chambers 6,7,13,14; block
2 - chambers 4,5,11,12; and block 3 - chambers 2,
3,9,10.
Adiagrammatic illustration of an individual terracosm
is shown in Figure 4-9. Hie aboveground canopy is
an aluminum frame which is covered by a 3 mil clear
Teflon film. Teflon was selected as opposed to
Mylar because of its optical clarity, resistance to
photodegradation, broad spectral transmission which
extends into both the IR and UV bands, and its
chemical inertness. Hie chamber is 13 m tall at the
back, and slopes to 1.2 m tall at the front It is 2 m
wide and 1 m front-to-back, as seen from a front
view, the south exposure. The total canopy volume
is 3.18 m3.
Each chamber canopy is mounted on a soil lysimeter
that is 2 m wide, 1 m front-to-back, and 1 m deep,
giving a total volume of 2m3. The lysimeters are
water tight, and constructed of 60 mm thick alumi-
num plate. They were sandblasted and painted on the
inside with a white, nontoxic epoxy paint, and al-
lowed to cure outdoors for 6 months. Finally, they
were covered with a dear, 25 mil thick oriented-
Page 29 Corvallis Environmental Research Laboratory
-------
TERA
Terrestrial Ecophysiological Research Area
m ijwji imtmii.'i.i i.ijj mi,
VA?V
ZI 0O0o
, A'A'A'.'
30 x 78
'olvhouse
WfiB
77^
AV'M^VAV'/^V'A'AW
f / V V V *P V V '** V j-*
Terracosm Field Chambers
ft
COjA^Tf C02f, Tf
dT*#\ A 1*4
COjA, if
co2t,Tf co2i,ta co2a,ta
.'A*>V<*
V,V,V
C02f,TA C02A, TA CC^f.Tf C02A,TA C02A, Tf C02t,TA
Chamberfess
Control
Chamberless
Control
-50 m (164*)-
Figure 4-8, Layout of the Terrestrial Ecophysiological Research Area (TERA), drawn to scale. Experimental treatment, chamber number; and
soil instrumentation quadrant are indicated for the individual terracosms.
-------
Effects ofC02 and Climate Change on Forest Trees
Side View of Terracosm
Daw Point Hygrometer
Hot and Cold Water
Beat Eicbangen
Host/Chamber COj
ling Porta
Data AcquUltioa/
System Control
li McUrt
TDR Profe*
Mftttipltxcr
Litter ujtf
A Hortrwi
I
B Hortmi
'I "[I p
C Horizon
Root Obttroiioa
Tsbeป
Figure 4*9. Side view of terracosm chamber showing
details of soil horizons, minirhizotron root observation
tubes, data acquisition packages, dew point hygrometer,
and CO} sampling port.
strand adhesive-backed Teflon film (Du Pont Elec-
tronics, Wilmington, DE) before they were filled
with soil. The terracosm soils have been instru-
mented to collect a variety of data in situ. A detailed
description of sensor type and location is presented
in Appendix A.
The C02 concentration and climate within each
terracosm are controlled independently using a pro-
grammable logic controller (PLC). Hie PLC serves
as an intelligent interface to an array of sensors,
valves, and flow controllers. Ambient weather
conditions and C02 levels are monitored continu-
ously at the site weather station and are transmitted
to the terracosms over a communications network.
The terracosm PLCs use the site ambient conditions
and internal computer logic to determine and control
their individual target C02, temperature,
and dew point treatments. With this design,
dew point and dry bulb temperatures can be
tracked to ฑOJฐC, and C02 concentration
tracked to ฑ10 pprn. A486/DX2 PC serves
as the network interface, and receives data
transfer messages from each terraoosm PLC
at 1 minute intervals. These data, which
include temperature, dew point, light level,
C02 concentration, soil moisture, etc., are
used toprovidechamberstatus displays and
simultaneously relayed to a Sparc IPX work-
station over a TCP/IP ethernet where they
are logged into the network data base. A
more detailed description of the process
control/data acquisition system is presented
in Appendix A
In addition to the chamber field, the terra-
oosm facility has a 9 m x 24 m polyhouse
(lexan and plastic covering over temporary
metal frame), a physical plant, a shop, and
a storage building (Figure 4-8). The
polyhouse contains the network interface
computers and Sparc workstation, analyti-
cal instrumentation, several indoor plant
growth chambers, benches for plant rear-
ing, the gas exchange/image analysis
laboratory, a water purification system, and
a compressed air drier.
This facility was specifically designed to conduct
long-term growth studies on forest trees, evaluating
the effects of temperature, C02> and drought stress
on ecophysiological processes. All facilities, includ-
ing the physical plant and electrical service, were
designed to allow for die eventual expansion to 24
terracosms and 4 controls. Because of the long
duration of the planned experiments, special atten-
tion was paid to certain areas of the facility design to
provide fail-safe operation. The facility physical
plant which supplies hot and cold water to each
chamber for climate regulation was designed with
integrated backup systems to minimize any down
time caused by equipment failure. These backup
systems include a dual compressor 50-ton water
chiller that will continue to operate in spite of com-
Pagt 31 CarvoUis Environmental Mesearch Laboratory
-------
Effects of COj and Climate Change on Forest Trees
plete failure of one of the compressors, a backup
275,000 BTU boiler that is automatically activated if
there is a failure of the first system, insulated 1600
gallon chilled water storage tank and 800 gallon hot
water storage tank to buffer supply system demands,
redundant 3 HP water pumps built into the hot and
cold water delivery system, and a 100KW emer-
gency power generator that will supply site power if
there is any interruption in city power.
Selection of Plant Material
The forests of the northwestern United States are
dominated by evergreen conifers that are long-lived,
grow to sizes unmatched in other parts of the world
and accumulate biomass in greater amounts than any
other vegetation type (Waring and Franklin, 1979;
Franklin, 1988; Harmon et al., 1990). In sum, these
forests are unique among northern temperate forest
types. Besides their intrinsic value as unique eco-
logical systems, Northwest forests also serve as an
important source of timber and are a focus of the
regional tourism industry.
About 75% of the forest land in the Northwest is
managed for timber production (USD A, 1990). The
value of timber harvested in Oregon and Washing-
ton and hauled to local delivery points in 1986 was
3.9 billion dollars, about 30% of the national total
(USDA, 1990). No other subregion (as defined by
the Forest Service) of the U.S. had a higher monetary
value. In the region, about 63% of the timberland is
publicly owned, while the forest industry owns
about half of the privately-held forest lands.
The selection of a tree species to serve as the experi-
mental material was driven by both policy and
scientific perspectives as well as by practical rea-
sons.
Policy Perspectives
In its current research and policy activities,
EPA is placing a greater emphasis on forest
issues rather than agricultural ones, with
respect to climate change issues.
Within the Agency's Global Change Re-
search Program, ERL-Corvallis has the lead
for forestry research.
Scientific Perspectives
There has been substantially more research
on the effects of elevated C02 on agricultural
crops and herbaceous annuals than on woody
perennials.
Most vegetation models used to evaluate the
impact of climate change impacts and veg-
etation distribution have ignored the direct
effects of C02 because of limited data on
woody perennial vegetation.
Limited studies have suggested that trees
respond to elevated C02 via increased C02
uptake, growth and water-use-efficiency.
However, there is no scientific consensus if
these responses will occur under natural
forest conditions. Resolution of this uncer-
tainty is essential to predict the response of
forest vegetation to elevated C02 and cli-
mate change.
No group is studying the effects of climate
change on Pacific Northwestern tree spe-
cies, even though the region is the major
timber producing area of the U.S. Currently
other groups are funding research on the
effects of elevated C02 on Loblolly pine
(southeastern species), tulip poplar and white
oak (eastern hardwood species) and ponde-
rosa pine (southwestern species).
The species selected should have broad eco-
logical and economic importance. This also
implies that it would be widely distributed.
Practical Reasons
To insure that the experimental data are
realistic, the seed sources for the species
selected should be adapted to the location in
which the experiment will be conducted.
Based on the above Policy, Science and Practical
criteria, Douglas fir (Pseudotsuga menziesii(Miib.)
Franco var. menziesu) was selected for use in the
experiment It forms long-lived conifer forests that
dominate the mountainous landscapes of western
Oregon and Washington. It is currently the most
important timber species in the Pacific Northwest
and is widely distributed (Little, 1971) through the
Pacific Northwest and into the Rocky Mountains
Page 32 CorvatUs Environmental Research Laboratory
-------
Effects of COt and Climate Change on Forts! Trtts
(Figure 4-10). Its latitudinal range is the greatest of
any commercial conifer in western North America
and it grows under a wide range of climatic condi-
tions (Hermann and Lavender, 1990). The species
exhibits a great deal of genetic differentiation, much
of which is associated with geographic or topo-
graphic features (Hermann and Lavender, 1990).
In the Pacific Northwest most Douglas fir stands
originated following natural catastrophes (i.e., wild
fires). It is a pioneer species that frequently follows
wild fires; it may be replaced, however, by more
shade-tolerant species such as western hemlock.
However, true climax forests may not be attained
because Douglas fir can persist in stands for over a
thousand years, which is longer than the frequency
of wildfire occurrence (Spies and Franklin, 1991).
Seedlings were grown from "woods run" seed lots
rather than half-sib or full-sib seed lots. As the
genetic variability of Douglas fir is high, we decided
that selecting seeds with a narrow genetic composi-
tion would increase the chances of collectingseedling
response data not representative of the larger popu-
lation. Seeds from five low elevation seed zones
(less than 500 m) surrounding Corvallis were se-
lected in conjunction with Weyerhaeuser Company
Northwest Research Division scientists (Figure 4-
11).
Seedlings (l+l)wereprovidedby the Weyerhaeuser
Company, i.e., grown forone year in a seed bed, then
one year in a nursery bed, and then transplanted into
terracosms as bare-root, 2-year-old stock. Two-
year-old bare-root nursery seedlings were selected
rather than germinants grown by us in containers
Seed Zone Percent
252 19
262 10
461 17
472 41
491 13
*Source of Seeds used in Study
*Percent of seed in seed lot used for planting
BENTOI
IANEFJ
OCSCMI
Figure 4-11. The map illustrates the geographic
location from which the seeds for the study were
collected.
r
*
Figure 4-10. The current regional distribu-
tion of Douglas fir (Little, 1971).
Page 33 Corvallis Environmental Research Laboratory
-------
Effects of CO j and Climate Changซ on Fomt Trtts .
under elevated C02, to optimize conflicting experi-
mental oiteria.Thebare-rootnuisery seedlingswere
selected because the initial target LAI could be
readied with significantly fewer plants than if con-
tainer stocks were used, the nursery plants have
field-grown root architectures, and roots that are
field-inoculated with mycorrhizal fungi. Container-
grown seedlings would not have root architectures
resembling nursery-grown plants.
Duration of Experiment
The physiological responses of the Douglas fir/soil
system to be measured are linked primarily or sec-
ondarily to the flow of C through space and time.
Thus, it is necessary to run our experiment for more
than one growing season because the current C status
of coniferous trees is a function
of both current and previous C
physiology, e.g., breaking dor-
mancy and initial growth of
shoots is affected by previous
season's growing condi dons and
C storage and current growth
conditions. In our experiment, it
may be the second growing sea-
son when measured seedling and
soil system responses greatly
reflect treatment effects. We
intend to conduct this first ex-
periment for at least two,
possibly three years (if the plants
still fit in the terracosms and
policy direction permits).
Planting Desip
Fourteenseedlingspertenaoosm
will be placed in two outer rows
of five plants and one inner row
offourplants (Figure 4-12)with
watering soaker hoses inter-
spersed among seedlings. This
planting array will result in two
plants within the center and 12
plants along the edges of each
chamber. Hie potential exists
for differences in responses be-
tween the two groups of plants
as the center plants fully compete for light and soil on
all sides, while the edge plants compete only on two
orthree sides with their othersidesdirectly fating the
terracosm mils. To reduce die difference in light
intensity between the two groups of plants, shade
cloth will be attached to the outside of die chambers.
The cloth will be along the east, south, and west sides
of the terraoosms to reduce lateral light penetration
to edge plants similar to that of the center plants. The
height and layers of shade cloth will be determined
based on measurements of light intensity for the
seedlings growing in the control plots without cham-
bers and will increase in height over the course of the
study as the trees increase in size.
Stolen
30 cm
10 cm
Utter Layer
A-Horizon
Horizon
C-Horizon
Drainage
Gravel
Mlnlrblzotron Tuba
#
#
*
#
~
#
#
#
1 Meter
#
#
#
#
2Meten
Figure 4-12. Planting design showing rear and top view
of terracosm. Also shown is the placement of the
minirhizotron tubes.
Pag* 34 CorvalliM Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
Experimental Treatments
The experimental treatments were selected to reflect
"current" and "future" conditions (Figure 4-13) and
are all defined in relation to "current" conditions at
the experimental site, i.e., the conditions in the
ambient temperature and ambient C02 terracosms.
The specific treatment levels and the rationale for the
selection are:
Carbon Dioxide: Two levels were selected, ambient
("current") and ambient plus 200 ppm ("future").
This will be a constant addition to the current ambi-
ent concentration. Consequently, the C02 exposure
will display the same diurnal, seasonal and yearly
variability as the current levels. The level was
selected for four reasons:
The C02 ievel associated with a doubling of
radiative forcing is in the range of450 to 500
ppm. The plants will experience the tem-
perature effects of a "double C02
environment" but the actual C02 will be
much lower. This difference needs to be
considered in the experimental design.
Projected time for the C02 level to increase
by 200 ppm will occur much sooner than
will a doubling of concentration. Conse-
quently, it is near enough to be of policy
interest
The difference between treatment levels is
sufficiently large suggesting a high prob-
ability that treatment differences will be
detected.
The difference between treatment levels is
sufficiently large suggesting that the C02
control system will be able to reliably pro-
vide two different treatment levels.
Preliminary monitoring at the TERA site during
the summer of 1991, indicated that daily mean
C02 concentration was 361 ฑ 7.75 ppm. The
typical diel variation was 50 to 60 ppm.
Temperature: Two levels were selected, ambient
and ambient plus 4ฐC. This will be a constant
addition to the current ambient temperature. Conse-
quently, the elevated temperature will display the
same diurnal, seasonal and yearly variability as the
current temperature (Figure 4-14). The level was
selected for three reasons:
r- \
g 20-
10-
1 2 3 4 S 6 7 8 9101112
Months
Mem Temp C Mean Temp *4 C
Figure 4-14. Comparison of monthly mean tem-
peratures for the two experimental regimes. The
data are derived from 1989 climate data from
CorvaUis, OR,
Experimental Treatments
f
Ambient Temperature
Ambient Temperature + 4 C
Ambient C02
Ambient COj
Ambient Tern pen tore
Ambient Temperature + 4 C
Ambient COj ~ 200 ppm
Ambient CO) * 200 ppm
*
Figure 4~13. The experimental design is a complete
randomized block, with three replications of each treat-
ment
Page 35 CorvaUis Environmental Research Laboratory
-------
of COt and Climatซ Chang* on Fort# Tr**a
Four degrees is within die range of probable
temperature change forecast to occur from
climate change models for the Pacific North-
west
The difference between treatment levels is
sufficiently large suggesting a high prob-
ability that treatment differences will be
detected.
The difference between treatment levels is
sufficiently large suggesting that the tem-
perature control system will be able toreliably
provide two different treatment levels.
Although various GCM scenarios suggest that the
warming may vary seasonally, we decided to apply
the warming uniformly (+ 4ฐQ throughout the year.
An analysis of the seasonal warmingpattems showed
that they did not agree on the period of maximum
warming. Because a consistent trend among models
was not displayed, we chose the uniform approach as
the most reasonable at this time.
While some evidence suggests that warming will not
occur uniformly over the 24-hr period (Figure 4-15),
we chose to apply the warming uniformly. TWs does
not mean that we do not accept the observation, but
rather is a reflection that this is an area of uncertainty
that we do not feel able to resolve at this time. Also,
the temperature control of the terracosms (ฑ OS ฐC)
is not sufficiently sensitive to reliably create long
term differences of 0.1 to 03ฐC among treatments.
Dew Point: Holding atmospheric humidity constant
while elevating temperatures is unrealistic in any
environment, as indicated by nearly all GCM's. The
natural tendency of the atmosphere is to attempt to
satisfy its increased water holding capacity through
increased evaporative demand.
Thus, in addition to selecting the elevated tempera-
ture level, it is important to determine the appropriate
level of moisture in the atmosphere. Evaporation
from the soil and transpiration from the plant are
controlled by the moisture gradient between the soil/
plant and the atmosphere, i.e., the lower the atmo-
spheric moisture content, the greater the potential
moisture loss from soils and vegetation. An analysis
of output from GCMS (GFDL and GISS) for the
Pacific Northwest suggests an annual average mois-
ture content of the atmosphere will increase by 25%.
U.S. Annual Mean Minimum
21 U.S. Annual Mean Maximum
1990 1950
1990
1950
1970
Figure 4-15. Trend of warmer night (minimum) temperatures and relatively constant day (maximum)
temperatures for the United States (Kerr, 1992). In climate model simulations, global warming is reflected
nearly equally in day and nighttime temperatures. However, in a recent analysis of40 years of climate records,
scientists at the National Climatic Data Center found that much of the measured warming has come during
the night (measured as minimum temperature). The scientists studied the climate records of die United States,
the former Soviet Union, and the People's Republic of China andfound a similar trend m the three data sets
(Karl et al, 1991). The cause of the great night warming is not yet resolved.
Pag* 36 Corvaliis Environmental Research Laboratory
-------
Effects of CO j and CUmatt Cluing* on Forest Trees
Experimentally, the ambient temperature and dew
point will be measured at the site's meteorological
tower, adjacent to the terracosms. The dew point
depression will be calculated. Hie dew point will be
controlled in each terracosm to display the same dew
point depression as measured at the ambient sam-
pling site. In the+4ฐC treatment, the same dewpoint
depression will be applied. This method of increas-
ing the atmospheric moisture was chosen as we are
routinely measuring dew point not relative humid-
ity. However, analyses established that the constant
dew point depression has approximately the same
effect on potential evapotranspiration (PET) as in-
creasing the humidity a uniform 25%.
Potential Evapotranspiration(PEH: Toevaluate the
effects of the ambient and ambient plus 4ฐC treat-
ments on PET, a turbulent transfer model (Brutsaert,
1982; Marks, 1988, 1991; Gucinski, et al, 1990;
Dolph, et al, 1992) was used to calculate PET from
daily weather data for Corvallis, OR (for 1989).
Average daily data of surface and air temperature,
humidity, and wind were used, along with estimated
surface roughness (0.0075 m during winter and fall,
and 0.01 m during spring and summer) to drive the
model. Saturation vapor pressure at the surface
temperature was used as the surface vapor pressure,
to calculate potential evaporation. To approximate
possible 2 x C02 conditions, 4ฐC was added to both
air and surface temperature, and the surface vapor
pressure adjusted. Because the air and surface
temperature are physically coupled, due to turbulent
exchange between them (in 1989 air temperature
was on average -0.7ฐC cooler than surface tempera-
ture) it is realistic to assume that an increase in air
temperature would be coupled to a similar increase
in surface temperature.
To illustrate the reliability of the turbulent transfer
model, PET was derived for current conditions and
compared to pan evaporation (note: pan evaporation
was measured only during April-October). During
this period pan evaporation was 977 mm and calcu-
lated PET was 973 mm. As expected, the pan
method overestimated evaporation during cooling
periods, and underestimated it during wanning trends.
PETwas calculated to be 1140 mm for the entire year
using current (1989) environmental conditions. To
forecast PET under a 2 x C02 scenario, atmospheric
vapor pressures were increased by 25% to corre-
spond to the increase in humidity predicted by the
GCM for 2 x C02 conditions for the Willamette
Valley region. With these assumptions annual PET
for the 2 x C02 conditions are predicted to be 1585
mm, about 1.4 times the level calculated for current
(1989) conditions.
Water In the Pacific Northwest there is a strong
mediterranean rainfall pattern that affects vegetation
distribution and will likely influence the response of
forest trees and soils to elevated C02 and climate
change (Figure 4-7). We intend to mimic, in a
general way, this rainfall pattern and consequent
seasonal soil moisture levels. Griffiths et al. (1990,
1991) collected monthly and seasonal soil water
content data in the central Oregon Cascade and
Coast Range Mountains. They found the lowest soil
moisture contents (approximately 20% at 10 cm
depth in a forest soil 30 km southwest of Corvallis)
in September and October. We used this general
pattern and long-term data (30 years) of monthly
precipitation and PET for the Corvallis area to
develop the seasonal pattern of our watering sched-
ule.
In general, during the period when mean monthly
precipitation exceeds mean monthly PET (Figure 4-
16), terracosm soils will be watered to field capacity.
We will impose a drying schedule when PET first
exceeds precipitation (April), and a soil water re-
charge schedule when monthly precipitation equals
or exceeds PET (October). During the dry-down
phase the rate of soil drying increases through time,
and during the recharge phase the rate of wetting also
increases through time (Figure 4-17). The duration
of the dry-down period is twice as long as the
recharge period; dry-down occurs in five 30-day
increments and recharge spans five 15-day incre-
ments. The driest soil condition will be 18%, which
is equivalent to approximately -0.1 MPa (Figure 4-
18). We will key our water additions to the mean soil
water content of the ambient C02 and ambient
temperature chambers. The amount of water added
to these chambers to bring the soil water content to
Page 37 Corvallis Environmental Research Laboratory
-------
Effects o/COt and Climate Change on Forest Trees
Comparison of Moathfr Precipitation and PET
I Precipitation
20.00
10 It 11
Momto
Figure 4-16, Monthly precipi-
tation andpotentialevaporation
for Corvallis, OR. Values are
the mean of 30 years of data.
) II I I 1 I I 1 1 I I II I I I I I I I I I
2 4 6 8 10 12 14 16 18 20 22 24
Bi-Weekly Interval
Figure 4-1 7. The annual watering schedule
will have two distinct periods; soil moisture
content at field capacity and below field ca-
pacity. Sail dry-down and recharge proceed
at increasing rates through time. Driest soil
conditions in the soil lysimeters (18% volu-
metric water content) will be similar to, and
occur at approximately the same time as in
soils of Oregon forests.
1
a
J
9
ฃ
s
e
o
>
A Horizon
B Horizon
C Horizon
Figure 4-18, Volumetric soil moisture versus
tension curves for the three horizons of the terra-
cosmsoiL Data were collected from reconstructed
soil horizons.
Tension (-MPa)
Page 38 Corvallis Environmental Research Laboratory
-------
Effects of COt and Climate Change on Forest Trees
the comet value will also be added to the other
chambers.
In the first year of the study we intend to follow the
watering schedule presented above unless seedlings
exhibit severe water stress. In this case we will
depart from the watering regimen and apply water as
needed to enhance seedling survival and establish
the soil microbial community. Then, starting with
the second growing season, the watering schedule
described above will be imposed regardless of seed-
ling response.
The watering schedule was selected for two reasons:
1. From GCM outputs, precipitation is forecast
to remain unchanged (same as current) or
increase up to approximately 20%. Selec-
tion of the driest condition in the annual
watering schedule will simulate projections
from the GCM's. We have decided to
simulate the condition of no change in pre-
cipitation.
2 A fundamental hypothesisof climate change
is that plants will display increased WUE
compensating for climate change. Acounter
hypothesis is that as a result of increased
WUE, plants will develop more leaf area
making them more susceptible to drought
With the watering regime we have selected
we will obtain data to test these hypotheses.
Hie soil volume containing roots will be the basis
upon which we determine the soil volumetric mois-
ture content. The volume of soil reflects root
occupancy and therefore, will change over time. For
example, the soil volume containing roots in the first
year (likely the A-horizons and portions of the B-
horizons) will be less than the soil volume used for
calculations in subsequent years. Hie soil volume
containing roots will be determined from root obser-
vations made using the video camera and
minirhizotrons (Task 7). Soil water content will be
expressed on a volumetric basis using the TDR
probes (Task 4) in the horizons of the soil volume
containing roots.
The amount of water added to all terracosms will be
identical, and it will be calculated using the amount
of water collected from the ambient climate treat-
ment due to evaporation and transpiration, leaf water
potential and volumetric soil water content (Task 4).
Exact wateradditions during dry-down and recharge
cannot be predicted a priori. Therefore, watering
will be a highly iterative process.
Nutrients: ManagementplansformostPacificNorth-
west forestsdo not include fertilizer additions. There
is no reason to believe that short-term soil nutrient
capital levels will change significantly under climate
change scenarios. Consequently, plant adaptations
to altered climate will occur with approximately the
existing capital of nutrients. We understand that
some lines of reasoning indicate that C flow
belowground will alter nutrient availability. How-
ever, it is uncertain whether altered nutrient
availability ultimately will lead to enhanced or de-
creased forest productivity. Therefore, we will add
nutrients to the terracosms only if analyses of soil or
plant tissue in the control indicate that they are
required.
Soil Selection
Soils are an important component of forest ecosys-
tems supplying water and nutrients for plant growth
and maintenance. Forest systems generally rely
upon an almost closed nutrient cycle (i.e., uptake ->
litter fall -> decomposition -> uptake). Because of
the dependence of forests on soils, climate change
driven alterations of soil processes or the amount of
water held in soils may affect the extent and magni-
tude of the overall forest system response to climate
change.
During the development of the climate change ex-
periment, consideration was given to a number of
possible rooting mediums. Using a soil substitute,
such as a potting mix, would have some practical
advantages, e.g., homogeneity, good rooting me-
dium for chamber studies. However, it would create
an artificial system lacking the characteristic fea-
tures (organisms, chemistry) of natural forest soils,
preventing an assessment of soil processes respond-
ing to climate change. We decided to use natural
Page 39 Corvallis Environmental Research Laboratory
-------
Effects oJC03 and Climate Chang* on Forest Trtu
forest soil in our study because a cumber of the
effects of climate change are likely to be soil-medi-
ated.
Rationale for Soil Selection: Once Douglas fir was
selected for use in our study we evaluated published
soil surveys to identify potential sites to obtain soil.
Many of the soils where Douglas fir occurs are
heavy-textured and are considered unsuited for ex-
cavation and reoonstitution. Amore coarse-textured
soil seemed better suited forretaining or reestablish-
ing favorable characteristics for plant growth.
From our discussions with U.S. Forest Service soil
scientists we found that Douglas fir in the Cascade
Mountains of Oregon and Washington is found
primarily on two kinds of soils. One, accounting for
about 70% of Douglas fir sites, is a heavy-textured
soil derived from colluvium and residuum support-
ing Site Class Q and ID (Legard and Meyer, 1973).
In general these soils are found at elevations between
300 to 1100 m. The second soil type, accounting for
about 30% of Douglas fir sites, is coarser-textured
(sandy loam) and derived from volcanic ejecta and
glacial till. In general, these soils are found mainly
at higher elevations (900 to 1400 m), yielding lower
Site Classes of HI or IV.
We characterized both soil types to determine which
one is better suited to our research needs. The lower
elevation, heavy-textured soil had a higher nutrient
status than the higher elevation, coarse-textured soil.
Both had exceptionally high water infiltration rates,
but the lower elevation soil contained more clay.
The two soils are managed very differently by the
U.S. Forest Service since the lower elevation soil is
more susceptible to effects of compaction and distur-
bance. We concluded that the higher elevation soil
was better suited for use in the terracosms, primarily
because of the ease with which it could be excavated
and reconstituted and its resiliency to disturbance.
Location of Soil Collection Site: Working with U.S.
Forest Service soil scientists we selected a soil
collection site on the perimeter of a500- to600-year-
old Douglas fir stand. Access and sampling damage
to the site were also considered before final selec-
tion. Hie collection site is approximately 140 km
east of Corvallis off Oregon State Highway 20 near
Tombstone Pass in the Sweet Home Ranger District
of the Willamette National Forest It is at approxi-
mately 1200 m elevation with a southeast aspect.
Under the litter layer the soil has three master hori-
zons: A, B, and C. The A is approximately 10 cm
thick, the B approximately 60cm, and the C approxi-
mately 20 cm. To prevent weather-related problems
with collecting soil in the winter, the soil was col-
lected in mid-August 1991. Approximately 80 mJ
(-10 m3 of A, -46 m3 of B, and -24 m3 of C) of soil
were excavated by horizon and hauled to Corvallis
where it was stored as covered piles. The chemical
and physical properties of the collected soil are given
in Table 4-5.
Soil Handling and Placement in the Soil Lvsimeters:
Soil profiles were reconstructed in a stepwise man-
ner. Soil lysimeters were prepared by cutting and
drilling the various sensor and access ports, followed
by cleaning and lining the lysimeters with an adhe-
sive-backed Teflon film to minimize soil contact
with the aluminum walls. Ten cm of coarse gravel
were placed at the bottom of each chamber to
facilitate drainage. The gravel was covered with a
geotextile cloth to reduce sedimentation. Soil of
each horizon was sieved separately to remove roots,
rocks and other debris larger than 3 cm and moist-
ened to reduce soil settling. Soil was placed in the
chamber in four lifts. The first lift consisted of 20 cm
of C-horizon. The second lift was 30 cm of B-
horizon. The third lift was another 30 cm of B-horizon.
The final lilt, 10 cm of A-horizon, will be added
when the seedlings are planted. In addition to
placing the soil in the lysimeters, sensors (Task 4),
samplers (Tasks 3 and 7), and minirhizotron tubes
(Task 6) were buried in the soil. To reduce settling,
the various layers of soil were lightly tamped after
they were placed in the lysimeter and leveled.
Page 40 Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
Table 4-5. Chemical and physical characterization of forest soil selected for the experiment.
Horizon
Depth
pH
Organic
Total N
N03-
NH4*
P
(cm)
Matter (%)
(*)
(ppm)
(ppm)
(ppm)
A
Oto 10
5.8
9.07
0.12
0J
2.8
7
B
10 to 70
6.1
3.93
0.07
0.3
4.1
3
C
70 to 90
63
2.35
0.06
0.7
5.6
3
Horizon Depth Extractable Bases CEC Bulk
(cm) Ca Mg K Na Density
meq/lOOg (g/m3)
A
Oto 10
23
0.86
036
0.06
27.1
0.78
B
10 to 70
23
0.92
0.28
0.06
25.5
0.90
C
70 to 90
2.4
1.10
0.29
0.07
24.7
0.88
'Chemical analyses were conducted at the Oregon Slate University Soil Testing Laboratory and bulk density data
are from the Oregon State University Soil Physics Laboratory. Methods: pH -1:2, soil to water, Organic Matter -
Walkley-Black; Total N acid digest follwed by Kjedldahl; N03- and NH4+ KCI extraction followed by
Kjeldahl; P-Bray P-l method; Extractable Bases unbuffered IN ammonium acetate extraction, CEC (Cation
Exchange Capacity) - unbuffered IN ammonium acetate method.
litter Studies
Litter Collection: Two types of forest floor litter will
be collected for the terracosm study. Forest floor
litter (Oi and Oahorizons) will be used to form a litter
layer in the terracosms and needle litter will be used
for decomposition studies.
The forest litter will be collected near the site where
the terracosm soils were collected and will be placed
on the upper mineral soil horizon (A-horizon) in the
terracosms. This layer will function as the forest
floor does in natural settings by storing moisture,
reducing soil evaporation, and as a key component in
the forest nutrient cycle. The forest floor litter will
consist of new litter and old litter. The new litter will
be relatively young and is characterized by recogniz-
able (e.g., needles) detrital material. The old litter is
more compact than the young litter and consists of
partially deoomposed detritus of indistinguishable
origin-
In the terracosms the initial forest floor litter will
consist of two layers, an Oi horizon, or new litter
layer (uppermost layer of slightly decomposed for-
est litter), and the Oa horizon, or old litter layer
(highly decomposed litter layer between the Oi and
the upper mineral soil horizon). At the initiation of
the study the Oi horizon will be approximately 4 cm
deep and the Oa 2 cm. Hie addition of these litter
layers will complete the forest soil profile recon-
struction in the terracosms. The nutrient and carbon
content of the added litter material will be quantified
for use in building terracosm nutrient and carbon
budgets.
Litter Replacement: We expect that the litter layers
will decompose, to some degree, over the course of
the study. Consequences of this decomposition will
be the release of organic carbon, nutrients, C02, and
increased evaporative demand. Twice a year, at the
time of soil sampling (Figure S.2), we will assess the
status of the litter layer in the three ambient COJ
ambient temperature terracosms. If the mean thick-
ness of the litter layer in these chambers has
decomposed to less than 3 cm, based on an initial
depth of 6 cm, we will determine the amount of litter
required to bring the ambient chambers back to the
full compliment of 6 cm of litter and add an equiva-
lent amount of litter to all terracosms and experimental
plots. The litter addition will consist of fresh new
Page 41
Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
litter, characterized by recognizable detrital material
(Oi horizon). By making such additions in the
tenacosms across treatments we will maintain a
consistent input of exogenous nutrients and carbon.
The litter will be obtained from the terracosm soil
collection site or other nearby sites. The nutrient and
carbon content of the added litter material will be
quantified whenever litter is added.
Litter Decomposition: Needle litter, collected in the
Fall of 1992 in the old-growth forest adjacent to the
terracosm soil collection site in the Oregon Cascade
Mountains, will be used in litter bags and needle
packs to assess the effects of elevated C02 and
climate change on litter decomposition. The needle
litter was air-dried and cleaned by removing the
larger non-needle litter by hand. The remaining
needle litter was stored in plastic bags and frozen
until needed. Subsamplesofthe homogenized needle
litter were collected for chemical analysis and meth-
ods development Decomposition studies will be
conducted in both the terracosms and at field sites
(see Section 5, Task 5).
Soil Fauna Collection and Inoculations
As the A-horizon and forest floor is introduced into
the terracosms, some members of the soil fauna
community may be excluded. Hie procedures to
collect, process and place the A-horizon and the
forest floor into the terracosms will likely hinder the
inclusion of certain soil fauna. Also, due to the lower
population density of some soil fauna in forest
ecosystems, they simply may have been excluded
from the harvested soil when it was collected. Fi-
nally, since it is vital to the decomposition process in
the terracosms that members at all trophic levels of
the soil food web be present, we will attempt to
ensure given population densities of critical groups.
Therefore, we will periodically introduce a selected
group of forest soil/forest floor fauna into the
terracosms, beginning at the start of the experiment,
and also when soil cores, litter bags and needle packs
are removed at the twice-yearly sampling times.
The soil fauna of the collected soil, in its native state,
is comprised of several thousand species, and each of
their roles are poorly understood. To attempt to meet
the concerns described above, the critical inverte-
brates listed in Table 4-6 will be introduced into the
tenacosms:
Table 4-6. Critical invertebrates introduced, into
the terracosms.
Earthworms (burrowers/
microbiovorts),
Oligochaeta
Arctiostrotus (litter layer)
Argilophilus (deep soil)
Millipedes (shredder),
Diplopoda
Harpaphe
Spiders (predators),
Araneae
Metaphidippus (surface and
seedling foliage)
Xysttcus (litter surface)
Centipedes (burrowing
predator), Chilopoda
Geophilomorphs
SUPPORTING STUDIES
While the overall study will focus on the long-term
effects of increasing C02 and climate change on
Douglas fir seedlings growing in the terracosms,
supporting experiments also will be conducted in
pots, large soil lysimeters, and at field sites. These
studies will provide additional data necessary for
modeling activities and for comparison of responses
of trees in the terracosms compared to trees growing
under native conditions.
Specific experimental plans will be prepared as
supporting studies are developed. However, care
will be taken so that the data obtained in the support-
ing studies will be fully complimentary to data from
the terracosms. Trees will be selected from the same
initial population as for the terracosms. Soils will be
similar to those for the terracosms, either by incorpo-
rating soil into pots or the large lysimeters, or through
planting trees in the field. Plant cultural and mea-
surement procedures will be the same as for the
seedlings in the terracosms.
Periodically, many of the measurements made on
the terracosm seedlings will also be made on the
Page 42 Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
supporting study seedlings as resources permit
During each growing season baseline data will be
taken on physiology and nondestructive growth
measurements such as stem diameter. Annually,
some of the seedlings will be destructively harvested
for biomass and growth measurements and the tissue
saved for biochemical measurements.
Pot Studies
Pot studies will provide plant material for intensive
gas exchange and other measurements under a vari-
ety of conditions, both outside and possibly in
controlled environment chambers. Use of pots will
allow for movement of plants to different areas; for
treatment of individual root systems with nutrients
such as nitrogen to look at particular nutrient-tree
response relationships, and possibly to enclose whole
plants for gas exchange measurements. The size and
the dimensions of the pots will be considered care-
fully because of possible impacts of root restriction
on C02 enhancement effects (Arp, 1991).
Large Lysimeters
To provide for soil and root observations for larger
trees grown in the Corvallis climate, trees will also be
grown in large soil lysimeters at ERL-Corvallis near
the terracosms. The lysimeters are 152 m x 1.83 m
x 1.22 m deep, and made of fiberglass. Seedlings
will be planted in each of four lysimeters at the same
density used in the terracosms. The annual harvest
will include destructive sampling of the entire lysim-
eter to obtain growth and biomass measurements for
the entire root systems in addition to the shoot
systems.
Field Studies
To help extrapolate the findings of the terracosm
study compared to forest trees in natural settings, tree
seedlings, from the seed lotplanted in the terracosms,
will be planted at three locations in the Willamette
National Forest The field plantings, or plots, will be
sited along an elevational gradient east of Sweet
Home, OR. The first plot will be located between
305 and 457 m above sea-level; the second plot
between 457 and 762 m; and the third plot between
762 and 1066 m, which is near the site where the
terracosm soil was collected. The specific sites for
these plots will be selected using the following
criteria: sites to have a relatively flat terrain with a
southern aspect; soils to be regionally representative
of soils on which Douglas fir is commonly found;
one site to be on the same kind of soil as that was used
in the terracosms (Forest Service Mapping Unit 66);
the sites not to have atypical climatic conditions or
orographic effects; and the sites to be easily acces-
sible from Oregon Highway 20 to provide year-round
access.
At each of the plots, five subplots (1 m x 2 m) and
buffer strips (1 m on all sides of the subplots) will be
established. The tree planting pattern and density
will be the same as that used in the terracosms. Litter
layer additions will mimic those in the terracosms
and litter bags and needle packs will be used to
estimate decomposition. Because of wildlife graz-
ing, the plots will be fenced. Soils will be characterized
at the start and end of the study. Soil temperature and
moisture will be measured at these sites throughout
the year.
TREE GROWTH MODEL SIMULATIONS
TO PROJECT EXPERIMENTAL
OUTCOME
After the experimental design and treatment levels
were chosen, the TREGRO simulation model (Sec-
tion 6) was used to provide a preliminary evaluation
of potential effects for the experiment levels on trees.
The primary goal was to assess the magnitude of the
growth response to these changes in environmental
conditions. These simulations were used to assess
the relative impact of changes in temperature and
C02 on seedling growth, and not the absolute amounts.
The simulations also assisted in the development of
hypotheses to be tested during the experiment
TREGRO was used to simulate the growth response
of ponderosa pine seedlings (a parameterized ver-
sion of the model for Douglas fir is not available at
present) to ambient and ambient + 4ฐC changes in
temperature (based on 1989 weather conditions in
Corvallis) and/or ambient and ambient + 200 ppm
cor
Page 43 Corvallis Environmental Research Laboratory
-------
Effects ofC03 and Climate Change on Forest The*
The version of the model used (v. 2.0a.l3) incorpo-
rates a number of elaborations over earlier versions.
These include a more mechanistic gas exchange
module, a soil water module, and a soil nutrient
module. Thenewgasexchangemodulewasusedfor
these simulations. Runs which added the soil water
module produced results similar to those without
that module. Further work with the model and
discussions with the modelers will be needed before
additional simulations with the water module are
carried out
The model simulations project that the temperature
and C02 will have a greater effect on belowground
than on aboveground bioraass (Figure 4-20). The
ambient + 4ฐC treatment displays a significant de-
cline in fine root biomass. This reduction coupled
with the projected decline in needle growth suggests
that this treatment will have the greatest impact on
tree growth, over time.
Model parameters were initially devel-
oped to mimic the growth of ponderosa
pine seedlings in the open-top chambers.
Photosynthesis and growth parameters
were taken where possible from mea-
surements on control plants grown in the
open-top chambers. Not all growth pa-
rameters could be directly measured, so
they were adjusted based on literature
data and on the output of the model.
Environmental data was taken from a
combination of meteorological data gath-
ered at Hyslop Experiment Station
(Oregon State University) and at the
FERF (ERL-Corvallis) site from 1989.
Even though version 2 of TREGRO is
still in development, the simulations ap-
pear to respond in a reasonable manner.
The TREGRO simulations suggest that
cumulative photosynthesis will be in-
creased, above the ambient C02 level in
both the elevated C02 treatments (Figure
4-19). Hie cumulative photosynthesis is
significantly depressed in the ambient+
4ฐC treatment, partly as a consequence
of reduced needle formation in die sec-
ond year of the study (Figure 4-20). TTie
combination of lower photosynthesis and
higher respiration reduced the carbohy-
drate reserves so that new needles failed
to form.
i Ambient
Amb ~ 200 ppm
Ambient + 4 C
*200ppm + 4C
r
ฆI
\ i i! 1tri 1 r
1 78 155 232 309 386 463 540 617 694
Days
30.000
Ambient
Amb ~ 200 ppm
Ambient 4 C
+ 200 ppm + 4 C
25.000
ฎ 20.000-
9
15.000-
ฃ 10.000-
5.000-
"i 1 1 r
1 78 155 232 309 386 463 540 617 694
Days
Figure 4-19. TREGRO simulations of the effects of CO, and
temperature on tree photosynthesis and respiration over a 2-
year period.
Page 44 Corvallis Environmental Research Laboratory
-------
Effects of COt and CUmate Change on Forest Trees
Am bleat
Amb + 200 ppm
AmbJcst ~ 4 C
+ 200ppm + 4C
Am Mint
Amb + 200 ppm
Ambient+ 4 C
~ 200 ppra ~ 4 C
Ambient
Amb ~ 200 ppm
Ambient ~ 4 C
> ~ 200 ppm ~ 4 C
S
1
4
4
2
ซ
1
1
Figure 4-20. TRECRO simulations of the effects of COl and temperature on tree growth over a 2-
year period.
Page 45
CarvaUis Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees <
V. EXPERIMENTAL TASKS
INTRODUCTION
This project is a highly integrated set of experimental
studies and data analyses. The experimental tasks
have two separate objectives:
Provide data that can be used to understand
the effects of elevated C02 and climate
change on tree growth and associated im-
pacts on soil processes.
Provide data that can be used to parameter-
ize a process-based tree growth model to
project the results from the experimental
study to other conditions.
Because of the highly integrated experimental de-
sign, relatively long experimental duration, and a
limitation in plant tissue available for destructive
harvests, it is essential that various sampling activi-
ties be coordinated to maximize inter-comparability
of data. Sample collection and measurement will be
closely linked between above- and belowground
phenological events, i.e., bud set, shoot elongation,
rapid root growth. The general sampling scheme for
integrating the collection of samples and measure-
ments is presented in Figure 5-2 to illustrate the
temporal relationships. More detail on sampling is
presented in the individual task descriptions.
The dual objectives are re-
flected in the description of
the experimental tasks. Spe-
cific tasks were selected to
provide a detailed understand-
ing of tree processes and
growth (Figure 5-1). The spe-
cific arrangement of the tasks
in the figure was selected to
illustrate the physical and spa-
tial relationship of the research
tasks.
In developing the specific ex-
perimental tasks, the modeling
needs were considered. An
analysis of the specific ex-
perimental measures was
conducted to insure that ap-
propriate data would be
available for the modeling ac-
tivities. This is reflected in a
subheading under each task
which lists anticipated model
inputs.
Figure 5-1. Research
tasks for the experiment.
Experimental Research Tasks
Task I
Shoot Carbon and
Water Fluxes
Task 3
System Nutrients
Plant Nutrients
Soil Nutrients
i
Task 3
Litter Layer
a
Task 2
Shoot Growth and
Phenology
Task 4
System Water
Plant Water
v,,'.,.1,.,-..,... !.. '.."..'am
Soil Water
TaskS
Root Growth and
Phenology
r
vf Task 7
Soil Biology
,v4V
Page 46
Corvatlis Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
e
a
E
eg
w
1
3
e
oป
o
>
FALL-
FALL
Whole Plant Gas
Exchange
Needle & Branch
Gas Exchange
Stem Diameter
CERES Devices
Plant Water
Status
Stem Height &
Diameter Manual
Needle Area
Image Analysis
Bud Phenology
Branch & Stem
Architecture
Needle
Samples
| Continuously |
Every Eight Weeks |
Every Four Weeks
Every Eight Weeks
Continuously
X
X x
X
| Every Eight Weeks
Every Four Weeks
Every Eight Weeks
Every Four Weeks
Every Eight Weeks
Every Four Weeks
Every Eight Weeks
X
X
X
Shoots Dormant
Bud
Breii
Shoot Growth
Bod
Set
Shoots Dormant
Soil Surface
Rapid Root Growth
Rapid Root Growth
8
a
E
a
ป
a
c
3
2
?
o
ฎ
m
Co res-to-Depth
Soil & Root Samples
Litter Bags &
Needle Packs
Root Images
Soil Solutions
Soil Profile
Gases
Soil Surface
Gases
Soil Water
Content
X
X
X
X
Every Four Weeks
Every Four Weeks
Every Four Weeks
Every Four Weeks
Continuously
Figure 5-2. Physiological-basedschedule of above- and belowground sample collection timing andfrequency
-------
Efftcts of CO j and ClimaSt Chang* on Fortst Trtts
TASK 1: SHOOT CARBON AND WATER
FLUXES
Introduction
There are two fundamental science questions relat-
ing to the effects of increased C02 and climate
change on gas fluxes of vegetation. The first ques-
tion is:
Will the net carbon flux for plants change in
response to elevated C02 and climate
change?
This question focuses on the basic uncertainty con-
cerning predictions about the consequences of
increased C02 and global climate change on essen-
tial vegetation carbon flux characteristics. Important
components of this question are as follows: 1) Will
the C02 fertilization effect result in a continuing net
increase in carbon uptake, allowing plants to grow
larger and faster; 2) will net carbon uptake be af-
fected both by net photosynthetic rates and respiration
(maintenance and growth) rates; and 3) will climate
change modify the net carbon uptake by limiting
some other resource such as water or nutrients, or by
an environmental stress such as increased tempera-
ture?
The second fundamental question is:
Will plant water-use efficiency (WUE) in-
crease in response to elevated C02 and
climate change, and will this WUE increase
occur on a vegetated area basis as well as on
a single plant basis?
This question is based on the relationship between
increased atmospheric C02 concentration and de-
creased stomatal conductance and, therefore
decreased water vapor flux from plants, i.e., transpi-
ration. If pi ants can fix caibon at constant or increased
rates while expending less water, overall water use
efficiency should increase. However, in a realistic
environment water relations are also affected by
water requirements due to overall tree growth rates
and available water in the soil. If leaf area-to-land
ratios (Leaf Area Index or LAI) also increase with
increasing C02 until limited by available water, trees
on a stand (area) basis may ultimately be just as, or
less tolerant to periodic drought stress with increased
C02. Furthermore, climate change (increased tem-
peratures or drought) will modify tree growth rates,
the vapor pressure of the air, and available soil
moisture; and all these factors can modify WUE.
To answer these questions with respect to Douglas
fir trees, the basic gas exchange physiological re-
sponse of young trees exposed to either elevated
002, increased temperature, or a combination of
these two variables must be understood in greater
detail.
Objectives
The following objectives have been defined to ad-
dress the science questions:
To measure at the whole plant canopy level
photosynthetic, respiration, and transpira-
tion rates in response to the individual and
combined effects of increased C02 and in-
creased temperature.
To measure at the needle/branch level pho-
tosynthetic, respiration and transpiration
rates, and stomatal conductance changes in
response to elevated C02and climate change.
These measurements will be made with
different photosynthetically active radiation
(PAR) levels, temperatures, and C02 con-
centrations; and for different needle age
classes and leaf nitrogen levels.
To measure at the canopy and needle/branch
levels, diel and seasonal patterns in photo-
synthetic, respiration, and transpiration rates,
and stomatal conductance in response to
elevated 002and climate change.
To measure at the needle level/branch and
whole plant level the influence of leaf water
potential (WP), and air vapor pressure defi-
cit (VPD) on stomatal conductance and
transpiration. These measurements will be
made with different photosynthetically ac-
tive radiation (PAR) levels, temperatures,
Pag* 48
CorvalUs Environmental Research Laboratory
-------
Effects of COj and CUmate Change on Forest Trees ฆ
and COj concentrations; and for different
needle age classes and leaf nitrogen levels.
* To derive photosynthesis, respiration and
stomatal conductance input variables for the
TREGRO model based on the above mea-
surements and literature values.
will be at field sites, in large soil lysimeters, and/or
in pots, based on particular research questions.
However, a limited number of needle/branch
measurements will be made in the terracosms to
determine how the C02, temperature, and drought
treatments affect the shoot responses character-
ized in the supporting studies.
Approach
The study will focus on the long-term effects of
increasing C02 and climate change on canopy gas
flux for Douglas fir seedlings growing in the
terracosms. These will be accompanied by periodic
needle/branch measurements, also taken from the
terracosms, to characterize the effects of increasing
C02, temperature and drought on gas fluxes. The
measurement frequency will be limited in order to
minimize distuibance of the terracosms. Supporting
experiments will provide more intensive needle/
branch and whole tree measurements using trees at
field sites, in large soil lysimeters, and/or in pots.
Photosynthesis: Photosynthesis will be mea-
sured at two scales: 1) total plant canopy, and 2)
needle/branch. Measurements may also be made
on a wholeplantlevel
to assist in scaling
from the needle/
branch to canopy lev-
els. Canopy level
measurements will
be made in the terra-
cosms, where
measurements rep-
resent the integrated
response of the
shoots fiomall trees.
Needle/branch (and
possibly whole
plant) measure-
ments will be made
primarily in sup-
porting studies to
minimize the intru-
sion into the
terracosms. The
supporting studies
Canopy Scale: Canopy photosynthetic rates will be
measured using a mass balance approach for carbon
in the terracosms as illustrated in Figure 5-3. Details
regarding terracosm operation are given in Appen-
dix A. Two methods will be used to measure gross
terracosm C02 uptake: 1) Each chamber will peri-
odically be operated in the draw-down mode, that is,
C02 injection will be withheld for a period of about
20 minutes, and the C02 concentration measured
several times during this draw-down; and 2) The
amount of C02 dispensed into each chamber will be
measured continuously. Gross canopy photosyn-
thetic rates then will be calculated by measuring
chamber leakage rates and soil C02 emission rates,
and then subtracting the chamber and soil rates from
the gross terracosm C02 uptake rates. Net canopy
photosynthesis will be calculated by subtracting
Terracosm Canopy Carbon Balance
Inputs
Q
Mass Row Controller
C02 Input Rata
LX leaf Area
" Ten
Light Ft
i
a
A
Soil Respiration
Rite
nature
Ambient CO]
Concentration
Q
Ambient Air
Leakage Rate
u.
Photo synthetic
Rate
Outputs
60
Chamber
Leakage Rate
Dark Respiration
Rate
FigureS-3. Carbonbalanee in chamber, showing input and output rates. Curved lines
indicate transfer of information that change input mid output rates.
Page 49 Corvallis Environmental Research Laboratory
-------
Effects of COt and CUmatt Change on Forest Trees
canopy dark respiration and soil respiration rates
from gross canopy photosynthesis. Plant canopy
photosynthesis will be expressed on the basis of total
leaf area and possibly total leaf dry weight based on
the shoot growth measurements (Task 2).
Needle/Branch Scale: At the needle/branch level
photosynthesis will be measured with a LI-COR
6200 gas exchange system using a quarter-liter
chamber. This is a small draw-down system that is
used for rapid, simultaneous determination of photo-
synthesis, transpiration, and stomatal conductance.
Measurements may also be made using a PACSYS
9900 or similar gas exchange system if available.
The PACSYS system has the advantage that it
provides climate control so that carbon assimilation
rates can be measured without potentially overheat-
ing the chamber during measurement periods.
Needle/branch measurements will be made on a
limited basis in the terracosms to determine how the
C02, temperature, and drought treatments affect the
shoot responses. Measurements will be made by
using access ports built into the plexiglass rear panels
of the chambers. These ports will facilitate gas
exchange measurements without upsetting the cham-
ber climate control. Measurements will be made at
the time of key phases of tree phenology (Figure 5-
2), and at other key times of the diel photosynthetic
cycle.
To provide for more intensive measurements and
destructive harvests, photosynthetic measurements
will also be made intensively on trees from the same
popul ation and stage of development as the terracosm
trees. These supporting studies (described in more
detail under Task 2) will use trees in the field, large
lysimeters, and/or pots. These trees will be used to
measure the photosynthetic responses with different
photosynthetically active radiation (PAR) levels,
temperatures, as a function of the C02 concentration
internal to the stomata (A/Ci response curves); and
for different needle age classes and leaf nitrogen
levels.
Respiration: Dark respiration rates will be mea-
sured throughout the duration of the experiment to
quantify net carbon exchange for terracosms and
trees and to characterize metabolic rates for shoots.
Respiration will be partitioned into growth and
maintenance components. Respiration rates will be
compared to shoot C/N ratios and total nonstructural
carbohydrate (TNC) (see Task 3) to suggest mecha-
nisms for elevated C02 and temperature effects.
Respiration will be measured on the canopy and
needle/branch scale using a darkened chamber dur-
ing the day and under natural darkness at night, as
necessary, to determine accurate temperature re-
sponses.
Canopy Scale: Canopy respiration rates will be
measured using a mass balance, similar to that for
photosynthesis (Figure 5-3). Nighttime respiration
will be estimated on a hourly basis for the total
seedling canopy by monitoring the rate of increase in
chamber C02. Soil respiration will be deducted from
this measured rate to calculate the maintenance
respiration. Task 7 discusses in greater detail mea-
surements of soil gas emissions.
Needle/Branch Scale: Measurements at the needle/
branch level will be made with the Ll-COR 6200.
Respiration rates will be measured at mid-day using
a darkened cuvette and/or during the natural dark
period if necessary. Stem respiration measurements
will also be evaluated for potential usefulness.
Growth vs. Maintenance Respiration: As feasible,
we will partition needle respiration into growth and
maintenance components based on the procedures
described by Amthor and Cumming (1988). This
procedure requires respiration measurements on a
dry weight basis per day, as well as growth rate per
day. Because intensive harvest of needles for growth
analysis can not occur in the terracosm study, we will
obtain the growth measurements either by using
needle size as a surrogate in the terracosm study, or
by harvesting needles from trees from the supporting
studies.
Page 50 CorvalUs Environmental Research Laboratory
-------
Effects of CO 2 and Climate Change on Form Tree*
TVanspiration: Transpiration will also be mea-
sured at the following three scales: 1) plant canopy
as in the terra cosms, 2) whole plant in the terracosms,
and 3) needle/branch in supporting experiments.
Canopy Scale: Transpiration will be measured at the
terracosm level in a manor similar to that described
above for total canopy photosynthesis to provide
canopy water balance data (Task 4). Plant transpired
water and water evaporated from the soil surface will
be collected, and measured continuously as conden-
sation collected from the chilled water heat exchanger.
Estimates of soil/litter surface evaporation will be
made based on litter temperature and moisture con-
tent These estimates will be deducted from collected
condensate. The resultingtotal daily canopy transpi-
ration volume will also be adjusted for chamber
leakage as necessary. Using estimates of canopy leaf
area, average hourly transpiration estimates will be
derived and compared to measurements made by the
stem sap flow gauges.
Whole Plant Scale: Hiese measurements will be
carried out in coordination with Task 4, Plant Water
Status. Stem sap flow gauges will be used to provide
a continuous nondestructive measure of whole plant
transpiration. TTie gauges use a tiny strip heater that
is used to heat a zone of the stem. The radial and axial
conductive heat fluxes away from the heated seg-
ment are measured, as well as the rise in sap
temperature. These values are used to calculate the
mass flow rate of the sap. Gauges patterned after
those described by Baker and van Bavel (1987), and
Steinberg et al. (1989), will be built and integrated
into the current process controller/data acquisition
system. By comparing transpiration measurements
made with enclosure techniques, and estimates made
with stem flow gauges, the accuracy of this tech-
nique in this application will be evaluated (Ham and
Heilman, 1990).
Transpiration measurements will also be calculated
on the whole plant level using the CERES devices
described in Task 4. The CERES devices provide a
highly sensitive measurement of stem diameter which
can be associated with transpiration rates, based on
correlation with branch transpiration measurements.
Needle/Branch Scale: Measurements at the needle/
branch level will be made simultaneously from
photosynthesis/respiration measurements with the
LI-COR 6200.
Stomatal Conductance: Stomatal conductance
will be derived from transpiration and leaf tempera-
ture measurements on both the needle/branch and
whole plant scale.
Canopy Scale: At present conductance measure-
ments are not obtainable on a canopy scale due to
difficulties in obtaining a measurement of leaf tem-
perature across the canopy. However, future
consideration will include moving to a nondestruc-
tive infrared temperature measurement technique so
that more continuous leaf temperature monitoring
can be made on a canopy scale. Using miniaturized
IR devices, a spot size of as small as 0.75 mm
diameter can be measured with an accuracy of
ฑ0.1CC (Everest Interscienoe, Inc., Fullerton, CA).
Whole Plant Scale: Whole plant measurements will
be taken in combination with the transpiration mea-
surements with the stem flow gauges and CERES
devices (see Task 4). Needle temperatures will be
measured with three fine wire thermocouples (34-36
gauge) inserted into different needles of a seedling.
Each group of three thermal couples will be grouped
so that a single average temperature is measured.
These measurements will be taken on a minimum of
three seedlings in each terracosm for several days
prior to, and during gas exchange measurements.
Measurements will be read every minute and aver-
aged to record measurements every 5 minutes.
Needle/Branch Scale: Measurements at the needle/
branch level will be taken simultaneously with pho-
tosynthesis/respiration measurements with the
LI-COR 6200, based on calculations obtained from
the transpiration measurements. The stomatal con-
ductance measurements will depend on either careful
measurement of leaf temperature in the LI-COR
6200, or on non-contact energy-balance calculations
if another type of gas exchange system is used.
Page 51 CorvaUis Environmental Research Laboratory
-------
Effects of CO2 and Climate Chang* on Form Trttt
Task Outputs
Characterization of net caibon flux for Dou-
glas fir shoots in response (o elevated C02
and climate change,
Characterization of WUE for Douglas fir
shoots in response to elevated C02and cli-
mate change.
Characterization of diel and seasonal pat-
terns of carbon and water fluxes for Douglas
fir shoots in response to elevated C02 and
climate change.
Characterization of relationships among
photosynthesis, respiration, tissue C/N
ratios, and TNC concentrations.
Evaluation of potential for changes in plant
canopy temperature induced by transpira-
tion reductions.
Model Inputs
Task 1 will provide input for the TREGRO model as indicated in Table 5-1.
Table 5-1. Measurements required to determine photosynthesis and respiration parameters for
TREGRO model
Photosynthesis (Ball/Berry Equa-
tions)
KC= Ka of rabisco for C02 at 25ฐC(Pa)2
QTKC=Q 10 of K of nibisco for CO/
QTKO=Q 10 of Kn of nibisco for 0/
QTRDs=Q 10 for dark respiration3
QTSP=Q 10 of nibisco specificity for C032
QTVM=Q 10 for VMax'
SP=Specificity for COj at 25ฐC (Pa/Pa)1
AMBPP=Ambient partial pressure, C02 (Pa)1
Theta=curvature term in quadratic for CXX, re-
sponse2
RBW=Boundary layer resistance to water (m2 s1
mol')'
RSW=Stomatal resistance to water (mJsr1 mol*')'
SWABS=Absorptivity to shortwave2
VMAX=Vmax C02 of ribulosebisphos-phate Q
O-ase*
ABSPAR=Absorptivity of leaf to photosyntheti-
cally active radiation3
SLOPEBB=Slope of the B-B model2
DRPERCENT=The % of VMax Jo taJce to calcu-
late dark respiration from VMax
KOsK. of nibisco for 02 at 25#C (Pa)1
PP02=Partial pressure of O, (Paf
Respiration
Fraction of compartment in carbon lost per hour
(leaf by age class) or per day (stem, branch,
buds) (%)'
'Measured in task.
Obtained from literature.
Q|0 for respiration (leaf by age class, stem, branch,
buds)l
Growth respiration rates as fraction of allocated C used
for respiration (leaf by age class, stem, branch, buds)
(%)'
Page 52 CorvalOs Environmental Research Laboratory
-------
Effects of CO, and Climate Change on Forest Tries
TASK 2: SHOOT GROWTH, MORPHOL-
OGY, ALLOMETRY, PHENOLOGY, AND
CARBON PARTITIONING
Introduction
Characterizing the relationships among elevated
C02 and climate changes on shoots is a key to
understanding the impacts of these stresses on tree
productivity, Here are four fundamental science
questions relating to the effects of increased C02 and
climate change on tree shoot responses at the plant
level. This first question is:
Will shoot growth change in response to
elevated CO2 and climate change?
One of the observed effects of C02 enrichment in
previous research was increased rates of carbon
fixation producing what las been termed a C02
fertilization effect This effect was noted as in-
creases in the gross rate of dry matter production,
total leaf mass and number, and mass of fine and
coarse roots. While this fertilization effect has been
repeatedly noted in experiments run under condi-
tions typical of agricultural systems, i.e., no water or
nutrient limitations, Jarvis (1989) recently summa-
rized C02 effects on the growth of young trees aid
stated that C02 enrichment compensated to a consid-
erable extent for limitations in light, water or nutrients
as would be expected in a resource-limited natural
system. Yet, because of the limited number of
extended C02 enrichment studies on tree seedlings,
it is still open to speculation if the fertilization effect
will be maintained through several years of growth.
Some recentexperiments suggest thatthe magnitude
of the C02 fertilization response appears to be posi-
tively correlated to the size of rooting volume (Thomas
and Strain, 1991). Rootingvolumelimitationsoould
effect plant nutrient status, but also available sinks
for additional photosynthate (Strain and Oechel,
1985). These results suggest that the physiological
response of seedlings to increased atmospheric C02
is more complex then simply a productivity en-
hancer.
The second question is:
Will shoot morphology and allometric rela-
tionships change in response to elevated
CO2 and climate change?
The potential alterations in tree carbon balance and
water-use efficiency (WUE) (Task 1) due to el-
evated C02 and global climate changes may produce
fine level modification in shoot morphology, i.e., the
architecture and number of stems, branches, etc., in
addition to general impacts on tree growth. Altered
branching patterns especially may alter the light
interception by the canopy.
In addition, the standing stock of shoot C is
allometrically distributed among buds, needles, and
stems of different age classes. Increasing concentra-
tions of C02 and climate change may shift the
relative proportion of C among these stocks, thereby
affecting the amount of needle area available for gas
exchange and/or amount of wood produced by the
tree.
The third question is:
Will shoot phenology change in response to
elevated C02 and climate change?
Trees growing in areas with pronounced seasonal
variation in climate, such as the Cascade Mountains,
have genetically adapted timing to respond to envi-
ronmental signals before initiating developmental
stages. The cumulative increment above a minimum
temperature (degree days), date of first frost, etc.,
have implications for adaptation to cold and freez-
ing, bud break with onset of the spring, and long-term
productivity of the trees. These environmental sig-
nals may be altered by increased temperatures
associated with climate change, and may also be
affected by die carbohydrate reserves in the trees,
which are a function of both atmospheric C02 and
climate.
Page S3 Corvallis Environmental Research Laboratory
-------
Effects of CO j and CUmate Change an Forest Trees ฆ
The fourth question is:
Will the biochemical partitioning of C in
shoots change in response to elevated C02
and climate change?
Carbon in shoots exists in two general classes of
compounds: structural compounds (e.g., cellulose)
and nonstructural compounds (e.g., sugars). The
partitioning of shoot C between these two groups is
indicative of the interaction of a plant with its envi-
ronment and associated stress.
Objectives
The following objectives have been defined to ad-
dress the science questions as they refer to the
aboveground portion of tree seedlings:
To measure, at the individual plant level,
effects of elevated C02and climate change
on shoot biomass (dry weight) by age class
of the main stem, branches, needles, and
buds.
To measure, at the individual plant level,
effects of elevated C02and climate change
on shoot allometric parameters, i.e., stem
diameter, height, and needle elongation.
To measure, at the individual plant level,
effects of elevated C02and climate change
on shoot morphology and allometric rela-
tionships including numbers, rank, and
weights of branches, needles, and buds for
all age classes of tissue. Needle areas will be
token to determine specific needle weights.
To measure, at the individual plant level,
effects of elevated C02and climate change
on shoot phenology. The datesofkey events,
such as onset of bud break, secondary bud
break, and first frost, will be carefully noted.
To quantify the changes in the biochemical
partitioning of C between structural and
nonstructural compounds in the various shoot
fractions in response to elevated C02and
climate change.
Approach
The study will focus on the long-term effects of
increasing C02 and climate change on Douglas fir
seedlings growing in the terracosms. Supporting
experiments will be conducted at field sites, in large
soil lysimeters, and/or in pots, based on particular
research questions. For each type of study initial
(baseline) measurements will be based on a single
destructive harvest of 50 bare-root seedlings taken
from a larger population of3000trees received for all
studies. Intermediate measurements will be taken to
follow the course of tree growth over time; they will
be nondestructive for the terracosms but destructive
in the supporting experiments. Final measurements
will be made to look at the cumulative effects of the
treatments and experimental conditions on overall
tree growth. The following information is for the
terracosm study, details will be described later for
specific supporting studies as they are developed.
Shoot Biomass: Initial measurements will be taken
to define baseline characteristics of the seedling
population from which the trees are taken. Interme-
diate measurements will only be taken for tissue
analysis purposes. The primary focus will be on the
final measurements which represent the cumulative
effects of the treatments over the course of the entire
study.
Initial: At the time of planting, 246 of 3000
seedlings in the population acquired for the study
will be selected that fall, within what is defined as
the normal distribution. Fifty of the seedlings
will be randomly selected and harvested. The
remaining 196 seedlings will be planted in the 14
terracosms. Harvested plants will be divided into
axillary and terminal: buds, needles by age class,
branches, and main stem. Dry weights will be
taken for each biomass component. Biomass
samples will be saved for analysis relating to type
of carbon content in support of plant nutrient
evaluation activities (described below and inTask
3). Root systems will be saved for analysis in
Task 6.
Page 54 CorvaUis Environmental Research Laboratory
-------
Effects of CO3 and Climate Change on Forest Trees
Intermediate: Only needle samples will be taken for
carbon and nutrient analysis. Needles will be sampled
periodically based on key phenological stages (Fig-
ure 5-2). Mature needles from each age class will be
clipped from a representative group of plants in each
terracosm. Care will be taken to sample needles that
have similar locations in respect to seedling architec-
ture and terracosm design. Potential impact of
destructive sampling on the total canopy needle area
dictates that size must be minimized. Needles from
specific age classes will be pooled and analyzed
separately. Needle area and mass of pooled needles
will be measured, and total needle biomass will be
estimated. The needle samples will be saved for
carbon partitioning.
Final: All 1% terracosm trees will be harvested and
components measured for diy weights at the end of
the treatments, approximately 25 years after plant-
ing. The biomass samples will be saved for caibon
partitioning analysis. Root systems will be saved for
analysis in Task 6.
Shoot Morphology and Allometry: Initial and
final measurements will be destructive and will
occur at the same time as the biomass measurements.
Intermediate measurements will be nondestructive
indicators of rates of shoot growth and development
during the course of the experiment
Initial: For the 50 seedlings described above basal
stem diameters will be measured with calipers and
stem heights will be measured with a ruler. Fre-
quency plots will be generated and the normal
distribution of these measurements determined. The
stem diameter and tree height data will be used as
covariates for subsequent statistical analysis of tree
growth. Bud and branch numbers, and location
(axillary or terminal) will be counted. Intemodal
length may be measured. For each age class a sub-
sample of the needles will be counted, measured for
planar leaf area, and weighed to determine specific
leaf weight
Intermediate: Periodically, during the study, the
following nondestructive measurements will be
made:
stem height/stem diameter Individual tree height
and stem diameter will be measured primarily be-
fore, during, and after the shoot growth period
(April, May, June) (Figure 5-2), and at other times of
the year, as necessary, to quantify changes in growth.
An electronic hand-held caliper/data logger will be
used to measure stem diameter, and a standard meter
stick employed for stem height measurements. All
field measurements will be keyed into hand-held
data loggers and the data directly downloaded into a
database to minimize transcription errors.
ceres devices A pair of CERES devices (Beedlow
et al., 1985) will be employed in each chamber to
give continuous measurements of stem diameters.
These devices, described in more detail inTask 4, are
sensitive to diameter changes as small as 300 nm.
These devices have not been routinely used at this
lab, so this work will provide an evaluation of the
performance of the CERES for growth rate analysis
as compared to measurements manually taken with
stem calipers.
BRANCH NUMBER/INTERNODE LENGTH Total branch
numbers and intemode lengths will be determined in
the fall after bud set
needle AREA/LAI In order to determine canopy leaf
area to volume ratios, total seedling leaf area and leaf
area index (LAI) will be determined nondestructively
using computer aided photo image analysis. The
development of this technique is described in Ap-
pendix B. Sampling will be periodically (Figure
5-2). The image analysis techniques may also be
used to calculate needle elongation rates from initia-
tion in the spring until it ceases.
Final: At the end of the study the trees will be
harvested and growth and morphology measured as
initially.
Shoot Phenology: All measurements will be non-
destructive indicators of timing of key phases of
shoot growth and development during the course of
the experiment Characteristics include timing of
dormancy onset and bud break, and the number of
buds that set Bud location will be differentiated in
Page 55
Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
terms of plant architecture. Sampling will occur at
biologically relevant times and frequencies (Figure
5-2). In the spring several measurements will be
made on a regular basis to determine the time neces-
sary for a certain percentage ofbud break. During the
summer the trees will be closely monitored and
measured for a second, or possibly multiple, bud
breaks and flushes as they occur. Bud set will be
determined in the fall when the seedlings are fully
dormant The timing of needle flushing will be
noted. Needle elongation will be measured on a
regular basis (e.g., every 3 weeks) until needles reach
their maximum length. Measurements will be made
on a subset of the trees in each chamber.
Carbon Partitioning: Biomass samples will be
saved for analyses which will include percent carbon
based on Carbon/Hydrogen/Nitrogen/Sulfur con-
centrations and total nonstructural carbohydrates
(TNQ. Tissue samples will be lyophilized, re-
weighed, and then ground to an even texture using a
Wiley mill. After being passed through a 40 mesh
screen, samples will be analyzed for C, N, and S,
macronutrients, micronutrients, and TNC. Descrip-
tion of analytical procedures are provided in Task 3.
Task Outputs
Characterization of shoot growth of Dou-
glas fir in response to elevated C02 and
climate change.
Characterization of shoot morphology and
allometric relationships of Douglas fir in
response to elevated C02and climate change.
Characterization of shoot phenology of
Douglas fir in response to elevated C02
and climate change.
Characterization of changes in the bio-
chemical partitioning of C between
structural and nonstructural compounds
in the various shoot fractions in response
to elevated C02and climate change.
Evaluation of the performance of the CERES
device for continuous analysis of seedling
growth through stem diameter measurement
Model Inputs
Task 2 also provides input for the TREGRO
model as indicated in Table 5-2.
Table 5-2. Measurements of morphology, shoot
biomass, andphenologyfor the TREGRO model
Number of Leaf Age Gasses
Number of Leaf Primordia
Biomass (grains carbon in structural, nonstructural,
and wood)
Leaf primordia
Leaves (by age class)
Branches
Stems
Buds
Phenology (degree days for initiation of)
Pre-growth period
Root growth period
Leaf growth period
Branch and stem growth period
Root storage and growth period
Page 56 Corvallis Environmental Research Laboratory
-------
Effects of C03 and CUmat* Change on Forest Trees
TASK 3: SYSTEM NUTRIENTS
Introduction
This task has two distinct functions: 1) a research
function, and 2) a general support function. The
research function is to specifically evaluate the ef-
fects of increased COp increased temperature, and
altered soil moisture on the size and relationships
among plant and soil nutrient pools. The support
function is toprovidechemicalanalysisofplant,soil,
mid soil solution samples as required by other tasks.
This will centralize similar analytical methodolo-
gies within one task area, helping to clarify the
overall responsibilities and sequencing of chemical
analyses.
There are two fundamental questions relating to the
interactions between increased C02 and climate
change on plant nutrient status. Hie first question is:
Witt increased C02 and climate change
affect plant nutrient balance?
It is generally recognized that for optimum plant
growth and yield, sufficient amounts and propor-
tions of structural elements (C, H, and O), and
macro- and micronuirients must be available. Maxi-
mum yields will only be realized when both, the
optimum concentration of nutrients and the opti-
mum ratios of nutrients, are present within plant
tissue (Tinnier, 1992).
The second question is:
Will the response of forest trees to increas-
ing concentrations of C02 and climate
change alter plant and soil nutrient pools?
While the general short-term response of plants
exposed to elevated C02 is increasing photosyn-
thetic rates (Oechel and Strain, 1985), other
environmental factors in combination with C02
concentration will ultimately determine the long-
term plant response. Insufficient data exist on the
response of forest trees to elevated C02 and in-
creased temperature to allow an adequate assessment
of either the short- or long-term impact on plant and
soil nutrient pools, or to assess the potential feedback
between nutrient pools and plant response. Elevated
plant nutrient demands imposed by increased photo-
synthesis may be partially mitigated through greater
partitioning of photosynthate to belowground struc-
tures. This could lead to increased resource
acquisition through expanded root surface area, in-
creased root exudates, and/or through increased
mycorrhizal colonization.
Objectives
The following objectives have been defined to ad-
dress the science questions and to supply chemical
analysis to other tasks:
To monitor changes in inorganic nutrient
concentrations in above- and belowground
plant tissues, litter material, soils and soil
solutions as a function of C02 and climate
change.
To evaluate the effects of elevated C02 and
climate change on inorganic nutrient bal-
ance in Douglas fir seedlings.
To evaluate the physiological significance
of nutrient availability in respect to the ob-
served responses to increased C02 and
climate change.
To measure C and N, S, and TNCconcentra-
tion in above- and belowground plant tissue,
litter material, soil, and soil solutions.
Approach
Chemical analysis will be conducted on plant
tissues, litter material, soil samples, and soil
solutions to determine C and nutrient concentra-
tions, to quantify C and nutrient pools, and to
monitor changes in these pools over time.
Samples collected in Tasks focused on above-
and belowground responses will be analyzed
within this task, but the results of these analyses
will be evaluated within the task where the .
samples originate (Figure 5-4). Questions on
the whole plant and soil nutrient status will be
addressed within this task.
Page 57 Corvallis Environmental Research Laboratory
-------
Efftcts of COj and ClimaSt Change on Forest Tries
Task 2
Shoot Growth
and Phenology
TaskS
Litter Layer
Litter
Samples
Shoot
Samples
Chemical
Analysis
Chemical
Analysis
Task 3
System Nutrients
Root/Soil
Samples
Chemical
Analysis
Task 6
Root Growth
and Phenology
Figure 5-4. Samples collected in Task 2,5, and 6 will be analyzed in this
task with the chemical analysis reported back.
Plant Tissue and Litter: Needles, root tissue, and
litter material will be sampled at the beginning and
end of the experiment, and also during the experi-
ment at frequencies that correspond to significant
phenological events. The sampling times are de-
tailed in Figure 5-2, and the methods described in
Task 2 (shoots), Task 5 (litter material), and Task 6
(root material). Branches and stems will be collected
for analysis only at the beginning and end of the
experiment Samples will be weighed, dried at 35ฐC,
reweighed, and then ground to an even texture (using
a Wiley mill, ball mill, or mortar and pestle as sample
size dictates), and passed through a 40-mesh screen.
Elemental AnalvsisofC/MS: TotalelementalC,N,and
S will be determined with a combustion-based elemen-
tal analyzer. Analysiswill be conducted on a CarioErba
EA1108 using standard procedures (Bremner and
Tabatabai, 1971). Analysis of chemical standards,
standard orchard leaves, and pine needles, (National
Institute of Standards and Technology) will be done
routinely to assess instrument accuracy and stability. In
addition, tissue samples
will be chemically ex-
tracted into three fractions
and die C and N composi-
tion of each fraction
determined (expressed cm
ash-free basis). While a
variety of extraction/frac-
tionation procedures exist,
(see Bremner and
Tabatabai, 1971; Nelson
and Sommers, 1982; Aber
eta!., 1990, Stevenson and
Elliot, 1989), we will be
employing the method
used by Aber et al. (1990)
as it provides operational
fractions that fit directly
into the TREGRO and
TEM modeling structures.
Using the Aberetal.(1990)
method, the three fractions
are operationally defined
as: (1) Extractives - de-
fined as the sum of the
nonpolar (CHjQj extractable) and polar (HjO extract-
able) fractions, (2) Cellulose - defined as the soluble
fraction of an acid hydrolysis of residue from (1), and (3)
Lignin - defined as the unhydrolized residue of (2).
Total Nonstructural Carbohydrates fTNO: The
principal energy reserves used by plants consist of
various forms of carbohydrates. Sugars, starches
and fructosans are the most important carbohydrate
classes which make up the energy reserves, and
taken together they are the TNC. Classical TNC
analytical methods often use an enzymatic digestion
followed by subsequent HPLC analysis as described
by Dionix (1989) and White and Widmer (1990).
The sum quantity of the extractive and cellulose
fractions generated by using the Aber et al. (1990)
extraction scheme (see above) will likely be very
close to TNC as measured by an enzymatic digestion
technique. We will calibrate the relationship be-
tween the two different methods of obtaining TNC
through a comparative analysis of matched Douglas
fir tissue samples, but routinely apply the Aber et al.
Page 58 Corvailis Environmental Research Laboratory
-------
Effects of COj and CUmate Change on Forts! Trees
(1990) fractionation method for TNC determina-
tion.
Inorganic Nutrient Analysis: Macronutrients (Ca2%
Mg2*, K\ m;, NOj', HjPO;, HPO*, S042) and
micionutrients (Fe3*, Mn2*, Zn2+, Cu2*, Q" X and Na*
will be analyzed using a Dionix 4000i ion chromato-
grapb. Dry, ground material will be acid digested to
destroy organic materials, as described by Allen
(1974). The wet ashing technique has the advantage
that there are no losses due to volatilization and the
procedure is rapid (-2 hours). A perchloric add
hood is available for this purpose. Nutrients will be
quantified and expressed in terms of concentration
(e.g., g nutrient/g dry needle). Nutrients quantified
in samples, collected at the beginning and end of the
experiment, will be expressed on the basis of both
concentration and content (e.g., g nutrient in canopy
needles). The ionic balance in plant tissue (calcu-
lated as the [mole X charge] sum of inorganic cations
and [mole X charge] sum of the inorganic anions)
will be evaluated across treatments. Changes in the
source of inorganic nitrogen among treatments (NH/
vs. N03") may be indicated through changes in the
ionic balance of the plant tissue, as well as through
rhizosphere pH and composition changes.
Plant Nutrient Balance: The relationships among
plant nutrient concentration, plant nutrient content,
and physiological response will be evaluated using
two different methods. This first method is the
simple ratio method, described by Ingestad (1979).
The evaluation of plant nutrient balance using the
ratio of nutrient concentrations is preferable because
nutrient ratios are less affected by growth dilution
and aging processes then nutrient concentrations.
TTirough controlled experimentation, Ingestad (1979)
determined the optimum nutrient (N, P, Kป Ca, Mg)
ratios of young oonifer seedlings relative to N. The
scaling of the ratios is normalized by setting the N to
N ratio equal to 100. The published ratios for 7
different conifer seedlings, including Douglas fir,
are all relatively similar (Ingestad, 1979). Ratios
higher than the experimentally derived values indi-
cate a nutrient excess, lower values indicate a nutrient
deficiency.
A second method used for plant nutrient balance
evaluation is the Diagnosis and Recommendation
Integrated System (DRIS). This system involves
multiple two-way comparisons of plant nutrient
ratios with standard norms (Walworth and Sumner,
1987). This system has the advantage of not being
keyed to a single element, but it requires a survey
approach to derive a relatively large data base of
nutrient ratios from high- and low-yielding sub-
populations. Mean values of the nutrient ratios from
thehigh-yieldingpopulations are designated as norms
and subsequently classified by their comparative
ability to discriminate between the high- and low-
yield populations. In our application we will use the
nutrient conditions in the control chambers (ambient
treatment) to develop one set of norms, and samples
collected from field sites to develop a second set of
norms. The nutrient ratios measured in tissue samples
from experimental treatments will then be used with
the norms to calculate relative nutrient imbalances.
These data will be compared with physiological
performance factors (photosynthetic capacitance,
maintenance respiration,biomass accumulation, etc)
measured in other tasks to assess their significance.
Soils: Soil cores will be collected bi-annually, and
separated by horizon (A, B-l, B-2, Q (Task 6), from
the terracosms and field sites. Samples will be
weighed, dried at 35 ฎC, reweighed, and then ground
to an even texture using a rotary ball mill. Afterbeing
passed through a 40-mesh screen, samples will be
analyzed directly usingacombustion-basedelemental
analyzer, and subsequent to digestion analyzed for
macronutrients using ion chromatography or other
analytical methods.
Elemental Analysis of C/N/S: Total elemental C,
N, and Swill be determined with a combustion based
elemental analyzer on ground and homogenized soil
samples. In addition, samples will be chemically
extracted (described above in the plant analysis
section) into three fractions (Extractives, Cellulose,
and Lignin) and the C and N composition of each
fraction will also be determined (Aber et al., 1990).
These C and N composition will be expressed on an
ash-free basis.
Pag* 59 CorvaUis Environmental Research Laboratory
-------
Effects of CO j and Climate Chang* on Forest Trees
Nutrient Analysis: At the beginning of the experi-
ment, and on an annual basis after that, the status of
exchangeable cations (Ca2+, Mg3*, K*, Na% Mi*%
extractable anions (N03% SOf, PO/-, CT), extract-
able microDutrieots (Fe, Mn, Cu), and pH will be
measured on terracosm soil samples passing a 2 mm
screen. To assess changes in soil pools of various
elements, a total elemental analysis (Ca, Mg, K, Na,
N, S, Fe, Mn, Cu) will follow a complete soil sample
digestion on samples collected at the beginning and
end of the experiment. Soil samples from the field
sites will only be analyzed at the beginning aid end
of those experiments. Soil samples will be collected
twice a year in the terracosms but will be analyzed
only once. Hie soil samples that are collected, but
not immediately analyzed, will be stored in field-
moist condition in plastic bags at 4ฐC (Bartlett and
James, 1980).
Soil Solutions: Soil solution samples will be col-
lected from six tension lysimeters in each terracosm
on a monthly basis. Lysimeter placement is detailed
in Figure 5-5 and sampling frequency relative to
other sampling events and plant phenology is de-
5 to 8 cm
10 cm
20 cm
Lysimeters TOR Probes Lysimeters
litter Layer
A Horizon
B Horizon
C - Horizon
Drainage
Gravel
Neutron Probe
Access Port
M M M
1 Meter
-2 Metere-
Figure 5-5. Location ofTDR probes, neutron probe access tube and
tension soil lysimeters.
Page 60 Corvallis Environmental Research Laboratory
-------
Effects of CO j and Climate Change on Forest Tries
picted in Figure 5-2. The samples will be collected
by drawing a vacuum on the lysimeters and collect-
ing the soil solution that moves into the lysimeters.
Soil solutions will be passed through a 0.45 pirn filter
prior to analysis to remove particulate/biological
material that may have passed through the lysimeter.
Elemental Analysis of C/N/S: The total dissolved
organic C, and elemental N and S will be directly
determined on the soil solution filtrate after acidifi-
cation with HQ to eliminate dissolved C02. This
will be accomplished by depositing approximately
30 |ฑLof filtrate onto a solid adsorbent (chromosorb),
followed by analysis using standard combustion
methods on a Carlo Eurba EA1108 Elemental Ana-
lyzer.
Nutrient Analysis: All soil water filtrates will be
analyzed for pH, macronutrients (Ca2*, Mg3*, K%
NH/, NO,, HjPO/, HPO/", SO,2-) and micronutri-
ents (Fe3*, Mn2+, Zn2+, Cu2+, G"), and Na+ using ion
chromatography. Chromatographic methods will
be identical to those employed for the analysis of
fractionated plant, litter and soil samples.
* Analysis of C/N and lignin/N ratios in plant
tissues (needles and roots), and total C and N
in soil and net C and N storage.
Model Inputs
Task 3 will provide inputs for the TREGRO model
as indicated in Table 5-3.
Table 5-3. Measurements of nutrient con-
centrations andC/N ratiosforusein TREGRO.
Plant Tissue Nutrient Concentrations
N, P, K, S, Ca, and Mg (g elements/
g plant carbon)
Soil Nutrient Concentrations
N, P, K, S, Ca, and Mg (g elements/
g soil)
Soil Solution Nutrient Concentrations
N, P, K, S, Ca, and Mg (g elements/
mL soil water)
C/N ratios in plant tissue and plant litter
Task Outputs
Characterization of complete soil macro-
and micronutrient composition at the begin-
ning and end of the experiment both in the
individual terracosms and at the field sites.
Evaluation of changes in plant nutrient con-
centration, composition, and relative nutrient
ratios using the DRIS method to assess
difference between experimental treatments.
Characterization of changes in plant avail-
able soil nutrient levels over the period of the
teiTacosm study.
Evaluation of the dynamic relationships be-
tween plant and soil nutrient pools as effected
by elevated C02 and climate change.
Page 61 CorvaUts Environmental Research Laboratory
-------
Effects of CO j and CUmate Change on Forest Trees
TASK 4: SYSTEM WATER
Introduction
To evaluate the physiological response of plants to
elevated C02 and increased temperature, an under-
standing of the functional relationship between plant
and soil water status, plant water demands, and
photosynthetic rates is essential. Decreased plant
water availability may be one of the principal effects
of climate change. This decrease will be driven by
warmer temperatures, i.e., increased evaporative
demand, or changes in precipitation patterns or
amounts. In the short-term, decreased plant water
availability will very likely limit photosynthesis.
Over the long-term, it may cause a redistribution of
vegetation species across landscapes (Leverenz and
Lev, 1987).
There are two basic science questions addressed by
this task. This first question is:
WiU elevated C02 and climate change affect
plant water balance?
Water is extracted from soils by roots. To maintain
the continuous supply of water to the plant there must
also be continuity of water in soil pores and capillar-
ies. Between precipitation events plants must rely
upon soil water storage to meet their water needs.
Plant water stress caused by decreased soil water
potential can be minimized not only through increas-
ing the resistances to leaf-air water transfer, but also
by reducing the resistance to soil-root water transfer.
One adaptive measure observed in drought stressed
plants is that root systems often enlarge during
extended dry periods to insure continuous water
supply. Increased partitioning of photosynthate to
belowground structures has been observed in some
C02 enrichment experiments, although the mecha-
nism for this partitioning is not clear. If increased
canopy C02 does lead to an increase in fine root
production and/or increased incidence of mycor-
rhizal colonization, there may be benefits not only to
mineral resource acquisition but also through pro-
viding greater drought resistance.
The second and related question posed is:
Will elevated CO2 and climate change sig-
nificantly change the driving forces and
resistances that determine water flow in the
soil-plant-atmosphere continuum?
Water movement through the soil-plant-atmosphere
continuum is a series of interrelated, interdependent
processes which combine to determine water flow in
plants. These driving forcesand resistances are often
described as analogous to electrical flow in a con-
duction system. Overall plant water potential is the
sim of the osmotic, pressure, matrix, and gravita-
tional potentials (Kramer, 1983). The resistances to
water flow are related to stomatal aperture, cuticle
thickness, xylem transport, and root-soil interac-
tions. Leaves transpire water in response to die
evaporative demand of the air. Ordinarily the pri-
mary resistances that regulate water movement in
plants are the cuticular and stomatal resistances at the
leaf-air interface. In times of water stress, plants can
reduce leaf water loss (to avoid desiccation and
injury) by increasing stomatal resistance (reducing
stomatal aperture). But in closing their stomata,
plants significantly reduce photosynthetic C assimi-
lation.
With global warming, potential evapotranspiration
(PET), i.e., evaporative demand, will increase and
subsequently increase the overall potential driving
plant water movement. Yet, one of the short-term
responses of plants exposed to elevated C02 is for
photosynthetic rates to increase while stomatal con-
ductance and transpiration rates decrease (see Figure
1.1), If elevated C02 levels cause a net decrease in
stomatal conductance, and thus transpiration rates,
plants may be more adapted to periods of low soil
moisture.
Objectives
The objectives of this task are:
To measure the effects of elevated C02 and
climate change on the relationship between
plant and soil water potential.
Page 62
Corvaiiis Environmental Research Laboratory
-------
Effects o/COj and CUmat* Change on Forest Trees
To measure the effects of elevated C02 and
climate change on overall system water
balance.
To measure and monitor volumetric water
content in each soil horizon. These data will
be used to regulate irrigation schedules and
to calculate system water budgets.
Approach
Plant Water Status: A variety of techniques are
available for measurement of plant water status
(Turner 1981; Koide et al., 1991). Plant water
potential will be measured at the plant needle level
four times during the year using destructive sam-
pling and thermocouple psychrometry. Efforts will
be made early on in the experiment to develop and
apply a method of continuous and nondestructive
measurement of water status on a whole plant basis.
This technique will be based on the application of the
CERES Device (Task 2).
Leaf Psvchrometrv: Thermocouple psychrometry
will be used for the destructive measurements of
needle water potential and osmotic status (Kramer
1983; Koide et al., 1991; Wescor Inc., Logan Utah).
The technique is based on measuring changes in
water vapor concentration in small equilibration
chambers enclosing needle samples. After the atmo-
sphere surrounding the tissue has equilibrated with
the needle tissue (chamber is held at constant tem-
perature), the dew point depression is measured in
the chamber. This depression is directly propor-
tional to the water potential of the needle tissue.
Thermocouple psychrometry is applied in an similar
manner to determine the needle osmotic status,
except in this case the psychrometer chamber is first
emersed into liquid nitrogen to rupture cell walls,
then thawed and allowed to equilibrate. The pre-
dawn water potential and osmotic potential
measurements will occur four times during the year,
coinciding with the two needle sampling/soil coring
events, and at two periods during the summer when
soil moisture is the lowest (see Figure 5-2). Both, a
predawn water potential and a midday measurement
will be made during drought stress periods.
CERES Device: Continuous stem diameter mea-
surement will be developed as a method to provide
a nondestructive measure of whole plant water defi-
cit Reported observations indicate that the rapid
radial expansion and contraction of plant stems is a
quantifiable measure of the cellular hydration and
dehydration that occurs in response to changes in
plant water potential (Kozlowski, 1967; Homes and
Shim, 1968). A number of different devices have
been designed to accurately measure stem diameter
changes in plants ranging in size from small plants to
full size trees (Schutte and Burger, 1981). The
CERES device is an example of a highly sensitive
stem diameter gauge. The gauge, developed by
Battelle-Pacific Northwest Laboratories, resembles
a C-clamp, with a strain gauge and thermocouple
attached in the middle of the clamp structure. The
gauge is sensitive to diameter changes as small as
300 jim (Beedlow et al., 1985).
We propose to attach the CERES device to test trees
to provide continuous measures of stem diameter,
and to couple these measurements with frequent
thermocouple psychrometry or Scholander pressure
bomb destructive measures of plant water status.
These data will be combined to develop a math-
ematical relationship between stem diameter
dynamics and plant water status. After this relation-
ship has been established, we will move to apply the
technique to the terracosms. Two CERES devices
will be used in each terracosm, and will be attached
to the same seedlings as the stem sap flow gauges
(see Task 1). If successful, the data from these two
types of sensors will provide conductance/transpira-
tion rates and plant water status on both a continuous
and whole plant basis.
Soil Water Status: Assessing the role of soil water
in the response of forest trees and soil processes to
climate change requires that the quantity of soil
water be known. Because regular collection and
drying of soil samples to determine soil water is not
practical due to the number of samples and time
required to process them, we selected two non-
destructive technologies to provide measures of soil
water. Hie first is relatively new technology called
time-domain reflectometry (TDR), and the second is
Page 63 Corvallis Environmental Research Laboratory
-------
Effects of CO j and Climate Change on Forest Trees
the neutron moisture probe. A more detailed de-
scription of these techniques and the specific
equipment involved is provided in the Appendix.
TDR: As the soil was placed in the terracosms, five
TDR probes were installed. Four probes were placed
horizontally as shown in Figure 5-5. One in the
center of the A-horizon, one each in the center of the
upper and lower halves of the B-horizon, and one in
thecenteroftheC-horizon. A fifth probe was placed
with a vertical orientation to measure soil water in the
A- and upper B-horizons where fine roots are likely
to proliferate and for monitoring soil water for
irrigation scheduling.
The terracosm TDR system is designed so that
multiple (up to hourly) daily measures of soil water
content can be made at each probe. Daily volumetric
soil water values will be used to calculate the total
soil water content of each soil horizon. These data
will be monitored through time and used to make
terra cosm water balance calculations and to deter-
mine the amount of water to be added to each
chamber to maintain its respective water treatment
(see Experimental Design Section in Chapter 4).
Neutron Probe: The four horizontal miniihizotron
tubes will also serve as access tubes for the neutron
probe. This will allow soil moisture measurements
to be made at four depths in the terracosms. A fifth
tube will be installed vertically so that soil moisture
measurements can be made at any depth with the
neutron probe. The Deutron probe measurements
require substantial operator time, and access to the
vertical tube requires that the front of the chamber be
opened. Therefore, soil moisture measurements will
be made every four weeks with the neutron probe
functioning only as a check on the TDR system. The
neutron probe will also be used if soil temperatures
become so low that ice is formed, since the TDR
method cannot detect water in the solid form (Baker
and Allmaras, 1990).
Task Outputs
Characterization of the independent and in-
teractive effects of elevated C02 and climate
change on plant water balance and soil water
status.
Characterization of the relationship between
short-term seedling stem diameter changes
and plant and soil water status.
Evaluation of the potential for the continu-
ous nondestructive measurement of plant
water status and plant water flux through the
combined use of the CERES device and
stem flow gauges.
Daily characterization of volumetric soil
water content by soil horizon and rooting
volume to determine seasonal irrigation
scheduling.
Model Inputs
Task 4 will provide inputs for the TREGRO
model as indicated in Table 5-4.
Table 5-4. Measurements of volumetric soil
water content and waterflux by soil horizon for
input in the TREGRO model
Volumetric Soil Water Content in A-, B-, and C-
Horizon (L)
Water Flux Between Soil Horizons (L/mJ/s) Atmo-
sphere to A, A to B, B to C, C to Drain
Root Water Uptake (cm'/s)
Irrigation Rate, Time Interval, Date and Time of
Occurrence
Page 64
CorvaUis Environmental Research Laboratory
-------
Effects of CO j and Climate Change on Forest Trees
TASK 5: UTTER LAYER
Introduction
He uppermost layer of forested soils consists of
plant litter in various stages of decomposition. This
layer, known as the litter layer, is an important
component of forested ecosystems serving as a
reservoir of carbon and nutrients. It also functions to
store moisture and to insulate underlying mineral
soil horizons from rapid changes in air temperature.
The forest floor is the site of high microbial and
faunal activity. The extent of the litter layer depends
on the rate of litter addition and decomposition.
Carbon and nutrients are released from plant litter
through decomposition.
The first question to be addressed by this task is:
Will the rate of litter decomposition change
in response to elevated C02 and climate
change?
Decomposition is controlled largely by environ-
mental factors, i.e., temperature and moisture. The
quality and physical size of the litter are also factors
in litter decomposition. Altered climatic conditions
(elevated temperature and changes in precipitation
patterns) will likely affect the rate of decomposition.
Elevated C02 may only have a slight direct affect on
decomposition but may have a larger indirect affect
since it may increase primary productivity, poten-
tially affecting litter inputs, and altering litter quality.
The litter layer is a critical component of the nutrient
cycle of forested systems. Changes in litter layer
decomposition caused by elevated C02 and climate
change may affect tree productivity by affecting the
nutrient cycle.
The second question addressed by this task is there-
fore:
Will nutrient cycling through the litter layer
change in response to elevated C02 and
climate change?
Objectives
The specific objectives of this experimental task are:
To measure the rate of litter decomposition
with elevated C02 and climate change.
To determine how elevated C02 and climate
change affect nutrient cycling in the forest
floor litter layer.
To measure changes in litter quality (C/N
ratio, "lignin" [see definition below]/N ra-
tio, etc.) throughout the terracosm study.
a To determine the effect of elevated C02 and
climatic change on the net storage of carbon
in the litter layer.
Approach
This task focuses on the long-term effects of elevated
C02 and climatic change on decomposition and
nutrient cycling in the litter layer in the terracosms.
Weight loss and changes in mineral nutrient and
organic chemistry of the litter layer will be used as
integrative measures of litter processing and carbon
storage. Rates of litter layer decomposition and
changes in chemistry will be monitored using litter
contained in inert mesh bags. Needle packs will also
be used to provide another measure of decomposi-
tion.
The mineral soil in each of the terracosms will be
covered with a litter layer at the initiation of the
terracosm study. The chemistry of the litter layer
will be characterized to determine the amount of
nutrients and caibon added. Periodically, litter will
be added to replace litter that has decomposed. Abi-
annual assessment of the litter layer condition will be
made to determine if litter additions are required in
the ambient C02 and ambient temperature terra-
cosms (see Section 4 for details). If litter is needed,
it will be added equally to all of the terracosms. Fresh
litter for these additions will be obtained from the
terracosm soil collection site.
Pagt6S
Corvallis Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
As described in the Experimental Design section
and Task 2 we will be establishing supporting stud-
ies at three field sites in the Oregon Cascade
Mountains. At these sites Douglas fir seedlings,
from the same stock planted in the terracosms, will
be planted at the same density as those in the
terracosms. The purpose of the field sites is to
provide a mechanism for comparing the perfor-
mance of seedlings in the controlled environment of
the terracosms to seedlings in a natural setting.
These field sites will also provide information that
may be helpful for extrapolating the findings from
the terracosms to trees under natural conditions.
Measurements of litter decomposition, using litter
bags and needle packs, paralleling those in the
terracosms, will be made at the field sites. However,
only a limited set of environmental parameters will
be measured at the field sites. The litter bags, needle
packs, and litter layer components of the terracosm
study will also be replicated at each of the field sites.
litter layer additions: Initially, the litter layer in
the terracosms will consist of two layers, an Oi layer
(uppermost layer of slightly decomposed forest lit-
ter) and the Oa layer (highly decomposed litter layer
between the Oi and the upper mineral soil horizon).
At the initiation of the terracosm study the Oi horizon
will be approximately 4 cm thick and the Oa 2 cm.
As the experiment proceeds we anticipate some loss
of these layers through decomposition. Twice a
year, at the time of soil sampling (Figure 5-2), we
will assess the status of the litter layer in the three
ambient C02 and ambient temperature terracosms.
If the mean thickness of the litter layer in these
chambers has decomposed to less than 3 cm, based
on an initial depth of 6 cm, we will determine the
amount of litter required to bring the ambient cham-
bers back to the full compliment of 6 cm of litter and
add an equivalent amount of litter to all terracosms
and experimental plots. The litter addition will
consist of fresh new litter, characterized by recogniz-
able detrital material (Oi horizon). By making such
additions in the terracosms across treatments we will
maintain a consistent input of exogenous nutrients
and caitoon. Subsamples of the litter being added
will be collected and chemically characterized.
Decomposition: Litter decomposition and changes
in litter chemistry will be estimated using litter bags
(Vogt et al., 1983) and needle packs (the needle
version of litterpacks described in Triska and Sedell
(1976)). Each of these techniques will provide an
estimate of decomposition. The litter bag technique
may lead to an underestimate of decomposition
since the bag limits grazing by soil fauna. On the
other hand, the needle pack may lead to an overesti-
mate of decomposition since grazers may clip off
pieces of needles that may not be decomposed but
will not be included when needle packs are retrieved
and weighed.
Utter layer mass loss calculations will be based on
air-dried weights. When collected, litter bags and
needle packs will be air-dried and weighed; air-
drying effectively stops further decomposition or
degradation of the sample. A subsample of the litter
bag contents will be oven-dried to determine the
water content of the air-dried samples. New litter
bags with nondecomposed standard needles (col-
lected in 1992) will replace the harvested litter bags.
All replacement litter bags will be harvested at the
end of the experiment.
Litter decomposition studies will be conducted in
both the terracosms and at three field plots. In
addition to the weight loss measurements, litter
chemistry will also be assessed as samples are col-
lected throughout the terracosm study. These
analyses are described below.
Litter bags: Twelve nylon fine mesh (approximately
25 mm2,1.6 x 1.6 mm holes) litter bags (10x10 cm)
will be placed on top of the old litter (Oa horizon) and
covered with the new litter (Oi horizon). The needle
Jitter used in the litter bags was collected in the old-
growth forest adjacent to the terracosm soil collection
site in the Oregon Cascade Mountains. A sufficient
amount of needle litter for the first terracosm study
was collected in the fall of 1992.
Two grams of needle litter (air-dried weight) will be
placed in each litter bag and the overall weight of the
litter bag and contents determined. The bags will be
located between trees within each of the three rows
Page 66
Corvallis Environmental Research Laboratory
-------
Effects ofCOj and Climate Change on Form Trees
(Figure 5-6). Two litter bap will be removed from
each terracosm twice a year (see Figure 5-2) and
analyzed. As litter bap are removed they will be
replaced by new ones. At the end of the experiment
all litter bags will be removed and analyzed. All litter
bap will be made prior to the initiation of the
terracosm study. Replacement litter bap will be
kept frozen until needed.
"needle packs" (akin to leaf packs, Triska and Sedell,
1976). Needle packs will likely produce overesti-
mates of decomposition because of grazing by soil
fauna. Non-decomposed fragments of grazed
needles, which are no longer attached to the
monofilament line, will remain in the terracosm
when the packs are harvested. Therefore, weight
loss estimates can be exaggerated.
Needle packs; We recognize that rates of needle
decomposition, determined by using litter bags, may
underestimate decomposition. TTius, we will bracket
our estimates of needle decomposition by using
StoScm
idem
60 cm
m,
Otter
(1 mm11
15x15
Minirhizotron Tubes
5 cm dla. x 100 cm L)
A needle pack will consist of 15 to 25 air-dried
needles threaded on a monofilament line. Eighteen
needle packs will be placed in each of the ambient
C02 chambers. Weighed needle packs will be
placed adjacent to the litter
bap. Needle packs will be
collected and replaced at the
same frequency as the litter
bags. Collected needle packs
will be air-dried and
weighed. Needle pack
weight loss will be compared
with weight loss of needles
in the litter bap. All needle
packs will be made prior to
the initiation of the terracosm
study. Replacement needle
packs will be kept frozen
until needed.
liner Layer
A Horizon
B Horizon
C Horizon
Drainage
Gravel
Headspace
Chambers
(10 cm dia.)
Cores to Depth
(4 cat dia. x 95 em depth)
Soil Fauna Sample
Collection Area
5k "lib
# #
4:4
1 Meter
-2Metera-
Figure 5~6. Cross section and top view of soil chamber giving details of
plant spacing, soil horizons, and sample locations. Dotted line represents
the separation of the instrumented and noninstnimentedportions of the soil
fysimeter.
Decomposition substrate
chemistry: Needle litter, at
the initiationofthe terracosm
study and from the litter
bags, will be collected
throughout the experiment
and at the end of the experi-
ment These litter samples
will be analyzed for total C,
N, S, P, K, Ca, Mg, and Na
using the methods described
in Task 3. To characterize
the changes in litter organic
chemistry, subsamples will
be fractionated into "cellu-
lose", "extractives", and
"lignin" using the methods
described by Aber et al.
Page 67 Corvallh Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
(1990); the C, N and S contents of these fractions will
be determined using an elemental analyzer (de-
scribed in Task 3). The fractionated "lignin" is the
residue following removal of "cellulose" and "ex-
tractives" and is not in the strict chemical sense.
Ratios of C to N, "lignin" to N, and "lignin" divided
by "lignin" plus cellulose (the lignocellulose in-
dexLCI), as described by Melillo et al. (1989),
will provide indices of litter quality.
Litter decomposition at the field sites: Eighteen litter
bags and needle packs will be used at each of the
three field sites where the Douglas fir seedlings are
planted. The placement and sampling will mimic
that described above for the terracosms. Litter layer
additions will also mimic those in the terracosms.
Litter production: Because the first terracosm study
is scheduled to last two to three years, a measurable
needle fall event will be minimal because of the age
of the needles. If, however, senescent needles are
observed on the trees, steps will be taken to collect
these needles when they fall to quantify the extent of
this litter input
Task Outputs
Characterization of litter layer decomposi-
tion rates, and carbon and nutrient cycling of
Douglas fir litter under elevated C02 and
climate change.
Characterization of changes in litter quality
while undergoing decomposition under el-
evated C02 and climate change.
Characterization of net storage of carbon in
the litter layer under elevated C02 and cli-
mate change.
Model Inputs
Task 5 will provide inputs for the TREGRO model as indicated in Table S-S.
Table 5-5. Measurements of seedling characteristics and selectedprocesses for input in the TREGRO model
Values will be obtained either from our experiments or from the literature.
Initial amounts' of "cellulose"2, "extractives", "lignin", and
humus in Soil Layers 1 (upper portion of litter layer) and 2
(lower portion of litter layer).
Initial C/N ratios' (g C/g N) of "cellulose", "extractives",
"lignin", and humus in Soil Layers 1 (upper portion of litter
layer) and 2 (lower portion of litter layer).
Transformation rates' (fraction/month) for conversion in
the litter layer of 1) "cellulose" to "extractives", 2) "extrac-
tives" to "lignin", 3) humus to "extractives", 4) "lignin " to
"extractives", and 5) "lignin" to humus.
Transformation efficiencies' (fraction of material trans-
ferred and not respired) for conversion in the litter layer
of 1) "cellulose" to "extractives", 2) "extractives" to
"lignin", 3) humus to "extractives", 4) "lignin" to "ex-
tractives", and 5) "lignin" to humus.
LCI shielding parameter1 for "cellulose" (unitless).
LCI shielding parameter3 for "extractives" (unitless).
1 Measured in task
1 "cellulose", "extractives", "lignin" and humus are operationally-defined organic matter fractions of Aber et al. (1990)
1 Obtained from literature
Page 68 CorvaUis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
TASK 6: ROOT GROWTH, PHENOLOGY,
AND CARBON PARTITIONING
Introduction
A likely response of trees to elevated C02 and
climatic change will be increased growth. Concomi-
tant with this growth will be increased water and
nutrient demands. To meet these demands, trees
may produce a modified root system, e.g., a larger
(increased biomass) root system, or a root system
with a different architecture (iproportion of fine roots,
mycorrhizae, etc.). Therefore, a major effect of
increased C03 and climatic change may be expected
in partitioning of C between the above- and
belowground components of forested ecosystems;
in particular, changes in root development (mycor-
rhizal and nonmycorrhizal), root turnover and
biochemical partitioning of C Carbon acquired by
roots may eventually be released to symbionts, the
rhizosphere, and the bulk soil microbial community
thus altering nutrient cycling and influencing the
production of greenhouse gases. The uptake and
allocation of N will also be an important factor in the
response of root systems to elevated C02 and cli-
matic change.
The purpose of this task is toevaluate the belowground
response of trees (roots and mycorrhizae) to elevated
C02 and climate change. Several scientific ques-
tions guide this task. The first question explores root
growth:
Will root growth change in response to
elevated C02 and climate change?
Previous research suggests that there may be dra-
matic effects of elevated C02on roots (Johnson etal.,
1991; Rogers et a!., 1992). Since these were only
short-term experiments, long-term C02 exposures,
along with temperature and moisture treatments,
will provide a more complete picture of the
belowground response to climatic change. In the
terracosm study, root growth, measured as numbers
of roots, total root biomass, and changes in the spatial
distribution of roots throughout the soil will be
evaluated.
The second question deals with the allocation of C to
various root system components and how this allo-
cation changes through time:
Will elevatedC02andclimatechangeaffect
the allometric relationships among coarse
wots, fine wots, and mycorrhizae?
The production, development, and mortality of fine
and coarse roots, and mycorrhizae, and rates of root
turnover may be altered due to elevated C02 and
climate change. Hie relative proportion of fine roots
to coarse roots may increase as plants attempt to
acquire additional water and nutrients. A shift to
more mycorrhizal roots could be indicative of an
increased dependence on this symbiotic association
for resource acquisition. This association exists,
however, with a C cost to the host and it will be a
factor in whole plant C economy. A decrease in the
proportion of mycorrhizal roots could signal an
increased reliance on the host's uptake mechanisms.
Finally, the life expectancy of roots may change and
root turnover could be much faster due to elevated
temperatures.
The third question concerns the timing of root growth:
Will root phenology be altered by elevated
CO2 and climate change?
Characterizing changes in root phenology will pro-
vide an important insight into the response of plants
to changes in atmospheric and soil conditions result-
ing from elevated C02 and climate change. For
example, will changes in the timing of the produc-
tion of roots predispose the plant to greater or lesser
success in surviving different soil drying regimes
under climate change?
The fourth question concerns the partitioning of
root C:
Will the biochemical partitioning of root C
and N be affected by elevated C02 and
climate change?
Page 69 Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Drees
Caibon in roots exists in two general classes of
compounds: structural compounds (e.g., cellulose)
and nonstructural compounds (e.g., sugars). The
partitioning of root C between these two groups is
indicative of the interaction of a plant with its envi-
ronment and associated stresses. One potential
response to elevated C02 may be increased use of C
to build root systems (structural Q for increasing
resource uptake. Another potential response is in-
creased production of nonstructural C to support
symbionts.
Objectives
The following objectives have been developed to
address the science questions as they relate to the
belowground portion of the Douglas fir tree seed-
lings:
To quantify root growth with numbers of
roots produced; their distribution and turn-
over, and the total weight of the standing
stock of roots under elevated C02 and cli-
mate change.
To quantify dynamics of root production,
development, and mortality under elevated
C02 and climate change, and determine the
effects on root allometries, i.e., distribution
of biomass among coarse roots,
nonmycorrhizal fine roots, and mycorrhizae.
To characterize effects of elevated C02 and
climate change on root phenology.
To quantify biochemical partitioning of C
between structural and nonstructural com-
pounds in the various root fractions.
Approach
Destructive sampling must be limited in the terra-
cosms to avoid destruction of the biological and
physical integrity of the belowground component
Unfortunately, even in the well-mixed soil that we
are using, spatial variability may be large, requiring
large numbers of samples. We must achieve a
balance between these needs. We recognize that the
infrequent destructive sampling we propose may be
insufficient to characterize root biomass with a high
degree of accuracy. Therefore, we will assess roots
by two methods, coring (cores-to-depth) and using
minirhizotrons.
Cores-to-depth: One soil core (5 cm i.d. x 95 cm)
will be collected twice a year (Figure 5-2). A larger
diameter core was selected because smaller diameter
corers performed poorly in the terracosm soil and the
holes left by the larger corer will be easier to refill
with soil and to track over time. Root production will
be assessed by separating the cores into 10-cm
segments by depth. Roots/mycorrhizae will be
separated from the soil by hand sorting. The sepa-
rated soil and root litter will be used for additional
analyses in Task 3. Separation oflive and dead roots
and mycorrhizae will be done using stains, e.g.,
triphenyltetrazolium chloride (TTQ (Knievel, 1973).
Samples will be sorted into four fractions: live coarse
roots (> 2 mm), live fine roots (< 2 mm) and
mycorrhizae, dead coarse roots, and dead fine roots
and mycorrhizae. All root fractions will be lyo-
philized and weighed. Hie dry weight data and
samples will also be used in Task 7. Root and
mycorrhizae samples will be analyzed for C (total
and biochemical partitioning), nutrients (N, S, P, K,
Ca, Mg, and Na). Total C and N will be measured in
the root "cellulose", "extractives", and "lignin" frac-
tions using methods described in Task 3.
Minirhizotrons: Recent developments in the use of
minirhizotrons, coupled with miniature video cam-
eras, fiber-optic root periscopes or cameras, provide
a nondestructive measure of root production and
dynamics (Brown and Upchurch, 1987). Measure-
ments can be made at greater frequency than that
possible with destructive sampling. As this is a
nondestructive method, we can observe the same
roots over time (Hendrick and Pregitzer, 1992).
As the soil was being placed in each of the soil
lysimeters, four minirhizotron tubes (round, clear
plastic tubes, 5 cm i.d.) were installed. They were
placed horizontally as shown in Figures 4.9 and 5.7.
One tube was placed with the upper tube surface in
the center of the A-horizon, one tube each in the
center of the upper and lower halves of the B-
Page 70 Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
<0 cm
Litter Layer
A Horizon
B Horizon
20 cn
10 ca
IPRPS
it* htj+slfhi. if-
C Horizon
Drainage Gravel
//
Horizontal Mlnlrtilzotroo Tube*
1 Meter
-2 Meters-
Figure 5-7. Location of minirhizotron access tubes.
horizon, and one in the center of the C-horizon. A
horizontal orientation forminirhizotrons is preferred
to a vertical one because roots encountering a verti-
cal surface tend to grow along that surface. Whereas,
roots encountering a round horizontal tube (much
like a rock) tend to grow around the tube (Upchurch
et al., 1988), giving better root-minirhizotron con-
tact but not altering the rooting pattern or root system
behavior. Because roots will most likely come into
contact with the upper surface of the minirhizotrons,
root images will be collected from this surface. A
fifth tube was installed vertically after the soil lysim-
eters were filled with soil. This tube primarily
provides access for a neutron moisture meter (Task
Page 71 Corvatlis Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
4) but occasionally will also be used to observe the
vertical stratification of roots.
Video images in the minirhizotrons will be recorded
every four weeks during the first year of the TERA
experiment The sufficiency of sampling every four
weeks will be evaluated after the first year. If the
frequency needs to be altered, it will be changed in
the second and subsequent years.
A number of root parameters will be measured using
the minirhizotron-video camera system. Initially,
these will include: root count, root length, root
diameter, root color, presence of mycorrhizae, root
branching, root tracking (following individual root
development over time). Initially, these data will be
collected with the assistance of root imaging soft-
ware such as ROOTS, described by Hendrick and
Pregitzer (1992). This software provides a conve-
nient way to collect and record data as video images
but requires a significant amount of operator time.
We may move to a completely computer-automated
image processing system, as described by Smucker
et al. (1987), if such a system becomes available.
Model Inputs
Task 6 will provide inputs for the TREGRO model
as indicated in Table 5-6.
Table 5-6. Measurements of root parameters for input in the TREGRO model
Total initial, intermediate, and final coarse and fine
root biomass in each soil layer1 (g C).
Fine and coarse root growth rates1 (fraction of com-
partment per day)
Root radius1 (cm)
Fine and coarse root TNC1 (g Q
Specific root length1 (m/g C)
Total woody roots1 (g Q
Root absorbing power for various nutrients2 (cm/s)
Coarse root starch capacity2 (percent)
Total C and N in the root "cellulose", "extractives",
and "lignin" fractions in each soil layer (horizon)1-1
(gCorgN)
Fine and coarse root respiration rates2 (g C/day)
Fine and coarse root respiration rate doubling tem-
perature2 (ฐC)
1 Measured in this task
2 Obtained from the literature
' "Cellulose", "extractive", and "lignin" are operationally-defined organic matter fractions of Aber et al. (1990)
Page 73 Corvallis Environmental Research Laboratory
Task Outputs
Characterization of the effects of elevated
C02 and climate change on root growth.
Characterization of changes in root phenol-
ogy caused by elevated C02 and climate
change.
Characterization of changes in the distribu-
tion of C, nutrients, "cellulose", "extractives",
and "lignin" in the belowground standing
stocks of coarse roots, nonmycorrhizal fine
roots and mycorrhizae.
Characterizationofchangesinthebiochemi-
cal partitioning of C between structural and
nonstructural compounds in the various root
fractions.
-------
Efftcti of COj and Climate Chang* on Forest Trees
TASK 7: SOIL BIOLOGY
Introduction
Soil biological processes are critical for nutrient
cycling and supply in forested systems. Decompo-
sition is primarily a biologically-mediated process
that releases nutrients and carbon from detritus.
Symbioses between tree roots and some fungi and
bacteria can enhance the nutrient absorption poten-
tial of the tree. These symbionts are common in
forested systems. Climate change may have direct
effects upon soil biology through changes in tem-
perature and moisture availability, whereas the effect
of elevated C02 is likely to have a plant-mediated
effect, i.e., affecting the amount of photosynthate
available for symbionts or released as exudates.
The first question to be addressed by this task is:
Will bacterial and fungal populations, soil
fauna, nematode andprotozoan community
structure, and the colonization of tree roots
by mycorrhizalfungi, be affectedby elevated
CO2 and climate change?
Altered C allocation under elevated C02 and climate
change will occur first from shoots to belowground.
Carbon will flow to nonmycorrhizal and mycor-
rhizal roots, and then to rhizosphere and soil microbes,
protozoa, nematodes and fauna. Depending on the
extent of the altered C flow, N cycling may be
affected, which may in turn alter feedback responses
of the host plant for continued C assimilation and
productivity.
The mycorrhizal symbiosis represents a substantial
C pool and flux in forest systems. The sink for C
created by this symbiosis is hypothesized to affect
long-term host C02 assimilation under elevated C02
and temperature regimes. Increased C flow
belowground may result in greater numbers of my-
corrhizal root tips and increased extramatrical hyphae
development. This in turn may affect continued C
assimilation by shoots and allocation to roots be-
cause of the larger belowground sink for C.
Additionally, as C flow belowground changes, the
community structure of fungi forming mycorrhizae
may differentiate among treatments in response to
different amounts of available C and the need to
acquire additional nutrients. It is essential to deter-
mine the changes in mycorrhizae colonization and
diversity in order to interpret long-term adjustments
by forest trees to elevated C02 and altered global
climate.
As for mycorrhizae, the flux of C into bulk soil
fungal and bacterial populations will affect fertility
and alter feedback responses of tree seedlings to
continued C assimilation and allocation. Estimates
of the size of microbial populations and some mea-
sure of their activity are necessary to understand the
movement of C and the dynamics of N in forest
ecosystems.
Soils can be a source and sink of greenhouse gases.
Since the production and consumption of these gases
are primarily biologically-mediated, factors that af-
fect biological processes will affect greenhouse gas
production and consumption.
The second question to be addressed by this task is:
Will soil greenhouse gas production, pro-
cessing, and emissions be effected by elevated
C02 and climate change?
Soil microbes mediate mineralization and trace gas
fluxes, and are sinks for C in the soil. Understanding
the composition, vertical distribution, and timing of
soil gas fluxes (C02, CH4, N20, and Oj) will give
insight into the distribution and processes of the
microbial populations affected by elevated C02 and
climate change. Caibon dioxide will be an integra-
tive measure of all biological activity in the soil, e.g.,
roots, microbes and animals. Methane is released
primarily from selected animals and microbes, and
N20 is a microbial product of denitrification. Data
of trace gas flux coupled with soil moisture and
temperature data will provide a more complete un-
derstanding of the seedling system response to
elevated C02 and climate change.
Page 73
CorvaJUs Environmental Research Laboratory
-------
Effects of COt and Climate Change on Forest Trees
Objectives
The objectives of this task are to:
To quantify the effects of elevated C02 and
climate change on total and active soil mi-
crobial populations (bacteria and fungi),
nematode community structure, protozoan
populations, and soil fauna populations.
To characterize the carbon transformation
rates of the bulk soil microbial population
under elevated C02 and climate change, as
indicated by die activities of enzymes pro-
cessing organic compounds.
To quantify the effects of elevated C02 and
climate change on the colonization of roots
by mycorrhizal fungi, and on the diversity of
myconhizal fungi colonizing roots.
To measure trace gas production and loss
within thesoil profile and the physical, chemi-
cal, and environmental factors affectingtheir
production and loss.
Approach
Measures of soil bacteria, protozoa, nematodes,
fungi, mycorrhizae and soil enzymes will be deter-
mined using samples taken from the cores-to-depth
(Task 6). These cores will be collected twice a year
(Figure 5-2). Samples of soil gases will be collected
from pairs of soil gas samplers placed in the soil
horizons (Figure 5-8) and from headspace chambers
placed on top of the soil (Figure 5-7) (Steudler et al.,
1989; Mattson et al., 1991). Gas samples will be
collected monthly.
Microbiological Indices:
Microbial Biomass; Bacterial and fungal total
biomass estimates will be performed by direct
microscopy on hyphae and bacterial cells. Bacte-
rial and fungal active biomass will be determined
by fluorescein diacetate (FDA) staining followed
by direct microscopy (Lodge and Ingham, 1991).
Nematode and Protozoan Populations: Counts of
nematodes and protozoa in soil samples will be used
to estimate community structure. Nematode mor-
phological characteristics will be used to develop the
nematode community structure. Four main feeding
groups will be considered: 1) bacterial-feeding, 2)
fungal-feeding, 3) root-feeding, and 4) nematode-
feeding. Protozoa will include dilates, flagellates
and amoeba.
Soil Fauna;
Faunal Groups: Soil fauna are an important compo-
nent of processes that occur in soil particularly those
related to litter decomposition. Twice a year a 15 by
15 an square of soil will be removed from each
terracosm for extraction and quantification of soil
fauna. The soil sample will include the litter layer
and 3 cm of A horizon. After the faunal extraction
is complete, the soil and litter will be returned to the
terracosms. Four groups of soil fauna will be stud-
ied: 1) burrowers/microbiovores, 2) shredders, 3)
predators, and 4) burrowing predators.
Soil Enzymes:
Enzvmatic Activity of Soil: The following measures
of soil microbial activity will be done: activities of 6-
glucosidase, peroxidase, phenoloxidase, acid
phosphatase, and proteinase.
Mycorrhizae:
Mvcorrhizal Fungi Colonization: Mycorrhizal
fungi colonization (percent mycorrhizal root tips
[%MRT]) will be determined using pooled sub-
samples of roots by microscopy after samples are
cleared and fungal structures stained by standard
procedures (Givannetti and Mosse, 1980; Koske and
Gemma, 1989; or Daughtridge et al., 1986).
Mvcorrhizal Fungi Diversity: Mycorrhizal fungi
diversity, e.g., at the taxonomic scale of either genus
or species, cannot be determined easily as mycor-
rhizal fungal species cannot be identified from root
tips alone. We will do limited assessments of
differences in the frequency of nucleic acid "finger-
prints" of myconhizal fungi of individual myconhizal
root tips, and possibly samples from the bulk soil.
Relative "fingerprint" frequencies through time will
Page 74 Corvallis Environmental Research Laboratory
-------
ZfftctsofCOj and CUmat* Chtuig* on Forest Tries
Stolen
10 on
Men
10 as
Sou Gu Samplers
SoilTkmniston
Litter Layer
A Horizon
-2 Metere-
B Horizon
C Horizon
Drainage Gravel
1 Meter
Figure 5-8. Location of Soil Thermistors and Soil Gas Samplers. In this
example, sensor locations are shown for a terracosm with sensors
concentrated in the NW quadrant.
Page 75 CorvalUs Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
be compared among the root samples. "Fingerprint"
frequencies of a subsample of 50-100 mycorrhizal
root tips per soil lysimeter will provide a qualitative
assessment of the dynamics of the fiingal rhizo-
sphere community.
One of two types of "fingerprints" will be produced:
1) restriction fragment length polymorphism (RFLPs)
following nucleic add amplification by "traditional"
PCR, or 2) RJFLP's following random amplified
polymorphic DNA (RAPD) PCR (Welsh and
McClelland, 1990,1991 a,b; Welsh et al., 1991 a,b;
Caetano-Anoles et al, 1991; Williams et al, 1990).
The latter technique has been used with prokaryotes
and eukaryotes to identify genera (Welsh and
McClelland, 1991a), species (Quiros et al, 1991;
Welsh and McClelland, 1991a), strains (Welsh and
McClelland, 1990; Welsh etal, 1991b)andcultivars
(Hu and Quiros, 1991).
Trace Gases:
Soil Gas Samples: Two kinds of soil gas samples
will be collected and analyzed for C02, CH4, N20,
and Or The first will be collected from the soil gas
samplers placed at five depths in the terracosm soil.
These samples will be collected every four weeks
and used to provide information about the location
and nature of soil biological activity. The frequency
of sampling may be adjusted to monitor periods of
high and low biological activity (Figure 5-2). The
second kind of soil gas sample will be collected at the
soil surface (litter layer-air interface) with headspace
chambers (Steudler etal, 1989; Mattson etal, 1991)
and will be used to estimate trace gas emissions from
forested soil under elevated C02 and climate change.
Headspace samples also will be collected every four
weeks. Soil gas samples will be analyzed on a gas
chromatograph using the methods described by
Bremner and Blackmer (1982).
Task Outputs
Estimates of total and active bacterial and
fungal biomass, nematode and protozoan
community structure, and soil fauna popula-
tions, under elevated C02 and climate change.
Estimates of soil microbial activity as af-
fected by elevated C02 and climate change.
Estimates of root colonization by mycor-
rhizal fungi under elevated C02 and climate
change.
Characterization of the effects of elevated
C02 and climate change on differentiation of
the mycorrhizal fungi community on roots.
Estimates of annual emissions of green-
house gases from terracosm soils.
Characterization of greenhouse gas produc-
tion and processing in terracosm soils.
Model Inputs
TREGRO in it's current form does not require any
data gathered in this task.
Page 76
Corvallis Environmental Research Laboratory
-------
mjtcti of CO j and CUmate Change on Forest Trees
VL MODELING TASK
Individual tree physiological models can play an
important role in studying the responses of trees to
elevated C02and climate change. The primary goal
of this task will be to adapt a tree growth model that
reasonably incorporates the processes important to
tree functioning, especially those affected by C02
and climate change for simulating tree responses to
COj and climate change scenarios. The output of this
model will be an estimate of tree growth as a function
of time and environmental conditions. A process-
based tree growth model will be used for simulating
the response of mature trees to elevated C02 and
climate change. Also, data from the experimental
studies and output from the tree growth model will
be used in the landscape scale modeling being con-
ducted at ERL-Corvallis.
In this Research Program process-based models will
serve four functions:
1. Identify essential areas where our research
should be concentrated.
2. Model the growth of individual trees from
seedling to maturity to provide a means of
extending the experimental studies at the
seedling/small to the mature/large size trees.
3. Test the completeness of our data and cor-
rectness of our understanding of key plant
and soil process affected by elevated C02
and climate change.
4. Simulate tree response to a range of elevated
002 and climate change scenarios.
MODEL SELECTION
In early 1990, the Ozone Program at ERL-Corvallis
conducted a detailed review and analysis of process-
based tree-growth models to use in their risk
assessment of tropospheric ozone on U.S. forests.
Based on their analyses, they selected TREGRO, a
process-based tree growth simulation model
(WeinsteinandBeloin, 1990; Weinsteinetal., 1991;
Weinsteinetal., 1992) as their tree growth model. As
our modeling needs are very similar to theirs, we also
propose to use TREGRO as the growth simulation
model in this research project because:
TREGRO simulates the growth of both
above- and belowground plant components
and incorporates the processes likely to be
affected by elevated C02 and climate change.
TREGRO is based on fundamental plant
processes that provide a reasonable simula-
tion of plant growth and is currently
operational.
By selecting the same simulation model as the
Ozone Program, we will benefit from their knowl-
edge and experience with TREGRO and experience
significant monetary savings as the Ozone Program
has funded recent modifications to TREGRO.
TREGRO FEATURES
TREGRO is a physiologically-based simulation
model that was developed to investigate the response
of plants to multiple environmental stresses. The
model is designed to predict the growth and pattern
of carbon allocation expected for an isolated tree
under various conditions, e.g., nutrient stress,
water stress, temperature, C02, and 03 (Figure 6-
1). In the model, the tree is divided into the
following compartments: a canopy (consisting of
up to ten age classes of needles), brandies, stem and
fine and coarse root pools in each of three soil layers.
The model calculates the flow of carbon from the
sites of fixation within the leaves (based upon the
availability of light, water, and nutrients) to other
plant compartments. The model also simulates the
amount of essential nutrients and water available
within the 3 soil layers and the tree.
Within TREGRO, water is tracked as it enters the
soil and moves through it Roots absorb water which
is subsequently transpired. The model estimates
water uptake from each soil layer, root water poten-
Page 77 Corvallis Environmental Research Laboratory
-------
Effects o/COt and CUmatt Change on Forest Trees
TREGRO Model
Atmospheric/Climatic
Conditions
Photosynthesis
Stomatal Conductance
Needle Area J
Total Nonstructural
Carbon Pool
Plant Water
Balance
Aboveground Structural
Biomass
Plant
Nutrient
Pool
ฆWPWWP
"U1"!.1111 1 1 ,-J, LU
ปฃ'Vป ' 'v'vX'VaV%'ซ'X '.'a'M'a
v, \v,< /,* V// V,' >,ป /,ซV ป
Belowground Structural
Biomass
0/1*, *yo>
'vVWMMA
V-''A'ซV'VA'-V.\v,
ปvvVVVvvV
A' V V V' *'ป' *'
J 1 ((> r,*W<," ','V'
w
-y.y.v
VAA^\AWAVA'A'.
VV'V'vWAv'
V^V/AV
''a'a'av!
vAv>Vo
fM
s?M4tv
VVvw
;.^v,v;;v
iVVVV'A V'1 * *VV
* wV Vav
>Vป V*V' ปVVV /,ปVซVi
^/*yป w ^'^ViV'Aw1
'Va W! A**
W.'AV
IV W V, IV Vtftftf if >,<
y.y.fe.-.i.S-JAS'.}':
't' i'A'jVi'A'/i A,
%>tปi> (>*,, yVVVV'A'VVVVV cV'/VVV' '|J'''' i'v, ,/av wVVAvvV vVVv iWvvVA VvV
#*&&$/&&?&&&&
i^vA\w!w/Ava av
t*&V f,'VVv'( 'ซ 'r V* ' '
is*"
!ซ,V,\^v ฃVVKh*>'ป*'A'''/^'A'^'A'V^V/A'A''1 'n'^A ?
*YAVS\ซ\>AA '>A>A
ซ,>V(>iปy* (> ป(>>ป(,ป,*/*(>(
'vi/i'/VAiV V Vv/.'.v,',', >,ป/, /,ซxปf,i VAvVA'AAV.VA1'
/OA^V.V^V,
ฆ,-v 'yA'A->'A v 'A'Av'A,
'" 'AVtV/'W
ปv >V/>v>
vjnjv >'vv>,'(\'A'v'VV''A' vV VV v VปV*' <
vAiVaCva% ป a'^a!va''*V VV**! 'WV'^'V'W'V''a> 4*
Figure 6-1. Flaw diagram showing the major compartments and their interactions in
TREGRO, the physiology based process model used to simulate tree growth.
Page 78 Corvatlis Environmental Research Laboratory
-------
EJJtcts of CO f and Climate Change on Forest Trees
tial, plant water content, water budget and actual
transpiration. If the rate of precipitation exceeds the
amount needed by the plant or retained in the soil,
water drains from the system. Hie availability of soil
water influences other plant processes (e.g., carbon
allocation, root growth, transpiration).
The model operates on a daily time step, with some
processes such as photosynthesis calculated on an
hourly time step and aggregated to the daily level.
The model projects the growth of a tree over time
periods ranging from a day to years. The model has
been most accurately parameterized and tested for
red spruce, but it is readily applicable to other plant
species. The Ozone Program at ERL-Corvallis is
currently parameterizing the model for 6-8 conifer-
ous and deciduous tree species.
TREGRO is designed to integrate soil processes
with plant processes to project the effects of elevated
C02 and climate change on individual trees.
TREGRO includes algorithms that estimate: (1)
nutrient availability and supply based upon soil
chemical, physical and mineralogical properties; (2)
nutrient uptake based upon plant need and availabil-
ity from user-designated soil horizons; (3) root
turnover and decomposition; and (4) water supply
and use.
In its current form TREGRO does not consider the
effects of mycorrhizae on caibon allocation and
nutrient dynamics. Nor does it consider specific soil
biological processes that transform organic material
into variousgreenhouse gases. Yet the integration of
soil processes, even though not exhaustive, with
plant processes in TREGRO imparts a large degree
of realism to modeling the effects of elevated C02
and climatic change on individual trees.
A litter decomposition module, based on the Gen-
eralBiogeochemicalModel of Rastetter et al. (1991)
has been incorporated into die model. The younger
organic matter in the litter and soil is divided into
three operationally defined fractions: (1) extractives,
(2) cellulose and (3) lignin. Older organic matter is
converted into humus. The model simulates the
movement of C and N among these fractions.
RESEARCH TASKS
Many of the experimental measures described in
Section S were specifically taken to provide data to
support the simulation modeling task. The activities
associated with the modeling effort will continue
throughout the project and can be separated into
three main areas:
Model development
Model parameterization
Model calibration/verification
Model Development
Initially we will use the model as written by Weinstein
and co-workers (1990,1991,1992).
Model Parameterization
The data for the parameterization of the model will
come from three sources:
The published literature will be reviewed to
find appropriate data for the model; for
example, data on the influence of tempera-
ture on photosynthesis or changes in stomatal
conductance with leaf water potential.
The Ozone Program is currently collecting
physiological data from Douglas fir grown
in open-top field-exposure chambers at ERL-
Corvallis. These data include the maximum
assimilation rate and needle, branch and
stem concentrations of total nonstructural
carbohydrates (TNC).
The initial biomass values needed for the
model will be obtained from Douglas fir
trees that will be harvested at the start of the
experiment The data will include, number
of needle classes, needle weight (by age
class), needle TNC, weight of coarse roots
and fine roots.
Page 79
Corvailis Environmental Research Laboratory
-------
Effects of CO j and Climate Chang* on Forest Trees
Model Calibratioo/Verification
This task will involve several discrete steps that will
be performed in an iterative fashion through the
experimental phase of the work. There will be a
period of refining or adjusting parameter values so
that the results from the simulations reflect measured
plant responses. The data for the model calibration
will come ฃrom:
On-going experiments being coaducted by
the Ozone Program in their open-top field-
exposure chambers.
Interim measurements collected from the
Douglas fir trees in the terracosms and sup-
porting studies.
In either case, modeled output will be compared with
measured plant responses.
It will be difficult to experimentally determine all the
parameters needed for the model. Some of the pa-
rameters will be based on data from other species.
Sensitivity analyses will be performed to determine
which parts of the model are most sensitive. These
data will be used to indicate the areas that will require
the most reliable parameter estimates.
Model Validation
It would be desirable to independently validate the
model performance. However, it is unlikely that the
model will be validated as an independent data set is
not available. It may be possible to validate portions
of the model from data sets yet to be identified.
Model Outputs
* Parameterized and calibrated version of
TREGRO for Douglas fir for use in studying
the effects of elevated C02 and climate
change.
Page 80
Corvattis Environmental Research Laboratory
-------
Effects of CO3 and Climate Chang* on Forest Trees
VD. INTEGRATION AND
INFERENCE
The research goal for this project is to assess the
impacts of elevated C02 and global climate change
on the terrestrial biosphere to determine the: (1)
effects of global climate change on ecosystems and
(2) influences (feedbacks) of ecosystems on atmo-
spheric C02 concentrations and climate change
processes. The researchsupports the followingpolicy
objectives of the Committee on Earth and Environ-
mental Sciences (GEES) (1990).
* What are the probable magnitudes, rates,
and variations of human-induoed change in
ecological systems; how can these changes
be distinguished from natural fluctuations?
* In which ecological systems and species are
significant changes most likely to occur,
what attributes of importance to humans
(e.g., harvestable resources, arable land, and
species diversity) will be at risk?
* How will predicted changes in terrestrial
ecosystems alter biospheric C02 fluxes, ra-
diation, heat or water fluxes and how will
these change with time?
OBJECTIVES
The research outputs are designed to respond to the
GEES policy objectives and will focus in two areas:
(1) integration of the experimental results into a
cohesive understanding of the effects of elevated
C02 and climate change on forest trees and soils and
(2) inference of these effects across time and space
through the application of a tree growth model.
INTEGRATION
Although the experimental tasks (Section S) are
presented as discrete entities for ease of understand-
ing and implementation, the ultimate goal was to
develop an integrated understanding of the effects of
elevated CO} and climate change on forest trees and
soils. The integration activity will involve several
different approaches:
Conceptual Summary - A summary paper
(i.e., for Science) will be developed de-
tailing the major results of the experiment
System Balances - Because the terracosms
can be treated as a well-monitored semi-
closed systems, with respect to carbon, water
and plant nutrients, mass budgets will be
developed. These budgets will be one of the
principle integration activities. Hie follow-
ing mass balance budgets will be developed;
(1) Carbon Budget, (2) Water Budget (in-
cluding an analysis of water use efficiency),
and (3) Nitrogen Budget (including an analy-
sis of nutrient use efficiency).
Plant Morphology, Phenology and Behav-
ior - The experimental facility presents an
unique opportunity to study the effects of
elevated C02 and climate change on both the
above- and belowground components. For
example, to determine the relationship be-
tween the root activity (e.g., root initiation,
root turn-over) and shoot activity (i.e., bud
break, shoot elongation).
INFERENCE
The Inference activities will be focused on the
application of simulation model(s) that were devel-
oped and parameterized in Section 6. The model will
be applied to several specific tasks:
Scale the calibrated model from seedlings to
trees. This will permit the results from simu-
lation to be applied to both seedlings and
older trees. Initially we will rely on scaling
studies being conducted by the Ozone Pro-
gram which has the objective of developing
the necessary parameters for scaling from
seedling to larger trees. After a review of
Page 81
Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
their results it may be necessary to fund
additional scaling studies.
Use the model with selected climate change
scenarios to project the potential effects of
elevated C02 and climate change on seed-
lings and forest trees. Hie specific climate
scenarios to be used will be selected later.
Use the model to determine the effects of
elevated C02 and climate change on carbon
allocation to the roots and their subsequent
impacts) on nutrient mineralization and
carbon sequestration or loss from the soil.
OUTPUTS
The Research Project will contribute to the follow-
ing EPA deliverables:
Ecophysiological response of terrestrial veg-
etation to atmospheric and climatic changes.
The interactive effects of climate change
and enhanced C02 concentrations on veg-
etation distribution and productivity at
continental scales.
Changes in caibon allocation between above-
arid belowground systems in response to
elevated levels of C02and climate change.
Effect of elevated levels of C02 and climate
change on belowground systems and feed-
backs to the atmosphere.
Ecosystem models that simulate both the
impacts of climate change and enhanced
levels of C02 on important ecosystem pro-
cesses.
Improved models of carbon storage and
turn-over in forest soils in response to el-
evated levels of C02 and climate change.
Page 82
Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
Vm. PROGRAM MANAGEMENT
To successfully conduct a complex experiment, as
described in this research plan, it is imperative that
there be good communications among the partici-
pants and that there be clearly assigned project
responsibilities.
COMMUNICATIONS
The project scientists will meet frequently (at least
twice a month and probably more often during
periods of intense activities) to: (1) coordinate sam-
pling and experimental activities, (2) exchange data
and information among the various tasks, and (3)
share scientific information.
The project scientists and facilities scientists will
meet every two weeks to: (1) coordinate experimen-
tal activities (e.g., availability of equipment, harvests,
etc.), (2) exchange information, and (3) to resolve
possible problems.
PROJECT RESPONSIBILITIES
The overall project management is the responsibility
of the Project Leader for Effects of C02 and Climate
Change on Terrestrial Vegetation.
To insure that all facets of the project progress on
schedule and that important parts of the project are
not omitted, individual project scientists are as-
signed specific tasks or portions of tasks (Table 8-1).
The specific task assignments were derived by first
conducting an analysis of the skills and training of
the EPA and LAG professional staff. The tasks that
could not be conducted by these individuals were
assigned to the on-site contractor.
Page 83 Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
Table 8-1. Program Management
TASKS/Subtaks
Principle
Participant
Participant
PaiUdpimt
Investigator
SCOPING STUDIES
D. Tingey
M. Johnson
D. Olszyk
P. Rygiewicz
EXPERIMENTAL TASKS
TASK I - Shoot Carbon and Water Flux
Gas Exchange - Needle
D Olszyk
C Wise
Gas Exchange - Canopy
D Tingey
D. Olszyk
R. Waschmann
B. Baker
Needle Area Image Analysis
D. Olszyk
B Baker
Stem Flow/Transpiration
D Olszyk
C Wise
D, Tingey
TASK 2 ฆ Shoot Growth and Phenology
Shoot Growth/Phenology
D. Olszyk
C. Wise
TASK 3 - System Nutrients
Biochemistry
D Tingey
D Olszyk
P Rygiewicz
B Gnffis
Plant Nutrients
D, Tingey
P Rygiewicz
D, Olszyk
B Gnffis
Soil Nutrients
M Johnson
P, Rygiewicz
B. Gnffis
TASK 4 - System Water
Plant Water
D Olszyk
TOR - Soil Water
M Johnson
P, Rygiewicz
G Jarrell
TASKS-Litter Layer
Litter Layer Addition
M Johnson
P Rygiewicz
M Storm
Decomposition
M Johnson
P Rygiewicz
M Storm
TASK 6 - Root Growth and Phenology
Cores-to-depth
P Rygiewicz
M Johnson
M Storm
Mimrtiizotron
M Johnson
M Storm
P. Rygiewicz
D Tingey
TASK 7 - Soil Biology
Microbiological Indices
P Rygiewicz
E Ingham
M. Johnson
Soil Fauna
P, Rygiewicz
A, Moldenke
M Johnson
Soil Enzymes
P, Rygiewicz
B Caldwell
R, Griffiths
M Johnson
Mycorrtiizae
P. Rygiewicz
E, Ingham
M Johnson
Biogenic Gases
M Johnson
P Rygiewicz
TASK 8 - Soil Organic Matter
1 Gnffis
M Johnson
P Rygiewicz
MODELING TASK
TREGRO
D. Tingey
J Weber
M Johnson
INTEGRATION AND INFERENCE
M Johnson
D Olszyk
P Rygiewicz
D, Tingey
TERA OPERATIONS
TERA Hardware/Software
M Johnson
G. Janell
R. Waschmann
P. Rygiewicz
TERA Database
P Rygiewicz
B. Baker
FIELD SITES
M Johnson
P. Rygiewicz
D Olszyk
M Storm
Page 84
Corvallis Environmental Research Laboratory
-------
Effects of CO | and Climatt Change on Forest Trees
IX. QUALITY ASSURANCE
STATEMENT
EPApolicy requires that a Quality Assurance Project
Plan (QAPP) be developed for all EPA sponsored
research that collects environmentally-related mea-
surement data. This insures that all data collected are
of known and documented quality.
Prior to the initiation of the actual experimental
study, a QAPP, covering the research described in
this Plan will be developed. The QAPP will conform
to EPA and ERL-Corvallis guidelines and will in-
clude the following elements:
Data collection methods
Reliability of the data collection systems
Traceability and security of data
Data management (collection, transfer be-
tween points, and archiving)
Standard operating procedures will be de-
veloped, approved and will cover all
measurement activities.
In addition to the QAPP, a facilities operations
manual will be developed covering the operation
and maintenance of the terracosms and associated
facilities. The manual will include:
- Description of the terracosm facility and its
capabilities.
- Drawings of the overall design of the facility
and all hardware.
- Documentation of software.
- Standard operating and calibration proce-
dures.
- Performance evaluation of environmental
control capabilities.
- Preventative maintenance activities and
schedules will be establish for equipment.
Page 85 Corvatlis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
X. OTHER RELEVANT RESEARCH
PROGRAMS
U.S. ENVIRONMENTAL PROTECTION
AGENCY - ERL CORVALLIS
Vegetation Modeling Work
Estimating the impact of climate change on broad-
scale vegetation patterns is one of the primary goals
of EPA's climate change program. Until recently,
models for simulating regional- to continental-scale
vegetation patterns were stricdy based on correla-
tions between climate parameters and the vegetation
character of interest These models are of limited
utility for simulating the effects of future climate
change on vegetation because (1) current correla-
tions between climate and vegetation may change in
the future, and (2) the direct effects of C03 on plant
growth are not simulated by these models. ERL-C
has been sponsoring work over the past several years
to develop process-based broad-scale vegetation
models. R. Neilson (U.S. Forest Service/ERL-
Corvallis) has developed a process-based model for
the continental U.S. fundamentally based on coupled
vegetation-water interactions. This model, called
Mapped Atmosphere-Plant-Soil System (MAPSS),
calculates water flow through a vegetation canopy,
including canopy control on the rate of transpiration.
The strength of this model is that it is based on the
fundamental biological needs of different plant life
forms for water and energy, and, through stomatal
control, can incorporate the effects of enhanced C02
concentrations on water use efficiency.
Experimental data for calibrating and parameteriz-
ing MAPSS currently are very limited. However,
several types ofdata from the terracosm study will be
used directly in the future refinement of MAPSS.
Data on the relationship of stomatal conductance to
soil water potential and atmospheric vapor pressure
deficit (vpd) will be most useful. This relationship is
fundamental to how MAPSS extracts soil water,
modulates competition between life forms, and con-
trols water use efficiency. Information on how the
relationships among stomatal conductance, soil
moisture, and vapor pressure deficit vary under
enhanced C02 concentrations will be critical for
parameterizing MAPSS to simulate both climate
and C02 impacts on plant growth.
Spatial Analysis of Water, Energy and Bio-
geochemical Processes
This program is developing methodologies to
simulate energy and water balance response to
different climate conditions over regions of
varying sizes and scales. Much of the work is
centered on development of a water balance
model for the Columbia River Basin. The
model is designed to simulate soil moisture
and evapotranspiration (ET) over a digital
elevation model (DEM) grid representing the
basin. The model accounts for vegetation
effects, snow cover volume and ablation, and
topographic effects on precipitation, tempera-
ture, humidity, and wind. It requires daily
meteorological data, and information on soil
hydraulic properties, organic carbon content,
and vegetation type and condition. Satellite
remote sensing data are used to estimate
surface temperature, snow cover extent and
condition, and surface roughness and vegeta-
tion. The model will be used to estimate
impact of climate change on the water balance
and the impact that these changes will have
on vegetation, soil moisture, streamflow, and
regional water resources.
Experimental data from the terracosm study will be
used to calibrate and verify the numerical formu-
lations in the model, and to improve simulation of the
interactions between climate and the water and
carbon cycles in forested ecosystems. While the
range of climatic conditions used to define the
TERA experiment will be limited, the sensitivity of
measured ET to changes in temperature, humidity,
and moisture, as determined by the experiment, will
be critical in development of the regional model.
The models will be used to insure that coupled
climate conditions (e.g., temperature, humidity, wind,
etc.) used in the experimental chambers are realistic
and possible. Conversely, coupling the model
development to the experimental data will allow
extension of the experimental results to conditions
Page 86 Corvallis Environmental Research Laboratory
-------
Effects of CO2 and CUmatt Change on Forts! Trtts
and ecosystems not directly considered in the terra-
cosm study.
Tropospheric Ozone; Forest Impart
The Research Program addresses theneedsofEPA's
Office of Air Quality Planning and Standards
(OAQPS) to assess the need for a National Ambient
Air Quality Standard (NAAQS) for ozone that pro-
tects public welfare (forest vegetation) from adverse
effects. Specifically, the program focuses on (1) the
biological database for understanding the nature and
extent of ozone's impact on forest trees, and (2)
developing a biologically meaningful index of ozone
exposure.
Research studies are focusing on (1) experimental
exposure studies with seedlings addressing mecha-
nistic questions of ozone effects, growth response,
environmental interactions, and the role of exposure
dynamics on growth, and (2) process-model param-
eterization. The mechanistic studies have focused on
the role of ozone on carbon fixation and allocation.
These are the two processes identified as critical
points of interaction with ozone and tree growth
response, and the processes that age and size may
influence in simulating long-term ozone effects.
TREGRO is the process-based simulation model
selected to support the experimental studies and to
extrapolate the experimental results. Currently, the
model has been parameterized for conifers (e.g.,
ponderosa pine, red spruce, loblolly pine), but ulti-
mately it will be extended to include deciduous
species.
The critical task in this program is the integration of
mechanistic and exposure-response studies with the
process-based model (TREGRO) and stand-level
model (e.g., ZELIG). Both models will be used to
simulate ozone effects over tune and different envi-
ronments, and die Geographical Information System
(GIS) model will be used for spatial integration. The
integration of the response functions and model
simulations with the GIS allows integration of expo-
sure, species/stands/habitat distribution, and
environment in a spatial framework for risk assess-
ment, as well as identifying data gaps.
Study at Harvard Research Forest, Petersham,
MA
In a long-term "soil warming" project at the Harvard
Research Forest (HRF) Long-term Ecological Re-
search site in Petersham MA, scientists from several
institutions are studying effects of increased soil
temperature on traoe gas fluxes and mineralization
rates. This work is jointly funded through The
Ecosystems Center of the Woods Hole Marine Bio-
logical Laboratory by NASA, DOE and EPA-Athens.
Scientists from Woods Hole, Harvard University,
University of New Hampshire, University of Cali-
fornia-Davis and EPA-Corvallis are studying aspects
of the forest soil ecosystem response under the
overall coordination of Drs. Jerry Melillo and Paul
Steudler (Woods Hole).
EPA-Corvallis is contributing to this project in col-
laboration with Dr. Caroline Bledsoe, University of
Califomia-Davis. The collaborative effort directly
supports the HRF by providing estimates of soil
carbon pools in fine roots, as well as biomass of soil
organisms which affect rates of trace gases and C02
fluxes from soils. This field research supports the
EPA-Corvallis project on global climate effects on
Douglas fir in that assessments of several similar
responses for soil biology processes are being made
at HRF and in the terracosms.
Cartoon-Nitrogen Interaction in Brazilian
Forest Species
A collaborative study was begun in 1990
between Dr. Rosa Muchovej, Universidade
Federal de Visosa (UFV) (in tropical Brazil)
and EPA-Corvallis to investigate the use of
molecular biology techniques to assess changes
in mycorrhizal fungi populations as part of a
larger program to develop research capabilities
in molecular soil ecology. A second objective
of the collaborative work was to develop ex-
perimental capabilities to estimate linkages
between C assimilation, N acquisition and N
assimilation enzymes in tropical eucalyptus to
support their efforts in developing nursery
reforestation programs for south central Brazil.
Page 87 CorvaUis Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Fortst Trtes
A joint experiment was conducted in Brazil in 1991
using several isolates of mycorrhizal fungi and euca-
lyptus to assess relative C acquisition and allocation
in seedlings, and N acquisition and activities of N
assimilating enzymes in the fungal isolates. This
first phase of this work was supported by the Brazil-
ian National Science Foundation.
We are also making arrangements through Brazilian
programs to support students from two Brazilian
universities (UFV and Universidade Federal de Santa
Catarina, in subtropical Brazil) to do graduate study
at Oregon State University while using the TERA
facility to do their dissertation research. The first
graduate student hopes to matriculate in January
1994. The student intends to investigate an aspect of
water and nutrient use, and mycorrhizae under the
altered climate conditions in the tenacosms.
U.S. ENVIRONMENTAL PROTECTION
AGENCY - ERL ATHENS
Earth Systems Model (ESM)
The current EPA/ORD research program focuses on
developing the critical information and tools needed
to conduct global change risk assessments. The
additional, central element needed to provide this
risk assessment capability is a modeling framework
for the relevant interacting components of the earth
system. An earth system framework implemented
as an integrated, dynamically-coupled model is es-
sential for understanding the environmental
consequences of alternative scenarios used in risk
assessment, and for determining the critical weak-
nesses and knowledge gaps for which additional
research is indicated. Ecological risk assessments
that reflect the global and regional impacts expected
from an array of alternative scenarios will be an
essential part of EPA's continuing role in science
and policy assessments. The earth systems model-
ing projects will play a pivotal role in ensuring that
related research programs and data collection efforts
within the Agency are optimized for maximum
benefit
The overall goal of this project is the systematic
development of an earth systems modeling frame-
work that is modular in design, enables the
exploitation and further development of terrestrial
biospheric modeling components and tropospheric
chemistry relationships, and that produces models
and modeling experiments that demonstrate the fea-
sibility of fully coupled, three-dimensional models
of the earth system. The major elements of an ESM
framework will include atmospheric and ocean cir-
culation and biogeochemistry models, ciyospheric
models, and physical representations of the terres-
trial system including the hydrologic cycle.
U.S. DEPARTMENT OF AGRICULTURE/
AGRICULTURAL RESEARCH SERVICE
Temperature and C02 Interactions on Rice
Growth and Yield
The USDA Agricultural Research Station Plant
Stress and Protection Unit in Gainesville, Florida has
spent the last decade studying the effects of elevated
C02 and climate change on agricultural plants while
developing sun-lit phytorhizotron technology. The
phytorhizotrons are unique to the field of plant
exposure facilities because they not only control gas
concentrations, but they can control dry bulb tem-
perature, dewpoint temperature, and rooting zone
conditions precisely (Jones et al., 1984a; 1984b;
1985 and Baker et al., 1990). This gives the
phytorhizotrons an advantage in measuring the in-
teracting effects of rising C02 and climatic change
factors on photosynthesis, transpiration, other gas-
eous exchanges, growth, and yield. Furthermore,
these plant growth chambers use natural solar irradi-
ance rater than artificial lamp irradiance that is used
by indoor growth chambers.
Over the past several years, the ERL-Corvallis has
been working cooperatively with the USDA-ARS/
University of Florida-Gainesville, Institute of Food
and Agricultural Science to develop a new genera-
tion of phytorhizotron technology. The group of 12
chambers described in this research plan have been
constructed with technical guidance from the USDA/
ARS while a similar group of 8 chambers have been
Page 88 CorvaUis Environmental Research Laboratory
-------
Effects of COj and ClimaXt Chang* on Forest Trees
constructed simultaneously in Florida. The two
research groups are currently working together to
solve process/climate control data acquisition prob-
lems to successfully move the two new phytorhizotron
installations to an operational status. Once com-
pleted, the chamber complex in Florida will be
dedicated to researching the interactions between
rice growth, yield, and gas exchange with atmo-
spheric C02 concentrations and climatic change.
The effect of climatic factors and cultivar selection
on biogenic methane flux from paddies grown in the
phytorhizotrons will also be studied.
ELECTRIC POWER RESEARCH
INSTITUTE (EPRI)
Forest Response to C02
One of the emerging environmental issues of the
decade is increasing greenhouse gas concentrations
in the atmosphere and the attendant effects upon
climate change. In terms of terrestrial ecosystem
response, there are two overriding questions: (1)
what effects will climate change have, should it
occur; and(2)whateffectswill increasingC02levels
have? Of the two questions, the latter is most directly
addressed because it is well known that C02 levels
are increasing, whereas changes in climate are not
yet fully apparent
This project is designed to address the C02 question.
The basic questions being addressed in this research
are:
Howwillnutrient-deficientorwater-stressed
forests respond to elevated C02?
Will potential C02-induced increases in
growth be prevented by these resource limi-
tations.orwill increases in water and nutrient
use efficiency allow growth responses to
occur?
In the event that the latter is true, will there be
a permanent increase in nutrient- or water-
use efficiency or will ecosystems become
progressively more limited for instance, by
sequestering of nitrogen in unavailable forms
in litter and soil?
Ultimately, the aim of this research is to project
whether increased atmospheric C02 will result in
increased carbon sequestering in forest ecosystems.
This projection will be based upon process-level
studies and model extrapolation, because the costs of
a full-scale forest ecosystem C02 fumigation are
prohibitive and would likely be indicative of only a
local situation.
Under present levels of atmospheric C02 it is gener-
ally believed that forest productivity (i.e., growth) is
typically limited by nutrients and/or water. It is not
clear that as atmospheric C02 levels rise these re-
source limited forests will be able to fix more C02.
Nor is it clear that any initial increase in the rate of
carbon fixation will be sustained indefinitely. To
investigate these issues, EPRI has posed the follow-
ing specific questions:
Initial carbon acquisition in ecosystems can
be limited by soil resources commonly N, P,
Mg,B, and water. What adjustments in plant
processes might occur as atmospheric C02
rises to increase resource acquisition or use
efficiency allowing increased plant growth?
How will patterns of carbon and nutrient
allocation/partitioning within plants affect
and be affected by the possibility of in-
creased carbon gain by plants?
Will soil nutrient availability be altered by
changes such as litter quality or biomass
sequestration so that a growth response is
only temporary?
As a first step in addressing these questions, EPRI is
supporting studies of C02 enrichment in two con-
trasting forest types in the United States - the relatively
moist loblolly pine forests of the Southeast (Duke
University, Durham, NQ and the relatively dry
ponderosa pine forests of the West (Desert Research
Institute, Reno, NV). ERL-Corvallis scientists are
cooperating with scientists from DRJ to study the
effects of C02 enrichment on rhizosphere dynamics.
Page 89
Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
U.S. DEPARTMENT OF ENERGY
Tall Grass Prairie Elevated C02 Experiment
One of the DOE supported elevated C02 exposure
facilities is located in a pristine tall grass prairie near
the campus of Kansas State University. This is an
open top chamber facility studying the effects of
elevated C02 on a mixture of Ca and C4 species which
are dominate by Andropogon gerardii and
Sorghastrum nutans. Several sub-dominate species
included in the study are the CABouiebua curipendula
and the C}'s Poapratens and several Carex species.
There are also several species of forbs including the
C3's Sporobolus asper and Ambrosia psilostachya.
(Strain and Thomas, 1992). One of the scientists
working on this site, Jay Ham, is developing new
techniques to measure sap flow in small diameter
stems under low flow conditions. His techniques are
based on the heat balance method, but the gauge
designs have been modified to provide better heater
contact and proportional heater control for improved
measurement accuracy. We are currently working
with Dr. Ham to test the new gauge designs. Through
collaborative experimentation on Douglas fir seed-
lings we will better define the constraints imposed by
stem diameter and sap flow rates to identify the
conditions under which acceptable results can be
obtained. Ultimately, this work will lead to
noninvasive real time measures of plant water de-
mand that will play an important roll in understanding
both plant and system water balance.
MICHIGAN STATE UNIVERSITY
Hardwood Root Dynamics and Root Image
Analysis
We have been in consultation with two research
groups at Michigan State University that have been
conducting research on root dynamics using
minirhizotrons and video cameras for several years.
The first group is in the Department of Crop and Soil
Sciences and is led by Dr. Alvin Smucker. This
group has worked on automating root data extrac-
tion, using artificial intelligence, from root images
recorded on video tape. The second group is in the
Department of Forestry and is led by Dr. Kurt
Pregitzer. This group has been working on the use of
minirhizotrons in forested systems. They have de-
veloped a model of root demography and
human-guided software for extracting root data from
minirhizotron tapes. Recently, this group has been
conducting research on the effects of elevated C02
on tree root dynamics. Both of these groups provided
valuable information and help during the experi-
mental design phase of the TERA project. They
helped us decide on the number of minirhizotron
tubes to use in each terracosm, minirhizotron tube
orientation, what kinds of video equipment and data
extraction software would best meet our needs. We
continue to follow their research and collaborate
with them on developments in minirhizometry.
Page 90 CorvalUs Environmental Research Laboratory
-------
Effects of COj and Climat* Chang* on Forest Trees
XL REFERENCES
Aber, JD., J.M. Melillo and GA. McClaugherty.
1990. Predicting long-term patterns of mass loss,
nitrogen dynamics, and soil organic matter forma-
tion from initial fine litter chemistry in temperate
forest ecosystems. Can. J. BoL 68:2201-2208.
Agren, G J., R.E McMurtie, WJ. Parton, J. Pastor
andH.H.Shugart. 1991. State-of-the-art models of
production-decomposition linkages in conifer and
grassland ecosystems. Eool. Appl. 1:118-138.
Allen, LH., Jr., S.E. Beladi and S.H. Shinn. 198S.
Modeling the feasibility of free-air carbon dioxide
release for vegetation response research. 17th Agri-
cultural and Forest Meteorology Conference, Amer.
Meteorol. Soc., Scottsdale, AZ, May 21-24, pp 161-
164.
Allen, LH., Jr. 1990. Plant response to rising carbon
dioxide and potential interactions with air pollutants.
J. Environ. Qual. 19:15-34.
Allen, SJL 1974. Chemical Analysis of Ecological
Materials, Blackwell, Oxford.
Amaranth us, M.P. and DA. Perry. 1987. Effect of
soil transfer on ectomycorrhiza formation and the
survival and growth of conifer seedlings on old,
nonreforested clear-cuts. Can. J. For. Res. 17:944-
950.
Amthor,J.S.and J.R. Cumming. 1988. Low levels
of ozone increase bean leaf maintenance respiration.
Can. J. BoL 66:724-726.
Anderson, R.C. 1981. Osmoregulation in cotton in
response to water stress. II. Leaf carbohydrate status
in relation to osmotic adjustment Plant Physiol.
67:489-493.
Ansoult, M., LW. DeBacker and M. Declerq. 1985.
Statistical relationship between apparent dielectric
constant and water content in porous media. SoilSci.
Soc. Am. J. 48:47-50.
Arp,WJ. 1991. Effects of source-sinke relations on
photosynthetic acclimation to elevated C02. Plant
Cell Environ. 14:869-75.
Atzet,T. and D.L. Wheeler. 1984. Preliminary plant
associations of the Siskiyou Mountain Province.
USDA Forest Service, Pacific Northwest Region,
Portland, OR.
Aussenac, G. and A. Granier. 1978. Quelques
rgsultats de cinltique journalifcre du potentiel de seve
chez les arbes forestiers. Annal. des Sci. Forest.
35:19-32.
Baker, J.M. and R.R. Allmaras. 1990. System for
automating and multiplexing soil moisture measure-
ment by time-domain reflectometry. Soil Sci. Soc.
Am. J. 54:1-6.
Baker, J.M. and RJ. Lascano. 1989. The spatial
sensitivity of time-domain reflectometry. Soil Sci.
147:378-384.
Baker, J.M. and C.H.M. van Bavel. 1987. Measure-
ment of mass flow of water in the stems of herbaceous
plants. Plant Cell Environ. 10:777-782.
Baker, J.T., L.H. Allen, Jr., KJ. Boote, J.W. Jones
and P. Jones. 1990. Developmental responses of
rice to photoperiod and carbon dioxide concentra-
tions. Agricul. For. Meteorol. 50:201-210.
Baker, J.T., F. Laugel, KJ. Boote, and L.H. Allen, Jr.
1992. Effects of daytime carbon dioxide concentra-
tion on dark respiration in rice. Plant Cell
Environment, 15:231-329.
Barker, J.E 1973. Diurnal patterns of water poten-
tial in Abies concolor and Pinusponderosa. Can. J.
For. Res. 3:967-984.
Bamosky, CW, P.M. Anderson and PJ. Bartlein.
1987. TTie northwestern U.S. during deglaciation:
Vegetational history and paleoclimatic implications.
Ill: W.F. Ruddiman and H.E Wright, Jr. (eds.),
North America and Adjacent Oceans During the
Page 91
Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
LastDeglaciation. The Geology of North America,
Vol. K-3. Geol. Soc. Amer., Boulder, CO.
Bartlett, R., and B. James. 1980. Studying dried,
stored soil samples - some pitfalls. Soil Sci. Soc.
Am. J. 44:721-724.
Beadle, C.L., P.G. Jarvis and Rฃ. Neilson. 1979.
Leaf conductance as related to xylem water potential
and carbon dioxide concentration in Sitka spruce.
Physiol. Plant 45:158-166.
Beadle, C.L., N.C. Turner and P.G. Jarvis. 1978.
Critical water potential for stomatal closure in Sitka
spruce. Physiol. Plant. 43:160-165.
Beedlow, PA, D.S.Daly and M.EThiede. 1986. A
new device for measuring fluctuations in plant stem
diameter Implications for monitoring plant re-
sponses. Environ. Monit Assess. 6:277-282.
Boyer,J.S. 1968. Relationship of water potential to
growth of leaves. Plant Physiol. 43:1056-1062.
Boyer, J.S. 1976a. Water deficits and photosynthe-
sis. In: T.T. Kozlowski (ed.), Water Deficits and
Plant Growth, Vol. IV. Academic Press, NY.
Boyer, J.S. 1976b. Photosynthesis at low water
potentials. Philosoph. Trans. Roy. Soc. London B
273:501-522.
Brandle, J.R., T.M. Hinckley and G.N. Brown.
1977. The effects of dehydration-rehydration cycles
on protein synthesis ofblack locust seedlings. Physiol.
Plant 40:1-5.
Bremner,J.M.and AM.BIackmer. 1982. Compo-
sition of soil atmospheres. pp. 873-901. 2q: Page,
A.L, R.H. Miller and D.R. Keeney (eds.), Methods
of Soil Analysis (Part 2): Chemical and Microbio-
logical Properties. 2Dd Ed. Soil Sci. Soc. Amer.,
Madison, WI.
Bremner, J.M. and M A Tabatabai. 1971. Use of
automated combustion techniques for total carbon,
total nitrogen, and total sulfur analysis of soils, pp 1-
15. Iq: L.M. Walsh (ed.), Instrumental Methods for
Analysis of Soils and Plant Tissue. Soil Sci. Soc.
Amer., Madison, WI.
Brinkman, R. 1990. Resilience against climate
change? Soil minerals, transformation and surface
properties, Eh, and pH. pp. 51-60. |q: H.W.
Scharpenseel, M. Schomaker and A. Ayoub (ed.),
Soils OnaWarmer Earth. Proc. International Work-
shop on Effects of Expected Climate Change on Soil
Processes in the Tropics and Sub-tropics, February,
Nairobi, Kenya.
Brix,H. 1967. An analysis of dry matter production
in Douglas-fir seedlings in relation to temperature
and light intensity. Can. J. Bot. 454:2063-2072.
Brown, D.A. and D.R. Upchurch. 1987.
Minirhizotrons: A summary of methods and instru-
ments in current use. pp. 15-20. La: H.M. Taylor
(ed.), Minirhizotron Observation Tubes: Methods
and Applications for Measuring Rhizosphere Dy-
namics. Amer. Soc. Agron. Spec. Publ. 50. Amer.
Soc. Agron., Crop Sci. Soc. Amer. and Soil Sci. Soc.
Amer., Madison, WI.
Brubaker,L.B. 1986. Responses of tree populations
to climatic change. Vegetatio 67:119-130.
Brubaker,L.B. 1988. Vegetation history and antici-
pating future vegetation change. In: Agee, J. and D.
Johnson (ed.), Ecosystem Management for Parks
and Wilderness. University of Washington Press,
Seattle, WA
Brutsaert, W. 1982. Evaporation into the Atmo-
sphere. D. Reidel, Dordrecht, 299 p.
Bunce, J A and LN. Miller. 1976. Differential
effects of water stress on respiration in the light in
woody plants from wet dry habitats. Can. J. Bot.
54:2457-2464.
Burke, M J., L.V. Gusta, HA Quamme, C J. Weiser
and P.H. U. 1976. Freezing injury in plants. Ann.
Rev. Plant Physiol. 27:507-528.
Page 92 CorvaUis Environmental Research Laboratory
-------
Effects of COj and CUnusit Change on Forest Trees
Caetano-Anolles, G., BJ. Bassam and P.M.
Gresshoff. 1991. DNA amplification fingerprinting
using very short arbitrary oligonucleotide primers.
Bio/Technol. 9:553-557.
Campbell, R.K. 1978. Regulation of bud burst
timing by temperature and photoregime during dor-
mancy. Jn: CA. Hollis (ed.), Proc. Fifth N. Amer.
For. Biol. Workshop.
Gark,J.S. 1988. Effects of climate change on fire
regimes in northwestern Minnesota. Nature 334:233-
235.
Qeaiy, B.D. and R.H. Waring. 1969. Temperature:
Collection of data and its analysis for the interpreta-
tion of plant growth and distribution. Can. J. Bot.
47:167-173.
Cole, PJ. and A.M. Alston. 1974. Effect of transient
dehydration on absorption of chloride by wheat
roots. Plant Soil 40:243-247.
Committee on Earth and Environmental Science
(CEES). 1990. Our Changing Planet: The FY 1991
Research Plan. Committee on Earth and Environ-
mental Science, c/o U.S. Geological Survery, Reston,
VA.
Copes, D.L 1983. Failure of grafted Douglas-fir
planted at Monterey, California. Tree Planters Notes
34:9-10.
Cwynar,LC. 1987. Fire and the forest history of the
North Cascade range. Ecology 68:791-802.
Daubenmire, RJ7. 1943. Vegetational zonation in
the Rocky Mountain. BoL Rev. 9:326-393.
Daughtridge, A.T., S.R. Boese, S.G. Pallardy and
H.E Garrett 1986. A rapid staining technique for
assessment of ectomycorrhizal infection of oak roots.
Can. J. Bot. 63:1101-1103.
Davis, M.B. 1981. Quaternary history and the
stability of forest communities. Iq: West, D.C., H.H.
Shugart and D.B. Botkin (eds.), Forest Succession:
Concepts and Application. Springer-Verlag, N.Y.
517 pp.
Davis, M.B. 1989. Lags in vegetation response to
greenhouse warming. Clim. Change 15:75-82.
Dionex. 1989. Analysis of carbohydrates by anion
exchange chromatography with pulsed amperometric
detection. Dionex Technical Note TN 20, March
1989.
Dolph, J., D. Marks and G. A. King. 1992. Sensitiv-
ity of the regional water balance in the Columbia
River basin to climate variability: Application of a
spatially distributed water balance model, pp. 233-
265. In: R J Naiman (ed.), Watershed Management:
Balancing Sustainability and Environmental Change.
Springer-Verlag, NY.
Dougherty, P.M. and Y.Morikowa. 1980. Influence
of elevation on the growth, photosynthesis and water
relations of Pseudotsuga menziesii. Plant Physiol.
65 (Supplement):155.
Drake, B.G., H.H. Rogers and LH. Allen, Jr. 1985.
Methods of exposing plants to elevated C02. pp. 11-
31. In: B.R. Strain and J.D. Cure (eds.), Direct
Effects of Carbon Dioxide on Vegetation. DOE/ER-
0238, U.S. Dept. of Energy, Carbon Dioxide Res.
Div., Washington, D.C.
Drew, A.P. and W.K. Ferrell. 1979. Seasonal
changes in the water balance of Douglas fir
(Pseudotsuga menziesii) seedlings grown under dif-
ferent light intensities. Can. J. Bot. 57:666-674.
Dunham, RJ. and P.H. Nye. 1976. The influence of
soil water content in the uptake of ions by roots, m.
Phosphate, potassium, calcium and magnesium up-
take and concentration gradients in soil. J. App. Sci.
13:294-299.
Eamus, D. and P.G. Jarvis. 1989. Direct effects of
C02 increases on trees and forests (natural and
commercial) in the U.K. Adv. Ecol. Res. As cited
in Jarvis (1989)
Page 93 CorvaUis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
Edwards, N.T. and S.B. McLaughlin. 1978. Tem-
perature-dependent diel variations of respiration rates
in Quercus alba and Liriodendron tulipifera. Oikos
31:200-206.
Emanuel, W.R., H.H. Shugart and M.P. Stevenson.
1985a. Climatic change and the broad-scale distri-
bution of terrestrial ecosystem complexes. Clim.
Change 7:29-43
Emanuel, W.R., H.H. Shugart and M.P. Stevenson.
1985b. Response to comment: Climatic change and
the broad-scale distribution of terrestrial ecosystem
complexes. Clim. Change 7:457-460.
Feil, W., I. Kottke and Oberwinkler. 1988. The
effect of drought in mycorrhizal production and very
fine root system development of Norway spruce
under natural and experimental conditions. Plant
Soil 108:221-231.
Fernandez, IJ. and PA. Kosian. 1987. Soil air
carbon dioxide concentration in a New England
spruce-fir forest Soil Sic. Soc. Am. J. 51:261-263.
Franklin, J.F. 1988. Pacific Northwest forests, pp.
103-130. In: M. Barbour and W.D. Billings, Jr,
(eds.), North American Terrestrial Vegetation. Cam-
bridge University Press, New York.
Franklin J.F. and C.T. Dyrness. 1973. Natural
vegetation of Washington and Oregon. USD A For.
Serv. Gen. Techn. Rep PNW-8.
Franklin, J.F.. and C.T. Dyrness. 1988. Natural
Vegetation of Oregon and Washington. Oregon
State University Press, Corvallis, OR.
Franklin, J J", and R.G. Mitchell. 1967. Succes-
sional status of subalpine fir in the Cascade Range.
USDA For. Serv. Res. Paper PNW-46. Pac. North-
west For. and Range Exp. Stn., Portland, OR.
Franklin, J.F, FJ. Swanson, M.E Harmon, DA
Perry, TA Spies, V.H. Dale, A. McKee, W.KL
Ferrell, J.E. Means, S.V. Gregory, J.D. Lattin, T.D.
Schowalter and D. Larsen. 1991. Effects of global
climatic change on forests in North America. North-
west Environ. J. 7:233-254.
Fritts, H.C. 1958. An analysis of radial growth of
beech in a central Ohio forest during 1954-1955.
Ecol. 39:705-720.
Gardner, W.H. 1965. Water content pp 82-127. In:
CA Black et al. (eds.), Methods of Soil Analysis.
Part 1. Physical and Mineralogical Properties In-
cluding Statistics of Measurement and Sampling.
Agron. No. 9, Amer. Soc. Agron., Madison, WI.
Gardner, W.H. 1986. Water content p. 493-544. In:
A. Klute (ed.), Methods of Soil Analysis, Part 1.2nd
ed. Amer. Soc. Agron., Soil Sci. Soc. Amer., Madi-
son, WI.
Gholz, H.L. 1982. Environmental limits on
aboveground net primary production, leaf area, and
biomass in vegetation zones of the Pacific North-
west. Ecol. 63:469-481.
Givannetti, M.B. and B. Mosse. 1980. An evalua-
tion of techniques for measuring vesicular aibuscular
mycorrhizal infection in roots. NewPhytol. 84:489-
500.
Graham, R.L., M.G. Turner and V.H. Dale. 1990.
How increasing COz and climate change affect
forests. Bioscience 40:575-587.
Graumlich, LJ. 1987. Precipitation variation in the
Pacific Northwest (1675-1975) as reconstructed from
tree rings. Ann. Assoc. Amer. Geog. 77:19-29.
Greacen,E.L 1981. Soil Water Assessment by the
Neutron Method. CSIRO, Australia.
Greaves, R.D., R.K. Hermann and B.D. Geary.
1978. Ecological principles. In: B.D. Cleary, R.D.
Greaves and R.K. Hermann (eds.), Regenerating
Oregon's Forests. Oregon State Univ. Exten. Serv.,
Exten. Man. No. 7. Oregon State University Press,
Corvallis, OR.
Page 94 Corvallis Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
Greenway, H., P.G. Hughes and B. Kleppers. 1969.
Effects of water deficit on phosphorus nutrition of
tomato plants. Physiol. Plant. 22:199-207.
Griffiths, R.P., BA Caldwell, K. Cromack, Jr. and
R.Y. Morita. 1990. Douglas-fir forest soils colo-
nized by ectomycorrhizal mats. I. Seasonal variation
in nitrogen chemistry and nitrogen cycle transforma-
tion rates. Can. J. For. Res. 20:211-218.
Griffiths, R.P., ER. Ingham, BA Caldwell, MA
Castellano and K. Cromack, Jr. 1991. Microbial
characteristics of ectomyconhizal mat communities
in Oregon and California. Bio. Fert. Soils 11:196-
202.
Gucinski, H., D. Marks and D. P. Turner. 1990.
Biospheric feedbacks to climate change: The sen-
sitivity of segional trace gas emissions,
evapotranspiration, and energy balance to vegeta-
tion redistribution. U.S. Environ. Protect. Agency,
Environ. Res. Lab., Corvallis, OR. Techn. Rep.
EPA/600/3-90/078,265 p.
Ham,J.M..andJ.L.Heilman. 1990. Dynamics of a
heat balance stem flow gauge during high flow.
Agron. J. 82:147-152.
Hansen, J., G. Russell, D. Rind, P. Stone, A. Lacis,
S. Lebedeff, R. Ruedy and L Travis. 1983. Efficient
three-dimensional global models for climate stud-
ies: Models I and II. Mon. Weath. Rev. 3:609-662.
Harmon, MI.,W.ICFerrell and J.F. Franklin. 1990.
Effects on caibon storage of conversion of old-
growth forests to young forests. Science247:699-702.
Heimovaara, TJ. and W. Bouten. 1990. A com-
puter-controlled 36-channel time domain
reflectometry system for monitoring soil water con-
tents. Water Resour. Res. 26:2311-2316.
Hendrey, G.R., F.W. Lipfert, BA Kimball, D.R.
Hileman, and N.C. Bhattacharya. 1988. Response
of Vegetation to Carbon Dioxide046.
Hendrick, R.L. and K.S. Pregitzer. 1992. The
demography of fine roots in a northern hardwood
forest. Ecol. 73:1094-1104.
Hendrix, D.L. and R.I. Grange. 1991. Caibon parti-
tioning and export from mature cotton leaves. Plant
Physiol. 69:327-331.
Hermann, R.K. and D.P. Lavender. 1990.
Pseudotsuga menziesii (Miib.) Franco. Douglas-
Fir. Silvics of North America. Vol. 1 Conifers.
pp.527-539. R.M. Burns and B.H. Honkala (techni-
cal coordinators). USDA For. Serv., Washington,
DC., Agricul. Handbook 654.
Hinckley, T.M., D.R. Thompson, M.P. McGinness
and A.R. Hinckley. 1976. Stem growth and phenol-
ogy of a dominant white oak. |q: J.S. Fralish, G.T.
Weaver and R.C. Schlesinger (eds.), First Central
Hardwood Forest Conference Proceedings, South-
era Illinois University, Carbondale, IL.
Hinckley, T.M., J.P. Lassoie and S.W. Running.
1978. Temporal and spatial variations in the water
status of forest trees. For. Sci. Monog. No. 20.
Holdridge, L.R. 1947. Determination of world
formulations from simple climatic data. Science
105:367-368.
Holdridge, L.R. 1967. Life Zone Ecology. Tropical
Science Center, San Jose, Costa Rica.
Hollinger,D.Y. 1987. Gas exchange and dry matter
allocation responses to elevation of atmospheric
C02 concentrations in seedlings of three tree species.
Tree Physiol. 3:193-202.
Holmes, J.W. and S.Y. Shim. 1968. Diurnal changes
in stem diameter of Canary Island pine trees (Pinus
canariensis C. Smith) caused by soil water stress and
varying microclimate. J. Exp. BoL 19:219-233.
Houghton, J.T., GJ. Jenkins and JJ. Ephraums
(eds.). 1990. Climate Change: The IPCC (Intergov-
ernmental Panel on Climate Change) Scientific
Page 95
CorvaUis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trees
Assessment. Cambridge University Press, Cam-
bridge, England.
Hu, J. and C.F. Quiros. 1991. Identification of
broccoli and cauliflower cultivars with RAPD mark-
ers. Plant Cell Reports 10:505-511.
Hurewitz, J. and J.W.Janes. 1983. Effect of altering
the root-zone temperature on growth, translocation,
carbon exchange rate, and leaf starch accumulation
in the tomato. Plant Physiol. 73:46-50.
ICF.Inc. 1989. Summary Report: Scenarios Advi-
sory Meeting. Nat. Ctr.Atmos. Res., Boulder, CO.
August 31-September 1,1989. U.S. Environ. Pro-
tect Agency, Off. Policy, Planning and Evaluation,
Off. Policy Analysis. Washington, D.C.
Ingestad, T. 1979. Mineral nutrient requirements of
Pinus silvestris and Picea abies seedlings. Physiol.
Plant. 45:373-381.
Jackson, J.D. and G.C. Spomer. 1979. Biophysical
adaptations of four western conifers to habitat water
conditions. Bot Gaz. 140:428-432.
Jarvis, P.G. 1989. Atmospheric Carbon Dioxide
and Forests. Phil.Trans. R. Soc. Lond. 324:369-392.
Jarvis, P.G. and M.S. Jarvis. 1965. The water
relations of tree seedlings. V. Growth and root
respiration in relation to osmotic potential of the root
medium. In: B. Slavik (ed.), Water Stress in Plants,
Hie Hague.
Jenkinson, D.S., D.E Adams and A. Wild. 1991.
Model estimates of C02 emissions from soil in
response to global wanning. Nature 351:304-306.
Jenne, R.L. 1988. Data From Climate Models, the
C02 Warming. Nat Ctr.Atmos. Res., Boulder, CO.
Johnson, D.W., J.T. Ball and R.B. Walker. 1991.
Effects of C02 on nitrogen uptake in Ponderosa pine
seedlings, p. 351. Agronomy abstracts. ASA,
Madison, WI.
Jones, M.M. and C.B. Turner. 1980. Accumulation
of solutes in leaves of sorghum and sunflower in
response to water deficits. Austral. J. Plant Physiol.
7:193-205.
Jones, P., L.H. Allen, Jr., J.W. Jones, KJ. Boote and
WJ. Campbell. 1984a. Soybean canopy growth,
photosynthesis, and transpiration responses to whole-
season carbon dioxide enrichment. Agron. J.
76:633-637.
Jones, P., J.W. Jones, L.H. Allen, Jr. and J.W.
Mi shoe. 1984b. Dynamic computer control of closed
environment plant growth chambers. Design and
verification. Trans. ASAE. 27:879-888.
Jones, P. L.H. Allen, Jr., J.W. Jones and R. Valle.
1985. Photosynthesis and transpiration responses of
soybean canopies to short- and long-term C02 treat-
ments. Agron. J. 77:119-126.
Karl, T.R., G. Kukla, V.N. Razuvayev, M.J.
Changery, R.G. Quayle, R.R. Heim, D.R. Easterling
andC.B.Fu. 1991. Global warming - Evidence for
asymetric diurnal temperature-change. Geophys.
Res. Letters 18:2253-2256.
Kaufmann, M.R. and A.N. Eckard. 1977. Water
potential and temperature effects on germination of
Engelmann spruce and lodgepole pine seeds. For.
Sci. 23:27-33.
Keeling, C.D., R.B. Bacastrow, A.F. Carter, S.C.
Piper, T.P. Whorf, M. Heinmann, W.G. Mook and
H. Roeloffzen. 1989. A three dimensional model of
atmospheric C02 transport based on observed winds:
4. Mean annual gradients and interannual variations.
Ia: D.H. Peterson (ed.), Aspects of Climate Variabil-
ity in the Pacificand the Western Americas. Geophys.
Monog.55:305-363. Amer. Geophys. Union, Wash-
ington, DC.
Kerr, R A. 1992. Hot nights in the greenhouse. Sci.
255:682-683.
Page 96 CorvaUis Environmental Research Laboratory
-------
Effects of CO2 and Climait Change on Forest Trees
Khali], MAK. and RA Rasmussen. 1987. Atmo-
spheric methane: trends over the last 10,000 years.
Atmos. Environ. 21:2445-2452.
Knievel,D.P. 1973. Procedure for estimating ratio
of living to dead root dry matter in root core samples.
CropSci. 13:124-126.
Koide, R.T., R.H. Bobichaux, S.R. Morse and C.M.
Smith. 1991. Plant water status, hydraulicresistance
and capacitance, pp 161-183. In: R.W. Pearcy, J.
Ehleringer, HA Mooney and P.W. Rundel (eds.),
Plant Physiological Ecology. Field Methods and
Instrumentation. Chapman and Hall, London, En-
gland.
Koske, R.E and J.N. Gemma. 1989. A modified
procedure for staining roots to detect VA mycorrhi-
zas. Mycol. Res. 92:486-505.
Kottke,I. and R. Agerer. 1983. Untersuchungenzur
Bedeutung der Mykorrhiza in Laub-und Nadelwald-
bestanden des Sudwestdeutsdien Keuperberglandes.
Mitt Ver. Forstl. Standortskd. Forst. Pfl., 30:30-39.
Kozlowski, T.T. 1967. Diurnal variations in stem
diametersofsmall trees. BoLGaz. (Chicago) 128:60-
68.
Kozlowski, T.T. 1982. Water supply and tree
growth. Part I. Water deficits. For. Abstr., Common.
For. Bur. 43:57-95.
Kozlowski, T.T. 1983. Reduction in yield of forest
and fruit trees by water and temperature stress. In:
CD. Raper and P J. Kramer (eds.), Crop Reactions
to Water and Temperature Stresses in Humid, Tem-
perate Climates. Westview Press, Boulder, CO.
Kozlowski, T.T., PJ. Kramer and S.G. Pallardy.
1991. The Physiological Ecology of Woody Plants.
Academic Press, NY.
Kramer, PJ. 1983. Water Relations of Plants.
Academic Press, Inc., San Diego, 489 pp.
Kramer, PJ. and T.T Kozlowski. 1979. Physiology
of Woody Plants. Academic Press, NY.
Kramer, P J. and S.SioniL 1987. Effects of increas-
ing carbon dioxide concentrations on the physiology
and growth of forest trees. Iq: W.E. Shands and J.S.
Hoffman (eds.), The Greenhouse Effect, Climate
Change, and the U.S. Forest. Thomson-Shore, Inc.,
Dexter, MI.
Lassoie, J.P. 1982. Physiological activity in Dou-
glas-fir. |q: R.L. Edmonds (ed.), Analysis of
Coniferous Ecosystems in the Western United States,
US/IBP Synthesis Ser. 14, Hutchinson Ross Pub-
lishing Co., Stroudsburg, PA.
Lassoie, J.P., T.M. Hinckley and C.C. Grier. 1985.
Coniferous forests of the Pacific Northwest. In: B.F.
Chabot and HA. Mooney (eds.), Physiological Ecol-
ogy ofNorth American Plant Communities. Chapman
and Hall, NY.
Lavender, D.P. 1978. Seeds, cone collection, pro-
cessing and storage. In: B.D. Cleary, R.D. Greaves
and R.K. Hermann (eds.), Regenerating Oregon's
Forests. Oregon State Univer. Exten. Serv., Exten.
Man. No. 7. Oregon State University Press, Corvallis,
OR.
Lavender, D.P. 1981. Environment and shoot
growth of woody plants. For. Res. Lab., Sch. of For.,
Oregon State Univ., Corvallis, OR. Res. Pap. 45.
Lavender, D.P. and R.K. Hermann. 1970. Regula-
tion of the growth potential of Douglas-fir seedlings
during dormancy. New Phytol. 69:675-694.
Lavender, D.P. and W.S. Overton. 1972.
Thermoperiods and soil temperatures as they affect
growth and dormancy of Douglas-fir seedings of
different geographic origin. For. Res. Lab., Sch. of
For., Oregon State Univer., Corvallis, OR. Res. Pap.
13.
Lawrence, W.T. and W.C. Oechel. 1983a. Effects
of soil temperature on the carbon exchange of taiga
Pag* 97
Corvallis Environmental Research Laboratory
-------
Effects of CO j and Climate Change on Forest Trees
seedlings. I. Root respiration. Can. J. For. Res.
13:840-849.
Lawrence, W.T. and W.C. Oechel. 1983b. Effects
of soil temperature on the carbon exchange of taiga
seedlings. D. Photosynthesis, respiration and con-
ductance. Can. J. For. Res. 13:850-859.
Leemans, R. 1990. Possible changes in natural
vegetation patterns due to a global wanning. Pub.
No. 108 of the Biospheric Dynamics Project, Int.
InstiL for Appl. Systems Anal. A-2361, Laxenburg,
Austria.
Leemans, R. and W.P. Cramer. 1990. The EASA
database for mean monthly values of temperature,
precipitation and cloudiness on a global terrestrial
grid. Working Pap. 90-41. Int Inst, for Appl.
Systems Analysis. Laxenburg, Austria.
Legard, HA. and L.C. Meyer. 1973. Willamette
National Forest soil resource inventory. USD A For.
Ser., Pac. Northwest Region.
Leverenz, J.W. 1981a. Net photosynthesis as re-
lated to shoot hierarchy in a large dominant
Douglas-fir. M.S. thesis, University of Washington,
Seattle, WA.
Leverenz, J.W. 1981b. Photosynthesis and transpi-
ration in large forest-grown Douglas-fir: Diurnal
variation. Can. J. Bot. 59:349-356.
Leverenz, J.W. 1981c. Photosynthesis and transpi-
ration in large forest-grown Douglas-fir. Interactions
with apical control. Can. J. Bot. 59:2568-2576.
Leverenz, J.W. and DJ. Lev. 1987. Effects of
carbon dioxide-induced climate changes on the natu-
ral ranges of six major commercial tree species in the
Western United States, pp. 123-155. In: W.E.
Shands and J.S. Hoffman (eds.), The Greenhouse
Effect, Climate Change, and U.S. Forests. The
Conservation Foundation, Washington, DC.
Levitt, J. 1972. Responses of Plants to Environmen-
tal Stresses. Academic Press, NY.
Little, E.L 1971. Atlas of United States Trees. Vol
1. Conifers and Important Hardwoods. USDA For.
Serv., Washington, DC., Misc. Pub. No. 1146.
Lodge, DJ. and E.R. Ingham. 1991. A comparison
of agar film techniques for estimating fungal
biovolumes in litter and soil. Agric. Ecosys. Environ.
34:131-144.
Loffroy, 0.,C. Hubac and J.B. Vieira da Silva. 1983.
Effect of temperature on drought resistance and
growth of ootton plants. Physiol. Plant. 59:297-301.
Lopushinsky.W. 1975. Stomatal closure in conifer
seedlings in response to leaf moisture stress. Bot
Gaz. 130:250-263.
Luukkanen, O. 1978. Investigations on factors
affecting net photosynthesis in trees: Gas exchange
in clones Picea abies (L.) Karst. Acta Forest. Fenn.
162:1-63.
Manabe,S.andR.T.Wetherald. 1987. Large-scale
changes in soil wetness induced by an increase in
carbon dioxide. J. Atmos. Sci. 44:1211-1235.
Marks, D. 1988. Climate, energy exchange, and
snowmelt in Emerald Lake watershed, Sierra Ne-
vada. Ph.D. Dissertation, Departs, of Geography and
Mechanical Engineering, University of California,
Santa Barbara, CA, 158 pp.
Marks, D. 1991. A continental-scale simulation of
potential evapotranspiration for historical and pro-
jected doubled-C02 climate conditions. Submitted
to Clim. Change.
Mattson, PA, C. Volkmann, K. Coppinger and
WA Reiners. 1991. Annual nitrous oxide flux and
soil nitrogen characteristics in sagebrush steppe
eoosystems. Biogeochem. 14:1-12.
Mattson, WJ. and RA Haack. 1987. The role of
drought in outbreaks of plant-eating insects.
Bioscience 37:110-118.
Page 98 CorvaUis Environmental Research Laboratory
-------
Effects of CO j and Climate Change on Forest Trees
Melillo, J.M., J.D. Aber, and J.F. Muratore. 1982.
Nitrogen and lignin control of hardwood leaf litter
decomposition dynamics. Ecology 63:621-626.
Melillo, J.M., PA. Steudler, J.D. Aber and R.D.
Bowden. 1989. Carbon and nitrogen dynamics
along the decay continuum: plant litter to soil or-
ganic matter. Plant Soil 115:189-198.
Miller, J.E, R.P. Patterson, WA Pursley, AS.
Heagle and W.W. Heck. 1989. Response of soluble
sugars and starch in field-grown cotton to ozone,
water stress, and their combination. Environ. Exp.
BoL 29:477-486.
Minore, D. 1979. Comparative autecological char-
acteristics of northwestern tree species: A literature
review. USDA For. Serv. Gen. Techn. Rep. PNW-
87.
Mitchell, J.F.B. 1989. The "greenhouse" effect and
climate change. Rev. Geophys. 27:115-139.
Mitchell, R.G. 1966. Infestation characteristics of
the balsam wooly aphid in the Pacific Northwest.
USDA For. Serv. Res. Pap. PNW-35. Pac. North-
west Res. Stn., Portland, OR.
Mooiby, J. and Graves, CJ. 1980. Root and air
temperature effects on growth and yield of tomatoes
and lettuce. Acta Hortic. 98:29-43.
Morison, J.I.L. 1985. Sensitivity of stomata and
water use efficiency to high COr Plant Cell Environ.
8:467-474
National Oceanic and Atmospheric Administration
(NOAA). 1989a. Climatological data annual sum-
mary. Oregon Vol. 95, No.13. Nat Climatic Data
Ctr., Asheville, NC
National Oceanic and Atmospheric Administration
(NOAA). 1989b. Climatological data annual sum-
mary. Washington Vol. 93, No. 13. Nat. Climatic
Data Ctr., Asheville, NC.
Neilson,R.E.andP.G.Jarvis. 1975. Photosynthesis
in Sitka spruce (Picea sitchensis [Bong.] Carr.). VI.
Response of stomata to temperature. J. Appl. Ecol.
12:879-891.
Neilson, R.P., GA King, R.L DeVelice, J. Lenihan,
D. Marks, J. Dolph, B. Campbell and G. Glick. 1989.
Sensitivity of ecological landscapes and regions to
global climate change. U.S. Environ. Protect.
Agency, Environ. Res. Lab., Corvallis, OR. EPA/
600/3-89/073.
Nelson, D.W. and L.E. Sommers. 1982. Total
carbon, organic caibon, and organic matter. In:
Page, A.L., R.H. Miller and D.R. Keeney (eds.),
Methods of Soil Analysis (Part 2): Chemical and
Microbiological Properties. 2nd Ed. Soil Sci. Soc.
Amer., Madison, WI.
Nobel, P. 1991. Physicochemical and environmen-
tal plant physiology. Academic Press, Inc. San
Diego, CA 635 pp.
Noodfin, L.D. and J A Weber. 1978. Environmen-
tal and hormonal control of dormancy in terminal
buds of plants, pp. 221-268. In: M.E. Gutter (ed.),
Dormancy and Development Arrest. Academic
Press, Inc, N.Y.
Norby, RJ., CA Gunderson, S.D. Wullschleger,
E.G. O'Neill, and M.K. McCracken. 1992. Produc-
tivity and compensatory responses of yellow-poplar
trees in elevated COr Nature 357:322-324.
Norse, EA 1990. Ancient Forests of the Pacific
Northwest. Island Press, Washington, D.C.
Oechel, W.C. and B.R. Strain. 1985. Native species
responses to increased atmospheric carbon dioxide
concentration. In: Direct Effects of Increasing Car-
bon Dioxide on Vegetation. U.S. DOE, DOE/
ER-0238
Oosterhuis, D.M. and S.D. Wullschleger. 1987.
Osmotic adjustment in cotton (Gossypium hirsutum)
leaves and roots in response to water stress. Plant
Physiol. 84:1154-1157.
Page 99 Corvallis Environmental Research Laboratory
-------
Effects of COj and Climate Chang* on Forts! Trees
Overpeck, J.T., D. Rind and R. Goldberg. 1990.
Climate-induced changes in forest disturbance and
vegetation. Nature 343:51-53.
Parry, M.T..T.R. Carter, N.KonijinandJ.Lockwood.
1987. The impact of climatic variations on agricul-
ture. 2q: Introduction to the OASA/UNEP Case
Studies in Semi-Arid Regions. Int. Inst for Appl.
Systems Anal., Laxenburg, Austria.
Patching, W.R. 1987. Soil Survey of Lane County
Area, Oregon. USDA Soil Conservation Serv.
Penning de Vries, F.W.T. 1975. The cost of mainte-
nance processes in plant cells. Ann. Bot. 39:77-92.
Perry, DA. 1988. Landscape pattern and forests
pests. NW Environ. J. 4:213-228.
Perry, DA. and J. Maghembe. 1989. Ecosystem
concepts and current trends in forest management:
Time for reappraisal. For. Ecol. Manag. 26:123-
140.
Perry, DA., J.G. Borchers, S.L. Borchers and M.P.
Amaranthus. 1990. Species migrations and ecosys-
tem stability during climate change: The belowground
connection. Conserv. Biol. 4:266-274.
Peterson, C.E and LS. Heath. 1990. The influence
of weather variation on regional growth of Douglas-
fir stands in the U.S. Pacific Northwest. Water Air
Soil Pollut. 54:295-305.
Pitman, M.G. 1981. Ion uptake. 1q: L.G. Paleg and
D. Aspinall (eds.), The Physiology and Biochemis-
try of Drought Resistance in Plants, Academic Press,
NY.
Prentice, K.C 1990. Bioclimatic distribution of
vegetation for GCM studies. J. Geophys. Res.
95:811-830.
Prentice, K.C. and I.Y. Fung. 1990. The Sensitivity
of Terrestrial Carbon Storage to Climate Change.
Nature 346:48-51.
Quiros, C.F., J. Hu, P. This, AM. Chevre and M.
Delseny. 1991. Development and chromosomal
localization of genome-specific markers by poly-
merase chain reaction in Brassica. Theoretical and
Applied Genetics 82:627-632.
Ramanathan, V., R J. Cicerone, H.B. Singh and J.T.
Kiehl. 1985. Tracegastrendsandtheirpotentialrole
in climate change. J. Geophys. Res. 90:5547-5566
Raschke, K. 1979. Movements of stomata. pp 383-
441. la: W. Haupt and M.E. Feinleib (eds.),
Physiology of Movements. Encyclop. of Plant
Physiol. 7. Springer-Verlag, NY.
Rastetter, E.B., M.G. Ryan, G.R. Shaver, J.M. Melillo,
KJ. Nadelhoffer, J.E Hobbie and J.D. Aber. 1991.
A general biogeochemical model describing the
responses of the C and N cycles in terrestrial ecosys-
tems to changes in C02 climate, and N deposition.
Tree Physiol. 9:101-126.
Rogers, H.H., G.E. Bingham, J.D. Cure, J.M. Smith
and K.A. Surano. 1983a. Responses of selected
plant species to elevated carbon dioxide in the field.
J. Environ. Qual. 12:569-574.
Rogers, H.H., W.W. Heck and AS. Heagle. 1983b.
A field technique for the study of plant response to
elevated Carbon Dioxide concentration. J. Air Pollut.
Control Assoc. 33,42-44.
Rogers, H.H., C.M. Peterson, J.N. McCrimmon and
J.D.Cure. 1992. Response of plant roots to elevated
atmospheric carbon dioxide. Plant Cell Environ.
15:749-752.
Running, S.W. 1976. Environmental control of leaf
water conductance in conifers. Can. J. For. Res.
6:104-112.
Russell, EW. 1973. Soil Conditions and Plant
Growth. Longman, London, UK.
Rutter,M.R. 1977. An eco-physiological field study
of three conifers. Ph.D. thesis, University of Califor-
nia, Berkeley, CA
Page 100 Corvallls Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
Ryan, M.G. 1991. Effects of climate change on plant
respiration. Ecol. Appl. 2:157-167.
Sakai, A 1983. Comparative studies on freezing
resistance of conifers with special reference to cold
adaptation and its evolutive aspects. Can. J. Bot.
61:2323-2332.
Salo.DJ. 1974. Factors affecting photosynthesis in
Douglas-fir. Ph.D. thesis, University of Washing-
ton, Seattle, WA
Schlesinger, M.E and Z.C. Zhao. 1989. Seasonal
climatic change introduced by doubled C02 as simu-
lated by the OSU atmospheric GCM/mixed-layer
ocean model. J. dim. 2:429-495.
Scholander, P.F., H.T. Hammel and E.D. BradstreeL
1965. Sap pressure in vascular plants. Science
148:339-46.
Schutte, K.H. and C.P. Burger. 1981. Sensitive
dendrometers for contemporary research: A critical
evaluation of strain gauge dendrometers. J. S. Afri-
can Bot 47:273-291.
Scott, D.R.M. 1980. The Pacific Northwest region,
pp 447-493. Iq: J.W. Barrett (ed.), Regional Silvi-
culture of the United States. John Wiley & Sons, Inc.,
NY.
Shone, M.G.T. and AY. Flood. 1983. Effects of
periods of localized water stress on subsequent
nutrient uptake by barley roots and their adaptation
by osmotic adjustment. New Phytol. 94:561-572.
Sionit, N. and PJ. Kramer. 1984. Woody plants
reactions to carbon dioxide enrichment Iq: Carbon
Dioxide Enrichment of Greenhouse Crops. CRC
Press, Boca Raton, FL.
Sionit, N.,B.R. Strain and E.P. Flint 1987. Interac-
tion of temperature and C02 enrichment on soybean:
Growth and dry matter partitioning. Can. J. Plant
Sci, 67:59-67.
Smith, J.B. and DA. Tirpak. 1989. The Potential
Effects of Global Climate Change on the United
States. US Environ. Protect Agency, Washington,
DC, EPA/230/05-89/051.
Smith, T.M., H.H. Shugart, G.B. Bonan and J.B.
Smith. 1991. Modeling the potential response of
vegetation to global climate change. Adv. Ecol. Res.
22:93-116.
Smucker, AJ.M, J.C. Ferguson, W.P. DeBruyn,
R.L Belford and J.T. Richie. 1987. Image analysis
of video-recorded plant root systems, pp 67-80 la:
Minirhizotron Observation Tubes: Methods and
Applications for Measuring Rhizosphere Dynam-
ics. ASA Special Pub. No. 50.
Sorensen, F.C. and W.K. Ferrell. 1973. Photosyn-
thesis and growth of Douglas-fir seedlings when
grown in different environments. Can. J. Bot
51:1689-1698.
Spies,TA and J.F. Franklin. 1991. The structure of
natural young, mature, and old-growth Douglas-fir
forests in Oregon and Washington, pp. 91-109. Iq:
L.F. Ruggiero, K.B. Aubry, AB. Carry and M.H.
Huff (technical coordinators), Wildlife and Vegeta-
tion of Unmanaged Douglas-fir Forests. USDA For.
Serv., Portland, OR. Gen. Techn. Rep. PNW-GTR-
285.
Steinberg, S., C.H.M. van Bavel and M J. McFarland.
1989. A gauge to measure mass flow rate of sap in
stems and trunks of woody plants. J. Amer. Soc.
Hort. Sci. 114:466-472.
Steudler, PA, R.D. Bowden, J.M. Melillo and J.D.
Aber. 1989. Influence of nitrogen fertilization on
methane uptake in temperate forest soils. Nature
341:314-316.
Stevenson, FJ. 1986. Cycles of Soil. John Wiley
and Sons, Inc. NY.
Stevenson, FJ. and E.T. Elliott 1989. Methodolo-
gies for assessing the quantity and quality of soil
organic matter, pp. 173-199. In: D.C. Coleman, J.M.
Page 101 Corvatlis Environmental Research Laboratory
-------
Effects of CO2 and Ctimat* Chang* on Fortst Trtts
Oades and G. Uehara (eds.) Dynamics of Soil
Organic Matter in Tropical Ecosystems. University
of Hawaii Press, Honolulu, HI.
Sucoff,R 1969. Freezing of conifer xylem and the
cohesion-tension theory. Physiol. Plant 22:424-
431.
Surano, KJl, P.F. Daley, J.LJ. Houpis, J.H. Shinn,
J A. Helms, RJ. Palassou and M.P. Costella. 1986.
Growth and physiological responses of Firms port-
derosa Dougl ex P. Laws, to long-term elevated C02
concentrations. Tree Physiol. 2:243-259.
Tan, C.S., T.A. Black and J.U. Nnyamah. 1977.
Characteristics of stomatal diffusion resistance in a
Douglas-fir forest exposed to soil water deficits.
Can. J. For. Res. 7:595-604.
Teskey, R.O. 1982. Acclimation of AbksamabUis
to water and temperature stress in a natural environ-
ment Ph.D. thesis. University of Washington,
Seattle.
Thomas, R.B. and B.R. Strain. 1991. Root restric-
tion as a factor in photosynthetic acclimation of
cotton seedlings grown in elevated carbon dioxide.
Plant Physiol. 96:627-634
Timmer, V.R. (1991) Interpretation of seedling analy-
sis and visual symptoms, pp 114-134. Jn: "Mineral
Nutrition of Conifer Seedlings". R. van denDriessche
(ed), CRC Press, Boca Raton, FL.
Tolley, LC 1982. The effects of atmospheric
carbon dioxide enrichment, irradiance and water
stress on seedling growth and physiology of Liq-
uidambar styraciflua and Pirns taeda. Ph.D.
dissertation. Duke University, Durham, NC.
Tolley LC. and B.R. Strain. 1984a. Effects of C02
enrichment on growth of Liqmdambar styraciflua
and Pirns taeda seedlings under different inadiance
levels. Can. J. For. Res. 14:343-350.
Tolley L.C. and B.R. Strain. 1984b. Effects of C02
enrichment and water stress on growth of Liquidam-
bar styraciflua and Pinus taeda seedlings. Can. J.
Bot 62:2135-2139.
Topp, G.C, J.L. Davis and A.P. Annan. 1980.
Electromagnetic determination of soil water con-
tent: Measurement in coaxial transmission lines.
Water Resour. Res. 16:574-582.
Topp, G.C. and J.L Davis. 1985. Measurement of
soil water content using time-domain refiectometry:
A field evaluation. Soil Sci. Soc. Am. J. 49:19-24.
Triska, FJ. and I.R. Sedell. 1976. Decomposition
of four species of leaf litter in response to nitrate
manipulation. Ecology 57:783-792.
Tucker, CX, I.Y. Fung, C.D. Keeling and R.H.
Gammon. 1986. Relationship between atmospheric
C02 variations and a satellite-derived vegetation
index. Nature 319:195-199.
Turner, N.C. 1981. Techniques and experimental
approaches for the measurement of plant water
status. Plant SoU 58:339-366.
USDA Forest Service. 1970. In National Atlas of
the United States. US Geol. Surv., Washington D.C.
Plates 154-155.
USDA Forest Service. 1990. An analysis of the
timber situation in the United States: 1989-2040.
Appendix C. Gen. Techn. Rep. RM-199. USDA
For. Serv. Rocky Mtn. For Range Exp. Stn., Ft.
Collins, CO.
US DOE. 1987. Free air carbon dioxide enrichment
(FACE) facility development: n. Field tests at Yazoo
City, MS. BNL-43502, Prog. U.S. Dept. of Energy,
Carbon Dioxide Research Division, Office of En-
ergy Research. Washington, D.C 159 pp.
Upchurch,D.R.,B.L McMichael and H.M. Taylor.
1988. Use of minirhizotrons to characterize root
system orientation. Soil Sci. Soc Amer. J. 52:319-
323.
Pag* 102 CorvaUls Environmental Research Laboratory
-------
Effects of COj and CUmate Change on Forest Trees
Urban, D.L. 1990. A versatile model to simulate
forest pattern: A user's guide to ZELJG Version 1.0.
Environmental Sciences, University of Virginia,
Charlottesville, VA.
Urban, D.L, M.E Harmon, C.B. Halpem and FJ.
Swanson. 1990. Potential response of Pacific
Northwest forest ecosystems to climate change.
Report to the US EPA, Environmental Research
Laboratory, Corvallis, OR.
Vaadia, Y., F.C. Raney and R.M. Hagan. 1961.
Plant water deficits and physiological processes.
Ann. Rev. Plant Physiol. 12:265-292.
van Veen, J A, E Liljeroth, LJ A Lekkerkerk and
S.GvandeGeijn. 1991. Carbon fluxes in plant-soil
systems at elevated atmospheric C02 levels. Ecol.
Appl. 1:175-181.
Van den Driessche, R. 1975. Flushing response of
Douglas-fir buds to chilling and to different air
temperatures after chilling. BC For, Serv, Res, Note
No. 71.
Vogt, KA, C.C. Grier, C.E Meier and M. R. Keyes.
1983. Organic matter and nutrient dynamics in
forest floors of young and mature Abies amabilis
stands in western Washington, as affected by fine-
root input Ecol. Monog. 53:139-157.
Walworth, J.L., and M.E. Sumner. 1987. The diag-
nosis and recommendation integrated system (DR1S).
Adv. Soil Sci. 6:149.
Wambolt, C.L. 1973. Conifer water potential as
influenced by stand density and environmental fac-
tors. Can. J. Bot 51:1333-2337.
Wareing, P.F. 1953. Growth studies in woody
species. V. Photoperiodism in dormant buds of
Fagus sylvatica L. Physiol. Plant 6:692-706.
Wareing, P.F. 1956. Photoperiodism in woody
plants. Ann. Rev. Plant Physiol. 7:191-214.
Waring, R.H. and J.F. Franklin. 1979. Evergreen
coniferous forests of the Pacific Northwest Science
204:1380-1386.
Waring, R.H. and S.W. Runnning. 1978. Sapwood
water storage: Its contribution to transpiration and
effect upon water conductance through the stems of
old-growth Douglas-fir. Plant, Cell Environ. 1:131-
140.
Water Information Center (WIC). 1974. Climate of
the States. Vol, 2. Western States. Water Infor.Ctr,
Port Washington, NY. 975 pp.
Webb, T., HI. 1986. Is vegetation in equilibrium
with climate? How to interpret late-Quaternary
pollen data. Vegetatio 67:75-91.
Webb, W.L. 1971. Photosynthetic models for a
terrestrial plant community. Ph.D. thesis, Oregon
State University, Corvallis, OR.
Weinstein, DA and R. Beloin. 1990. Evaluating
effects of pollutants on integrated tree processes: A
model of carbon, water and nutrient balances, pp.
313-323. Jq: R.K. Dixon, R.S. Meldahl, G A Ruark
and W.G. Warren (eds.), Process Modeling of Forest
Growth Responses to Environmental Stress. Timber
Press, Portland, OR.
Weinstein, DA, R.M. Beloin and R.D. Yani. 1991.
Modelinng changes in red spruce carbon balance
and allocation in respone to interacting ozone and
nutrient stress. Tree Physiol. 9:127-146.
Weinstein, DA, R.D. Yani, R.M. Beloin and C.G.
Zollweg. 1992. The Response of Plants to Interact-
ing Stresses:: TREGRO Version 1.74. Description
and Parameter Requirements. Electric Power Re-
search Institute, PleasantHill,CAEPRITR-101061.
Wells, S.P. 1979. Chilling requirements for optimal
growth of Rocky Mountain Douglas-fir seedlings.
US For. Serv. Inteimount. For. Range Exp. Stn.
Ogden, UT. Res. Note INT-254.
Page 103 Corvallis Environmental Research Laboratory
-------
Effects of CO j and Climate Change on Forest Trees
Welsh, J. and M. McClelland. 1990. Fingerprinting
genomes using PCR with arbitrary primers. Nucl.
Acid Res. 18:7213-7218.
Welsh, J. and M. McClelland. 1991a. Genomic
fingerprints produced by PCR with consensus tRNA
gene primers. Nucl. Acid Res. 19:861-866.
Welsh, J. and M. McClelland. 1991b. Genomic
fingerprinting using arbitrarily primed PCR and a
matrix of pairwise combinations of primers. Nucl.
Acid Res. 19:5275-5279.
Welsh, J., RJ. Honeycutt, M. McClelland and B.W.S.
Sobral. 1991a. Parentage determination in maize
hybrids using the arbitrarily primed polymerase
chain reaction (AP-PCR). TheoreL Appl. Genet
82:473-476.
Welsh, J., C., Petersen and M. McClelland. 1991b.
Polymorphism generated by arbitrarily primed PCR
in the mouse: application to strain identification and
genetic mapping. Nucl. Acid Res. 19:303-306.
White, D.R. and W.W.Widmer. 1990. Application
of high performance anion-exchange chromatogra-
phy with pulsed amperometric detection to sugar
analysis in citrus juices. J. Agric. Food Chem.
38:1918-1921.
Williams, J.G.K., A.R. Kublik, KJ. Livak, J A.
Rafalski and S.V. Tingey. 1990. DNA polymor-
phism amplified by arbitrary primers are useful as
genetic markers. Nucl. Acid Res. 18:6531-6535.
Wilson, C.A. and J.F.B. Mitchell. 1987. A doubled
C02 climate sensitivity experiment with a GCM
indudingasimpleocean. J. Geophys. Res.92:13315-
13343.
Wommack, D.R 1964. Temperature effects on the
growth of Douglas-fir seedlings. PhD. thesis, School
of Forestry, Oregon State University, Corvallis, OR.
Wong, S.C 1979. Elevated atmospheric partial
pressure of C02 and plant growth. I. Interactions of
nitrogen nutrition and photosynthetic capacity in C3
and C4 plants. Oecologia 44:68-74.
Wullschleger, RJ. Norby and D.L. Hendrix. 1992.
Carbon exchange rates, chlorophyll content, and
carbohydrate status of two forest tree species ex-
posed to carbon dioxide enrichment Tree Physiol.
10:21-31.
Zeiger, E 1983. The biology of stomatal guard cells.
Ann. Rev. Plant Physiol. 34:441-475.
Zobel, D.B., A. McKee, G.M. Hawk and C.T.
Dymess. 1976. Relationships of environment to
composition, structure, and diversity of forest com-
munities of the central western Cascades of Oregon.
Ecol. Monog. 46:135-156.
Page 104 Corvallis Environmental Research Laboratory
-------
Effects of CO j and Climate Change on Forest Trees
XH. APPENDIX A
EPA'S TERRESTRIAL
ECOPHYSIOLOGICAL RESEARCH AREA
(TERA) FOR CLIMATE CHANGE
RESEARCH
INTRODUCTION
The Global Change Research Program at EPA-
Corvallis constructed the Terrestrial
Ecophysiological Research Area (TERA) to provide
a state-of-the-science research capability to investi-
gate the effects of elevated C02 and climate change
on plants. This facility is unique to others because it
is designed to accurately measure and track ambient
C02, temperature and dew point while operating
continuously for several years.
The layout of the TERA facility is given in Figure 1
(compass orientation of facility is indicated on fig-
ure). The center of this facility is 12 experimental
systems, called terracosms, that are capable of pro-
viding complete climate control of an enclosed
plant/soil environment (Figure 2). Each row of 7
terracosms is separated by 4.9 m (160, each
chamber is separated from its eastern and western
neighbor by 3.4 m (11'). Chambers 1 and 8
(chamber!ess controls) differ from the 12 terracosms
in that the soil units were constructed, instrumented,
filled, and will be planted as the terracosms, but they
will not have an enclosure over the trees. A compari-
son of these chamberless controls vs. ambient
environment chambers will provide a measure of the
terracosm effects on seedling growth.
The intended C02 and climate treatments scheduled
for each terracosm are also given in Figure 1. Am-
bient conditions are indicated by the capital letter A,
and elevated conditions are indicated by the arrow
pointing upwards. For instance, the treatment as-
signed to chamber 5, COjA, Tf, is ambient C02 and
elevated temperature (+4ฐQ. The treatments have
been randomized among the chambers.
In addition to the terracosms, the TERA facility has
a 9 m x 24 m polyhouse (lexan and plastic covering
over metal frame), a physical plant, a shop, and a
storage building. The polyhouse contains the net-
work interface computers and Sparc workstation,
analytical instrumentation, several indoor controlled
environment chambers, benches for plant rearing,
the gas exchange/image analysis laboratory, a water
purification system, and a compressed air drier.
This facility was designed specifically to conduct
long-term growth studies on forest trees, evaluating
die effects of temperature, C02, and drought stress
on ecophysiological processes. All facilities includ-
ing the physical plant and electrical service were
designed to allow the eventual expansion to 24
terracosm and 4 controls. Because of the long
duration of the planned experiments, special atten-
tion was provided to fail-safe operation. The facility
physical plant which supplies hot and cold water to
each chamber for climate regulation is designed with
integrated backup systems to minimize any down
time caused by equipment failure. These backup
systems include a dual compressor SO ton water
chiller that will continue to operate in spite of com-
plete failure of one of the compressors, a backup
275,000 BTU boiler that is automatically activated if
there is a failure of the first system, insulated 1600
gallon chilled water storage tank and 800 gallon hot
water storage tank to buffer supply system demands,
redundant 3 HP water pumps built into the hot and
cold water delivery system, and a 100KW emer-
gency power generator that will supply site power if
there is any interruption in city power.
The following sections provide greater detail on the
design of TERA, site physical plant, the individual
terracosms, sensor layout and specifications, envi-
ronmental control system, site meteorological station,
and associated laboratory capabilities.
Page A-l CorvalUs Environmental Research Laboratory
-------
I
&
a
TERA
Terrestrial Ecophysiological Research Area
"K'K'W'l
fV'f',rWo
*/AV,'A'A f A
ปA'.VA'A V y
wjt, o,VปV,V/i Vw^
30' x 78'
'olvnouse
yV/4'X'/\v//'!v'vv.'#
l<ปI)|T,) >1I\ t\ >ฆ>< > I / ป >
W
\ A'A'A / V,V V 'A'A'A /
I VlVlIIIt\!f If tป/ 1(1) '
V/A'A'/WW.'A'A',
'\ป V< If ปI i' I ปA 'I '1 ' 'A/l'l 'I'l'l ซ> >< I/>/ A/*Y*/ ป.ปY> i)>3>ro<) oV>V' /.ป
rV/i #> o o ป.v> f>V>'y /> /> #> <> o i> o /? *
A'A'AV
'VAYA'AWWVVAWYA'AV / /ป-/,ฆ'ปIf .-y.v,-/'/./ซw.'WV'''ซ V'ซV^ v vv wvvvvv v
> V.'^'A AV.'A'A'A'A'A'Aป' ^VA'A'A'A'A'A'A'A'A'A'A'A'iVA'/VA'A'AV 'A A'A'AW W V 'A'A'A'A'/ WAV.'AV ,wAWA'A'A?
yAV''VA'A,'yifl'AViซNVi'\ViA'A'fWfoyW.?^
'A'A'A'A'A
'iWiW iVi' v/ป
V, A*ซ, / V V,V,'AV,V VVlVfV^VAV,V/AV^V|V/.^V/,VAV^lI'AV^','
VA'A'A'AV
g.vvflv
Terra cos hi Field Chambers
ttiaW
Vi'-v/
Chamber!ess
Control
COjAJ-f C02tปT| C02A,Tt
CCM.TI
COjA, TA
co2t,ta
VA'AV
?.W(
BR!
AV'AV,
Iฎ*
CQ2A,Tt
COjt.TA
COjt.Tt
co2a,ta
VrYA'A
CC^t.TA C02A, TA
Chamber! ess
Control
< 50 m (164*) >ฆ
Figure 1. Layout of the Terrestrial Ecophysiological Research Area (TERA), drawn to scale. Experimental treatment, chamber number, and soil
instrumentation quadrant are indicated for the individual terracosms.
f
a.
$
1
Q
*
f
i
!
-------
Effects of CO j and Climate Change on Forest Trees
TERA PHYSICAL DESCRIPTIONS
TERA Site
Polvhouse; The polyhouse was installed to provide
space for the following three functions: (1) shelter
for the data acquisition/computer control hardware,
(2) room to make experimental measurements in
support of field studies, and (3) provide space for
growth chambers and plant rearing benches to con-
duct research in support of field experiments. The
polyhouse was selected as the most cost effective
way of meeting these demands on an interim basis,
providing 223 m2 of finished floor space for about
$ 172/m2 ($ 16.00/ft2). Hie floorplan of the polyhouse
is shown in Figure 1. Although the text is small, the
figure is drawn to scale and gives the reader an idea
how the actual space is arranged. Currently, only 2
of the 5 PGR15 Conviron Environmental Growth
Chambers that are planned for the facility have been
purchased.
Chamber Field Layout: The layout of the terracosms
field is shown in Figure 1 (north towards top of
drawing). The field layout was designed to (1)
maximize separation of all chambers, (2) minimize
potential for shading by any adjacent chamber or
obstacle, (3) provide sufficient room for utility race-
ways and facility scientists to freely move about, and
(4) allow for the eventual expansion to a field of 24
canopied chambers, and 4 uncovered control cham-
bers. Each row of 7 chambers is separated by 4.9 m
(16'), and each chamber is separated from its eastern
and western neighbor by 3.4 m (11').
TERA Physical Plant
The physical plant supplies TERA with constant
temperature hot and cold water for use in chamber
environment control, and emergency power in case
of a city power failure. It was designed to accommo-
date a future expansion of TERA to twice its current
size, providing a total of 24 enclosed terracosms and
4 chamberless terracosms with minimal modifica-
tions or downtime. The long duration of the planned
experiments required that certain areas of the physi-
cal plant be designed with integrated backup systems
to minimize any down time caused by equipment
failure.
Water Chiller: The water chiller supplies water to
cold water heat exchanges at each terracosm, to a
water condenser on the air compressor, and to the
Conviron growth chambers in the polyhouse. The
system is built around a dual compressor 50 ton air
cooled Dunham-Bush water chiller that will con-
tinue to operate in spite of complete failure of one of
the compressors. Chilled water/propylene glycol is
circulated between the chiller and an insulated 6,056
L (1600 gallon) chilled water storage tank using a 3
HP Dunham-Bush low head water pump. The
chilled water is distributed to the field using two 3 HP
Dunham-Bush water pumps with one pump serving
as an in-line backup system.
Water Boiler: The low pressure water boiler is built
around two 275,000 BTU natural gas fired outdoor
boilers. The system is designed so that if one boiler
fails, the second boiler will increase heat output to
compensate for the energy loss. An 3,028 L (800
gallon) hot water storage tank is used to buffer
supply system demands, and three 3 HP Dunham-
Bush water pumps are used to circulate the water/
propylene solution to the field.
Emergency Power Generator A diesel 100KW
emergency power generator is located on the equip-
ment pad to supply site power if there is any
interruption in city power. The generator can supply
sufficient power to run the hot and oold water
pumping systems continuously, and also maintain
operation of all the environmental control sensors
and processors. Under emergency power we will be
able to maintain experimental treatments for several
hours while repairs are made.
Irrigation Water System: The reverse osmosis (RO)
water system is built to supply each terracosm and
the polyhouse with a source of ultra pure water
equilibrated with atmospheric C02. City tap water is
passed through a softener and carbon trap, and then
through a RO filter. Water is stored in a 1,893 L (500
gallon) fiberglass tank to allow temperature equili-
bration. Each chamber is fitted with a pure water and
nutrient supplemented water source. The water
supply lines are laid out in a continuously pumped
PageA-3
Corvallis Environmental Research Laboratory
-------
EfftctsofCOj andCUmatt Chang* on Fartst Tna
loop configuration with an integrated UV sterilizer
to minimize bacterial growth.
Air Compressor: Hie compressed air system sup-
plies each tenacosm with a source of dry compressed
air to drive the pneumatic valves to vent chambers
and bring in fresh air. The compressor is a 3 HP
oilless compressor capable of producing breathing
quality air at the rate of IS CFM. In conjunction with
the air compressor isaheatlessair drier thatproduces
22 CFM dry air at a -73ฐC dew point.
TERRACOSM DESIGN AND SENSOR
LAYOUT
They were then covered with a clear, 25 mil thick
oriented-strand adhesive-backed Teflon film (Du
Pont Electronics, Wilmington, DE) before filling
with soil. The terracosm soils have been instru-
mented to collect a variety of data; a detailed
description of sensor type and location is provided in
this section.
Chamber Pit Linen Each chamber sits in a steel pit
liner that measures 2.2 m wide, 25 m front to back,
and 1.4 m deep. The pit liners are built of steel plate
and are water tight Each liner has been sandblasted
and painted with a nontoxic white epoxy paint, and
are installed on a pad of pea gravel with two 10 cm
(4") drain pipes running through it to drain off
Terracosm Enclosure
Abovepround Canopy: A dia-
grammatic illustration of an
individual terracosm is shown in
Figure 2. The aboveground cham-
ber has a aluminum frame which
is covered by a 3 mil clear teflon
film. Teflon was selected because
of its optical clarity, resistance to
photodegradation, broad spectral
transmission which extends into
both the IR and UV bands, and its
chemical inertness. The chamber
is 15 m tall at the back, and slopes
to 1.2m tall at the front Itis2m
wide and 1 m front-to-back, as
seen from a front view, the south
exposure. The total canopy vol-
ume is 3.18 m3.
Soil Compartment: Each cham-
ber is mounted on a soil lysimeter
that is 2 m wide, 1 m front-to-
back, and 1 m deep, giving a total
volume of 2m3. The lysimeters
are constructed of 60 mm (1/4**)
aluminum plate, and are water
tight They were sandblasted and
painted on the inside with a white,
nontoxic epoxy paint, and allowed
to cure outdoors for 6 months.
Side View of Terracosm
Dew Point Hygrometer
Hot and Cold Water
Heat Exchangm
Host/Chamber COj
Sampling Ports
LSMeten
B Horizon
C Horizon
Meter
Data Acquisition/
System Control
TDR Probe
Multiplexer
\ \
Litter Layer
AHorizoo
Root ObMrattoa
Tube.
Figure 2. Side view of terracosm chamber showing details of soil
horizons, minirhizotron mot observation tubes, data acquisition
packages, dew point hygrometer, and C03 sampling port
PagaA-4 Corvaliit Environmental Research Laboratory
-------
Effects of CO j and CUmate Change on Forest Trees
ground water. A sump pump is installed in each
chamber pit with a moisture sensor to pump out any
accumulated rain water or irrigation drainage from
the soil lysimeter. The pump output feeds directly
into the underground drain field.
The purpose of the soil pit liner is to allow the soil
lysimeter to sit below ground level, while providing
access to equipment, minirhizotron access ports, and
other sensors from the back. The east, south, and
west walls of the soil lysimeters are insulated to R-
30 with extruded polystyrene, while the bottom and
north sides are insulated to R-45 with the same
material. The reason that there is 30% more insula-
tion on the north wall and the bottom is that these two
sides are not further insulated through soil contact
The intent of this design is to minimize any unnatural
downward or lateral heat loss in the system.
Aboveground Sensors
Dew point hygrometer: Each chamber is outfitted
with a General Eastern Dew-10 chilled mirror dew
point transmitter. The sensor is mounted on the
return duct of the air handling/climate control pack-
age. The instrument is powered by 24 VDC and has
a 350 mA draw. It has an accuracy of ฑ05ฐC with
0.05ฐC precision. It will operate over the dew point
range of -40CC to +70ฐC, with a linearized output of
0-5 VDC over this range.
Carbon Dioxide Analyzer Each chamber is outfit-
ted with a Valtronics (Concord, CA) Model 2080
CONSTAT infrared gas analyzer that is mounted in
a temperature controlled enclosure inside the Pro-
cess Controller/Data Acquisition package. The unit
is powered by 24 VAC and draws about 450 mA
The line feed is from a 2.7 KVA clean power line
conditioner which is stepped down at each unit with
a 1 A, 24 VAC transformer. Power is fed to each unit
through 12 gauge, 3 conductor, twisted shielded
cable fitted with a shield drain to minimize collection
of any errant electrical noise. Gas is sampled from
the air handler and pumped to the detection cell using
an Apollo diaphragm pump (Model 3000, Ontario,
CA) at 100 mL min"with the flow regulated using
a Dwyer (Michigan City, Indiana) rotameter (see
Figure 2 for gas sampling location). The C02
analyzer provides a 0-2 VDC output linearized over
0-2000 ppm C02. Under stable conditions, the
analyzer provides an accuracy of about ฑ10 ppm
C02at ambient levels. Precision is limited over time
because of electronic drift and temperature sensitiv-
ity. Heated enclosures, clean power supply, and
regular down loading of slope/intercept values in-
creases precision/accuracy of the C02 measurements
to an acceptable level.
Mass Flow Controller: Each chamber is outfitted
with aTylan General FC-280A mass flow controller
(Torrance, CA). The unit is powered by a ฑ15 VDC,
draws about 450mA, and is fed from a DC-DC solid
state converter powered with 12 VDC. Flow Con-
trollers are housed in a Process Controller/Data
Acquisition package at each terracosm. They are
factory calibrated with pure C02 for flows over the
range of 0 to 10 mL min1. Both the set point flow
and actual flow are linearized over the full scale
range of 10 mL min'1 and take input and give output
signals of 0-5 VDC, respectively. The accuracy is
ฑ0.5% full scale, which is 0.05 mL min'1 over the 10
mL min'1 range. The repeatability is ฑ0.2% full
scale, or ฑ0.02 mL min'1 over the 10 mL min'1 range.
Quantum Sensor A Li-COR (Lincoln, Nebraska)
LI -190S A quantum sensor is used wi thin each cham-
ber to measure photosynthetically Active Radiation
(PAR). The sensor is a high stability silicon photo-
voltaic detector which is blue enhanced. It has a
stability of <ฑ2 % change over 1 year period, with an
absolute calibration of ฑ5% traceable to the U.S.
NTSI. The sensor is sensitive to light between 400
and 700 nm, has a response time of 10 jis, tempera-
ture dependence of ฑ0.1%/ฐC maximum, outputs a
mV signal which is proportional to punol s"' m2 and
has a maximum deviation of 1% up to 10,000 (imol
s'1 m'2. The sensors are mounted on leveling plates
that will be adjusted to maintain sensors at average
canopy height as the seedlings grow.
Drv-Bulb Temperature: A pair of thermistors, sup-
plied as Campbell Scientific 107 temperature probes,
will be mounted within a triple layer radiation shield
for measurement of aboveground dry bulb tempera-
ture. The thermistors are accurate to within ฑ0.4ฐC
Page A -5 CorvalUs Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
over the range of -33 to +48ฐC and output a millivolt
signal linear with temperature. The radiation shield
is built from PVC parts, and centers the pair of
thermistors within a tube which has air continuously
pulled through it via a small DC box fan. The
exterior of the radiation shield is covered with adhe-
sive backed aluminum foil to reflect incident radiation.
The unit will be mounted at canopy height near the
center of the chamber and adjusted to account for
growth.
LeafTemperature: Leaf temperature will initially be
measured by insertion of a fine gauge (34-36)T-type
thermocouple into a needle just below its surface.
Type T thermocouples are accurate to ฑ03ฐC over
ambient temperature range. Because leaf tempera-
ture measurements of this type are somewhat
destructive in nature, we will investigate substituting
IR thermometry for thermocouple measurements in
the future. A decision on whether to substitute IR
thermometry for thermocouple measurements will
be made after considering results from both meth-
ods.
Stem Sap Flow Gauge: Stem sap flow gauges,
patterned after those described by Steinberg et al.
(1989), and Ham and Heilman (1990) will be built
and integrated into the current process controller/
data acquisition system. However, accuracy of the
stem sap flow system is currently unknown but will
be investigated over the course of the study. At least
three seedlings will be monitored in each chamber,
one seedling in each row of 7 trees.
Stem Diameter Gauge: Stem diameter gauges pat-
terned after those described by Beedlow et al. (1986)
are being constructed by Pacific Northwest Labora-
tories for use in these experiments. Two seedlings
will be monitored within each terracosm.
Wind Speed: Ahot wire anemometer will be used to
measure wind speeds within the chambers and in
chamber comers and through the canopy. Hie
chambers have been designed to provide thorough
mixing with few to no dead air zones. While the
chamber micrometeorology will not be one of the
initial focuses of the experimental studies, it is our
desire to understand the canopy energy balance and
chamber gas movement to determine the signifi-
cance of geometric design on these parameters.
Belowground Sensors
The sensors are concentrated in either the east half or
west half of the soil lysimeter because of the number
of sensors and minirhizotron tubes and the difficulty
of taking depth cores around them. The placement
of the sensor quadrant was distributed evenly over
the three terracosms that make up the replicates for
an experimental treatment to provide even coverage.
These locations are indicated in Figure 1.
Because there is a limited number of sensors for each
chamber, it was felt that the thermistors, gas sam-
pling ports, and suction lysimeters would provide
better correlation of related measures if they were
concentrated within a single quadrant Thus, the
sensors are concentrated under a 1 m wide and 0-5 m
front-to-back soil surface. The location of the quad-
rants were also randomized within a row. The field
layout given in Figure 1 shows the quadrant that the
sensors will be concentrated in.
Belowground Temperature: Each chamber is outfit-
ted with three groups of three thermistors. The
thermistors, supplied by Campbell Scientific as the
Model 107B temperature probe, accurate to within
ฑ0.4ฐC over the range of -33 to +48ฐC, are of the
same specifications as the aboveground units except
they have be treated with special shrink rap to inhibit
any water infiltration. It is expected that the soil
temperatures will increase as a function of the canopy
temperature, and that there may be loss of soil heat
to the soil lysimeter walls. Although the walls and
bottom have been insulated to prevent this, we will
monitor soil temperature gradients both with depth
and as a function of distance from chamber center
towards front or back wall. One group of three
thermistors will be planted in the center of the A-
horizon (5 an down from soil-litter layer interface),
another group of three in the center of the B-horizon
(40 cm down from soil-litter interface), and the final
group of three in the center of the C-horizon (80 cm
down from soil-litter interface). Figure 3 illustrates
these locations.
PageA-6 Corvallis Environmental Research Laboratory
-------
Effects of CO3 and CUmai* Change on For** Tries
5 to 8 cm ^
10 cm
60 cm
20 cm
10 cm
Soil Thermistors
Soil Gas Samplers
jL -4j>. #
w-
M. Jk
"nF
Utter Layer
A Horizon
B - Horizon
C - Horizon
Drainage
Gravel
1 Meter
^ 2 Meters *"
Figure 3. Location of Soil Thermistors and Soil Gas Samplers. In this example, sensor
locations are shorn for a terracom with sensors concentrated in the NW quadrant
Minirhizotron Access Porte: Four clear tubes(acry lie
or cellulose acetate butyrate (CAB)) have been
installed in each of the soil lysimeters. They were
purchased from Bartz Technologies (Santa Barbara,
CA), and are specifically sized and of sufficient
optical clarity to allow visual inspection of fine root
detail. Hie tubes are 5 cm in diameter, sealed at one
end, and installed horizontally through the back wall
of the soil lysimeter. Each tube is mounted in a
stainless steel dip plate to allow free movement
during soil settling. The relative locations of the
tubes are shown in Figures 2, and 4. One tube is
located in the center of the A-horizon, 5 cm down
from the soil-litter layer interface. There are two
tubes in the B-horizon. One tube is 25 an down from
the soil-litter interface, the center point of the top half
of the B-horizon, and the second tube located 55 cm
down from the soil-litter interface at the center point
Page A'7 CorvalUs Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
5 to 8 cm
10 cm
60 cm
20 cm
10 cm
Litter Layer
A Horizon
B - Horizon
C - Horizon
Drainage
Gravel
1 Meter
-2 Meters-
Figurt 4. Location ofminirhizotron access tubes.
of the lower half of the B-horizon. The fourth tube
is located at the center point of the C-horizon, 80 cm
down from the soil-litter layer interface.
Time-Domain Reflectrometrv; Soil moisture gradi-
ents down through the soil column will be measured
using time-domain reflectrometry (TDR) (Baker
and Lascano, 1989; Roth et al., 1990; Heimovaara
and Bouten, 1990). The TDR method of measuring
soil water is relatively new, but is becoming widely
accepted as the technique of choice. One of the
primary reasons for its popularity is that it can be
used to measure volumetric soil water content accu-
rately, rapidly and repeatedly using computer
controlled multiplexing (Baker and Allmaras, 1990).
The TDR method has been described in detail by
Topp et al. (1980) and Topp and Davis (1985). In the
TDR measurement of soil water, an electromagnetic
pulse is transmitted into the soil down parallel wave
guides consisting of a pair of stainless steel rods 3
mm in diameter and 300 mm long (also known as a
TDR probe). The velocity of the electromagnetic
pulse down the probe is a function of the apparent
dielectric constant of the soil. Soil consists of air with
a dielectric constant close to 1, soil solids with a
dielectric constant close to 4, and water with a
dielectric constant of about 80 (Ansoult et al., 1985).
Liquid water, therefore, is the major factor which
Page A-8 Corvallis Environmental Research Laboratory
-------
Effects of CO j and CUmate Change on Forest Trees
alters the apparent dielectric constant of soils. The
rate of travel of the electromagnetic pulse increases
with increasing water content but is independent of
temperature, bulk density, soil type, and the salt
content of water.
Our system is built around a Tektronix (Beaverton,
OR) 1502B cable tester, Campbell Scientific Probe
Multiplexers, and a Campbell CR-10 data logger.
Five TDR probes are installed in each terracosm.
Their locations with respect to the horizons are given
in Figure 5. When calibrated, the TDR system
measures the volumetric soil water content with an
accuracy of ฑ2%. Calibration of the TDR system
will be with 230 L plastic drums filled with the
terracosm soil. These will be packed to mimic the
terracosms with known densities and soil water
contents. TDR probes will be placed at the same
depths as in the terracosms.
Neutron Moisture Probe and Access Ports: The
neutron moisture probe method relies upon the ther-
malization (slowing) of fast neutrons by the hydrogen
atoms in water molecules (Gardner, 1965; Greacen,
1981; and Gardner, 1986). The hydrogen atom is
particularly effective at slowing neutrons generated
from a mixture of radioactive Americium 241 and
Beryllium because it has a similar mass. The extent
to which fast neutrons are thermalized is propor-
tional to the soil water content Timed measurements
5 to 8 cm EE
^ ^ V
10 cm
60 cm
Lyslmeters TDR Probes Lysimetera
Neutron Probe
Access Port
#1
M.
W-
Litter Layer
A - Horizon
B Horizon
C Horizon
Drainage
Gravel
1 Meter
-2 Metere-
Figure 5. Location of TDR probes, neutron probe access tube
and tension soil fysimeters.
Page A 9 Corvallis Environmental Research Laboratory
-------
Effects of CO2 and Climate Change on Forest Trees
of neutron theimalization with a neutron moisture
gauge requires that a fast neutron source and a slow
neutron detector be lowered into the soil through an
access tube. A calibration curve is then used to
convert these values to specific soil water contents.
This is a reliable, accurate, non-destructive soil
water measurement technique that is, however, some-
what labor intensive.
ATroxler (Research Triangle Park, NQ 4300 Soil
Moisture Gauge will be used for this analysis. The
probe uses a 10ฑ1.0 mCi Americi urn-241: Beryl-
lium source which has a 25,000 n/s yield. The unit
uses a microcomputer control panel that provides for
probe calibration and data acquisition, transmitting
coded soil readings on command to host computer
through RS-232 communication. A vertical acrylic
tube will be used as a neutron probe access port The
location of this tube is shown in Figure 5. Neutron
probe access tubes will also be placed in the control
drums mentioned above for calibration purposes.
Tension LvsimeteTs: Six tension lysimeters have
been placed in the soil of each terracosm to collect
soil solutions (Figure S). Two are 5 cm below the
soil-litter interface in the middle of the A horizon, 2
are 40 cm below the soil-litter interface in the middle
of the B-horizon,and 2 are 80 on below the soil-litter
interface in the middle of the C horizon. The glass
tension lysimeters are 6 cm diameter and are fitted
with a fritted glass filter disk with a nominal pore size
of4 to 5.5 nm (Coming Glass Works, Coming, New
York). Soil solutions are collected by applying a
suction to the lysimeters and collecting the water that
is pulled out of the soil.
Soil Gas Samplers: Ten soil gas sampling wells are
buried in each of the soil lysimeters. The sampling
wells are constructed from a stainless steel Swageloc
64mm to 16mm reducing union. Figure3 illustrates
the placement of sampling points. In the 64 mm end
of the union is placed a 16 cm piece of 64 mm
stainless steel tubing, which is pointed downward in
the soil column. A stainless steel frit (nominal pore
size of 2 iim) internal to the fitting is used to prevent
roots from growing into the gas well. Three meters
of teflon tubing (16 mm) connects the gas well to a
22 gauge needle for syringe attachment and sample
withdrawal. The total dead volume of each of these
samplers is approximately 1.8 ml.
TERRACOSM CO, AND CLIMATE CON-
TROL
Computer Data Acquisition/Process Control
There are several strategies for controlling a field of
devices such as the terracosms. One method is to use
a host system that does all the data acquisition from
the field sensors, provides the target set points, and
regulates processes to meet the set points. An
advantage of this design is that all the electronic and
computer hardware are centrally located, reducing
cost and maintenance. There are several disadvan-
tages of this approach which include the expense of
extending sensor leads from a field location to a host
location, total system reliance on a central processor,
and a less precise control of set point parameters
because of time sharing instruments. A second
method is to distribute the data collection/process
control devices in the field and communicate with
them through a host processor. This system design
is usually more expensive, but allows more precise
control over set points and can withstand a system
failure of a single field processor without impacting
data collection and operation of others. If properly
designed, even under conditions where the host
system fails, field process controllers can continue to
acquire data and control set point parameters, storing
data for later uplinks to the host
The terracosm facility is a hybrid of these two
designs, attempting to take advantages of the posi-
tive aspects of each. The strategy employed for the
control of the climate and C02 in the terracosms is
illustrated in Figure 6. The C02 concentration and
climate within each terracosm is independently con-
trolled using aprogrammable logic controller (PLC).
The PLC serves as an intelligent interface to an anay
of sensors, valves, and flow controllers. Ambient
weather conditions and C02 levels are continuously
monitored at the site weather station and are trans-
mitted to the terracosms over a communications
network. The terracosm PLC's use the site ambient
Page A'10 CorvaUis Environmental Research Laboratory
-------
Effects of COj and Climate Change on Forest Trtts
conditions and internal computer logic to determine point and diy bulb temperatures can be tracked to
and control their individual target C02, temperature, *03'C, and COa concentration tracked to ฑ10 ppm,
and dew point treatments. With this design, dew respectively.
Mission Control
Host Analytical System
liber Optics
*TCP/lPNetwork"
Sparc IPX
Workstation
INFORMIX
DgMMKtajjhit
WMt.HU
31 Mb RAM
SCSI
1.2 6b HD
1.2 Gb HD
4Gbtaa Tape
'.UUHAWU it'
Network laterfaq)
Site
Weather Station
ฅ-ir-V
Data Highway +
mTTiT?TT"
Inrormatlon
Terracosms 1-14
Data
Heated Enclosure
SF6 Detector
(Electron Capture)
Dew-
(12111
Point Hygrometers
H General Eastern)
i
k i
\
Dual Channel
Differential C02
IRGA (Binos)
F
Process Controller
(Allen-Bradley PLC 5/20)
44444444
Sensor Outputs
Hot Water EE*
f
Condensation
Gauge
K.T
W"* \ * V j vyi ^ -0
Ambient Ambient + 200
J 1
Maliisampler
Valra
MiiWrninpW
VซIป#
/uiAAAAAA AAAAAAA/
Heated Sampling Lines
Site Air
C02SampleUne
Cold Water HE/*
C02IRGA
Quantum Sensor
Dew-Polnt Temperature
Dry Bulb Temperature
Needle Temperature
Stem Flow Gauge
Stem Diameter Gauge
Soil Temperature
Soil Moisture
Suction Lysimeters
Gas Sampling Ports
MlnirhLtotron Tubes
SF5 Sample Line-
Figure 6, Flow diagram of data acquisition/systems control strategy for the terracosm field chambers.
Page A-ll Corvallis Environmental Research Laboratory
-------
Effects ofC03 and Climate Changซ on Forest Trees
A486/DX2 PC serves as the network interface, and
receives data transfer messages from each terracosm
PLC at 1 minute intervals. These data, which include
temperature, dew point, light level, C02 concentra-
tion, soil moisture, etc. are used to provide chamber
status displays and simultaneously relayed to a Sparc
IPX workstation over a TCP/IP ethemet where they
are logged into the network data base. A more
detailed description of the process control/data ac-
quisition system follows.
Field Process Controller: The process controllers
located at each terracosm perform the following
functions: 1) regulate the injection of C02 using a
mass flow controller to maintain target concentra-
tions, 2) execute IRGA calibration sequences, 3)
periodically injecting a pulse of dilute SF6 for leak
detection and triggering the solenoid for gas sam-
pling, 4) regulate the flow of hot and cold water
across heat exchangers, and proportionally regu-
lated electrical strip heaters to maintain target
temperature and humidity condition, S) trigger sole-
noids to open pneumatically controlled valves
allowing outside air into chambers, 6) actuate and
monitor irrigation sequences, and 7) acquires mea-
surements for the various sensors used in each
terracosm. Characteristics of sensors associated
with each terracosm have been described previously
(see section above on chamber instrumentation).
The process controller being used with each terra-
cosm is the Allen-Bradley PLC5/20 industrial based
process controller. Each system is comprised of a 5/
20, a 16 A 5 VDC power supply, 15-bit and 12-bit
analog input and output modules, counters, and 12
bit DC output modules. The components are rack
mounted in a 16 slot backplane, providing room for
future expansion.
Network Interface: The network interface is an
D3M/PS2-Model 77 with 32 mb RAM, a 200 mb
hard drive, and operating with the Microsoft Win-
dows operation system. It is powered through a
Best-uninterruptable power supply and linked to the
site emergency power generator. The network inter-
face computer is linked to the field process controllers
at each terracosm via a Data Highway + (Belden
9463 Twin Axial conductor COAX cable) network
that daisy-chains from chamber to chamber. This
netwoikindudes the site weatherstation and the host
analytical system. The network interface computer
is in constant communication with the distributed
process controllers uploading sensor data from the
field process controllers for subsequent transmis-
sion to the database workstation. The host analytical
system and the weather station regularly send C02
set point and climate set point information over the
network to the terracosm processors so that the target
treatments be established and met
Host Analytical System
The host analytical system also makes measure-
ments of chamber atmospheric conditions on a
sequential basis, providing more accurate and more
precise measurements, and a degree of redundancy
to help detect sensor failure. Instruments associated
with the host are described below. TTieir relationship
to the host and individual terracosms is illustrated in
Figure 6.
Gas Sampling Network: Gas samples will be pulled
to the host analytical equipment from each of the
terracosms through 45 m lengths of 9.6 mm OD 6.4
mm ID Bev-A-line XX tubing. Equal lengths will
be used foreach system to provide similar line losses
and sample travel times. The tubing is a flexible UV-
resistant PVC that is lined with a Hytrel polyester
lining made specifically for high purity gas sampling
applications. Hie manufacturer reports low line loss
characteristics for most gasesbut the material will be
checked with C02 and HjO to assure its acceptabil-
ity. The tubing has advantages over Teflon: costs are
lower and smaller bending radius makes it possible
to run the complete length from the individual cham-
bers to the host in a continuous run. Samples will be
pulled through Teflon 05 |im Teflon particle filters
(Nuclepore, Pleasanton, CA) to prevent entrainment
of particulate contaminants into sample gas streams.
At the host system, sample lines divide into two
groups: (1) the ambient level C02 lines, and (2) the
ambient + 200 ppm C02 lines. A rotary selector
valve (Samplivalve, Seanivalve Corp., San Diego,
CA) will be used foreach group, with the output feed
Pag* A-12 Corvallis Environmental Research Laboratory
-------
Effects of CO j and Climatt Change on Forest Trta
to the appropriate channel of the C02IRGA. The
sequencing of the selector valves will be controlled
through the host processor.
All sample lines will be heated using heat trace tape
(Raychem Corp., Redwood City, CA) from the point
of sample collection to the host analytical system.
Gasses will be pulled to the host instruments using a
stainless steel metal-bellows pump (Model MB-
158, Metal Bellows Corp., Sharon, MA). The
system will draw samples from the chambers at the
rate of 1,6 L/min, requiring slightly less than 1
minute for sample travel time. The continuous
sampling will require 25% of chamber volume on a
per hour basis.
A separate 3 mm stainless steel line will be used for
bringing samples from the chambers to the SF6
analyzer to reduce line loss and minimize any poten-
tial background contamination to the election capture
detector. This sampling system will employ a single
line that is tee-ed off to each chamber. A solenoid
valve will be located at each chamber and used to
select which chamber is being sampled at any time.
Hie stainless steel sampling line will be pumped
during sampling events at a flow rate of 0.5 L/minute
using a metal-bellows gas pump.
CO, Analyzer: The host system uses a BINOS
Model 4.2 (Rosemont GmbH and Co., Hanau,
Deutschland) infrared gas analyzer that has two
differential C02 analyzers built into the same instru-
ment Each channel has a ฑ100 ppm range; channel
1 will center at 400 ppm, and channel two will center
at 600 ppm. The signal output for each channel isO-
1VDC and linearized with C02 concentration. Each
cell is optically filtered to reduce cross interference
of water vapor, has a ฑ2% maximum zero drift per
week, and s03 % of full scale sensitivity drift per
week. The instrument accuracy is % ฑ 1 ppm on both
channels because the cells are operated in the differ-
ential analysis mode. The temperature of the gas
cells and internal gas lines are thermostatically con-
trolled to 55ฐC
Dew Point Hygrometer: A General Eastern Hygro-
M3 humidity analyzer will be used to measure the
dew point, temperature, and pressure of samples
drawn from the individual chambers. The dew point
temperature will be measured at the host computer
with a Model 1211H two stage chilled minor dew
point sensor which is accurate to ฑ0.2ฐC over the
range of -356C to +93ฐC. The host system measure-
ment will be used for comparison with the
measurements taken in the individual field chambers
by the Dew-10 chilled mirror sensors (see above
discussion of aboveground sensois), allowing detec-
tion of failed sensors or sensor drift. Other sensors
are for quality assurance purposes: the temperature
measurement will indicate the heating of sensor lines
in maintaining a constant temperature gas stream,
and the pressure sensor will indicate if there is any
clogging of the sample streams.
SF6 Detector: An electron capture based SF6 detec-
tor will be used to assess chamber leakage rates
(Model TGA-4000, SciTech Instruments, Pullman,
WA). Initially, the detector will be used to locate
leaks in chamber canopies. The instrument is por-
table and equipped with a wand for sample collection.
It responds in 0.2 sec with a limit of detection of
about 2 parts per trillion (ppt), with an accuracy of
about *1% in the range of 200 to 900 ppt.
In the future the detector will be installed on-line for
routine measurement of chamber leakage rates.
Pulses of SF6 will be added to each chamber in
sufficient quantity to raise the chamber concentra-
tion to about 0.9 ppb. The concentration in the
well-mixed chamber canopy will be measured every
20 minutes over a three hour period, or until the
chamber SF6 concentration is depleted by 80%. The
concentration change over time will be calculated
and converted to an exchange rate. This conversion
assumes that the diffusive movement of SF6 out of
the chamber is proportional to the diffusive move-
ment of COj/N/Oj into and out of the chambers.
Based on our current understanding of the properties
of SF6 and the design of our system this assumption
is reasonable, but it will be verified with further
testing.
PagtA-li Corvollis Environmental Research Laboratory
-------
Efftcti of CO, and CUmaU Chang* on Forest Trett
Data Storaee/Database Generation; Hie data up-
loaded from the distributed process controllers will
be transmitted over an etheraet linkage to a Sun
Sparc IPX work station. The workstation will serve
as the central node for a relational data base system
and will be linked into the laboratory wide network.
Informix's (Informix Software, Inc. Menlo Park,
CA) relational data base system will be used, allow-
ing 16 network workstations to up and download
data through the database file interface. Hiis system
will also allow network Apple Macintosh computers
and Sun Sparc workstations to communicate
bidirectionally with the database using Wingz
(Informix Software), aflat filespreadsheet interface.
The database will be stored on one of two 12
gigabite (Gb) (3JM, average access time of 92 msec)
hard drives that are linked via SCSI interface to the
field site Sparc IPX workstation. A1 Gb removable
magneto-optical disk drive system will be used for
backup storage of the field data using the Unix
system backup utility. Backups of coll ected site data
will be made on a daily basis.
Terracosm Site Meteorological Station
A 10m instrument tower located 30 m to the west of
TERA is used for monitoring site weather condi-
tions. Gas samples are also continuously pumped
from a filtered inlet mounted on the tower 3 m above
ground level. The gas sample stream is drawn into
the polyhouse and monitored continuously for C02
concentration. The measured C02 concentration,
dew point temperature, and dry bulb temperature are
used by the host processor to derive the set point
conditions for the individual terracosms. The weather
station has the following sensors:
Qgw fQmtffmmntm fcmrn Model 63GMP
Dew point/temperature transmitter (General East-
em, Wobum, MA). Dewpoint accuracy toฑ l'Cand
temperature to ฑ 0-5ฐG
Wind Direction/Speed: Model 5701 wind speed/
wind directionmonitor. (R.M. Young Co.,Traverse
City, MI)
Precipitation Gauge: Rain Gauge Model 525 Trans-
mitter (Texas Qectronics, Inc., Dallas, Texas) which
accurately measures precipitation levels as low as
0.1 mm.
Radiation Sensors: A Ii-OOR (Lincoln, Nebraska)
LI-190S A quantum sensor, the same as those used
within each terracosm, is mounted 10 m above the
field site to measure photosynthetically active radia-
tion (PAR). The sensor is a high stability silicon
photovoltaic detector which is blue enhanced. It has
a stability of <ฑ2 % change over 1 year, with an
absolute calibration of ฑ5% traceable to NT1S.
U-200SA Pvranometen Sensitive over the rangeof
280 -2800 nm with non-ideal sensitivity over this
range. Absolute error under natural daytime condi-
tions is ฑ5%, typically ฑ3%.
ERL-C LABORATORY CAPABILITIES
There are several support laboratories at ERL-C
directly linked to the terracosm studies. These
include a wet lab for sample workup, a instrument
lab for the ion chromatograph and elemental ana-
lyzer, a soil microbiology lab, and a lab for gas
exchange research and video image analysis. Equip-
ment associated with these areas is given below.
Gas Exchange Laboratory
This laboratory will be used for the analysis of gas
samples collected in the field chambers, and for the
analysis of water deficit It will also house equip-
ment for field use such as stem diameter calipers,
field data loggers, and portable gas exchange units.
Equipment associated with this work is described
below.
Plant Gas Exchange: AstandardU-COR6200draw
down system with a branch cuvette will be used. A
PACSYS gas exchange system also may be avail-
able in the future to provide gas exchange
measurements in an open loop configuration with
cuvette temperature control.
PagtA-14 Corvallis Environmental Research Laboratory
-------
Effects of CO j and CUmate Change on Forest Trees
Plant Moisture Stress: Plant moisture stress will be
measured with WES COR thermocouple psychrom-
eteroradigital pressure chamber(Model 1002, PMS
Instrument Co., Corvallis, OR). The system has a
digital readout, a range of 0 to 70 bar, and is accurate
toฑ035bar. It will store data from up to450samples
and will dump directly into a PC via an RS-232
communication link.
Biogenic Gas Analysis: A Perkin-Elmer packed
column gas chromatograph fitter with and FID and
a TCD will be used for the routine analysis of C02,
CH4, 02. A ECD will be added later to provide
measures of N20.
Video Analysis Laboratory
Video Image Collection and Analysis: Still image
video collection will be accomplished using the
Sony MVC-5000 still video camera/recorder. The
high resolution still video camera uses two CCD
chips to collect a 380,000 pixel image (768(H) x 493
(V)) which is recorded directly to a magnetic disk.
The camera will provide time/date stamping and 9
seconds of recorded sample description to help
image cataloging. The disks are played backed using
the Sony MVP-660 still video player.
Root activity in minirhizotron tubes will be moni-
tored with a specially designed high resolution color
video camera designed for this purpose (Bartz Tech-
nology, Santa Barbara, CA). This camera outputs
high resolution images (360H x 350V lines) col-
lected from a 12 mm x 18 mm view window in the
standardNTSCformat They will be displayed in the
field on a Panasonic high resolution color television
monitor and recorded with a JVC Super Video VCR.
Hie digital images will be recorded as RGB Super
video images for input into a PC using a TARGA
video input board.
The NEC PV-S98A computer controllable Super
VHS VCR will be used for conversion of the re-
corded images into a computer readable format
Video input will be accomplished using aTrue Vision
TARGA 16/64 color digital input board and an IBM
PC. Images will be shifted to a Sun Sparc IPX
workstation and analyzed for leaf area using algo-
rithms built within Visual Systems AVS image
analysis/visualization software.
Nutrient/Elemental Analysis Laboratory
Elemental Analyzer A Carlo Eurba EA1108 car-
bon, hydrogen, nitrogen, sulfur, and oxygen elemental
analyzer will be used for characterization of soils and
plant tissues. The instrument uses sample sizes from
0.1 to 100 milligrams, with an accuracy of ฑ10%
relative standard deviation in a sample containing
100 ppm CHNS, with the accuracy increasing with
increasing content of elements in sample. The
instrument uses an IBM PC for setting up the 200
position autosampler, acquiring data during runs,
and generating post-run reports. Theelectrobalance
used for sample weighing is tied directly into the
computer to minimize transcription errors.
A complete analysis of CHNS takes place in 12
minutes. After sample combustion, elemental sepa-
rations are done using gas chromatography (N2,
C02, HjO, SOj). A single thermal conductivity
detector is used for all elements. During analysis the
gases are not split or diluted so that the elemental
analyzer can be directly coupled to a isotopic ration-
ing mass spectrometer or other selective detectors.
Dionix Ion Chromatograph: Ion chromatography
will be used for soil and plant nutrient analysis. A
Dionix 4000i ion chromatograph consisting of a
quadinary solvent pumping system and CBH-1 Ba-
sic Chromatography Module, and a CDM-1
conductivity detector is dedicated to this project.
The liquid autosampler holds 200 samples, and will
inject samples of 0.5 mL or 5 mL, with the actual
sample volume measured using a calibrated injec-
tion loop. An AI-450 Data Acquisition/Instrument
Control Computer Interface and a IBM PS/2 Model
80 is used for instrument control, data acquisition,
and report generation. A Dionix PAX-100 column
is used for anion analysis, and a PCX-100 column
used for cation analysis.
Page A-15 Corvallis Environmental Research Laboratory
-------
Effects of CO3 and Climate Chang* on Fortst Trees
Soil Microbiology Laboratory
Soil Respirometen The respirometer built by Co-
lumbus Instruments International Corporation will
be used to simultaneously monitor C02 production/
03 consumption in litter/soil samples enclosed in
small chambers, and will be used in litter decompo-
sition experiments conducted in support of the
terracosms. The instrument has the capability of
sequentially measuring 20 individual experimental
chambers in a closed loop configuration with a
sensitivity to C02 and 02 volumetric changes of 0.2
nL/hour. This is essential to be able to conduct the
litter decomposition studies planned. The instru-
ment is also capable of interfacing to user designed/
supplied chambers with volumes between SO mL
and
30 L.
MOLECULAR BIOLOGY EQUIPMENT
Microscope with epifluorescence capabilities and
video camera
Sterile Techniques Facilities
HPLC
80ฐC Freezers
Incubators
Refrigerators
Wet Bench equipment/chemicals
Balances
Thermal cycler (PCR machine)
DNA sequence electrophoresis unit
Gel electrophoresis units
Power supplies
UV visualization stand
Radioisotope capabilities
Ultra centrifuge
High-speed centrifuge
REFERENCES
Baker, JM, and RJ Lascano. 1989. The spatial
sensitivity of time-domain reflectrometry. Soil Sci.
147:378-384.
Beedlow, PA, D.S. Daly and M.E. Thiede. 1986. A
new device for measuring fluctuations in plant stem
diameter: implications for monitoring plant re-
sponses. Environ. MoniL Assess. 6:277-282.
Gardner, WH. 1965. Water content In: Methods of
Soil Analysis. Part 1. Physical and Mineralogical
Properties Including Statistics of Measurement and
Sampling. Agronomy No. 9 (eds CA Black et al.)
American Society of Agronomy, Madison, pp 82-
127.
Greacen, EL. .1981. Soil Water Assessment by the
Neutron Method. CSIRO, Australia.
Ham, J.M., and J.L. Heilman. 1990. Dynamics of a
heat balance stem flow gauge during high flow.
Agron. J. 82:147-152.
Heimovaara, TJ. and W. Bouten. 1990. A com-
puter-controlled 36-channel time domain
reflectrometry system for monitoring soil water
contents. Water Resour. Res. 26:2311-2316.
Roth, K., R. Schulin, H. Fluhler and W. Attinger.
1990. Calibration of time domain reflectrometry for
water content measurement using a composite di-
electric approach. Water Resour. Res.26:2267-2273.
Steinberg, S..C.H.M. van Bavel andM J. McFarland.
1989. A gauge to measure mass flow rate of sap in
stems and trunks of woody plants. J. Amer. Soc.
Hon Sci. 114:466-472.
Pag* A-16 Comilis Environmental Research Laboratory
-------
Efftets of CO j and Climate Change on Forest Trees i
Xm. APPENDIX B
IMAGE ANALYSIS
INTRODUCTION
Because of limited plant material and the need to
minimize canopy, root and soil disruption, there is a
need for non-destructive methods for monitoring
above- and belowground plant growth over time.
Recording sequential images of above- and
belowground plant parts and comparing the images
ordata extracted from them will provide quantitative
data on plant growth and dynamics. These images
also will serve an important data archival function.
Image capture methods create far more data than is
feasible to examine and document by hand. We are,
therefore, interested in developing an image analysis
system that will become progressively more auto-
mated, while still returning useful data in its early
stages of development
APPROACH
In the terracosm study image collection and analysis
will focus on the above- and belowground plant
parts. The abovegiound component will use still
video images to obtain data on leaf area, branch
architecture, etc. A minirhizotron video camera
system will be used to record root images in the
minirhizotron access tubes in each terracosm. Both
components are described in detail below.
Aboveground
Image collection frequency, discussed within Task
2, will correspond with aboveground phenological
activity, and, thus, will vary from season to season.
Images of the seedlings will be collected using a
Sony MVC-5000 35 mm still video camera. The
high resolution still video camera uses two CCD
chips to collect a 380,000pixel image (768(H) x 493
(V)) which is recorded directly to a magnetic disk.
The camera will provide time/date stamping and 9
seconds of recorded sample description to help
image cataloging. Conversion of the recorded im-
ages into a computer readable format will be
accomplished using a Truevision TARGA 16/64
color digital input board for an IBM PC. Images will
be shifted to a Sun Sparc IPX workstation and
analyzed for leaf area using algorithms built within
Visual Systems AVS image analysis/visualization
software.
Conversion algorithms will be developed that relate
image area to true projected leaf area, allowing the
development of uncertainty estimates. This will be
accomplished using statistical correlation of image
based needle area estimates with actual needle area
measured from destructively harvested seedlings. It
is possible that we will not be able to define the
needle edges accurately using full color or grey scale
images, and may have better success with spectral
separation or band rationing. Techniques such as
this have been used successfully to separate terres-
trial vegetation from background in satellite acquired
images, and thus, we may be able to employ similar
methods of image enhancement.
Belowground
Seedling root growth and dynamics will be moni-
tored in the terracosms using the four minirhizotron
access tubes in the soil compartment of each terra-
cosm. These clear plastic tubes provide access for a
high resolution Bartz Technology minirhizotron
camera (Bartz Technology Company, 650 Aurora
Ave., Santa Barbara, CA, 93109). This camera
outputs high resolution images (360H x 350V lines)
collected from a 12 mm x 18 mm view window in the
standard NTSC format
Once the root images have been recorded on video
tape, root data can be extracted using software
developed at Michigan State University. The soft-
ware, oiled ROOTS, has been described by Hendrick
and Pregitzer (1992). ROOTS allows the user to
digitize an image input from a video camera or video
cassette recorder (VCR) and uses a mouse to trace
out various features and to create a database that
includes size, a label for the feature, its location in the
image, and information about when and where the
image came from. In any image with roots present
Page B-l Corvallis Environmental Research Laboratory
-------
Effects of CO j and Climate Change on Forest Trees
the ROOTS software will allow the user to extract
data on the number and kinds of roots present, the
length and diameter of these roots, and information
on their morphology, color, or other attributes. These
data are automatically entered into a database for
analysis. With these data we can determine root
growth dynamics and the effects of elevated C02 and
climate change on these dynamics.
REFERENCE
Hendrick, R.L. and K.S. Pregitzer. 1992. The
demography of fine roots in a northern hardwood
forest. Ecol. 73:1094-1104.
Page B-2
Corvallis Environmental Research Laboratory
------- |