Biological Services Program
FWS/OBS-80/40.6 Air Pollution and Acid Rain,
JUNE 1982 Report No. 6
THE EFFECTS OF AIR POLLLTTION AND ACID RAIN
ON FISH, WILDLIFE, AND THEIR HABITATS
FORESTS
Office of Research and Development
U.S. Environmental Protection Agency
Fish and Wildlife Service
U.S. Department of the Interior
-------
The Biological Services Program was established within the U.S. Fish and
Wildlife Service to supply scientific information and methodologies on key
environmental issues that impact fish and wildlife resources and their supporting
ecosystems.
Projects have been initiated in the following areas: coal extraction and
conversion; power plants; mineral development; water resource analysis, including
stream alterations and western water allocation; coastal ecosystems and Outer
Continental Shelf development; environmental contaminants; National Wetland
Inventory; habitat classification and evaluation; inventory and data management
systems; and information management.
The Biological Services Program consists of the Office of Biological Services in
Washington, D.C., which is responsible for overall planning and management;
National Teams, which provide the Program's central scientific and technical
expertise and arrange for development of information and technology by contracting
with States, universities, consulting firms, and others; Regional Teams, which
provide local expertise and are an important link between the National Teams and
the problems at the operating level; and staff at certain Fish and Wildlife Service
research facilities, who conduct inhouse research studies.
Kor »ale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402
-------
FWS/0BS-80/40.6
June 1982
AIR POLLUTION AND ACID RAIN, REPORT 6
THE EFFECTS OF AIR POLLUTION AND ACID RAIN
OM FISH, WILDLIFE, AND THEIR HABITATS
FORESTS
by
Louis Borghi
David Adler, Program Manager
Dynamac Corporation
Dynamac Building
11140 Rockville Pike
Rockville, MD 20852
FWS Contract Number 14-16-0009-80-085
Project Officer
R. Kent Schreiber
Eastern Energy and Land Use Team
Route 3, Box 44
Kearneysvi lie, VIV 25430
Conducted as part of the
Federal Interagency Energy Environment Research and Development Program
U. S. Environmental Protection Agency
Performed for:
Eastern Energy and Land Use Team
Office of Biological Services
F1sh and Wildlife Service
U. S. Department of the Interior
Washington, DC
-------
DISCLAIMER
The opinions and recommendations expressed 1n this series are those
of the authors and do not necessarily reflect the views of the U.S. Fish
and Wildlife Service or the U.S. Environmental Protection Agency, nor
does the mention of trade names consitute endorsement or recommendation
for use by the Federal Government. Although the research described in
this report has been funded wholly or in part by the U.S. Environmental
Protection Agency through Interagency Agreement No. EPA-31-D-X0581 to
the U.S. Fish and Wildlife Service it has not been subjected to the
Agency's peer and policy review.
The correct citation for this report 1s:
Borghl, L. 1982. The effects of air pollution and acid rain on fish,
wildlife, and their habitats - forests. U.S. F1sh and Wildlife Service,
Biological Services Program, Eastern Energy and Land Use Team,
FWS/OBS-80/40.6. 86 pp.
-------
ABSTRACT
Air pollution and acid rain impacts on living resources are a major
source of concern to the U.S. Fish and Wildlife Service and other govern-
ment agencies charged with the protection of natural resources and the
environment. This volume on forest ecosystems is part of a series synthe-
sizing the results of scientific research related to the effects of air
pollution and acid deposition on fish and wildlife resources. The other
accompanying reports in this series are: Introduction, Deserts and
Steppes, Grasslands, Lakes, Rivers and Streams, Tundra and Alpine Meadows,
Urban Ecosystems, and Critical Habitats of Threatened and Endangered
Species.
The first chapter presents an overview of forest ecosystems in the
United States and summaries of the effects of air pollutants on forests,
the factors that determine the type and degree of effects to be expected,
and the primary research needs. The bulk of the report summarizes the
current state-of-knowledge in this problem area. Effects are discussed
within the following pollutant categories: photochemical oxidants, parti-
culates, fluorides, and acidifying air pollutants. The final chapter
suggests areas where further research is needed, and a glossary of rele-
vant terms is included.
iii
-------
CONTENTS
Page
ABSTRACT 1i1
FIGURES V
TABLES vi
1.0 INTRODUCTION, ECOSYSTEM OVERVIEW AND SUMMARY 1
1.1 Introduction 1
1.2 Ecosystem Overview 1
1.3 Summary 12
2.0 EFFECTS OF AIR POLLUTION AND ACID RAIN ON FOREST
ECOSYSTEMS 26
2.1 Effects of Photochemical Oxidants 26
2.1.1 Acute and Chronic Injury 26
2.1*2 Ecosystem Effects 32
2.2 Effects of Particulates 35
2.2.1 Dust Particulates 36
2.2*2 Trace Metal Particulates 36
2.3 Effects of Fluorides 43
2.3.1 Acute and Chronic Injury 43
2.3.2 Ecosystem Effects 47
2.4 Effects of Acidifying Pollutants 48
2.4.1 Sulfur Dioxide 48
2.4.2 Acid Deposition 55
3.0 TOPICS FOR FURTHER RESEARCH 59
REFERENCES 62
APPENDIX 80
GLOSSARY 82
iv
-------
FIGURES
Number Page
1 Distribution of forest ecoregions in the United
States by province 3
2 Factors affecting the response of plants to air
pollutants 14
3 Potential points of interaction between nutrient
cycling in forest ecosystems and air pollution 22
4 Potential points of interaction between air
pollutants and sexual reproduction of forest trees .... 23
v
-------
TABLES
Number Page
1 Selected topographic, climatic, edaphic, and biotic
characteristics of the forest ecoregions of the
United States 4
2 Characteristics, major areas of impact, and effects
of individual air pollutants on forest ecosystem
components 17
3 Interaction of air pollution and temperate forest
ecosystems 21
4 Relative susceptibility of forest tree species to
injury from ozone exposure 28
5 Relative susceptibility of forest tree species to
injury by short-term exposure to ozone 29
6 Relative susceptibilities of selected forest tree
species to injury from nitrogen dioxide exposure 33
7 Concentrations of trace metals in U.S. forest foliage . * 40
8 Relative st/sceptibiJity of selected forest species
to injury from fluoride exposure 45
9 Relative susceptibility of selected woody plants
to acute damage by fluoride 46
TO Relattve susceptibiTity of selected forest species to
injury from SO2 exposure 50
vi
-------
1.0 INTRODUCTION, ECOSYSTEM OVERVIEW AND SUMMARY
1.1 INTRODUCTION
This document is part of a series of technical reports dealing with
the effects of air pollution and acid rain on the fish and wildlife re-
sources of various ecosystems. It has been prepared with the intention
that it (1) serve as an introduction to the scientific literature on the
effects of air pollutants on forest ecosystems and their component orga-
nisms to the uninitiated reader, and (2) provide a summation and assess-
ment of the current state-of-knowledge in this problem area in terms of
its application to forest wildlife resources. It is not an exhaustive
review of the literature available in this subject area. Some terminology
used throughout the text that may be unfamiliar to the reader is defined
in the glossary.
The remaining eight reports in this series provide similar infor-
mation, on an ecosystem-specific basis, for other terrestrial and aquatic
ecosystems. Information on the effects of air pollution on forest streams
and lakes can be found in the aquatic reports (Rivers and Streams, Lakes).
The introductory volume provides information on the sources and environ-
mental behavior of the major air pollutants discussed herein.
1.2 ECOSYSTEM OVERVIEW
Forests are terrestrial ecosystems whose dominant life-forms are
trees. They are distributed throughout the world in humid climates
outside of the polar regions, intergrading at their climatic tolerance
boundaries with the tundra and grassland biomes. Although compositionally
and structurally diverse, all temperate forests share a number of common
characteristics. They are composed of either pure or mixed stands of
coniferous or deciduous trees. Their stratified structure provides
sufficient habitat for a wide assemblage of species (Smith 1974). They
process energy via defined trophic relationships, and transfer matter in
hydrologic and biogeochemical cycles so efficiently that they are among
the most productive ecosystems on earth (Whittaker 1975). They provide
mankind with building materials, fuel, forage, watershed protection,
climatic regulation, and recreational opportunities. Being long-lived,
they are influenced to a large extent by past history; the most important
disturbances of these systems have been the result of anthropogenic
activities (principally those associated with logging, energy production
and the introduction of exotic arthropod and microbial pests), fire,
windthrow, and insect and disease outbreaks (Spurr and Barnes 1973; Smith
1981).
For analysis at the national level, forest communities can be class-
ified in a number of ways corresponding to the particular geographical
scale of interest. Broad classifications are based on physiognomic (and
environmental) characteristics, defining, for example, the temperate
-------
deciduous forest biome. More refined classifications are based on flor-
istic content, using the dominant tree genera to name the forest type,
for example, beech-maple, oak-hickory, or spruce-fir communities (Spurr
and Barnes 1973; Whittaker 1975). Bailey (1980) developed a holistic
approach to ecosystem classification which synthesizes such community
breakdowns with those based on climatic and soil characteristics into a
single geographical classification. He called the end product of this
process of ecosystem regionalization the "ecoregion" which is defined as
"a geographical area over which the environmental complex produced by
climate, topography, and soil is sufficiently uniform to permit develop-
ment of characteristic types of ecologic association"; (ecoregion differs
from biome in that the former implies spatial continuity whereas the
latter does not). Bailey's classification system has been used here to
describe the distribution of forest ecosystems in the United States, as
shown in Figure 1. Supporting information regarding the topography,
climate, soils, and flora and fauna of each region is presented in Table
1 (by corresponding map code number). The importance of these ecosystems
nationally is borne out in the fact that the provinces (broad vegetation
regions with the same type or types of zonal soils) shown in Figure 1
total approximately 52% of the entire land area of the country (Bailey
1980).
2
-------
G)
Figure 1. Distribution of forest ecoregions in the United States by province (Bailey 1980).
-------
Table 1. Selected topographic, climatic, edaphic, and biotic characteristics of the forest ecoregions of
the United States.
Province'5
Land-surface form
Climate
Soils
Veqetationc
Fauna
Yukon Forest
(interior
Alaska 185500
sq mi or
480600 sq km)
map code: 1320
broad valleys, dis-
sected uplands and
lowland basins cov-
ered by alluvial
deposits
elevation: general-
ly < 2000 ft (600
m); small mountain
groups and isolated
peaks to 5500-6500
ft (1700-1800 m)
short, hot summers
(100*F[38*C]) and
long, severe winters
(-75 F[-60*C])
average annual pre-
cipitation 17 inches
(430 mm)
river bottom and
lower slope - deep,
well drained Incep-
tisols with under-
lying sands, silts,
and gravels only
slightly weathered
soils on north-
facing slopes shal-
low, poorly devel-
oped, continuous
permafrost
upland soils sup-
porting spruce-
hardwood forests
well-drained, shal-
low Inceptisols
river bottoms - dense
white spruce - cotton-
wood-poplar forests on
flood plains and south-
facing slopes to about
1000 ft (300 m) eleva-
tion
outer valley edges -
evergreen and conifer-
ous forests often with
pure stands of black
spruce
upland areas - dense
white spruce-birch-
aspen-poplar forests
with pure stands of
white spruce near
streams
black and brown bear,
wolf, wolverine, cari-
bou, and moose common
game species
smaller mammals - red
fox, beaver, mink,
muskrat, weasel, river
otter, marten, squir-
rels and mice
upland birds -
sharptail, spruce and
ruffed grouse, ptarmi-
gan, hawks, woodland
owls and ravens
cliffs along Yukon and
Porcupine Rivers -
osprey, gyrfalcon,
hawks and endangered
American peregrine
falcon
Alaska Range
(Alaska Range,
Alaska Penin-
sula, Aleutian
Islands,
102200 sq mi or
264700 sq km)
map code: M1310
Alaska Range (in-
cludes Mt. McKinley
at 20320 ft [-6193
km]) and volcanic
Aleutian Mountains
(2000 mi or 3219 km
arc)
major rivers: Susitna
and upper Copper
several large lakes on
Alaska peninsula
coastlines dissected,
steep sloped, rocky
Alaska Range and
Alaska Peninsula -
transitional climate:
severe winters and
hot dry summers
(temperatures range
from 90*F[32"C] to
-70"F[-56 C]) and
precipitation aver-
ages 16 inches (420
ran) annually
south Alaska Penin-
sula and Aleutian
Islands - maritime
climate: winter
temperatures to -40 *F
(-40*C) and precipi-
tation to 65 inches
(1650 m)
bottom land and ter-
race soils of Copper
and Susitna Rivers -
stratified, well
drained Entisols
with no pedogenic
horizons
upland hardwood
forest soils - shal-
low, well drained
Inceptisols
Aleutian soils -
poorly developed
Inceptisols, Histo-
sols and rock areas
Alaska and Aleutian
ranges - bottom land
stands of white spruce
and cottonwood on flood-
plains and low terraces;
black spruce stands on
poorly drained areas up
to 1000 ft (300 m)
elevation
upland spruce-hardwood
forests of white spruce,
birch, aspen and poplar
extend to timber line
(about 2500 - 3500 ft
[760-1100 m])
Aleutian Islands -
foxes, bald eagles,
hawks are primary
predators on seabirds
using islands as rook-
eries; seals, sea
lions, sea otters are
abundant
Alaska Peninsula and
Range - mouse, Uall
sheep, black and brown
bear, wolf, caribou,
wolverine, beaver, red
fox, lynx, otter, mar-
ten, squirrels, weas-
els, rodents
coastal areas -
migrating waterfowl
and shorebirds (sum-
mer) bald eagles and
osprey
-------
Table 1. (Continued)
Province''
Land-surface form
Climate
Soils
Vegetationc
Fauna
Laurentian
Mixed Forest
(North-Central
Lake-Swamp-
Morainic Plains,
Adirondack-New
England High-
lands, 224700
sq mi or
582000 sq km)
map codes:
includes Spruce-
Fir (2111),
Northern Hard-
woods-Fir
(2112), Northern
Hardwoods (2113)
and Northern
Hardwoods-Spruce
(2114) Forests
Columbia Forest
(northern Idaho,
western Montana,
eastern Washing-
ton, 45300 sq mi
or 11700 sq km)
map codes: in-
cludes Douglas-
fir (M2111)
and Cedar-
Hemlock
Douglas-fir
(M2112) Forests
mostly low relief, but
rolling hills and low
mountains throughout
Adirondack-New England
Highlands 1000-3000 ft
(300-900 m)
elevation range - sea
level to 4000 ft
(1200 m); few iso-
lated peaks > 5000
ft (1500 m)
entire area glaciated
winters moderately
long, somewhat sev-
ere; > 120 days with
temperatures above
50*F (10*C); frost
free season: 100-
140 days
average annual temp-
erature range: 35-
50*F (2-10*C)
precipitation range:
24-45 inches (600-
1150 mm); maximum
in summer
high, rugged mountains
to >9000 ft (2700 m)
with local relief >
3000 ft. (900 m)
most of area glaciated
severe winters, hot
summer days with
cool nights
t average temperature
coldest month < 32*F
(0*C) and warmest <
72"F (22*C)
precipitation aver-
ages 20-40 inches
(500-1000 mm) annu-
ally, mainly in
fall, winter, and
spring
soils vary greatly
from place to place;
include peat, muck,
marl, clay, silt,
sand, gravel and
boulders in various
combinations
Spodosols are domi-
nant in New England
and along Great
Lakes coast
Inceptisols and Alfi-
sols dominate farther
inland; Alfisols are
medium to high in
bases and have gray
to brown surface
horizons and sub-
surface horizons of
clay accumulation
soils are mostly
cool, moist Incepti-
sols
variety of igneous,
sedimentary and met-
amorphic rocks form
mountains
shallowness and
stoniness of soils
play relatively
minor part in for-
est distribution
transitional between
boreal and deciduous
forest zones
consists of mixed stands
of few coniferous species
(mainly pine) and few
deciduous species or
macromosaic arrangements
with pure coniferous
forest on less favorable
sites and pure deciduous
forest on favoraDle sites
uplands - golden
eagles, ptarmigan,
ravens and hawks
ptarmigan, weasel,
snowshoe hare, black
bear, striped skunk,
marmot, chipmunk,
badger, striped ground
squirrel, beaver, and
muskrat
mixed coniferous-
deciduous forest pre-
dominates
subalpine belt dominated
by Engelmann spruce, sub-
alpine fir, and mountain
hemlock (in Bitterroot
Range)
mountain belt - western
red cedar, western hem-
lock, Douglas-fir,
western white pine,
western larch, grand
fir and western ponder-
osa pine
black bear, deer, elk,
mountain lion, bobcat,
mice, squirrels, mar-
tens, chipmunks, wood
rats
hawks, owls, jays,
chestnut-backed chick-
adees, red-breasted
nuthatches, great gray
owls
game birds - blue and
ruffed grouse
-------
Table 1. (Continued)
Province**
Land-surface form
Climate
Soils
Vegetation 1
Fauna
o»
Eastern Decidu-
ous Forest
{East-Central
Drift and Lakebed
Flats, Ozark-
Quachita High-
lands, Eastern
Interior Up- <
lands and Basins,
Appalachian
Highlands,
367800 sq mi or
952600 sq km) «
map codes:
includes Nixed
Mesophytic
(2211). Beech-
Maple (2212),
Maple-Basswood
(and Oak Savan-
na) C2211). Ap-
palachian Oak
(221A) and Oak-
Hickory (2215)
Forests
relief - most of area
is rolling, with some
parts nearly flat
Appalachian Mountains
to 3000 ft (900 m)
elevation range: sea
level to 2500 ft (?6C
m); few peaks higher
than 4500 ft (1370 m)
northern part of area
glaciated
average annual pre-
cipitation 35-60
inches (900-1500 mm);
markedly greater in
summer
strong annual temp-
erature cycle of
cold winters and
warm summers; average
annual temperature
40-60*F (4-15'C)
pedogenic process
associated with
deciduous forest is
is podzolization;
soils are charac-
teristically Alfisols
toward lower lati-
tudes, laterization
is more prevalent
and Ultisols are
encountered
toward continental
interior, deciduous
forest extends into
darker soils of
grasslands (Molli-
sols)
t deciduous forest
soils have abundant
Utter and humus
1ayers
temperate deciduous for-
est is characteristic;
common species in eastern
North America include
oak, beech, birch, hick-
ory, walnut, maple, bass-
wood, elm, ash, yellow
poplar, sweet chestnut
and hornbeam
in poorly drained areas,
alder, willow, ash, elm
found
pines are second-growth
in logged areas
white-tailed deer,
black bear, bobcat,
gray fox, raccoon,
gray squirrel, fox
squirrel, eastern
chipmunk, white-
footed mouse, pine
vole, short-tailed
shrew, cotton mouse
turkey, ruffed grouse,
bobwhite and mourning
dove are game birds
most abundant breeding
birds - cardinaI,
tufted titmouse, wood
thrush, summer tana-
ger, red-eyed vireo,
blue-gray gnatcatcher,
hooded warbler and
Carolina wren
characteristic rep-
tiles - box turtles,
comiion garter snake,
timber rattlesnake
Outer Coastal
Plain Forest
(Gulf of Mexico
coastal plain,
Florida, 150100
sq mi or 388800
sq km)
map codes:
includes Beech-
Sweetgum-Magnol-
ia-Pine-Oak
(2311) and
Southern Flood
Plain (2312)
Forests
restricted to flat
and irregular southern
Gulf Coastal Plains
well over 50 percent
of area gently sloping;
local relief is < 300
ft (90 m) plus some
gently rolling areas
average annual temp-
erature: 60-70*F
(15-21*C); little
variation over year
precipitation range:
40-60 inches (1000-
1525 mm); well dis-
tributed throughout
year
wide variety of up-
land soils which
tend to be wet,
acidic and of low
nutrient content
soils derived mainly
from Coastal Plain
sediments (predom-
inantly sand), are of
three orders: Ulti-
sols, Spodosols and
and Entisols
temperate rainforest
(also called temperate
evergreen and laurel
forests) is character-
istic
climax vegetation of
mesophytic habitats is
evergreen-oak and mag-
nolia forest; sandy up-
land areas support lob-
lolly and slash pine
forests; bald cypress
commonly found in swamps
white-tailed deer,
raccoons, opossums,
tree squirrels, rab-
bits, numerous species
rodents
a bobwhite ana wild tur-
key (game birds), res-
ident ana migratory
non-game birds, migra-
tory waterfowl
reo-cockaaed woodpeck-
er, American alligator
and Florida panther
are endangered species
black Dear (few iso-
lated areas)
-------
Table 1. (Continued)
Province b
land-surface form
CIimate
Soils
Vegetationc
Fauna
Southeastern
Mixed Forest
{Southeastern
United States,
257900 sq mi or
668000 sq km)
map code: 2320
irregular Gulf Coastal
Plains and Piedmont
50-80 percent area
gently sloping; local
relief 100-600 ft (30-
180 m) on Gulf Coastal
Plains and 300-1000 ft
90-300 m) on Piedmont
flat Coastal Plains
have gentle slopes and
local relief < 100 ft.
(30 m)
Willamette-
Puget Forest
(Oregon and
Washington,
13000 sq mi or
33700 sq km)
nap code: 2410
climate almost uni-
form throughout
region
winters are mild,
summers hot and
humid; average an-
nual temperature is
60-70*F {15-21*C)
precipitation aver-
ages 40-60 inches
(1000-1500 mm) an-
nually and is evenly
distributed through-
out year
growing season is
200-300 days; frost
occurs nearly every
wi nter
this region is a
north-south depression
between Coast Ranges
and Cascade Mountains
elevation range: sea
level-1500 ft (460 in)
Ultisols dominate
throughout region
Vertisols formed
from marls or soft
limestones conspic-
uous locally
InceptisoIs on flood
plains of major
streams
annual temperatures
average 48-55"F
(9-13 C)
average annual rain-
fall ranges from
15-60 inches (380-
1525 mm) but in much
of area from 30-45
inches (760-1120 nm);
most occurs in winter
Alfisols, Incepti-
sols and Ultisols
are principal soil
orders
climax vegetation is
medium tall to tall for-
ests of broadleaf ana
needleleaf evergreen
trees
at least 50 percent of
stands are loblolly pine,
short-leaf pine or other
southern yellow pines,
singly or in combination;
common associates in-
clude oak, hickory,
sweetgum, olackgum, red
maple, and winged elm
gums and cypress domi-
nate extensive Atlantic
Coast marshes and inter-
ior swamps
most upland areas sup-
port subclimax pine
forest (savannas)
dense coniferous forests
of western red cedar,
western hemlock and
Douglas-fir
interior valleys - con-
iferous forests less
dense than along coast
and often contain decid-
uous species such as
big-leaf maple, Oregon
ash and black Cottonwood
white-tailed deer,
cottontail, fox squir-
rel, gray squirrel,
racoon, fox
eastern wild turkey,
bobwnite and mourning
dove widespread
breeding birds include
pine warbler, cardi-
nal, summer tanager,
Carolina wren, ruby-
throated hummingbird,
blue jay, hooded
warbler, eastern tow-
hee, tufted titmouse
and red-cockadeO wood-
pecker (endangered
species)
reptiles include cot-
tonmouth, moccasin,
copperhead, rough
green, rat, coachwhip
and speckled king-
snakes, lizards and
slimy salamanders
mule deer, mountain
lion, boocat, western
gray squirrel, bushy-
tailed wood rat, orush
rabbit, gray fox,
ruffed grouse
Dusky Canada goose
winters only in
Willamette Valley
(Oregon)
-------
Table 1. (Continued)
Provinceb
Land-surface form
Climate
Soils
Vegetation'
Fauna
Pacific Forest
(Southeast
Alaska, Pacific
Northwest and
northern Calif-
ornia, 129700
sq mi or
335900 sq km)
map codes: in-
cludes Sitka-
Spruce-Cedar-
Hemlock (M2411).
Redwood (M2412),
Cedar-Hemlock-
Douglas-fir
(M2413), Calif-
ornia Mixed
Evergreen
(M2414), and
Silver Fir-
Douglas-fir
(M2415) Forests
series of steep,
rugged mountains
fronted in places
by a narrow coastal
plain
coastal mountains rise
5000 ft {1500 m) above
sea level and have
local relief of 1000-
3000 ft (300-900 m)
interior Cascade Range
Mountains rise 8000-
9000 ft (2400-2700 m)
dominated every 5-85 mi
(8-135 km) by a volcano
of much higher elevation
much of area, espec-
ially northern portion,
glaciated
average annual
temperature range;
35-50"F (2-10'C)
average annual
precipitation: 30-
150 inches (750-
3800 mm); maximum
rainfall occurs in
winter
Sierran Forest southernmost portion
(California,
32600 sq mi or
84400 sq km)
map code: M2610
of Cascade and Sierra
Nevada Mountains;
steeply sloping to
precipitous mountains
crossed by many val-
leys with steep
gradients
west slope of Sierra
Nevada rises from 2000-
14000 ft (600-4300 m);
east slope drops
abruptly to floor of
Great fiasin, about
4000 ft (1200 m)
much of region glaci-
iated
soil distribution
follows south-north
climatic gradient of
increasing precip-
cipitation and de-
creasing temperature;
Ultisols are found
in southern portion
of region and In-
ceptisols in more
northerly areas
base of west slope
receives about 10-15
inches precipitation
(250-380 mm) and has
long, unbroken, dry
summer
« at higher elevations,
precipitation in-
creases to up to 70
inches (1800 mm),
temperatures decrease,
dry summer season
shortens, more pre-
cipitation as snow
prevailing west winds
influence climate of
whole region; east
slopes much drier
than west sloDes
Ultisols extensive
on mountain slopes
Alfisols predominate
at lower elevations
lint i so Is occupy
narrow flood plains
and alluvial fans
of valleys
principal trees of
dense, montane conifer
forest are Douglas-fir,
western red cedar,
western hemlock, grand
fir, silver fir, Sitka
spruce and Alaska cedar
redwood is the charac-
teristic tree in the
fog belt along the
coast of northwestern
California; along with
Douglas-fir and a few
other conifers, redwoods
form perhaps densest of
all coniferous forests
with world's largest
trees
subalpine belt of moun-
tains consists of moun-
tain hemlock, subalpine
fir, whitebark pine and
Alaska cedar
vegetation zones very
marked; montane zone
lies between 2000-6000
ft (600-1800 m) in Cas-
cades, 4000-7000 ft
(1200-2100 m) in Central
Sierras and 5000-8000
(1500-2400 m) or more in
south; most important
species are western yel-
low pine (Jeffrey),
Douglas-fir, sugar pine,
white fir and incense
cedar
subalpine zone, between
6500-9500 ft (1980-2900
in), depending on latitude
and exposure, extends
1000 ft (300 m) vertical-
ly; mountain hemlock,
eik, deer, mountain
lion, bobcat, black
bear, brown Bear, and
moose
blue and ruffed grouse
(game birds;, hawks,
owls, chestnut-backed
chickadee, red-breast-
ed nuthatch, gray jay
and Steller's jay
mice, squirrels, mar-
tens, chipmunks and
Dushy-tailea wooa rats
mule deer, mountain
lion, coyote, black
bear, busny-tailed
wood rat, flying
squirrel, red fox,
fisher, yellow-haired
porcupine, long-eared
chipmunk and Trow-
bridge's shrew
common birds - moun-
tain quail, Lincoln's
sparrow, Audubon's
warbler, pine siskin,
Oregon junco, blue
goose, Williamson's
sapsucker, mountain
chickadee
predator birds - com-
mon nighthawk, pygmy
-------
Table 1. (Continued)
Prov i nee
Land-surface form
Climate
Soils
Vegetation c
Fauna
California
Chaparral
(California,
33500 sq mi or
86800 sq km}
map code: M2620
, central part of
California Coast
Ranges and mountains
of southern California
Coast Ranges - gently
to steeply sloping;
elevation range: sea
level to 2500 ft (760
ra); some peaks to
5000 ft (1500 m}
southern California
mountains steeply
sloping to precipi-
tous; elevation range:
2000-8000 ft (600-
2400 m); some peaks
to 1200 ft (3700 m)
winter precipitation
makes up 80-85 percent
total; nost falls as
snow at higher eleva-
tions
greatest precipita-
tion on slopes be-
tween 3000-7000 ft
(900-2100 m) in mon-
tane forest
subalpine zone co-
incides with alti-
tude of greatest
snowfall; precipi-
tation is 40-50
inches (1000-1270 mm)
and temperatures
average 35-52*F
(2-11 C)
hot, dry summers,
rainy, mild winters
t precipitation range:
12-40 inches (300-
1000 nm) evenly dis-
tributed through
fall, winter, and
spring; increases
with elevation
temperatures average
53-65"F (13-18'C) in
Coast Rnvtje and 12-
60"F (0-15*C) in
southern California
mountains; decreases
with altitude
California red fir,
lodgepole pine, western
white pine and whitebark
pine are important
lower slopes and foot-
hills, from 1500-4000
ft (457-1219 m) cover-
ed by coniferous and
shrub association
complex pattern of
Alfisols, Entisols
and Mollisols
Mollisols usually
along coast; Alfisols
in north; Entisols
in south
owl, great gray owl
bark beetles Ips
emarginatus and Ips
integer Infest ponder-
osa and lodgepole pines
California mountain
kingsnake
climax montane vegeta-
tion is sclerophyll
forest; found on north-
facing slopes and wetter
sites
most important evergreen
trees of sclerophyll
forest are California
live oak, canyon live
oak; interior live oak,
tanoak, California
laurel, Pacific madrone,
90 Wen chinquapin, and
Pacific bayberry
riparian forest of many
broadleaf species along
streams
shrub chaparral climax
on south-facing slopes,
drier sites
mule deer, coyote,
mountain lion, Calif-
ornia bobcat, gray
fox, uooa rat, spotted
and striped skunks
small mammals peculiar
to chaparral: Merriam
chipmunk, California
mouse, five-toed
kangaroo rat
conwon birds - wren-
tit, coswwn bushtit,
rufous-sided towhee,
white- and golden-
crowned sparrows, fox
sparrows, hermit
thrushes, ruby-crowned
kinglets, Audubon's
warbler
California condor
(threatened species)
-------
Table 1. (Continued)
Province b
Land-surface form
CIimate
Soi Is
Vegetation c
Fauna
Rocky Mountain
Forest (Blue
Mountains, Cen-
tral Rocky
Mountains,
187300 sq mi or
485100 sq km)
map codes:
includes Grand-
Fir-Douglas-fir
(M3111), Doug-
las^TTr (M3112),
Ponderosa Pine-
Douglas-fir
(M3113) Forests
Rocky Mountains -
rugged, glaciated, to
14000 ft (4300 m);
local relief between
3000-7000 ft (900-
2100 m)
several sections have
intermontane depres-
sions of "parks" that
have floor < 6000 ft
(1800 m)
climate is semi arid
steppe; precipitation
falls in winter;
bases of mountains
receive 10-20 inches
(250-500 ram) rain-
fall; upslope, pre-
cipitation increases
to 40 inches (1000
mm) and temperatures
decrease
climate influenced
by prevailing west
winds and north-south
orientation of moun-
tain ranges; east
slopes are much drier
than west slopes
average annual temp-
eratures are mainly
35-45*F (2-7'C) but
reach 50 F (10 C) in
lower valleys
soil orders occur in
zones corresponding
to vegetation zones;
Mollisols and Alfi-
sols in montane zone,
Aridisols in foot-
hill zone, and areas
of Inceptisols as re-
sult of steep slopes
and glaciation
well marked zones con-
trolled by combination
of altitude, latitude,
direction of prevailing
winds, and slope expo-
sure; generally various
zones at higher alti-
tudes in southern part
of region than in north
subalpine zone dominated
by Englemann spruce and
subalpine fir
montane zone dominated
by ponderosa pine and
Douglas-fir; ponderosa
pine dominant on lower,
drier, exposed slopes;
Douglas-fir dominant on
higher, moister, more
sheltered ones
aspen or lodgepole pine
are serai species in
fire disturbed subalpine
and montane zones
numerous reptiles;
amphibians (except
tree frog) scarce
elk, deer, mountain
lion, bobcat, black
bear, mice, squirrels,
martens, chipmunks,
bushy-tailed rats
hawks, owls, cnestnut-
backed chickadee, red-
breasted nuthatch, gray
jay, Steller's jay
blue and ruffed grouse
(upland game Diras)
Upper Gila
Mountains Forest
(Arizona, New
Mexico, 36100
sq mi or
93500 sq km)
map code: M3120
mostly steep foothills
and mountains but also
some deeply dissected
high plateaus
elevation range:
4500-10000 ft (1370-
3000 m) with some peaks
to 12600 ft (3840 m);
in many areas, relief
is higher than 3000 ft
(900 m)
t climate varies con-
siderably with alti-
tude
t average annual pre-
cipitation range:
10-35 inches (250-
875 mm); increases
with rising elevation
average annual temp-
erature is about 55*F
(13*C) in lower foot-
Mollisols and Aridi-
sols dominate upland
areas
stony land and rock
outcrops occupy large
areas of mountains
and foothills
zones similar to Rocky
Mountain zones but occur
at higher elevations; at
about 7000 ft (2100 m)
open forests of ponder-
osa pine found with
pinyon-juniper on south-
facing slopes
at about 8000 ft (2400 m),
Douglas-fir found first
on north-facing slopes and
a little higher on all
mule deer, mountain
lions, coyotes, bob-
cats, deer mouse,
long-tailed weasel,
porcupine, golden-
mantled ground squir-
rel, Colorado chip-
munk, red squirrel,
wood rat, pocket
gopher, long-tailed
vole, Kaibab (Abert)
squirrel, cottontail
-------
Table 1. (Concluded)
Province b
Land-surface form
Climate
Soils
Vegetation^
Fauna
hills and 40'F (5*C)
on upper mountain
slopes
slopes; aspen is common; I
limber pine found in
drier, rockier areas
at about 9000 ft (2700 m),
Englemann spruce and cork-
bark fir found; limber
pine and bristlecone pine
in rockier places
mountain bluebird,
pygmy nuthatch, wfiite-
breasted nuthatch,
Mexican Junco, Stel-
ler's jay, red-
shafted flicker,
Rocky Mountain sap-
sucker, goshawks and
red-tailed hawks
shorthorned lizard
only common, widely
distriDuted reptile
Hawaiian
Islands (Hawai-
ian Islands,
6700 sq mi or
17400 sq k»)
map code: M4210
hilly and mountainous
islands; about a fourth
of area rises < 650
ft. (198 ra), half is
650-2000 ft (198-600
m), and a fourth >
2000 ft (600 m)
tropical climate,
almost uniform
throughout year
temperature and
precipitation vary
greatly with alti-
tude and exposure
sea level average
annual temperature
range: 70-75*F (21-
24*C)
soils complex pat-
tern of leached
Ultisols and Oxi-
sols, Inceptisols,
rocky highlands
and coastlines
forests grow above shrub
lands on leeward side of
mountains; may extend to
sea level on windward
sides
at least four kfncis of
native forest distri-
buted according to
moisture availability;
ohia and koa important
tree species
hawks, owls, crows,
warblers, thrushes,
(native land birds)
axis deer, Hawaiian
wild boar, feral
sheep, goats (intro-
duced nimanals)
precipitation heav-
iest on windward side
of islands; leeward
slopes semi arid
aAdapted from Bailey (1980).
''Map code numbers preceded by M indicate mountainous regions.
cDominant species; does not include understory types.
-------
1.3 SUMMARY
The literature dealing with the effects of air pollution and acid
deposition on forest ecosystems varies in both quantity and quality of
information content. Generally, much more is known about the effects of
individual air pollutants on various forest tree species (usually domi-
nants or of economic importance) than on populations of those species or
on communities and forest ecosystems containing them. This distribution
of information results from the fact that effects at the lower levels of
biological organization can be discerned under the controlled conditions
of the laboratory or greenhouse, using seedling or sapling age trees,
whereas those at the community or ecosystem levels must be defined in the
field, where a greater number of complicating variables are involved,
frequently against a background of little or no baseline (control) infor-
mation on stand structure or function. These difficulties limited class-
ical field investigations to definition of the most obvious cases of
acute injury, those involving high pollution loads around point emission
sources, where well-defined gradients of vegetation response developed.
More recently, use of the analytical techniques of systems analysis
(modeling) and dendrochronology has provided the ability to predict and
define more subtle field responses to chronic air pollution stress
(Shugart et_al. 1980; Kercher and Axelrod 1981) by providing integrated
information afJbut both baseline and post-pollution community level
structure and functions.
Information quality of the literature varies in that the effects of
air pollution stress have been measured as a number of different response
variables which are frequently not directly comparable because their
relationships to one another are unknown. For example, reduced photosyn-
thetic activity has been found in the absence of visible foliar injury.
In turn, the significance of visible foliar injury in terms of the over-
all vigor of the organism is not always clear (Guderian and Kueppers
1980), and much remains to be known about how effects at the species
level of organization are integrated into the responses of communities
and ecosystems (Shugart et aK 1980; Shriner 1981).
Reconciliation of this information into an overall interpretation
of the effects of air pollution stress on forest ecosystem structure and
function is further complicated by the following factors:
y'l. Forests are spatially and temporally heterogenous. Spatially,
they vary in the vertical as well as the horizontal dimension.
Upper strata may act as a filter, effectively reducing the ex-
posure of understory constituents, or modify the composition of
the pollutant, as occurs during the transition of incident pre-
cipitation to throughfall. Temporally, forest processes and
functions are subject to diurnal, seasonal and successional
changes. Such temporal variation influences pollutant stress
response at two levels; at the shorter time frames, through
variations in metabolic activity in relation to pollutant expo-
sure, and over the longer term, through adaptation of community
constituents to the stress by replacement of the most sensitive
12
-------
individuals by more tolerant ones. Spatial and temporal vari-
ability are also interrelated in that stand structure is a
function of age. Systems analysis has shown that the stage of
stand development is an important factor modifying forest growth
response to air pollution exposure (Shugart et aK 1980). Smith
(1980) noted that successionally mature forest ecosystems pos-
sessed characteristics, such as low net production and slow,
closed nutrient cycling, that increased their resistance to air
pollution stress; he concluded that early and mid-successional
forests were particularly susceptible to air pollution distur-
bances. Unfortunately, most controlled condition investigations
do not account for stratification influences and most field
investigations are of short-term duration.
2. Interspecific competition has also been shown by systems analysis
to be an important factor modifying the response of a forest
stand to air pollution stress (Shugart et al. 1980; Kercher and
Axelrod 1981). Species shown to be sensitive to a pollutant
under controlled conditions may exhibit increased growth in an
exposed stand because of enhanced competitive ability over other
stand constituents suffering more adverse effects.
3. The response of an individual organism to a pollutant stress is
dependent upon pollutant and exposure event characteristics, and
to a large extent, a number of biotic and abiotic factors oper-
ating before, during, and in some cases, after exposure (Figure
2). The artificial nature of controlled condition investiga-
tions is often cited because of inconsistencies in the chemical
form (e.g., simulated acid rain solutions) and exposure charac-
teristics (e.g., greater than ambient concentrations) utilized
as compared to those experienced in the field. Of the biotic
and abiotic factors noted, inherent genetic susceptibility
probably exerts the most control over response. Environmental
factors operating before and after exposure probably alter plant
responses through their effect on physiological functions,
whereas those operating during exposure are more directly in-
volved in uptake of the pollutant, primarily by their influence
on stomatal function.
/4. In the field, forest communities are exposed to air pollutants
from many sources in mixtures of constantly varying composition
and concentration (e.g., SO? and trace metal particulates are
often simultaneously emitted from the same source; see also
McClenahen 1978). Therefore, interactions among pollutants are
possible, potentially producing responses which may be quite
different from those produced under controlled conditions, where
simple one pollutant-one dose stress studies predominate. Such
interactions may be additive, antagonistic, or synergistic in
nature. Well known examples of the latter type include induc-
tion of chlorotic dwarf disease in eastern white pine by sulfur
13
-------
Figure 2. Factors affecting the response of plants to air pollutants (Smith 1981).
14
-------
dioxide and ozone exposure (Dochinger and Heck 1969) and the
interactions of SO2 and acid deposition with trace metal
particulates in forest soils.
5. Forests are dynamic entities; they react to stresses in an inte-
grative way. These stresses include not only air pollution, but
also light, moisture, and nutrient deficiencies, predation, fire,
windthrow, disease, and logging. Therefore, responses to air
pollution stress must be defined against a background of any of
these other disturbances which may be operative. Currently, air
pollution-forest growth studies generally take only the effects
of moisture availability into account. Additionally, definition
of pollutant responses may be complicated by interactions among
these stresses, similar to those possible among pollutants; for
example, Voigt (1979) cautioned that sites subjected to inten-
sive harvesting management may be especially vulnerable to the
adverse effects of acid deposition on nutrient cycling.
In light of these factors, caution should be used in the interpre-
tation of dose-response and relative susceptibility information; such
autecological data are most meaningful when viewed in a synecological
context.
The air pollutants discussed in this document are solids, liquids,
and gases. They include primary pollutants [e.g., sulfur dioxide (SO?),
particulates, and fluorides (F)], which are important locally, as well as
secondary pollutants [e.g., oxidants (primarily ozone [O3]) and acid
deposition], which are important regionally. The primary pollutants often
vary in concentration in a decreasing spatial gradient away from a point
emission source, with the distribution pattern influenced by the quantity
of the pollutant, distance from and height of the source, prevailing wind
conditions, and the topographic characteristics of the site.
Generally, vegetation is the primary forest ecosystem component af-
fected by pollutant exposure, with the notable exception of forest soils
in the case of acid deposition. Very little is known about the direct
effects of these pollutants on the wildlife of forest ecosystems, with
the possible exception of fluorides. Ecosystem exposure to pollutant
doses producing alterations in plant species composition and community
structure, however, will also indirectly affect wildlife through
modifications in habitat and most likely in trophic relationships.
Responses at the (1) cellular, (2) organismal, (3) population, (4)
community, and (5) ecosystem levels of biological organization, common to
most of these pollutants (at the appropriate doses) include: (1) reduc-
tions in photosynthetic rates (demonstrated under controlled conditions,
sometimes reversible and in absence of, or prior to, visible foliar symp-
toms; field evidence meager; synergistic interactions noted); (2) foliar
injury (chlorosis, necrosis, premature abscission; see Appendix for symp-
toms) and reduced growth and vigor; (3) mortality and alterations in re-
productive efficiency (reductions in seed germination, seedling growth);
15
-------
(4) changes in species composition resulting from differential suscept-
ibility to injury; (5) changes in structure [simplification via decreased
production, standing crop biomass (hence, reduction in nutrients held
within the system), species diversity and elimination of sensitive strata]
and functions (trophic relationships, biogeochemical and hydrologic
cycles, forest soil processes), respectively. Characteristics and effects
more specific to the individual pollutants are summarized in Table 2 and
discussed in more detail in the appropriate subsections of the report.
It should be noted that although forest ecosystems are the focus of
this document, they are intimately interconnected with other terrestrial
and aquatic ecosystems of the biosphere through the processing of energy
and the cycling of water and nutrients. Therefore, any of the described
effects which alter the outputs of forest ecosystems can also be expected
to affect neighboring ecosystems.
The responses of forest ecosystems to air pollutant stress have been
alternatively categorized (for all pollutants in aggregate) by level of
exposure. Smith (1981) provided such a breakdown; his three classes of
interaction are presented in Table 3. Class I interactions are those
involving forest soils and vegetation as important sinks for pollutants
at low doses. Notable processes include potential stimulatory (ferti-
lizing) effects and accumulation of recalcitrant materials. In Class II
interactions, forest trees may be subtly and adversely affected by nu-
trient stress (Figure 3), impaired metabolism (reduced photosynthesis,
increased respiration) leading to direct disease induction, reduced
reproductive efficiency (Figure 4) and predisposition to entomological or
pathogenic stress (as a result of reduced vigor) following exposure to
intermediate pollutant doses. Concomitant effects at the higher levels
of biological organization include reduced growth, and hence biomass,
alterations in species composition, community structure and successional
patterns. Class III interactions are characterized by acute morbidity or
mortality of affected trees, resulting in structural simplification and
altered energy flow, biogeochemical and hydrologic cycling and edaphic
and climatic stabilization. Although Class III responses are the most
dramatic of those listed, they are of least overall importance because of
the relatively small forest areas involved in such interactions as
compared to Class I and II types (Smith 1981).
Despite the complexities noted earlier, several conclusions can be
made regarding the effects of air pollutants on forest ecosystems:
1. Ozone and sulfur dioxide are the most important growth-reducing
air pollutants of forest ecosystems (Skelly 1980; Smith 1981).
2. In eastern United States forests, ozone, acid deposition and
trace metal particulates appear to be the most important air
pollutants. In western forests, ozone, sulfur dioxide and
fluorides are the dominant pollutants (Smith 1981). Forest
ecosystems in the United States believed to be at particular
16
-------
Table 2. Characteristics, major areas of impact, and effects'
ecosystem components.
of individual air pollutants on forest
Pollutant
Effects on
Characteristics
Plants
Animals
Ecosystem
Major areas and
species afftcteQ
Oxidants
ozone (O3), peroxyacyl-
nitrates (e.g., PAN),
nitrogen oxides
gases; O3 most abundant,
little information on PAN,
N0X
chronic exposure in-
duces development of
the foliage diseases
"emergence tipburn"
of eastern white pine
and "chlorotic de-
cline" of ponderosa
pine
variety of effects in
mixed conifer forests
of San Bernardino
Mountains, California,
including:
reductions in wild-
life diversity in
moderate to severely
injured stands
predisposition of pol-
lutant stressed pon-
derosa pine to western
and mountain pine
beetle infestation,
Fomes annosus coloni-
zation, and increased
potential for fire
disturbance
regional pollutants,
important in the
western U.S. in
southwestern montane
forests, e.g., San
Bernardino, San
Gabriel Mountains;
ponderosa pine
in eastern U.S., in
Blue Ridge ana
southern Appalachi-
an Mountains; east-
ern white pine
Particulates
cement-kiln, limestone
and coal dusts; solids
form crusts on foli-
age
in deciduous forest, point source pollu-
trace metals; solids;
short atmospheric residence
tine as compared to that
in soils; tend to accumu-
late in tissues of exposed
organisms, soils
disagreement concern-
ing relative impor-
tance of root vs.
stomatal uptake as
routes of exposure
for elevated metal
levels in tissues
accumulation in tis-
sues and biomagnifica-
tion {trophic} in vi-
cinity of smelters and
remote areas known;
significance unclear,
although a few cases
of poisoning known
lowered reproductive
efficiency evidenced
by greatest changes
in species composi-
tion in lower strata
evidence of both
stimulation and in-
hibition of microbial
disease development
accumulation in soils,
especially upper or-
ganic layers
reductions in litter
input indicate re-
duced productivity
tants, of import
locally in vicinity
of industrial emis-
sion sources, mining
operations
point source pollu-
tants, although
sonewiiat of a re-
gional concern in
northeastern U.S.
some of ecosystem
effects noted may
-------
Table 2. (Continued)
Pollutant
Characteristics
Plants
Effects on"
Animals
Ecosystei"
Major areas and
species affected
03
Sulfur dioxide
acutely toxic primary
pollutant; gas
significance of ele-
vated metal levels in
tissues unclear
Fluorides gases and particulates,
former generally more
phytotoxlc; relatively
immobile, tend to accumu-
late in tissues of exposed
organisms
accumulates in
leaves and surviving
tissues, may or may
not be accompanied
by visible symptoms
pines particularly
sensitive
produces fluorosis
(fluoride poisoning)
and nutritional prob-
lems through effects
on dental systems;
latter may contribute
to deer population
mortality rates during
times of stress
at low doses may be
stimulatory to growth
at higher doses alters
stomatal function
conifers more sensi-
tive than deciduous
species
limited information
indicates foliar
microflora affected
increase In forest
floor litter layers,
decreases in soil bi-
ota, biomass and di-
versity, soil enzyme
activity, decomposi-
tion of organic mat-
ter, concentration of
exchanoeable nutrients
questionable evidence
of food chain accumu-
lation (insect) and
predisposition of pro-
ducers to infestation
by pine needle scale
and needle miner
F distribution in
soils around smelters
follows prevailing
winds; distribution
and concentration in
soil profile varies
with pollutant load
produces characteris-
tic zoned (ellipti-
cal) pattern of re-
sponse (loss of stra-
ta) around point
emission sources
at highest doses
(close to source),
complete stand mor-
tality with subse-
quent breakdown of
ecosystem structure
and functions
occur only in areas
of high loading,
e.g., industrial
emission sources,
urban areas, road-
ways
point source pollu-
tants; most notable
injury in U.S. in
Pacific northwest in
vicinity of alumi-
num, phosphate (also
in southeast U.S.)
production plants;
ponderosa pine
important locally in
vicinity of point
emission sources
such as smelters,
refineries, power
plants, and pulp
mills; eastern white
pine
-------
Table 2. (Continued)
Pollutant
Characteristics
Plants
Effects on
Animals
Ecosystem"
Major areas and
species affected
severe erosion, micro-
climate changes in
denuded areas
Acid wet (H2S04 and HNO3) and
deposition dry (includes SO4 aerosols)
deposition events
cuticle erosion (con-
trolled conditions)
leaching of foliar
nutrients
increased (as well as
decreased) growth
no well documented
cases of direct injury
in field
erosion, nutrient los-
ses impact neighboring
aquatic systems
soil chemistry (pH,
cation availability)
altered; potential in-
teractions with trace
metal availability,
producing toxicity
evidence of both pre-
disposition of plants
to disease (through al-
tered stomatal function)
and prevention of in-
fection (through direct
toxicity to pathogen)
direct effects on
vegetation in field
unknown
(significance of
foliar cation leach-
ing unclear)
important regionally
jn eastern U.S. and
in California and
Washington
no reductions in growth
directly attributable
to this pollutant found
in North American and
Norwegian studies, how-
ever Swedish and German
studies report capabil-
ity to Indirectly in-
fluence forest growth as
result of direct effects
on soil chemistry and
biology (nutrient loss
via leaching and metal
toxicity)
-------
Table 2. (Concluded)
Pollutant
Characteristics
Plants
Effects on
Animals
Ecosystem
Major areas and
species affected
primary influence appears
to be on forest soil
chemistry and biology;
main concerns are soil
acidification, leaching
of available nutrients,
increased availability of
A1 and trace metal cat-
ions, altered microbial
population dynamics and
biologically mediated
processes of organic mat-
ter decomposition, nu-
trient mineralization,
nitrification and nitro-
gen fixation
significance of soil ef-
forest productivity un-
clear because of mitigat-
ing site-specific soil
properties and potential
adaptations of microbial
communities to the stress
ro
O
fects over long term for
9Note that the effects listed are only those somevrfiat specific to the individual pollutants. Effects conmon to all
pollutants are discussed in the text.
-------
Table 3. Interaction of air pollution and temperate forest ecosystems.
Interaction
Air pollution
load
Forest soil and vegetation:
activity and response
Ecosystem consequences
and impact
Class I
Low
1. Forest soils and vegetation re-
lease particulate and gaseous
contaminants to the atomsphere
1. Atmospheric burden of contaminants
from anthropogenic sources supple-
mented by forest additions-scale
may be local, regional, or global
2. Forest soils and vegetation re-
move particulate and gaseous con-
taminants from the atmosphere
2. Air contaminants transferred from
the atmosphere to the biosphere,
forest ecosystems supplement nat-
ural removal mechanisms
Class II
Intermediate
3. Ho or minimal alteration of struc-
ture or metablism of forest soils
or vegetation
1. Forest tree reproduction, alter-
ation or inhibition
3. No adverse ecosystem change dis-
cernible, slight fertilization
possible
1. Altered species composition
2. Forest nutrient cycling, altera-
tion
a. Reduced litter decomposition
b. Increased plant leaching, soil
leaching, and soil weathering
c. Disturbance of microbial sym-
bioses
3. Forest metabolism, alteration
a. Decreased photosynthesis
b. Increased respiration
4. Forest stress, alteration
a. Phytophagous insects, increased
or decreased activity
b. Microbial pathogens, increased
or decreased activity
c. Foliar damage increased by
direct air pollution influence
2. Reduced growth, less biomass
3. Reduced growth, less biomass
4. Altered ecosystem stress
Increased or decreased insect
infestations;
Increased or decreased disease
epidemics;
Reduced growth, less biomass,
altered species composition
Class III High 1.
2.
Severe morbidity, excessive 1.
foliar damage
Mortality 2.
Dramatic change in species compo-
sition, reduced biomass, increased
erodeability, nutrient attrition,
altered microclimate and hydrology
Forest simplification or destruc-
tion
aAdapted fro* Smith (1981).
-------
Nutrient Cycle
Air Pollution Influence
Figure 3. Potential points of interaction between nutrient cycling
in forest ecosystems and air pollution (Smith 1981).
22
-------
Development Stage Air Pollution Influence
pollen production
pollination
toiilizaiicn
I rui md h:
flawers/strobili
reduce pollen production
^ reduce pollen distribution and germination
-« reduoe paBen gtowtti
rrduoe fruil » seed prcductior
wdi
SMd galmiraiicr | -4 isduoe 9«nrijneiion
seeeffings
seedling development I restrict seedling growth
juvenile development T
mature trees
I llower and cone initiation I ^ reduce flower or cone initiation
senescent trees
Figure 4. Potential points of interaction between air
pollutants and sexual reproduction of forest trees (Smith 1981)
23
-------
risk from chronic air pollution stress and in need of more in-
tensive investigation include the Northern Hardwood (approximate
representative map code, Figure 1, 2113), Central Hardwood
(2211-2215), and Western Montane (M2414, M2610) forest
associations (Smith 1981).
3. Little is known about the overall economic impacts of air pollu-
tion on forest ecosystems. Some estimates have been made in the
vicinity of point emission sources and in commercial forests,
based on reductions in the annual increment of wood growth
(Linzon 1971; Miller and McBride 1975), but they do not take
into consideration the "hidden" costs of damage resulting from
disruptions in ecosystem functions (Westman 1980).
4. Mosses, lichens, honeybees, and deer (antlers and bone) are
sensitive indicator organisms for the air pollutants discussed
in this document (Wiersma and Brown 1980; Nash and Sigal 1980;
Grodzinski and Yorks 1981). Sensitive, widely distributed,
dominant organisms include eastern white pine in eastern forests
and ponderosa pine in the west. In addition, Westman (1980)
proposed the following attributes as sensitive, community-level
indicators of probable pollution-induced changes: (1) physio-
gnomic characteristics (e.g., cuticle thickness, re: resistance
to absorption); (2) phenologic characteristics (e.g., ever-
greeness vs. deciduousness; age to reproduction); (3) life-
history characteristics (e.g., annual vs. perennial; generation
longevity); and (4) litterfall (re: indicator of nutrient budget
processes).
5. Current national air pollution exposure patterns can be
characterized as generally consisting of relatively low levels
of pollutants from multiple sources, as compared to those of the
prepollution-control past, when high pollutant loading sur-
rounding several notable point sources predominated. The latter
pattern (high, localized pollution) is today encountered only
where concentration of diverse source pollutants by meteorologic
or topographic conditions occurs regularly (e.g., Los Angeles
basin) (Shugart et aH. 1980). Consequently, gradual and subtle
changes in forest metabolism and composition over long periods
of time can be expected to be the primary responses of forest
ecosystems, over much of the United States, to air pollution
stress in the forseeable future. Such changes contrast sharply
with the dramatic, short-term destruction of forests in the
vicinity of point sources, witnessed in the past, but their
subtle nature belies their importance; the net result, over the
next decade, may be significant reductions in forest produc-
tivity (Smith 1981).
24
-------
6. The primary research needs in this problem area are:
Establishment of comprehensive, long-term field investigations
in the priority forest associations noted, supported by con-
tinued controlled environment testing, for elucidation of
Class I and II type interactions at the various levels of
biological organization;
t Definition of the direct and indirect effects of air pollu-
tants on forest wildlife and their relation to ecosystem
structure and function;
Definition of the major socioeconomic consequences of forest
injury.
25
-------
2.0 EFFECTS OF AIR POLLUTION AND ACID RAIN ON FOREST ECOSYSTEMS
2.1 EFFECTS OF PHOTOCHEMICAL OXIDANTS
The photochemical oxidants of importance in terms of injury to
forest ecosystems and their component organisms are ozone (O3), the
peroxyacylnitrates, [primarily peroxyacetylnitrate (PAN)] and the
nitrogen oxides [nitric oxide (NO) and nitrogen dioxide (NO2)]. Of
these compounds, ozone and PAN are the most ubiquitously distributed and
cause the most injury. Nitrogen oxides are included because of their
role in the formation of ozone and PAN in photochemical smog, although
they have been found to cause some injury to vegetation near industrial
emission sources. Although they are not discussed here, other constit-
uents of photochemical smog, such as aldehydes, are also known to cause
injury to plants. Most of the information in this section deals with
effects of exposure to ozone.
2.1.1 Acute and Chronic Injury
a. PI ants. The direct responses of plants to photochemical oxi-
dants are generally exhibited in the foliage since the principal
sites for entry of the pollutants into the plant are the leaf
stomata. Injury includes both visible and subtle responses; an
example of the former is a change in leaf coloration, while
changes in a physiological process or in growth or reproduction
are examples of the latter. Injury may also be classified as
acute or chronic. Acute injury is usually initiated by exposure
to high doses (concentration x time) of pollutants, including
exposure to low concentrations over extended periods of time.
Such injury involves expression of clinical symptoms leading to
the death of cells, tissues, organs, organisms, populations
and/or communities. An example of a readily detected acute
injury is leaf necrosis, the result of the death of constituent
leaf cells. On the other hand, chronic injury results from
lower dose or intermittent exposures that are not lethal at any
level of biological organization. Reduced photosynthetic and
growth rates are examples of chronic injuries (Skelly 1980).
Both acute and chronic injuries are the result of pollutant-
caused physiological disturbances at the cellular level. For
example, Miller et jil_. (1969) and Evans and Miller (1972) found
that ozone produced a number of histochemical and histologic
changes in current season and one-year needles of ponderosa pine
(Pinus ponderosa). Among the most important of these changes
reported by Miller et al. (1969) was a reduction in apparent
photosynthetic rates without the development of typical visible
symptoms. Similar results were reported by Carlson (1979) for
several eastern deciduous species [sugar maple (Acer saccharum),
black oak (Quercus velutina), and white ash (Fraxinus
americana)].
26
-------
At the organismal level, information on acute ozone injury to
forest tree species is plentiful. This information has been
reviewed and synthesized by Davis and Wilhour (1976) and the
National Research Council (1977a). Tables 4 and 5 contain
breakdowns of forest tree species into three relative suscepti-
bility groups. The species breakdown in Table 4 is based on
various fumigation chamber studies; Davis and Wilhour (1976)
presented no dose-response information corresponding to the re-
lative categories. The breakdown in Table 5 is also based on a
variety of laboratory fumigation studies, involving herbaceous
plants as well as trees grown under sensitive conditions. Expo-
sure to ozone took place under a variety of experimental condi-
tions; foliar injury was the most often studied response vari-
able (see caution on interpretation of visible foliar injury in
Appendix). The National Research Council (1977a) did provide
quantitative dose-response information for each of the relative
categories in Table 5. For example, the dose required to
produce a 5% injury to the species presented in Table 5 varies
as follows: Sensitive- 0.02-0.04 ppm for an 8 hour exposure;
Intermediate- 0.07-0.12 ppm for an 8 hour exposure;
Resistant- > 0.20 ppm for an 8 hour exposure.
The National Research Council (1977a) reported that eastern
coniferous species, in general, appear to be somewhat more
sensitive than western coniferous species to acute oxidant
exposure and that many eastern deciduous species are sensitive
to exposures of ozone at 0.20-0.30 ppm for 2-4 hours.
The reader is cautioned in the interpretation of this informa-
tion; the nature of the plant response depends a great deal upon
the operating or experimental conditions that existed before,
during and in some cases, after exposure. The influence of
these conditions on plant responses at least partially accounts
for the varying relative classification of an individual species
by different investigators, as of that for eastern white pine
(Pinus strobus) in Tables 4 and 5 (see also Tables 8 and 9).
The following biotic and abiotic (site) factors (shown also in
Figure 2) have been found to affect plant response to oxidant
exposure (National Research Council 1977a):
Biotic Factors
1. Inherent genetic susceptibility - determines or influences
such cellular factors as stomatal function, volume of in-
tercellular spaces, number of mesophyll cells per stomate
and extent of cutin formation on cell walls.
2. Age of tissue or organism - leaf age is important in that
plants generally are most sensitive to ozone exposure when
leaves are nearly completely expanded; young leaves are
more tolerant. However, leaves appear to be most sensitive
to PAN exposure at a younger physiologic age, just before
maximum expansion.
27
-------
Table 4. Relative susceptibility of forest tree species to injury from ozone
exposure.9
Sensitive Intermediate Tolerant
Green ash
Boxelder
Black Hills spruce
(Fraxinus pennsylvanica)
(Acer negundo)
(Picea qlauca densata)
White ash
Japanese larch
Colorado blue spruce
(Fraxinus americana)
(Larix leptolepis)
(Picea punqens)
Quaking aspen
Black oak
Norway spruce
(Populus tremuloides)
(Quercus velutina)
(Picea abies)
Honey locust
Pin oak
White spruce
(Gleditsia triacanthos)
(Quercus palustris)
(Picea qlauca)
European larch
Scarlet oak
Black walnut
(Larix decidua)
(Quercus coccinea)
(Juqlans niqra)
White oak
Eastern white pine
(Quercus alba)
(Pinus strobus)
Austrian pine
Lodgepole pine
(Pinus nigra)
(Pinus contorta)
Jack pine
Pitch pine
(Pinus banksiana)
(Pinus rigida)
Jeffrey pine
Scotch pine
(Pinus jeffreyi)
(Pinus sylvestris)
Loblolly pine
Shortleaf pine
(Pinus taeda)
(Pinus echinata)
Monterey pine
Slash pine
(Pinus radiata)
(Pinus elliottii)
Ponderosa pine
Sugar pine
(Pinus ponderosa)
(Pinus lambertiana)
Virginia pine
Torrey pine
(Pinus verqiniana)
(Pinus torreyana)
Hybrid poplar
(Populus maximowiezii x
trichocarpa)
Tulip poplar
(Liriodendron tulipifera)
American sycamore
(Platanus occidental is)
aAdapted from Davis and Wilhour (1976).
28
-------
Table 5. Relative susceptibility of forest tree species to injury by short-
term exposure to ozone.a
Sensitive^
Quaking aspen
(Populus tremuloides)
Eastern white pine
(Pinus strobus)
Jack pine
(Pinus banksiana)
Red pine
(Pinus resinosa)
Virginia pine
(Pinus virqiniana)
Intermediate
White ash
(Fraxinus americana)
Austrian pine
(Pinus nigra)
Jack pine
(Pinus banksiana)
Virginia pine
(Pinus virqiniana)
Resistant
Balsam fir
(Abies balsamea)
Douglas-fir
(Pseudostsuqa men-
ziesii)
White fir
(Abies concolor)
Eastern hemlock
(Tsuga canadensis)
Japanese larch
(Larix leptolepis)
Sugar maple
(Acer saccharum)
Scotch pine
(Pinus s.ylvestris)
Eastern white pine
(Pinus strobus)
Pitch pine
(Pinus riqida)
Red pine
(Pinus resinosa)
Black spruce
(Picea glauca var.
densatal
Blue spruce
(Picea punqens)
Norway spruce
(Picea abies)
White spruce
(Picea glauca)
aAdapted from National Research Council (1977a).
bDose required to produce a 5% injury in various susceptibility categories:
Sensitive: 0.02-0.04 ppm for an 8 hour exposure; Intermediate: 0.07-0.12 ppm
for an 8 hour exposure; Resistant: £ 0.20 ppm for an 8 hour exposure.
29
-------
Abiotic Factors
1. Light intensity - Davis and Wood (1973) found that placing
Virginia pine (Pinus virginiana) plants in the dark after
exposure to ozone delayed symptom development. Also, there
appears to be an absolute requirement for illumination, the
effects of which are not understood, before, during and after
exposure to PAN for development of visible symptoms (Taylor
et _al_. 1961; Taylor 1969J.
2. Temperature - Virginia pine and white ash (Fraxinus ameri-
cana) sensitivity to ozone exposure increased when the plants
were grown under warmer conditions and subjected to higher
temperatures after exposure (Wilhour 1971; Davis and Wood
1973).
3. Relative humidity - Davis and Wood (1973) found that the
sensitivity of Virginia pine to ozone exposure increased
with increasing relative humidity during exposure but did
not change with adjustments in relative humidity prior to
and after exposure.
4. Soil (edaphic) parameters - soil water status during exposure
is an important variable because it influences stomatal ac-
tivity (e.g., stomates normally close during times of
moisture stress). In addition, soil water status prior to
exposure influences the general physiological condition of
the plant and hence its susceptibility to injury. The
importance of soil fertility as a variable affecting plant
response is generally not well understood.
5. Temporal influences - There are normal diurnal and seasonal
variations in the above parameters Which will influence plant
responses to pollutant stresses. In addition, Barnes and
Berry (1969) noted seasonal physiological changes (soluble
sugar content) in eastern white pine needles that may
influence susceptibility to ozone injury.
These factors influence plant response during exposure primarily
by affecting stomatal activity. Their influence before and after
exposure is probably related to the effects they exert on various
physiological processes. Of the above factors, inherent genetic
susceptibility to injury is probably the most important in
determining plant response (National Research Council 1977a).
Chronic exposure to ozone has been implicated as a probable
cause or a contributing factor in the development of specific
foliage diseases in both eastern and western forests; "emergence
tipburn" (also known as "white pine needle dieback") of eastern
white pine and "chlorotic decline" (also known as "ozone needle
mottle of pine") of ponderosa pine (Berry 1961; Parmeter et al.
1962; Berry and Ripperton 1963; Parmeter and Miller 1968;
30
-------
Richards et aJ. 1968). "Emergence tipburn" is characterized as
a tip dieback of newly elongating needles. The disease occurs
throughout the range of eastern white pine. Random trees in a
stand are affected, with symptoms developing as a result of
exposures in successive years. Repeated needle injury often
results in the death of primary roots of affected trees. Berry
and Ripperton (1963) produced "emergence tipburn11 symptoms by
exposing eastern white pine to 0.06 ppm ozone for 4 hours.
"Chlorotic decline" is characterized by chlorosis and loss of all
but the current season's needles, with accompanying deterioration
of the fibrous root system, reductions in growth, and eventually
death of affected trees. Miller et aK (1963) produced "chlor-
otic decline" symptoms by exposing ponderosa pine to an ozone
dose of 0.5 ppm for 9 hours/day for 9-18 days.
The National Research Council (1977a) reported that "emergence
tipburn" is the only clearly defined ozone chronic injury in
eastern forest species. Virginia pine and jack pine (Pinus bank-
siana), whose natural ranges overlap with that of eastern white
pine, and which have been found to be relatively more sensitive
to acute ozone exposure than eastern white pine according to
Berry (1971) and Davis and Wood (1972), do not appear to exhibit
chronic injury. Ponderosa pine appears to be the most sensitive
western species; studies in the San Bernardino Mountain area sug-
gest that this species is moderately to severely injured in areas
receiving oxidant exposures of 0.08 ppm for 12-13 hours/day
(Taylor 1973a).
Of the peroxyacylnitrates, only PAN and peroxypropionylnitrate
(PPN) are at times found in sufficient quantities in ambient air
to cause visible injury (National Research Council 1977a). Mudd
(1975a) reviewed the physiological effects of PAN exposure.
Davis (1975) found that ponderosa pine cotyledons were resistant
to injury following 8 hour exposures to 0.08, 0.20 and 0.40 ppm
PAN, whereas Drummond (1971) reported variable symptoms in maple
(Acer sp.), ash (Fraxinus sp.), oak (Quereus sp.), and black lo-
cust (Robinia pseudoacacia) following 8 hour exposures to 0.20-
0.30 ppm. No information is available on chronic PAN injury in
eastern forests, although the National Research Council (1977a)
reported that the compound undoubtedly contributes to oxidant
injury in western forests, particularly for some deciduous
species. However, Davis and Wilhour (1976) reported that most
woody plants are relatively tolerant of PAN exposure.
Nitric oxide (NO) is not known to cause injury to forest tree
species in the field; such acute injury has resulted, however,
from accidental exposures to nitrogen dioxide (N0g) emitted
from certain industrial processes. The physiological basis for
these responses was reviewed by Taylor et al. (1975). The Na-
tional Research Council (1977b) reviewed-tTre" available litera-
ture and compiled a relative plant susceptibility distribution
31
-------
for exposure to nitrogen dioxide; an adaptation of this infor-
mation is presented in Table 6. No corresponding quantitative
information for the three general susceptibility categories was
presented.
b. Animals. No causal information could be found in the available
literature regarding the direct effects of oxidants on forest
wildlife. Potential types of direct effects, however, can be
extrapolated from results obtained with laboratory animals;
these may include changes in visual or olfactory functions which
may in turn influence the animal's competitive capability in
interactions with other organisms (Newman 1975). The most
important effects of photochemical oxidants on forest wildlife
are believed to be indirect, through the stresses they place on
food and habitat resources (i.e., acute and chronic injury of
forest vegetation) (National Research Council 1977a, 1977b).
These effects are described in the following subsection.
2.1.2 Ecosystem Effects
The effects of oxidant air pollution on forest communities and eco-
systems are much more poorly understood that those at the organismal
level of biological organization (Skelly 1980). Intensive analysis of
the mixed coniferous forest ecosystem of the San Bernardino Mountains of
southern California has provided the best available information in this
area to date. This ongoing research, which began in 1972, uses systems
analysis to integrate and interpret forest response data. The major
highlights of this research are presented here; for more detailed infor-
mation the reader is referred to Taylor (1973a, 1973b, 1974, 1980);
Miller and Elderman (1977); and Kickert and Gemmill (1980).
The dominant species of the mixed conifer ecosystem of the San Ber-
nardino Mountains include ponderosa pine, Jeffrey pine (Pinus jeffreyi),
sugar pine (Pinus lambertiana), white fir (Abies concolor), incense-cedar
(Libocedrus decurrens) and California black oak (Quercus kelloggii)
(Miller 1973j^ As would be expected, the responses of these species to
oxidant air pollution have been varied; foliar injury, as detected by
aerial photography (Wert 1969) and permanent plot inspection (Miller
1973; Miller and Elderman 1977), was most severe in stands of ponderosa
and Jeffrey pines. The remaining dominant species generally exhibited
only slight injury. Mortality was observed only in ponderosa and Jeffrey
pine. As a result of this differential susceptibility to oxidant injury,
Miller (1973) predicted a shift in species composition to a greater
proportion of white fir dominated stands. However, the responses of
forest communities and ecosystems are integrated responses, that is, they
are due not solely to any one particular stress but rather to all stresses
(biotic and abiotic) in aggregate (Kozlowski 1980). Therefore, shifts in
community composition cannot be predicted only on the basis of species
susceptibility to air pollutant injury, as shown by the work of West £t
(1980) and Kercher and Axelrod (1981). These investigators used
systems analysis to examine the responses of individual species and
32
-------
Table 6. Relative susceptibilities of selected forest
tree species to injury from nitrogen dioxide exposure.3
Sensitive
Intermediate
Resistant
European larch
(Larix decidua)
Japanese larch
(Larix leptolepis)
European white birch
(Betula pendula)
White fir
(Abies alba)
Nikko fir
(Abies homolepis)
White spruce
(Picea glauca)
Colorado blue spruce
(Picea pungens cv. glauca)
Norway maple
(Acer platanoides)
Austrian pine
(Pinus nigra)
European hornbeam
(Carpinus betulus)
Beech
(Fagus sylvatica)
Black locust
(Robinia
pseudoacacia)
aAdapted from National Research Council (1977b).
33
-------
entire stands in eastern deciduous and western coniferous forests to air
pollution stress. They found that plant competition (interspecific
competition) was a very important factor affecting species response and
hence community composition. For example, pollutant sensitive species
may exhibit increased growth as a result of pollutant stress because they
gain a competitive advantage over other species in the community, with
which they must interact, that have sustained greater injury. Along
these lines, Miller (1973) predicted that sugar pine and incense-cedar,
rather than white fir, would increase in importance on the poorer sites
in the San Bernardino Mountains because of the differing habitat toler-
ances and competitive abilities of these pollutant-resistant species.
Another important abiotic stress that affects community composition
in western forests is wildfire. Although white fir and incense-cedar are
resistant to oxidant stress, they are fire-sensitive species, and there-
fore would be expected to assume dominance only when fire is excluded
from the ecosystem. Wildfire in this system would eliminate these fire-
sensitive species and present a favorable seedbed for the oxidant sensi-
tive pines (Miller and Elderman 1977). Kickert and Gemmill (1980)
cautioned that the interaction of air pollution and wildfire stresses in
this system is likely to result in sudden, large qualitative changes in
species composition and successional patterns. They stated that there is
a likelihood that the mixed conifer stands may change to mixed deciduous
and shrub communities at mid-elevations and scrub field communities at
higher elevations as a result of these stresses.
Similar shifts in species dominance and community composition have
been reported for forests other than those in the San Bernardino Moun-
tains. Treshow and Stewart (1973) and Harward and Treshow (1975) examined
the effects of oxidant exposure on the population dynamics of several
plant communities. Fumigations carried out in portable and greenhouse
chambers in aspen (Populus sp.) communities led these investigators to
conclude that (1) sensitivity of the dominant aspen to ozone exposure
would result in changes in species composition not only through the loss
of aspen but also through the concomitant restricted development of white
fir (because white fir seedlings require the shade of an aspen overstory
for optimal juvenile growth); and (2) only one or two years of ozone
exposure may be sufficient to cause changes in the composition of under-
story species because of resulting varying seed production responses. In
eastern forests of the Blue Ridge and southern Appalachian Mountains,
shifts in species composition away from oxidant sensitive eastern white
pine have been noted by Hayes and Skelly (1977) and Skelly et_al_. (1979).
These changes in plant community composition and structure elicit
additional structural (e.g., in shrub and herb layers) and functional
(e.g., energy flow through food webs, nutrient and hydrologic cycles)
responses throughout the system. Some of these responses have been
documented in the San Bernardino Mountain Studies (Miller and Elderman
1977; Taylor 1980).
In terms of providing food and habitat for wildlife, ponderosa pine,
Jeffrey pine and black oak are the most important tree species within the
34
-------
forests of the San Bernardino Mountains; these species are also sensitive
to oxidant exposure. Oxidant injury leading to their reduced growth and
mortality therefore also indirectly affects community consumer and decom-
poser populations. For example, the small mammal fauna on study plots
exhibiting moderate to severe oxidant injury were found to be only half
as abundant as that on plots exhibiting slight to no injury (Miller and
Elderman 1977). Plots subject to lower levels of oxidant pollution had
larger and more diverse small mammal populations. Miller and Elderman
(1977) speculated that abundance and distribution of small mammals on the
study plots correlated closely with the quality of key vegetation and
soil habitat requirements and that oxidant pollution affected the mammal
populations through alteration of these habitat elements.
Wildlife, in turn, also exerts an important controlling influence on
vegetation composition through predation on seeds and fruits. The western
gray squirrel (Sciurus griseus anthonyi) is an important, abundant pre-
dator on pine and oak seeds in the San Bernardino Mountains. Predation
of immature seeds of oxidant stressed pines and oak may be an important
factor which reinforces oxidant injury in contributing to shifting plant
species composition (National Research Council 1977a).
Oxidant injury also predisposes affected trees to attack by biotic
agents, such as insects and pathogenic fungi, which hasten mortality and
modification of stand structure. For example, Stark et^ al_. (1968) found
increased incidence of western pine beetle (Dendroctonus brevicomis) and
mountain pine beetle (Dendroctonus ponderosae) infestation on ponderosa
pine trees exhibiting severe oxidant injury. Miller and Elderman (1977)
reported that (1) the western pine beetle was the most common killer of
ponderosa pine in oxidant stressed study plots; (2) beetles appeared to
attack the more seriously oxidant injured trees; (3) oxidant stressed
trees were killed by fewer western pine beetles than non-stressed trees.
Dahlsten and Rowney (1980) studied the effect of photochemical oxidants on
the population dynamics of the western pine beetle in the San Bernardino
National Forest. Their results indicated that a given population of
beetles could increase at a greater rate and kill more trees in stands
with a high proportion of oxidant injury. A secondary effect of such
enhanced insect activity in severely oxidant stressed stands could be
increased population levels of insectivorous predators, such as various
species of birds and small mammals (National Research Council 1977a).
Oxidant injury has also been found to predispose ponderosa and
Jeffrey pine roots and stumps to infection by the root pathogen Fomes
annosus (Miller and Elderman 1977; James et al. 1980; Taylor 198^TJ~-
Similarly, ozone induced injury of eastern wTiTte pine needles has been
found to affect subsequent colonization by parasitic and saprophytic
fungi (Costonis and Sinclair 1972). Diminished numbers of mycorrhizal
rootlets have been found on oxidant stressed ponderosa pine and eastern
white pine; saprophytic fungi replace these symbionts and further decay
small rootlets (Parmeter et 1962).
Oxidant injury in the San Bernardino Mountains also appears to have
affected stand litter fall and accumulation, physical and chemical
35
-------
characteristics of litter, the rate of litter decomposition, available
nutrient content of the upper layers of the soil profile, and community
microarthropod population dynamics (Miller and Elderman 1977; Taylor
1980). These changes in forest floor characteristics can in turn
influence stand composition because they represent unfavorable seedbed
conditions for the dominant tree species and a greater potential for
severe wildfire injury.
2.2 EFFECTS OF PARTICULATES
Particulates are conglomerates of chemically heterogenous substances
that have generally been found to cause injury only to those forest eco-
systems located near point emission sources. The most important phyto-
toxic constituents of this group include cement-kiln, limestone and coal
dusts, sulphate aerosols and trace metal particles (sulphate aerosols are
discussed in subsection 2.4.2). The toxicity of these pollutants is
determined by their chemical composition and the environmental and biotic
factors operating at the time of exposure, as previously discussed.
Little and Martin (1972) and Varshney and Garg (1980) provided evidence
that leaf surface morphology is a biotic factor of particular importance
in the deposition and foliar accumulation of this group of pollutants;
hispid leaves are more effective in retaining surface deposits than
glabrous leaves.
2.2.1 Dust Particulates
a. Acute and Chronic Injury - PI ants. Cement-kiln, limestone and
coal dusts disturb plant photosynthesis and heat exchange by
coating leaf surfaces, effectively preventing light absorp-
tion, and by blocking leaf stomata, preventing normal gas ex-
change. Foliar injury may also sometimes result from cuticle
dissolution by dust leachate (USDA 1973).
Deposition of cement-kiln and limestone dusts in the presence
of free moisture can result in the formation of a hard crust
on leaf and twig surfaces. Such encrustations are normally
confined to the upper surface of deciduous leaves but often
completely encase conifer needles. The covered leaf tissue
commonly becomes chlorotic or necrotic; needles often pre-
maturely absciss (Darley 1969).
Brandt and Rhoades (1972, 1973) examined the effects of lime-
stone dust on a deciduous forest surrounding a processing
plant in southwestern Virginia. Measurement of dust deposi-
tion at a town adjacent to the sampling sites showed median
pollutant inputs of 824 ug/m3/24 hrs for suspended matter
(particles from 0.5 to > 5 u) and 426 metric tons/kmvmonth
for dust fall (particles from 10 to >.150 u). They reported
leaf necrosis and decreased lateral growth of all but one of
the dominant tree species on the exposed site. Similar re-
ductions in growth resulting from cement-kiln and limestone
dust exposure have also been reported for conifers (Manning
-------
The effects of coal particulates on sessile oak (Quercus pet-
rea) in a deciduous woodland in England were examined by Wil-
TTaims et al. (1971) and Ricks and Williams (1974). They found
a spatial gradient of deposited particles with trees nearer
the emission source having the highest concentration and
greatest number of particle-blocked stomates. This blockage
was postulated to: (1) interfere with normal gaseous diffu-
sion; (2) possibly enhance penetration of gaseous pollutants,
for example, leaves from some test sites contained sulfur
levels over twice those of control leaves, which the authors
attributed to uptake of accompanying SO2 emissions; and (3)
facilitate entrance of fungal hyphae into the leaves.
Animals. No information was found in the available literature
concerning the direct effects of dust particulates on forest
wildlife. Given the nature of the plant responses discussed
in the previous and following subsections, indirect effects,
through disturbance of habitat and food supply, seem probable.
However, any such effects would be expected to be important
only close to point emission sources.
Newman (1975) stated that particulate toxicity can be consid-
ered in three ways: (1) intrinsic toxicity of the particles
(e.g., trace metals); (2) particulates as carriers of toxic
material (e.g., soot carbon as sorption site for gases); and
(3) particulates as inert particles which interfere with the
clearance of other airborne toxic material. He further stated
that inert particulates can be expected to primarily affect
the respiratory systems of exposed organisms. Newman (1980)
presents a summary of the responses of birds and mammals
(domestic, laboratory and wildlife) to acute and chronic
exposure of air pollutants, including particulates; the
relationship of these responses to those that can be expected
for forest wildlife in the field is unknown.
b. Ecosystem Effects. Brandt and Rhoades (1972) investigated the
long term effects of limestone dust accumulation on the spe-
cies composition and structure of a deciduous forest community
in southwestern Virginia. They noted a reduced reproductive
efficiency of some dominant species and decreased density of
total woody stems on a site receiving heavy dust input (see
subsection 2.2.1a, Plants). The species composition of the
forests according to strata (trees, saplings, seedlings and
shrubs) differed greatly, with the most significant changes
in structure found in the seedling-shrub and sapling strata.
A number of tree and shrub species increased in abundance on
the dusty site relative to their presence in the control
stand. Notable among these were chinquapin oak (Quercus
muehlenberqi i), a calciphile, sugar maple (Acer saccharum)
and yellow poplar (Liriodendron tulipifera)" The
investigators speculated that continued input of dust to the
site would result in these subordinate species assuming a
dominant position in the affected stands.
37
-------
In a companion study, Brandt and Rhoades (1973) examined the
effect of limestone dust exposure on the lateral growth of
four tree species of high relative density, common to both
control and dusty sites. Mean growth reductions were found on
the dusty site for the same three species, red maple (Acer
rubrum), red oak (Quercus rubra), chestnut oak (quercus prin-
us), shown in the previous study to have a reduced density in
aTl strata. Yellow poplar, however, exhibited a 76% increase
in growth, which also corresponded to previous results showing
increased density of the species in all strata. The authors
explained the increase in growth of yellow poplar as the re-
sult of decreased competition from the leading dominant spe-
cies, which apparently were less tolerant of dust accumulation
than yellow pcpl This interpretation of field results
substantiates the simulation findings of West et al (1980)
and Kercher and Axelrod (1981) discussed in suTisecTion 2.1.2.
Only limited information exists on the effects of dust par-
ticulates on disease expression in forest ecosystems. Manning
(1971) investigated the effects of limestone dust on the in-
cidence of foliar disease of hemlock (Tsuga canadensis),
sassafras (Sassafras albidum) and wild grape (Vitis vulpina)
in southwestern Virginia. Grape and sassafras leaves with
moderate dust deposits were apparently more susceptible to
fungal leaf spot diseases than leaves of the same species
without accumulated dust. Parmeter and Uhrenholdt (1975)
found that a single test exposure of Monterey pine (Pinus
radiata) seedlings to simulated wildfire smoke (from burning
needles) before inoculation with aeciospores of the western
gall rust fungus resulted in reduced development of galls on
the trees.
2.2.2 Trace Metal Particulates
Trace metal particulates are a broad group of pollutants that include
elements required by plants and animals in minute amounts (micronutrients
such as Fe, Mn, Cu, Zn), as well as those that have no known metabolic
function (e.g., Pb, Cd, Ni, Sn), all of which are potentially toxic in
sufficient quantities (Smith 1981). The environmental distribution of
these pollutants is characterized by fairly short (generally less than a
month) atmospheric residence times in comparison to those in soils of
hundreds to thousands of years (National Research Council 1972; Hutchin-
son 1980). Accumulated levels of trace metals in soils and plant tissues
are generally found in the vicinity of urban areas, mine sites, industrial
emission sources (such as smelters) or along roadways, although elevated
soil metal levels have also been noted in remote areas. The reader in-
terested in more information is referred to Kathny (1973), Drucker and
Wildung (1977), and Oehme (1978). For a more detailed discussion of
roadside and urban trace metal particulates see Smith (1981).
a. Acute and Chronic Injury - Plants. The limited information
available concerning acute and chronic injury of forest tree
38
-------
species by trace metal pollutants comes primarily from
solution culture tests of trace metal salts (e.g., PbCl2»
CdC"l2) on potted broadleaf and coniferous seedlings. Re-
ported plant responses include foliar chlorosis and necrosis
and reductions in photosynthesis and in leaf, stem and root
growth (Jordan 1975; Carlson and Bazzaz 1977; Lamoreaux and
Chaney 1977; Mitchell and Fretz 1977; Kelly et aK 1979). The
persistence and interference of metals with specific enzyme
systems are generally noted as the cause of these effects
(Hutchinson 1980); Bowen (1966) reviewed the altered biochem-
istry involved. Corresponding dose-threshold data from these
studies are quite variable, as would be expected for a variety
of metals in different forms under diverse operating condi-
tions. Although Smith (1981) stated that insufficient infor-
mation exists to allow identification of acute injury thresh-
olds for sensitive woody species, he suggested that the vari-
ous metal threshold values would probably fall within the
ranges presented in Table 7.
The applicability of these results to field conditions, how-
ever, is questionable, as there is disagreement in the
literature concerning the relative importance of root
absorption versus surface deposition and stomata? absorption
as causes of elevated metal levels in plant tissues (National
Research Council 1972; Buchauer 1973; Ruhting and Tyler 1973;
Reiners et^ al 1975; Siccama and Smith 197B; Freednan and
Hutchinson T?80a). Palmer and Kucera (1930) noted this
problem in their analysis of root versus stomatal uptake as
sources of foliar Pb. The specific metal in question, the
form of the metal salt [i.e., the fairly water soluble metal
nitrates and chlorides used in laboratory studies versus
those forms more frequently encountered in the field, such as
oxides, halides, sulphates and phosphates (Koslow et al.
1977)], the si2e of the metal particulates, cation exchange
capacity (CEC) of the soil, the quantity of the pollutant and
metal synergistic and antagonistic interactions encountered
in the field are all factors that are believed to affect the
relative importance of these various uptake pathways, and
hence plant response (Palmer and Kucera 1980).
Animals. None of the field studies cited in the following
subsection include information on the effects of trace metal
particulates on forest wildlife. The primary route of wild-
life exposure to trace metals is believed to be ingestion of
metal contaminated vegetation; direct inhalation is believed
to be of secondary importance (Newman 1975). The accumulative
nature of these pollutants in soils and plant tissues is also
operative in wildlife. In a recent review, Newman (1980)
cited numerous examples of biomagnification of trace metals
in birds and small mammals in the vicinity of smelters as
well as in small mammals in areas more remote from emission
sources. The effects of these elevated tissue levels are
39
-------
Table 7. Concentrations of trace metals in U.S. forest foliage.3
Baseline (uncontaminated) concentration (ppm)
Element'3 Mean Range
Cadmium
(Cd)
7.0
0.05 -
60
Chromium
(Cr)
8.0
< 2
150
Cobalt
(Co)
6.2
< 1
10,000
Copper
(Cu)
128
<10
3,000
Lead
(Pb)
135
<10
3,000
Merc ury
(Hg)
25
<25
50
Nickel
(Ni)
37
< 2
1,300
Thallium
(Tl)
4
2
100
Vanadium
(V)
7.7
< 5
70
Zinc
(Zn)
740
100
7,400
a Adapted from Smith (19B1); concentrations on ash weight basis.
b These ten metals are believed to have high potential to injure trees
because of widespread distribution or intensive local release from anthro-
pogenic activities.
40
-------
generally not known, although a few cases of poisoning and
mortality of domestic and wild animals in the vicinity of
point emission sources have been noted (National Research
Council 1972; Newman 1980).
b. Ecosystem Effects. Numerous field investigations in forest
ecosystems near industrial sources, such as power plants or
smelters, have provided evidence of trace metal accumulations
in soils and vegetation, with metal concentrations generally
sharply declining with distance from the source. The quantity
of the emissions as well as the prevailing wind conditions are
also important factors affecting accumulation (Little and
Martin 1972; Buchauer 1973; Hutchinson and Whitby 1974; Jack-
son and Watson 1977; VanHook et al. 1977; Strojan 1978a;
Coughtrey et al 1979; Freedman an? Hutchinson 1980a; Palmer
and Kucera~T9W).
The significance of these elevated concentrations in plant
tissues in relation to toxicity is unclear. Some investi-
gators have reported finding no accompanying signs of foliar
toxicity (Little and Martin 1972), while others have reported
poor growth and vigor (Buchauer 1973) [which may have at least
been partially due to exposure to another pollutant (SO2)]
and reduced litter input near the smelter (which can be an
indication of reduced productivity) (Freedman and Hutchinson
1980b). Surface deposits comprise a large percentage of
these elevated plant tissue levels (Buchauer 1973; Palmer
and Kucera 1980). Limited laboratory (Smith 1981) as well as
field (Gingell et_ al. 1976) investigation results suggest
that foliar microflora are affected by these surface metal
deposits; however, these interactions may be of significance
in terms of fungal phytopathology only in areas of high metal
i nput.
Trace metals have also been found at elevated levels in forest
soils in areas far from industrial sources, evidence of the
significant aerial transport of at least some of these ele-
ments (Reiners et al_ 1975; Siccama and Smith 1978; Heinrichs
and Mayer 1980;Ticcama et jH. 1980). The levels found
normally do not approaclfThose detected in the vicinity of
smelters and are commonly not accompanied by elevated plant
tissue concentrations. The latter point is interesting
because it is the unique surface area and microclimatic
characteristics of forests (relative to other terrestrial
biomes such as grasslands) that have been suggested as causes
of this remote filtering action. These characteristics are
further accentuated in montane forests by topographic
influences (Reiners et aj_. 1975).
Forest soils, especially the organic forest floor, are sinks
of variable efficiency for Pb, Zn, Cd, Cu, Ni, Mn, Vn, Cr.
Concentrations are generally highest in these upper organic
41
-------
layers and decrease with depth in the soil profile (Reiners et
al. 1975; Heinrichs and Mayer 1980; Siccama et aK 1980).
This sink action is due to the relative dominance of adsorp-
tion (onto exchange sites) and precipitation {as insoluble
salts) reactions over those such as leaching, loss to the at-
mosphere, metabolism by soil organisms and absorption by plant
roots (Smith 1981). The effects of these elevated soil metal
concentrations on vegetation, soil biota and ecosystem func-
tions are varied.
Buchauer (1973) and Jordan (1975) attributed mortality of
transplanted oak seedlings and suspected inhibition of seed-
ling germination or growth to the high metal levels in forest
soils near a smelter in Palmerton, Pennsylvania. Buchauer
(1973) found that soil metal content was a more important
factor than that of leaf tissue in the death of the oak seed-
lings; a suspected differential metabolic activity between
soil and foliar metals in the plant led the author to caution
against the sole use of tissue concentration information in
toxicity assessments. The continued inability of forests at
Sudbury, Ontario, to regenerate following reduction in
ambient SO? concentrations is believed to be the result of
residual pnytotoxic concentrations of trace metals in the
soils (Hutchinson 1981).
Tyler (1972) predicted that accumulation of trace metals in
soils would prove to be toxic to microorganisms. Concurrent
reductions in the rates of organic matter decomposition and
nutrient cycling were also forseen, leading ultimately to de-
creased productivity. These predictions have been borne out
in the results of some field and laboratory investigations
with trace metals, where decreases in soil biota biomass and
diversity, soil enzyme activity [reviewed by Smith (1981)],
decomposition of organic matter, soil concentrations of ex-
changeable macronutrients and increases in forest floor
litter layers have been found (Ruhling and Tyler 1973; Jordan
and Lechevalier 1975; Tyler 1975; Ebregt and Boldewijn 1977;
Jackson and Watson 1977; Inman and Parker 1978; Strojan
1978a,b; Freedman and Hutchinson 1980b).
The overall significance of these findings for temperate for-
est ecosystems has been questioned, however, by several other
investigators. Siccama et aj_. (1980) reinvestigated the
forest floor characteristics of eastern white pine stands in
central Massachusetts after 16 years. They found increases
in both forest floor organic matter and trace metal levels
over this period, but were careful not to attribute the
former to reduced decomposition resulting from the latter.
Coughtrey et ah (1979) reported a buildup of litter in the
vicinity oT~a smelter in Avonmouth, England, but disagreed
with Tyler's (1972) and Strojan's (1978a) conclusions
regarding the long term significance of this phenomenon for
42
-------
forest productivity. They cited the development of tolerance
to elevated metal levels by soil biota as a potential long
term mechanism capable of countering the trend toward de-
creased productivity. Smith (1981) also cited evidence of
microbial adaptability to high soil levels of trace metals
and stated that reduced decomposition of forest litter and
mineralization of macronutrients have been found only in
forests in excessively contaminated areas, such as near
industrial emission sources, roadways or urban areas.
Despite the tendency of trace metal pollutants to accumulate
in wildlife tissue via food chain intake, the limited data
available suggest that no such concentration occurs in insect
food chains, even in areas subject to high metal loading
(e.g., along roadways) (Smith 1981).
2.3 EFFECTS OF FLUORIDES
Fluorides (F) are gaseous and particulate pollutants that have
caused the most notable injury to U.S. forest ecosystems in the Pacific
Northwest. Such injury has occurred in the vicinity of point emission
sources such as aluminum and phosphorous production plants (USDA 1973;
Miller and McBride 1975). Gaseous fluorides (e.g., HF, SiF4, CF4)
are generally more phytotoxic than particulate forms (e.g., NaF,
AIF3). The toxicities of the latter are related to their water
solubility (USDA 1973; Treshow and Pack 1970). Like some of the trace
metals, a characteristic of this class of pollutants is their relative
immobility and hence tendency to accumulate in the tissues of exposed
organisms. Tissue analysis for F content is therefore a widely used and
heavily relied upon diagnostic tool in the study of these pollutants.
2.3.1 Acute and Chronic Injury
a> PI ants. Fluorides enter plants primarily through the leaf
stomata (Treshow and Pack 1970) or cuticle (Smith 1981); how-
ever, twigs of deciduous species have been found to accumulate F
in winter presumably as a result of F uptake through lenticels
(Keller 1978a). Once inside the leaf, F is translocated to the
leaf margins, where because of its general immobility, it accu-
mulates over time, ultimately causing necrosis (Treshow and Pack
1970; Carlson and Dewey 1971). Foliar F can be lost by leaching
and translocation to other plant parts (Treshow and Pack 1970;
Amundson and Weinstein 1980). The altered biochemical responses
at the cellular level caused by F uptake and accumulation have
been reviewed by Chang (1975), Weinstein (1977) and Amundson and
Weinstein (1980).
Acute and chronic laboratory exposures of coniferous and decid-
uous tree species to gaseous and particulate fluorides have
produced the following effects: (1) altered plant metabolism
(decreased photosynthetic and increased respiratory rates); (2)
43
-------
foliar necrosis and abscission; (3) decreased growth; and (4)
accumulation of F in surviving tissues (Adams et _al^. 1956; Davis
and Barnes 1973; McLaughlin and Barnes 1975; KeTler 1980a).
The relative injury susceptibility classifications developed by
Treshow and Pack (1970) and Weinstein (1977) are presented in
Tables 8 and 9. Treshow and Pack (1970) noted that injury to
the species in the sensitive group in Table 8 has often been
observed at foliar F levels of less than 50 ppm, whereas foliar
F levels in excess of several hundred ppm are generally required
for injury of species in the resistant group. The authors cau-
tioned that within any group, the degree of sensitivity would
depend largely on the following variables: F dose; time of year
of exposure; soil moisture regime; degree of temperature and
moisture stress before, during and after exposure; form of F
(gaseous or particulate); nutritional status of plant; age of
tissues; general plant vigor; and genetic sensitivity. The
importance of these site-specific factors in determining plant
response in the field was shown in a comparison by Amundson and
Weinstein (1980) of the results of field studies with various
coniferous species. The comparison indicated that the amount of
F accumulation and threshold for injury within a given genus or
species was different in different forest ecosystems.
Weinstein (1977) also provided tissue concentration threshold
data corresponding to the susceptibility breakdown in Table 9:
sensitive - typically less than 100 ppm; intermediate or
tolerant"- in excess of 200 ppm, often without development of
visible symptoms. He noted that the most tolerant species gener-
ally accumulate the most F; selected woody species accumulate
greater than 4000 ppm F without visible injury. USDA (1973)
stated that pines are generally particularly sensitive to F
injury while most hardwoods are at least intermediate in
susceptibility.
b. Animals. The acute and chronic effects of fluoride pollutants on
animals are well documented. Most of this information concerns
responses of domestic animals in the vicinity of point emission
sources (National Research Council 1974). Animal exposure is
primarily via ingestion of contaminated vegetation. The skeletal
system is commonly the sink for ingested fluoride. Acute effects
of fluoride poisoning (fluorosis) include gastroenteritis, chron-
ic convulsions and pulmonary congestion, whereas dental lesions,
tendon mineralization, anemia, periosteal hyperostosis and abnor-
mal tooth wear result from chronic exposure. Dental disfigure-
ment and other skeletal system changes are indicators of chronic
fluoride poisoning (Newman 1975).
In terms of forest wildlife, high fluoride concentrations have
been found mainly in deer near industrial emission sources (re-
viewed by Newman 1980). The symptoms of fluoride poisoning in
these animals are similar to those found in domestic species
44
-------
Table 8. Relative susceptibility of selected
forest species to injury from fluoride exposure.3
Sensitive13 Intermediate Resistant0
Arborvitae
(Thuja sp.)
Green ash
(Fraxinus pennsyl-
vanica var. lanceolata)
Quaking aspen
(Populus tremuloides)
European mountan ash
(Sorbus aucuparia)
Cutleaf birch
(Betula pendula
var. gracilis)
American elm
(Ulmus americana)
Boxelder
(Acer negundo)
Douglas-fir
(Pseudotsuga
menziesi i)
Western larch
(Lari x occidental is)
Eastern white pine
(Pinus strobus)
Lodgepole pine
(Pinus contorta)
Scotch pine
(Pinus sylvestris)
Ponderosa pine
(Pinus ponderosa)
Blue spruce
(Picea pungens)
Choke cherry
(Prunus virginiana)
European linden
(Tilia cordata)
Si 1ver maple
(Acer saccharinum)
Red mulberry
(Morus rubra)
Rhododendron
(Rhododendron sp.)
Serviceberry
(Amelanchier alnifolia)
White spruce
(Picea glauca)^
Juniper
(Juniperus sp.)e
American linden
(Tilia americana)
PIanetree
(Platanus sp.)
Willow
(Salix spp.)
Smooth sumac
(Rhus glabra)
Black walnut
(Juqlans nigra)
aAdapted from Treshow and Pack (1970); see caution in text.
^Corresponding foliar threshold level of < 50 ppm F.
corresponding foliar threshhold level of several hundred or more ppm F.
dyoung needles.
eMost species.
^Several species.
45
-------
Table 9. Relative susceptibility of selected
woody plants to acute damage by fluoride.3
Sensitive13
Intermediate
Tolerant
Boxelder
Green ash
Alder
Douglas-fir
Black spruce
Black birch
Western larch
Trembling aspen
White birch
Eastern white pine
Engelmann spruce
Cutleaf birch
Loblolly pine
Choke cherry
American elm
Lodgepole pine
White spruce
Black locust
Ponderosa pine
American linden
Honey locust
Scotch pine
Littleleaf linden
Oak spp.
Norway maple
London plane
Red maple
Balsam poplar
Silver maple
Carolina poplar
Sugar maple
Sweetgum
European mountain ash
Sycamore
Mulberry
Tulip tree
Rhododendron
Wi1 low spp.
Serviceberry
Arborvitae
Smooth sumac
Eastern red cedar
Staghorn sumac
Western red cedar
Black walnut
Cypress
Balsamf ir
Juniper sp.
Grand fir
Gingko
Western white pine
Jack pine
Austrian pine
Blue spruce
aAdapted from Weinstein (1977).
^Corresponding tissue concentration threshold values: Sensitive -
<100 ppm F; Intermediate and Tolerant - > 200 ppm F.
46
-------
(Newman 1975). Dental abnormalities, found in conjunction with
these elevated tissue concentrations in deer, are believed to
lead to disease and nutritional problems and ultimately to high
population mortality rates during times of stress (Newman 1980).
2.3.2 Ecosystem Effects
Field studies in Idaho, Montana, Washington and Kitimat, B.C., (Cana-
da) have shown a wide variety of plant responses to F pollution ranging
from accumulation accompanied by no visible injury to chlorosis, reduc-
tions in growth and mortality. The affected coniferous forests, consist-
ing of ponderosa pine, lodgepole pine, Douglas-fir, western white pine
(Pinus monticola), western hemlock (Tsuga heterophyl1 a), western red cedar
(Thuja "pTicata) and subalpine fir (Abies lasiqcarpa)7"were located near
aluminum and phosphorous production plantTI Measured F tissue concentra-
tions varied with the site and distance from the emission source (Lynch
1951; Shaw et jal_. 1951; Adams et a]_. 1952; Treshow et al. 1967; Carlson
and Dewey T971; Bunce 1978; CarTson 1978; Carlson et aTT 1979). The
changes in species composition resulting from differencial species sensi-
tivity to F injury also cause modifications in stand structure. For ex-
ample, Gilbert (1975) found changes in forest structure resulting from F
injury that corresponded to Woodwell's predictions of strata sensitivity
to acute pollution stress (see subsection 2.4.1b).
Lichens are components of forest ecosystems that are severely in-
jured by F pollution. For a more complete discussion of the effects on
lichen populations the reader is referred to reviews by Gilbert (1973)
and LeBlanc and Rao (1975).
Studies at Columbia Falls, Montana, have provided evidence that an
association exists between F contaminated vegetation and both food chain
accumulation of F and predisposition of producers to insect attack.
Carlson and Dewey (1971) reported insect tissue F concentrations of over
50 ppm for cambium feeders and predatory species and up to approximately
400 ppm for pollinators. Dewey (1973) examined a variety of insects
within 1 km of the Columbia Falls aluminum plant and found the following
body burdens (relative to control levels of 3.5-16.5 ppm): 8.5-52.5 ppm
F for cambium feeders; 6.1-170 ppm for predators; 21.3-255 ppm for foliar
feeders; and 58-585 ppm for pollinators. These results led the authors
to conclude that the following phenomena were occurring in the exposed
stands: (1) possible F contamination of vascular as well as foliar
tissue (re: cambium feeders); (2) food chain accumulation of F (re: pre-
dators); (3) insect ingestion of surface particulate F as well as that
contained in leaf tissue (re: foliar feeders); and (4) potential altera-
tion in vegetation reproduction-species composition (re: pollinators).
However, Amundson and Weinstein (1980) stated that the relationship
between F tissue concentrations in vegetation and insects is quite vari-
able and not well understood; they also questioned the role of foliar
particulate F in elevated insect tissue levels.
Carlson and Dewey (1971) also observed an increase in pine needle
scale (Phenacaspis pinifoliae) corresponding to foliar F levels in lodge-
pole pine, and Carlson et al. (1974) reported a relationship between
47
-------
needle miner (Zellaria haimbachi and Ocnerostyma strobivorum) injury and
foliar F concentration which they interpreted as evidence of a predisposi-
tion of host lodgepole pine to insect damage by F accumulation. This in-
terpretation has been disputed by Amundson and Weinstein (1980) who called
the evidence for a cause-and-effect relationship unconvincing and cited
the need for more research in this area.
The fates of leached foliar F and of soil F deposited directly from
the atmosphere have not been extensively studied but they are expected to
depend to a great extent upon site-specific soil characteristics
(Amundson and Weinstein 1980). Soluble F in soil solution can be readily
taken up by many plant species but most soil F exists in an insoluble
form. Forest species, with the possible exceptions of hickories (Carya
spp.) and flowering dogwood (Cornus florida), can therefore be expected
to take up relatively little soil F (Treshow and Pack 1970; McClenahen
1976). McClenahen (1976) found that the distribution of total F in soils
surrounding an alumina smelter followed prevailing wind patterns, with
distribution and concentrations in soil profiles varying according to the
extent of F deposition. Thompson et_ aK (1979) found a correlation
between plant response and the F concentrations of needles and soil humus
around a phosphorus plant in Long Harbour, Canada. Foliar F was found to
be positively correlated with the water-soluble F of soil humus. Both
varied inversely with distance from the plant in the direction of the
prevailing winds.
2.4 EFFECTS OF ACIDIFYING POLLUTANTS
The pollutants discussed in this section, sulfur dioxide (SO2) and
acid deposition, produce the greatest range of effects of any air pol-
lutants on forest ecosystems. Sulfur dioxide is an acutely toxic primary
pollutant. It is of importance on a local scale and has in the past pro-
duced a wide range of responses in impacted forests, including complete
destruction of stands surrounding point emission sources. Acid depo-
sition, on the other hand, is a secondary pollutant, of importance on a
regional scale. The effects of concern produced by this pollutant are
generally much more subtle and chronic in nature, indeed, much disagree-
ment currently exists as to their long term significance for forest
productivity. Since a very large and growing body of literature exists
on both pollutants, the following discussions are fairly general in
nature; references providing more detailed information are identified in
appropriate subsections.
2.4.1 Sulfur Dioxide
Sulfur dioxide (SO2) is a gaseous pollutant that has produced
notable injury in forest ecosystems in the United States and Canada in
the vicinity of point emission sources such as smelters, refineries,
power plants and pulp mills. Oil shale development in the western United
States is expected to be an important new source of this pollutant
(Soholt and Wiedenbaum 1981). A distinguishing characteristic of SO2
48
-------
pollution is the zoned pattern of response that it commonly produces
around point sources. A detailed review of some of the major incidents
of forest injury by SO2 can be found in Miller and McBride (1975).
a. Acute and Chronic Injury - PI ants. Sulfur dioxide is
readily taken up througn leaf stomata in dry conditions and
is absorbed in large amounts to wet external tree surfaces
{Garland and Branson 1977). Inside the leaf, SO? is dis-
solved and oxidized to sulfurous (H2SO3) and sulfuric
(H2SO4) acids. These acids, as well as the sulfite
(SO3) and sulfate (SO4) ions alter cellular biochemistry
(e.g., disruptions in amino acid metabolism and chloroplast
function) causing the injuries noted at the organismal
level; Mudd (1975b) reviewed the physiological effects of
SO2 exposure. However, because sulfur is also an impor-
tant plant macronutrient, exposure to low doses (e.g., <
ppm for 4-6 hours) of SO? has produced beneficial effecTs
such as stimulation of photosynthesis in laboratory studies
(Roberts et aK 1971; Knabe 1976; National Research Council
1978). Laboratory exposure of hardwood seedlings and sap-
lings, and conifer seedlings and grafts, to larger doses has
produced the following acute and chronic effects: (1)
altered stomatal function and corresponding changes in
transpiration; (2) foliar chlorosis, necrosis, abscission
and altered nutrient content; (3) reduced photosynthesis;
and (4) reduced leaf, stem and root growth (Roberts et al.
1971; Jensen and Kozlowski 1974; Knabe 1976; Keller T9T77
1978b, 1980b; Garsed et al. 1979, 1981; Carlson 1979;
Jensen and Dochinger 15737 Suwannapinunt and Kozlowski
1980). A relative susceptibility classification, as
compiled by Davis and Wilhour (1976), is presented in Table
10. No corresponding dose-threshold information was
provided by the authros. National Research Council (1978)
and Smith (1981) reviewed the very variable dose-response
data corresponding to the above-mentioned effects. Linzon
(1978) reported that, in general, acute injury thresholds
of 0.70 ppm SO2 for 1 hour or 0.18 ppm for 8 hour
exposures were representative for native vegetation, while
foliar symptoms in forests may occur with average SO?
concentrations over the entire growing season of 0.008-
0.017 ppm. National Research Council (1978) cautioned,
however, that the following operating variables exerted
important influences on these dose-response relationships:
(1) genetic factors; (2) plant developmental stage (e.g.,
deciduous trees most sensitive just after leaf expansion,
conifer needles most sensitive upon full shoot elongation);
(3) environmental factors, such as temperature, relative
humidity, light, and soil characteristics.
49
-------
Table 10. Relative susceptibility of selected
forest species to injury from SO2 exposure3.
Sensitive
Intermediate
Tolerant
Thinleaf alder
(Alnus tenuifolia)
Large-toothed aspen
(Populus grandidentata)
Trembling aspen
(Populus tremuloides)
Green ash
(Fraxinus pennsylvanica)
European birch
(Betula pendula)
Gray birch
(Betula populifoli a)
Western paper birch
(Betula papyrifera
commutata)
White birch
(Betula papyrifera)
Yellow birch
(Betula alleghanensis)
Lowbush blueberry
(Vaccinium angustifolium)
Bitter cherry
(Prunus emarginata)
Beaked hazel
(Cory!us cornuta)
Western larch
(Larix occidentalis)
Rocky Mountain maple
(Acer glabrum)
Mountain alder
(Alnus tenuifolia)
Basswood
(Tilia americana)
Water birch
(Betula occidentalis)
Boxelder (Acer negundo)
Bitter cherry
(Prunus emarginata)
Chokecherry
(Prunus demissa)
Black cottonwood
(Populus trichocarpa)
Eastern cottonwood
(Populus deltoides)
Narrowleaf cottonwood
(Populus angustifolia)
Red osier dogwood
(Cornus stolonifera)
Douglas-fir
(Pseudotsuga menziesi i)
American elm
(Ulmus americana)
Balsam fir
(Abies balsamea)
Grand fir (Abies grandis)
Wild grape
(Vitis riparia)
Arborvitae
(Thuja occidentalis)
Western red cedar
(Thuja piicata)
Silver fir
(Abies amabili s)
White fir
(Abies concolor)
Common juniper
(Juniperus communes)
Rocky Mountain juniper
(Juniperus scopulorum)
Western juniper
(Juniperus occidental is)
Little leaf linden
(Tilia cordata)
Norway maple
(Acer platanoides)
Silver maple
(Acer saccharinum)
Sugar maple
(Acer saccharum)
Gambel oak
(Quercus gambeli i)
Pin oak
(Quercus palustris)
Northern red oak
(Quercus rubra)
50
-------
Table 10.
Continued.
Sensitive Intermediate Tolerant
Sitka mountain-ash
(Sorbus sitchensis)
Eastern white pine
(Pinus strobus)
Jack pine
(Pinus banksiana)
Low serviceberry
(Amelanchier spicata)
Saskatoon serviceberry
(Amelanchier alnifolia)
Staghorn sumac
(Rhus typhina)
Black willow
(Salix nigra)
Witch hazel
(Hamamelis virginiana)
Western hemlock
(Tsuga heterophylla)
Rocky Mountain maple
(Acer glabrum)
Red maple (Acer rubrum)
European mountain-ash
(Sorbus aucuparia)
Western mountain-ash
(Sorbus scopulina)
Mountan laurel
(Ceanothus sanguineus)
White oak (Quercus alba)
Austrian pine
(Pinus nigra)
Lodgepole pine
(Pinus contort a)
Ponderosa pine
(Pinus ponderosa)
Western white pine
(Pinus monticola)
Balsam poplar
(Populus balsamifera)
Engleman spruce
(Picea engelmanni)
Limber pine
(Pinus flexilis)
Pinyon pine
(Pinus edulis)
London plane
(Platanus acerifolia)
Western poison ivy
(Toxicodendron radicans
rydbergiT)
Carolina poplar
(Populus canadensis)
Blue spruce
(Picea pungens)
Smooth sumac
(Rhus glabra)
White spruce
(Picea glauca)
aAdapted from Davis and Wilhour (1976).
51
-------
Animals. Very little i reformat ion exists on the direct effects
of SO^ alone on wildlife. Injuries have been reported for
domestic animals and a few species of free living small mam-
mals. Inhalation of SO2 is the primary route of exposure.
The respiratory systems and eyes of exposed organisms are the
most common sites of injury, although Newman (1975) cited
changes in the blood physiology of wild rabbits following ex-
posure to the pollutant. Bronchial constriction, salivation,
pulmonary edema, emphysema, hemorrhages and changes in the
sizes of the gall bladder and heart of exposed organisms are
symptoms of acute SO2 intoxication. Indirect effects,
through changes in habitat and food supply, are probably of
equal or greater importance than these types of direct ef-
fects, considering the extent of habitat disturbances often
found near point emission sources, as described in the
following subsection.
b. Ecosystem Effects. The effects of point source SO? emis-
sions on forest ecosystems are well documented. Trie following
discussion will describe representative responses and high-
light some of the most notable cases of injury.
A wide variety of acute and chronic effects in the field have
been reported, with conifers generally exhibiting greater
sensitivity than deciduous species. These effects include
foliar chlorosis and premature abscission, reductions in pho-
tosynthesis and wood production, reduced reproductive effi-
ciency, necrosis of plant tissues, death of individual trees,
and complete stand mortality with subsequent breakdown of eco-
system structure and function (Scheffer and Hedgcock 1955;
Gorham and Gordon 1960; Gordon and Gorham 1963; Linzon 1971;
USDA 1973; Houston and Dochinger 1977; Rosenberg et aj_. 1979;
Freedman and Hutchinson 1980c; Legge 1980; Hutchinson 1981).
Aside from the inherent sensitivity of the ecosystem compo-
nents and the duration of the exposure, the severity of the
forest response is dependent upon a number of factors which
influence the relative strength of the pollutant. These in-
clude the distance of the exposed site from the emission
source, the height of the emission source and the topographic
and meteorologic characteristics of the site (Knabe 1976).
For example, pollutant loading can be expected to be greatest
closest to the emission source and to decrease with distance
from the source. Stack height determines the extent to which
the pollutant is dispersed in and diluted by the surrounding
atmosphere, and hence the ambient SO2 concentration to which
the forest ecosystem is exposed. Implementation of pollution
control measures which contribute to a reduction in local
SO2 loading, such as increased stack height, has been fol-
lowed by regrowth of previously injured vegetation (Wood 1967;
Archibold 1978). Local topography is important because it
52
-------
predisposes certain sectors of the community to increased pol-
lutant exposure; upland forest stands and those on slopes fac-
ing the emission source are generally subject to greater expo-
sure than lowland stands or those on the leeward sides of
ridges. Prevailing wind conditions are an important influence
on the local pattern of disturbance; this factor accounts for
the well-known overall elliptical shape of impacted areas and
the fact that stands downwind of emission sources are subject
to greater pollutant loading than those upwind. The net
effect of these factors on forest exposure is normally a
zoned pattern of injury surrounding the emission source which
exhibits characteristics in close agreement with the general
ecosystem responses predicted by Woodwell (1970) following
acute pollution exposure, notably (1) reduced diversity
because of the elimination of sensitive species, and (2)
destruction of the forest overstory followed by survival of
resistant serai species. Although specific characteristics
of this type of response vary from site to site [e.g., Gordon
and Gorham (1963) described five zones of injury surrounding
the smelter at Wawa, Ontario, which emitted less SO2 than
the smelting complex at Sudbury, Ontario, where Linzon (1971)
reported three zones of injury], it generally consists of:
(1) a severely disturbed, often completely denuded, inner
zone followed by (2) one to several less impacted transition
zones radiating outward from the emission source made up of
tolerant species of herbs, shrubs and trees and differing
structurally by the conspicuous presence or absence of var-
ious strata (3) finally culminating in an outer zone where
chronic exposure produces marginal effects only in the most
sensitive species (Knabe 1976). The strata-by-strata
destruction of the forest ecosystem surrounding the Wawa,
Ontario, smelter described by Gordan and Gorham (1963) is an
extreme example of this gradient-of-injury type of response.
The resulting reductions in standing crop biomass and species
diversity in all strata produce an overall structural simpli-
fication of the forest ecosystem. Woodwell (1970) attributed
the differential susceptibility of trees versus shrubs versus
herbaceous species under such acute exposure conditions to
pollutant induced changes in the ratio of gross production to
respiration. For a given reduction in productivity, larger
plants are eliminated first because of their greater basal
respiratory load which, unlike productivity, is generally not
subject to alteration by pollution. However, in contrast to
this generalization, Rosenberg jst al. (1979) reported that
ground vegetation and understory sTFubs surrounding a coal
burning power plant in central Pennsylvania were more sensi-
tive to SO2 emissions than constituent overstory species.
Among other possible mechanisms, they postulated that such
a response was due to SO? altered surface soil character-
istics which differentially discriminated against the more
shallow-rooted species.
53
-------
This structural simplification of the forest ecosystem is ac-
companied by disruptions in the ecosystem functions of nutri-
ent cycling, soil stabilization and climatic and hydrologic
regulation. Reduced standing crop biomass alters water and
nutrient balances as less of these materials are cycled
through the vegetation. Any resulting losses of these mater-
ials from strongly disturbed systems produce subsequent
problems, such as severe soil erosion in areas completely
devoid of vegetative cover, especially those with steep or
unstable slopes (Gordon and Gorham 1963; Freedman and
Hutchinson 1980c), and changes in streamwater quality.
Destruction of the dominant vegetation drastically affects
the local microclimate. For example, Hursh (1948) found
three distinct microclimatic zones in the impacted area
surrounding the smelter at Copper Basin, Tennessee; Hepting
(1971) reported that the inner zone experienced greater
extremes in air and soil temperatures, increased wind
velocity and decreased rainfall relative to the surrounding
intact forest. Further evidence of altered microclimate
following stand destruction was found by Gordon and Gorham
(1963) in the increased albedo of the innermost zones
surrounding the Wawa, Ontario smelter. Nutrient cycling is
disrupted by transfer of nutrient stocks in standing crop
organic matter out of the system via losses due to leaching
and erosion and changes in soil chemistry. These soil
chemistry changes surrounding emission sources include in-
creased levels of soluble SO4 and decreased pH; these
effects generally diminish with distance from the emission
source and depth in the soil profile (Gorham and Gordon 1960;
Gordon and Gorham 1963; Legge 1980). A secondary effect
of SO? emissions on nutrient cycling is the increased avail-
ability of metal cations resulting from reduced soil pH.
It is important to note that it is often difficult to separate
the effects of SO2 pollution in the field from those of
accompanying emission pollutants, such as fly ash and heavy
metal particulates, or other anthropogenic disturbances. For
example, Freedman and Hutchinson (1980c) noted that the severe
destruction of the forest community at Sudbury was the result
not only of recent SO;? emissions but also of earlier ground
level emissions of this pollutant as well as heavy metal par-
ticulates from roast beds, of cordwood logging operations in
the area, and of the increased incidence of fire in the fumi-
gated and cut stands. However, the changes in tydrology,
nutrient cycling and microclimate noted greatly increase the
inhospitability of a site, making revegetation and return to
previous conditions extremely difficult, even given signifi-
cant reductions in SOg fumigation. For example, Hutchinson
(1981) attributed the continued inability of the forests at
Sudbury to regenerate to the toxicity of residual soil heavy
metals.
54
-------
Aside from these direct effects on forest ecosystem structure
arid function, SO2 appears to both predispose plants to dis-
ease and prevent their infection by pathogenic fungi. In gen-
eral, predisposition may involve reduced vigor of the host or
facilitated entry of the pathogen through the influence of
SO2 on stomatal function, while prevention normally involves
direct toxicity to the pathogen. Treshow (1975, 1980) more
fully reviewed the available information regarding these in-
teractions; Treshow (1980) stated that they may be becoming
less important as ground JeveJ concentrations of SO2 are re-
duced by modern technology or the use of tall stacks. In a
related type of study, Renwick and Potter (1981) found that
SO2 fumigation of five year old balsam fir trees resulted in
a significant release of volatile terpenes from the exposed
trees. They postulated that this type of response may be an
important mechanism by which predisposition to insect attack
occurs.
2.4.2 Acid Deposition
As used in this subsection, acid deposition includes dry deposition
of sulfate {SO4} aerosols as well as classical wet deposition events;
the former is chronic and cumulative in nature and only fairly recently
understood to be of importance, whereas the latter are episodic in na-
ture, less difficult to study, and hence, much better known. Since the
effects of acid deposition on forest ecosystems are subject to a great
deal of current and ongoing research effort, an extremely large and
rapidly growing body of information exists in this area. The reader
interested in becoming familiar with this literature is referred to sev-
eral excellent reviews in the conference, workshop and symposia proceed-
ings coordinated or edited by Dochinger and Seliga (1976), Howells (1979),
Hutchinson and Havas (1980), Drablos and To!Ian (1980), Overrein et aK
(1980), Shriner et aT. (1980), and Michigan State University (198TJ*. In
light of the generally subtle nature of the effects identified to date
and the ongoing research effort in this area, the reader should consider
the responses identified in the following discussion more tentative than
definitive at this time.
a. Acute and Chronic Injury - Plants. Laboratory, greenhouse and
field studies utilizing simulated "acid rain" solutions of pH
generally < 3 have produced the following acute and chronic
injuries in deciduous and coniferous seedlings and saplings:
(1) altered foliar growth and necrosis; (2) foliar cuticle
erosion; (3) leaching of foliar nutrients; (4) premature leaf
abscission; (5) decreased and increased growth (Abrahamsen and
Dollard 1979; Fowler et aK 1980; Overrein et al. 1980; Cowl-
ing 1981; Shriner 198TJ". Altered seed germTnaiTon following
application of simulated "rain" solutions has also been
reported (Lee and Weber 1979).
55
-------
The significance of these responses for forest stands under
natural conditions is unclear because the pH of the test solu-
tions employed is generally not representative of ambient con-
ditions and the simulated "rain" used differs from natural
precipitation in both chemical composition (total ion content)
and "pollution episode" characteristics (e.g., natural pre-
cipitation often consists of a flush of acidity early in the
event) (Abrahamsen and Dollard 1979; Wiklander 1979; Alexander
1980). In addition, other important factors, such as foliar
cuticle development of laboratory versus field specimens
(Shriner 1981), modification of the composition of incident
precipitation by interactions with other previously deposited
pollutants (e.g., dry deposition, trace metal particulates),
and contact with vegetative surfaces (i.e., throughfall and
stemflow versus incident precipitation - see subsection
2.4.2b), are quite different between these operating condi-
tions. Overall, no well documented cases of direct acute
injury in the field are known (Shriner 1981); such effects,
if operative at all under natural conditions, would be
expected to be found closer to urban areas or near point
emission sources (Abrahamsen and Dollard 1979; Overrein et
al_. 1980). ~~
Animals. No information was found in the available literature
regarding the direct acute or chronic injury of forest wild-
life by acid deposition. Indirect effects on wildlife through
habitat modification are probably of greater importance, al-
though even these effects may be of little short-term signif-
icance, given the generally subtle nature of known habitat
responses, as identified in the following subsection. How-
ever, forest streams and lakes may be more severly impacted
by acid deposition (see the Rivers and Streams and Lakes
documents in this series), therefore, forest wildlife
depending in whole or in part upon these aquatic systems may
be more strongly disrupted.
b. Ecosystem Effects. The direct effects of acid deposition on
forest vegetation in the field are generally unknown at the
present time. In addition to the lack of evidence in support
of direct acute injury, studies in North America and Norway
utilizing tree ring analysis methodology were unable to detect
reductions in growth attributable to acid deposition (Cog-
bill 1977; Abrahamsen et jH. 1977; Strand 1980). The most
direct effect on vegetation appears to be increased leaching
of foliar cations in throughfall, and in turn, accelerated
rates of nutrient cycling. Although well documented, the
significance of these effects in the long term for forest
productivity is unclear (Abrahamsen and Dollard 1979; Cronan
et al. 1980; Mayer and 111 rich 1980; Jacobson 1980; Lindberg
JT aT. 1981). However, acid deposition is believed to be
capable of indirectly affecting forest productivity as a
result of its direct effects on soil chemistry and biology,
and hence, fertility (Tamm and Cowling 1976). For example,
56
-------
Jonsson (1977) concluded that acid deposition may have been
an indirect cause of reduced growth in Swedish forests be-
cause of soil nutrient impoverishment as a consequence of
soil acidification. Similarly, Ulrich et £]_. (1980) con-
cluded that productivity in large areas of forest land in
central Europe is seriously endangered by aluminum (Al)
toxicity as a result of soil acidification from acid
deposition.
Therefore, unlike the other air pollutants discussed in this
document, acid deposition appears to exert its primary in-
fluence on the soil component of forest ecosystems. Field and
lysimeter studies have shown the following soil properties and
processes to be affected: (1) soil acidity (base saturation);
(2) leaching of nutrient cations, Al and heavy metals (also
altered P availability); (3) microbial population dynamics
and subsequently; (4) biologically mediated processes, such
as organic matter decomposition, nutrient mineralization,
nitrification and nitrogen-fixation (Abrahamsen and
Dollard 1979; Abrahamsen et al_. 1980; Alexander 1980;
Baath et_ a]_. 1980; Francis ert al_. 1980; Norton et al.
1980; Overrein et al,. 1980; Schnitzer 1980; Aber et_
al. 1981). Reports concerning the magnitude as well
as the direction (increase or decrease) of these effects
vary greatly; a compilation of some of these mixed
results can be found in McFee and Cronan (1981). These
discrepancies are understandable given the complexity
and variability of soil ecosystems, the general lack
of baseline data for these systems, and the fairly
subtle nature of the responses (Voigt 1980).
As for the acute and chronic injury results presented in sub-
section 2.4.2a, the significance of these effects on soil
properties and processes in relation to soil fertility over
the long term is presently unclear because of similar problems
regarding the representativeness of the simulated "rain" solu-
tions used (Wiklander 1979; Overrein et_ al_. 1980; McFee and
Cronan 1981) and the very large influence of site specific
soil characteristics (such as soil mineralogy, texture, struc-
ture, permeability, pH, base saturation and organic matter,
salt and sesquioxide contents) on the responses (Wiklander
1979; Bache 1980; Johnson 1980; Peterson 1980; Voigt 1980;
Shriner 1981). In addition, counterbalancing processes (some
of which are themselves initiated by acid deposition), such
as increased weathering of primary minerals, deposition of
nutrients (especially N and S) in incident precipitation,
short term buffering by internal cycling of nutrients, and
shifts in microbial community composition, may offset some of
these responses (Abrahamsen and Dollard 1979; Aber et al.
1981; McFee and Cronan 1981). Finally, several researchers
have noted the long term nature of a number of these antici-
pated responses, such as soil acidification, and have ques-
tioned the correctness of conclusions based on the one to two
57
-------
decades of observation available (Last et ^1_. 1980; Linzon
and Temple 1980; Troedsson 1980; Voigt 1380; McFee and Cronan
1981). Current opinions of the future significance of these
effects, based on present levels of acid deposition load-
ing, are varied. They range from potential enforcement of
latent nutrient deficiencies (other than nitrogen) induced by
the fertilizing action of N added to the system in incident
precipitation (Abrahamsen 1980) to possible future reductions
in forest productivity as a result of leaching losses of
nutrient cations and mobilization of toxic concentrations of
heavy metals (Abrahamsen and Dollard 1979; Overrein et al.
1980; Voigt 1980).
58
-------
3.0 TOPICS FOR FURTHER RESEARCH
Several researchers are in agreement regarding the important
research topics in this problem area (National Research Council 1977a,
1981; Guderian and Kueppers 1980; Kozlowski 1980; Shugart et al. 1980;
Westman 1980; Interagency Task Force on Acid Precipitation-TWT; Smith
1981). Perhaps the most exhaustive analysis of research needs was pro-
vided by Smith (1981). He cited the timely establishment of compre-
hensive, extended-term field investigations, for clarification of Class I
and II interactions (Table 3), as having the highest research priority.
These investigations would be similar to the San Bernardino National
Forest (see subsection 2.1.2) and the Polish Niepolomice Forest (see
Grodzinski and Wiener 1981 for summary information) research programs.
Forest ecosystems in the United States believed to be at particular risk
to chronic air pollution stress, and hence in need of this type of study,
are (1) the Northern Hardwood forest (approximate representative map
code, Figure 1, 2113), (2) the Central Hardwood forest (2211-2215), and
(3) the Western Montane forest (M2414, M2610). Research facilities are
already in existence at the following locations for the performance of
these studies: (1) the Hubbard Brook Experimental Forest, New Hampshire,
Isle Royale National Park, Michigan, and Itasca Forest, Minnesota; (2)
the Camp Branch Forest watershed, east-central Tennessee and Coweeta
Hydrologic Laboratory, western North Carolina; (3) the San Bernardino
National Forest, California (in progress), Andrew Experimental Forest,
Oregon, and Bitterroot National Forest, Idaho.
The investigations should include examinations of the influence of air
pollution on soil metabolism and structure, nutrient cycling, tree
reproduction, photosynthesis, respiration and transpiration, important
arthropod species (e.g., eastern spruce budworm and gypsy moth in eastern
forests) and microbial pathogens, and mycorrhizal fungi and nitrogen-
fixinq organisms. In addition, foliar symptoms of important vegetation
in all forest strata should be defined, and alterations in forest pro-
ductivity, successional trends, and species dominance examined. Con-
tinuous meteorological and air quality monitoring should be performed
concurrently to provide a better understanding of pollutant stress in the
field. The NADP (National Atmospheric Deposition Program) and similar
monitoring networks may provide some of this information (Interagency
Task Force on Acid Precipitation 1981).
The information provided by these studies will enable investigators
to make assessments of the ability of these ecosystems to resist (inertia)
and respond (resilience) to air pollution injury; information regarding
the latter attribute, system recovery, is sorely lacking (Westman 1980).
Smith (1981) also noted that such field investigations must continue
to be supported by controlled environment studies. He cited the following
research areas as being particularly important for both types of examina-
tions:
59
-------
1. Dose-response information on visible (symptomatic) responses
with experiments appropriately designed to accommodate and
consider the influence of genetic factors, environmental
factors, and interaction of air contaminants.
2. Development of accurate, relatively simple, and reproducible
methodologies to identify and inventory visible (symptomatic)
injury in the field.
3. Analysis of the ability of air pollution stress to predispose,
aggravate, or reduce stresses caused by insect, microbial,
edaphic, and climatic agents or human management strategies.
4. Dose-response information on invisible (asymptomatic) responses
including an evaluation of the ability of air pollution exposure
to influence tree metabolism, reproduction, competition, and
growth along with the associated ecosystem parameters of pro-
ductivity, succession, and species composition.
5. Determination of the physiological and biochemical bases of air
pollution stress on forest vegetation.
6. Determination of the ability of forest vegetation and forest
soils to act as sinks and sources for atmospheric contaminants.
7. Development of suitable models of air pollution interactions so
that future trends may be predicted and projected and informa-
tion extrapolated from one ecosystem to another.
8. Development of reliable and economically sound cultural pro-
cedures for protecting valuable trees and determination of the
utility of the use of resistant varieties to reduce air pollu-
tion significance.
The importance of model development in the combination of auteco-
logical and synecological information was also stressed by Shugart et al
(1980), and Westman (1980). These investigators further highlighted the
potential of dendrochronology as a powerful tool in the development and
extended application (e.g., analysis of rate of change at constant and
varying stress levels) of such simulation models.
In addition, the experimental designs of any comprehensive field
investigation should include provisions for (1) analysis of the direct
and indirect effects of air pollution stress on the wildlife constituents
of the ecosystem, and the subsequent impacts of such effects on ecosystem
structure and functions, as well as (2) definition of the major socio-
economic consequences of forest injury from air pollution, including the
"hidden" costs associated with disturbances in ecosystem functions
(Westman 1980).
Finally, on an individual pollutant basis, little is known about the
effects of the photochemical oxidants PAN and N0X on forest ecosystems.
60
-------
The overall significance of fluoride and trace metal accumulation in tis-
sues and soils, and the effects of acid deposition on foliar leaching and
soil chemistry in relation to forest productivity, remain unknown, and
should be addressed in long-term field investigations. The influences of
trace metal particulates and acid deposition on soil biota and the proc-
esses mediated by them (organic matter decomposition, nutrient minerali-
zation, nitrification, nitrogen fixation) are ambiguous and in need of
further study.
61
-------
REFERENCES
Aber, J.D.; Hendrey, G.R.; Botkin, O.8.; Francis, A.J.; Mellillo, J.M.
Potential effects of acid precipitation on soil nitrogen and productivity
of forest ecosystems. Michigan State University. Institute of Water
Research. Initial draft of the proceedings for the effects of acid
precipitation on ecological systems: Great Lakes region; 1981 April 1-3;
Michigan State University, East Lansing, MI; 1981. To be published by
Ann Arbor Science Publishers, Inc., Ann Arbor, MI.
Abrahamsen, G. Acid precipitation, plant nutrients and forest growth.
Drablos, D.; Tollan, A., eds. Ecological impact of acid precipitation:
Proceedings of an international conference; 1980 March 11-14; Sandefjord,
Norway. Oslo-As, Norway: SNSF Project; 1980:58-63.
Abrahamsen, G.; Dollard, G.J.; Effects of acid precipitation on forest
vegetation and soil. Howells, G., coordinator. Ecological effects of
acid precipitation - workshop proceedings; 1978 September 4-7; Galloway,
U.K. Palo Alto, CA: Electric Power Research Institute, Energy Analysis
and Environment Division; EPRI EA-79-6-LD; 7979.
Abrahamsen, G.; Horntvedt, R.; Tveite, B. Impacts of acid precipitation
on coniferous forest ecosystems. Water Air Soil Pollut. 8:57-73; 1977.
Abrahamsen, G.; Hovland, J.; Hagvar, S. Effects of artificial acid rain
and liming on soil organisms and the decomposition of organic matter.
Hutchinson, T.C.; Havas, M.; eds. Effects of acid precipitation on
terrestrial ecosystems. New York: Plenum Press; 1980:341-362.
Adams, D.F.; Mayhew, D.J.; Gnagy, R.M.; Richey, E.P.; Koppe, R.K.; Allan,
I.W. Atmospheric pollution in the ponderosa pine blight area, Spokane
County, Washington. Ind. Eng. Chem. 44:1356-1365; 1952.
Adams, D.F.; Shaw, C.G.; Yerkes, W.D. Or., Relationship of injury
indexes and fumigation fluoride levels. Phytopathology 46:587-591; 1956.
Alexander, M. Effects of acid precipitation on biochemical activities in
soil. Drablos, D.; Tollan, A., eds. Ecological impact of acid precipi-
tation: Proceedings of an international conference; 1980 March 11-14;
Sandefjord, Norway. Oslo-As, Norway: SNSF Project; 1980:47-52.
Amundson, R.G.; Weinstein, L.H. Effects of airborne F on forest eco-
systems. Miller, P.R., ed. Proceedings of a symposium on effects of air
pollutants on mediterranean and temperate forest ecosystems; 1980 June
22-27; Riverside, CA. Berkeley, CA: U.S. Department of Agriculture,
Forest Service, Pacific Southwest Forest and Range Experiment Station;
General Technical Report PSW-43; 1980:63-78.
Archibold, O.W. Vegetation recovery following pollution control at
Trail, B.C. Can. J. Bot. 56: 1625-1637; 1978.
62
-------
Baath, E.; Bjorn, B.; Lohm, U.; Lundgren, B.; Lundkvist, H.; Rosswall, T.;
Soderstrom, B.; Wiren, A. Soil organisms and litter decomposition in a Scots
pine forest - effects of experimental acidification. Hutchinson, T.C.; Havas,
M., eds. Effects of acid precipitation on terrestrial ecosystems. New York:
Plenum Press; 1980:375-380.
Bache, B.W. The acidification of soils. Hutchinson, T.C.; Havas, M.;
eds. Effects of acid precipitation on terrestrial ecosystems. New
York: Plenum Press; 1980:183-202.
Bailey, R.G. Description of the ecoregions of the United States.
Washington, DC: U.S. Department of Agriculture, Forest Service;
Miscellaneous Publication No. 1391; 1980. 77 p.
Barnes, R.L.; Berry, C.R. Seasonal changes in carbohydrates and
ascorbic acid of white pine and possible relation to tipburn
sensitivity. Asheville, NC: U.S. Department of Agriculture, Forest
Service, Southeastern Forest Experiment Station; Research Note SE-124;
1969. 4 p.
Berry, C.R. White pine emergence tipburn, a physiogenic disturbance.
Asheville, NC: U.S. Department of Agriculture, Forest Service, South-
eastern Forest Experiment Station; Paper 130; 1961. 8 p.
Berry, C.R. Relative sensitivity of red, jack, and white pine seedlings
to ozone and sulfur dioxide. Phytopathology 61:231-232; 1971.
Berry, C.R.; Ripperton, L.A. Ozone, a possible cause of white pine
emergence tipburn. Phytopathology 53:552-557; 1963.
Bowen, H.J.M. Trace elements in biochemistry. New York: Academic
Press; 1966. 241 p.
Brandt, C.J.; Rhoades, R.W. Effects of limestone dust accumulation on
composition of a forest community. Environ. Pollut. 3:217-225; 1972.
Brandt, C.J.; Rhoades, R.W. Effects of limestone dust accumulation on
lateral growth of forest trees. Environ. Pollut. 4:207-213; 1973.
Buchauer, M.J. Contamination of soil and vegetation near a zinc smelter
by zinc, cadmium, copper, and lead. Environ. Sci. Technol. 7(2):
131-135; 1973.
Bunce, H.W.F. Fluoride emissions and forest growth near Kitimat, B.C.,
Canada. Houston, TX: Air Pollution Control Association; 71st Annual
Meeting Paper 78-24.3; 1978. 14 p.
Carlson, C.E. Fluoride induced impact in a coniferous forest near the
Anaconda Aluminum Plant in northwestern Montana. Fluoride 11:211; 1978.
63
-------
Carlson, C.E.; Bousfield, W.E.; McGregor, M.D. The relationship of an
insect infestation on lodgepole pine to fluorides emitted from a nearby
aluminum plant in Montana. Missoula, MT: U.S. Department of Agri-
culture, Forest Service, Division of State Private Forestry; Report No.
7-14; 1974. 21 p.
Carlson, C.E.; Dewey, J.E. Environmental pollution by fluorides in
Flathead National Forest and Glacier National Park. Missoula, MT: U.S.
Department of Agriculture, Forest Service, Forest Insect and Disease
Branch; 1971. 57 p. Available from: Supt. Docs., GPO, Washington, DC;
796-468.
Carlson, C.E.; Gordon, C.C.; Gilligan, C.J. The relationship of fluoride
to visible growth/health characteristics of Pinus monticola, Pinus
contort a, and Pseudotsuga menziesii. Fluoride T2:9-17; 1979.
Carlson, R.W. Reduction in the photosynthetic rate of Acer, Quercus,
and Fraxinus species caused by sulfur dioxide and ozone. Environ.
Pollut: T8T159-170; 1979.
Carlson, R.W.; Bazzaz, F.A. Growth reduction in American sycamore
(Plantanus occidental is L.) caused by Pb-Cd interaction. Environ.
Pollut. T2:243-253; 1977.
Chang, C.W. Fluorides. Mudd, J.B.; Kozlowski; T.T., eds. Responses
of plants to air pollution. New York: Academic Press; 1975:57-95.
Cogbill, C.V. The effect of acid precipitation on tree growth in eastern
North America. Water Air Soil Pollut. 8:89-93; 1977.
Costonis, A.C.; Sinclair, W.A. Susceptibility of healthy and
ozone-injured needles of Pinus strobus to invasion by Lophodermium
pinastri and Aureobasidium puTlulans. Eur. J. For. Path. 2:65-73;
Coughtrey, P.J.; Jones, C.H.; Martin, M.H.; Shales, S.W. Litter accumu-
lation in woodlands contaminated by Pb, Zn, Cd and Cu. Oecologia 39:51-
60; 1979.
Cowling, E.B. An historical resume of progress in scientific and public
understandings of acid precipitation and its biological consequences.
Michigan State University. Institute of Water Research. Initial draft
of the proceedings for the effects of acid precipitation on ecological
systems: Great Lakes region; 1981 April 1-3; Michigan State University,
East Lansing, MI; 1981. To be published by Ann Arbor Science Publishers,
Inc., Ann Arbor, MI.
Cronan, C.S.; Reiners, W.A.; Reynolds, R.C., Jr. The impact of acid
precipitation on forest canopies and soils in the northeastern U.S.
Drablos, D.; Tollan, A., eds. Ecological impact of acid precipitation:
Proceedings of an international conference; 1980 March 11-14; Sandefjord,
Norway. Oslo-As, Norway: SNSF Project; 1980:158.
64
-------
Dahlsten, D.L.; Rowney, D.L. Influence of air pollution on population
dynamics of forest insects and on tree mortality. Miller, P.R., ed.
Proceedings of a symposium on effects of air pollutants on mediterranean
and temperate forest ecosystems; 1980 June 22-27; Riverside, CA.
Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific
Southwest Forest and Range Experiment Station; General Technical Report
PSW-43; 1980:125-130.
Darley, E.F. Symptomatology of particulate injury to vegetation.
Lacasse, N.L.; Moroz, W.J., eds. Handbook of effects assessment:
Vegetation damage. University Park, PA: Pennsylvania State
University, Center for Air Environment Studies; 1969:V1-V4.
Davis, D.D. Resistance of young ponderosa pine seedlings to acute doses
of PAN. Plant Dis. Reptr. 59:183-184; 1975.
Davis, D.D.; Wilhour, R.G. Susceptibility of woody plants to sulfur
dioxide and photochemical oxidants. A literature review. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental
Research Laboratory; EPA-600/3-76-102; 1976. 71 p. Available from:
NTIS, Springfield, VA; PB-260881.
Davis, D.D.; Wood, F.A. The relative susceptibility of eighteen
coniferous species to ozone. Phytopathology 62:14-19; 1972.
Davis, D.D.; Wood, F.A. The influence of environmental factors on the
sensitivity of Virginia pine to ozone. Phytopathology 63:371-376;
1973.
Davis, J.B.; Barnes, R.L. Effects of soil-applied fluoride and lead on
growth of loblolly pine and red maple. Environ. Pollut. 5:35-44; 1973.
Dewey, J.E. Accumulation of fluorides by insects near an emission source
in western Montana. Environ. Entomol. 2:179-182; 1973.
Dochinger, L.S.; Heck, W.W. An ozone-sulfur dioxide synergism produces
symptoms of chlorotic dwarf disease of eastern white pine.
Phytopathology 59:399; 1969.
Dochinger, L.S.; Seliga, T.A., eds. Proceedings of the first inter-
national symposium on acid precipitation and the forest ecosystem; 1975
May 12-15; Ohio State University, Columbus, OH. Upper Darby, PA: U.S.
Department of Agriculture, Forest Service; Northeastern Forest Experiment
Station; 1976. 1074 p. Available from: NTIS, Springfield, VA;
PB-258645.
Drablos, D.; Tollan, A., eds. Ecological impact of acid precipitation:
Proceedings of an international conference; 1980 March 11-14; Sandefjord,
Norway. Oslo-As, Norway: SNSF Project; 1980. 384 p.
65
-------
Drucker, H.; Wildung, R.E., chairmen. Biological implications of metals
in the environment: Proceedings of the fifteenth annual Hanford life
sciences symposium; 1975 September 29-0ctober 1; Battelle Pacific North-
west Laboratories, Richland, WA. Washington, DC: Energy Research and
Development Administration, Technical Information Center; ERDA Symposium
Series 42: 1977. 682 p. Avai1 able-from: NTIS, Springfield, VA:
C0NF-750929.
Drummond, D.B. Influence of high concentrations of peroxyacetylnitrate
on woody plants. Phytopathology 61:128; 1971.
Ebregt, A.; Boldewijn, J.M.A.M. Influence of heavy metals in spruce
forest soil on amylase activity, CO? evolution from starch and soil
respiration. Plant Soil 47:137-148; 1977.
Evans, L.S.; Miller, P.R. Ozone damage to ponderosa pine: A histo-
logical and histochemical appraisal. Am. J. Bot. 59:297-304; 1972.
Fowler, D.; Cape, J.N.; Nicholson, I.A.; Kinnaird, J.W.; Paterson, I.S.
The influence of a polluted atmosphere on cuticle degradation in Scots
pine (Pinus sylvestris). Drablos, D.; Tollan, A., eds. Ecological
impact of acid precipitation: Proceedings of an international con-
ference; 1980 March 11-14; Sandefjord, Norway. Oslo-As, Norway: SNSF
Project; 1980:146.
Francis, A.J.; Olson, D.; Bernatsky, R. Effect of acidity on microbial
processes in a forest soil. Drablos, D.; Tollan, A., eds. Ecological
impact of acid precipitation: Proceedings of an international confer-
ence; 1980 March 11-14; Sandefjord, Norway. Oslo-As, Norway: SNSF
Project; 1980:166-167.
Freedman, B.; Hutchinson, T.C. Pollutant inputs from the atmosphere
and accumulation in soils and vegetation near a nickel-copper smelter
at Sudbury, Ontario, Canada. Can. J. Bot. 58(1):108-132; 1980a.
Freedman, B.; Hutchinson, T.C. Effects of smelter pollutants on forest
leaf litter decomposition near a nickel-copper smelter at Sudbury,
Ontario. Can. J. Bot. 58(15):1722-1736; 1980b.
Freedman, B.; Hutchinson, T.C. Long-term effects of smelter pollution at
Sudbury, Ontario, on forest community composition. Can J. Bot. 58(19):
2123-2140; 1980c.
Garland, J.A.; Branson, J.R. The deposition of sulfur dioxide to pine
forest assessed by a radioactive tracer method. Tellus 29:445-454;
1977.
Garsed, S.G.; Farrar, J.F.; Rutter, A.J. The effects of low concentra-
tions of sulfur dioxide on the growth of four broadleaved tree species.
J. Appl. Ecol. 16:217-226; 1979.
66
-------
Garsed, S.6.; Rutter, A.J.; Retton, J. The effects of sulfur dioxide on
the growth of Pinus sylvestris in two soils. Environ. Pollut. 24:219-
232; 1981.
Gilbert, O.L. The effect of airborne fluorides. Ferry, B.W.; Baddeley,
M.S.; Hawksworth, O.L., eds, Air pollution and lichens. Toronto:
University of Toronto Press; 1973:176-191.
Gilbert, O.L. Effects of air pollution on landscape and land use around
Norwegian aluminum smelters. Environ. Pollut. 8:113-121; 1975.
Gingell, S.M.; Campbell, R.; Martin, M.H. The effect of zinc, lead and
cadmium pollution on the leaf surface microflora. Environ. Pollut.
11:25-37; 1976.
Gordon, A.G.; Gorham, E. Ecological aspects of air pollution from an
iron sintering plant at Wawa, Ontario. Can. J. Bot. 41:1063-1078;
1963.
Gorham, E.; Gordon, A.G. Some effects of smelter pollution northeast
of Falconbridge, Ontario. Can. 0. Bot* 38:307-312; 1960.
Grodzinski, W.; Weiner, J., eds. Forest ecosystems in industrial regions
- Studies on energy, nutrients and pollutant cycling in Niepolomice
forest, southern Poland. New York: Springer-Verlag ; 1981. 355 p.
Grodzinski, W.; Ycrks, J.P. Species and ecosystem level bioindicators
of airborne pollution: An analysis of two major studies. Water Air Soil
Pollut. 16:33-53; 1981.
Guderian, R.; Kueppers, K. Response of plant communities to air pollu-
tion. Miller, P.R., ed. Proceedings of a symposium on effects of air
pollutants on mediterranean and temperate forest ecosystems; 1980 June
22-27; Riverside, CA. Berkeley, CA: U.S. Department of Agriculture,
Forest Service, Pacific Southwest Forest and Range Experiment Station;
General Technical Report PSW-43; 1980:187-199.
Harward, M.; Treshow, M. Impact of ozone on the growth and reproduction
of understory plants in the aspen zone of western U.S.A. Environ.
Conserv. 2:17-23; 1975.
Hayes, E.M.; Skelly, J.M. Transport of ozone from the northeast U.S.
into Virginia and its effect on eastern white pine. Plant Dis. Reptr.
51:778-782; 1977.
Heinrichs, H.; Mayer, R. The role of forest vegetation in the biogeo-
chemical cycle of heavy metals. 0. Environ. Qual. 9:111-118; 1980.
Hepting, G.H. Air pollution and trees, Matthews, W.H.; Smith, F.E.;
Goldberg, E.D., eds. Man's impact on terrestrial and oceanic eco-
systems. Cambridge, MA: MIT Press; 1971:116-129.
67
-------
Houston, O.B.; Dochinger, L.S. Effects of ambient air pollution on
cone, seed, and pollen characteristics in eastern white and red pines.
Environ. Pollut. 12:1-5; 1977.
HoweUs, 6., coordinator. Ecological effects of acid precipitation -
workshop procedings; 1978 Steptember 4-7; Galloway, U.K. Palo Alto,
CA: Electric Power Research Institute, Energy Analysis and Environment
Division; EPRI EA-79-6-LD; 1979.
Hursh, C.R. Local climate in the copper basin of Tennessee as modified
by removal of vegetation. Washington, DC: U.S. Department of Agri-
culture; Circular No. 774; 1948. 38 p.
Hutchinson, T.C. Impact of heavy metals on terrestrial and aquatic eco-
systems. Miller, P.R., ed. Proceedings of a symposium on effects of air
pollutants on mediterranean and temperate forest ecosystems; 1980 June
22-27; Riverside, CA. Berkeley, CA: U.S. Department of Agriculture,
Forest Service, Pacific Southwest Forest and Range Experiment Station;
General Technical Report PSW-43; 1980:158-164.
Hutchinson, T.C. The ecological consequences of acid discharges from
industrial smelters. Michigan State University. Institute of Water
Research. Initial draft of the proceedings for the effects of acid
precipitation on ecological systems: Great Lakes region; 1981 April
1-3; Michigan State University, East Lansing, MI; 1981. To be published
by Ann Arbor Science Publishers, Inc., Ann Arbor, MI.
Hutchinson, T.C.; Havas, M., eds. Effects of acid precipitation on
terrestrial ecosystems. New York: Plenum Press; 1980. 654 p.
Hutchinson, T.C.; Whitby, L.M. Heavy metal pollution in the Sudbury
mining and smelting region of Canada. I. Soil and vegetation contami-
nation by nickel, copper, and other metals. Environ. Conserv. 1(2):123-
132; 1974.
Inman, J.C.; Parker, G.R. Decomposition and heavy metal dynamics of
forest litter in northwestern Indiana. Environ. Pollut. 17:39-51;
1978.
Interagency Task Force on Acid Precipitation. National acid precipita-
tion assessment plan. Draft; 1981. 129 p. Available from: Supt.
Docs., GPO, Washington, DC: 336-495/7128.
Jackson, D.R.; Watson, A.P. Disruption of nutrient pools and transport
of heavy metals in a forested watershed near a lead smelter. J. Environ.
Qua 1. 6(4):331-338; 1977.
Jacobson, J.S. Experimental studies on the phytotoxicity of acidic
precipitation: The United States experience. Hutchinson, T.C.; Havas,
M.; eds. Effects of acid precipitation on terrestrial ecosystems. New
York: Plenum Press; 1980:151-160.
68
-------
Jacobson, J.S.; Hill, A.C., eds. Recognition of air pollution injury to
vegetation: A pictorial atlas. Pittsburgh, PA: Air Pollution Control
Association; 1970.
James, R.L.; Cobb, F.U., Jr.; Wilcox, W.W.; Rowney, D.L. Effects of
photochemical oxidant injury of ponderosa and Jeffrey pines on
susceptibility of sapwood and freshly cut stumps to Fomes annostis.
Phytopathology 70:704-708; 1980.
Jensen, K.F.; Dochinger, L.S. Growth responses of woody species to
long- and short-term fumigation with sulfur dioxide. Broomall, PA: U.S.
Department of Agriculture, Forest Service, Northeastern Forest Experiment
Station; Research Paper NE-442; 1979. 7 p.
Jensen, K.F.; Kozlowski, T.T. Effects of SO2 on photosynthesis of
quaking aspen and white oak seedlings. North Am. For. 8iol. Workshop
Proc. 3:359; 1974.
Johnson, D.W. Site susceptibility to leaching by H2SO4 in acid
rainfall. Hutchinson, T.C.; Havas, M., eds. Effects of acid
precipitation on terrestrial ecosystems. New York: Plenum Press;
1980:525-535.
Jonsson, B. Soil acidification by atmospheric pollution and forest
growth. Water Air Soil Pollut. 7:497; 1977.
Jordan, M.J. Effects of zinc-smelter emissions and fire on a
chestnut-oak woodland. Ecology 56:78-91; 1975.
Jordan, M.J.; Lechevalier, M.P. Effects of zinc-smelter emissions on
forest soil microflora. Can. J. Microbiol. 21:1855-1865; 1975.
Katbny, E.L., ed. Trace elements in the environment. Washington, DC:
American Chemical Society, Advances in Chemistry Series No. 123; 1973.
149 p.
Keller, T. The effect of long term low SO2 concentrations upon photo-
synthesis of conifers. Proceedings Fourth International Clean Air
Congress; 1977:81-83.
Keller, T. Winter time atmospheric pollutants - do they affect the
performance of deciduous trees in the ensuing growing season? Environ.
Pollut. 16:243-247; 1978a.
Keller, T. Influence of low SO2 concentrations upon CO2 uptake of
fir and spruce. Photosynthetica 12:316-322; 1978b.
Keller, T. The simultaneous effect of soil-borne NaF and air pollutant
SO? on CO2 uptake and pollutant accumulation. Oecologia 44:283-285;
1980a.
69
-------
Keller, T. The effect of a continuous springtime fumigation with SO2
on CO2 uptake and structure of the annual ring in spruce. Can. J. For.
Res. 10:1-6; 1980b.
Kelly, J.M.; Parker, G.R.; McFee, W.W. Heavy metal accumulation and
growth of seedlings of five forest species as influenced by soil cadmium
levels. J. Environ. Qual. 8:361-364; 1979.
Kercher, J.R.; Axelrod, M.C. SILVA: A model for forecasting the
effects of SO2 pollution on growth and succession in a western
coniferous forest. Livermore, CA: Lawrence Livermore National
Laboratory, Environmental Science Division, UCRL-53109; 1981. 72 p.
Kickert, R.N.; Gemmill, B. Data-based ecological modeling of ozone air
pollution effects in a southern California mixed conifer ecosystem.
Miller, P.R., ed. Proceedings of a symposium on effects of air pollu-
tants on mediterranean and temperate forest ecosystems; 1980 June 22-27;
Riverside, CA. Berkeley, CA: U.S. Department of Agriculture, Forest
Service, Pacific Southwest Forest and Range Experiment Station; General
Technical Report PSW-43; 1980:181-186.
Knabe, W. Effects of sulfur dioxide on terrestrial vegetation. Ambio
5(5-6):213-218; 1976.
Koslow, E.E.; Smith, W.H.; Staskawicz, B.O. Lead-containing particles
on urban leaf surfaces. Environ. Sci. Technol. 11:1019-1021; 1977.
Kozlowski, T.T. Impacts of air pollution on forest ecosystems.
Bioscience 30(2):88-93; 1980.
Lamoreaux, R.J.; Chaney, W.R. Growth and water movement in silver maple
seedlings affected by cadmium. J. Environ. Qual. 6:201-205; 1977.
Last, F.T.; Likens, G.E.; Ulrich, B.; Walloe, L. Acid precipitation -
progress and problems. Drablos, D.; Tollan, A., eds. Ecological impact
of acid precipitation: Proceedings of an international conference; 1980
March 11-14; Sandefjord, Norway. Oslo-As, Norway: SNSF Project;
1980:10-12.
LeBlanc, F.; Rao, D. Effects of air pollutants on lichens and
bryophytes. Mudd, J.B.; Kozlowski, T.T., eds. Responses of
plants to air pollution. New York: Academic Press; 1975:237-
272.
Lee, J.J.; Weber, D.E. The effect of simulated acid rain on seedling
emergence and growth of eleven woody species. For. Sci. 25(3):393-398;
1979.
Legge, A.H. Primary productivity, sulfur dioxide and the forest eco-
system: an overview of a case study. Miller, P.R., ed. Proceedings of
a symposium on effects of air pollutants on mediterranean and temperate
forest ecosystems; 1980 June 22-27; Riverside, CA. Berkeley, CA: U.S.
Department of Agriculture, Forest Service, Pacific Southwest Forest and
Range Experiment Station; General Technical Report PSW-43; 1980:51-62.
70
-------
Lindberg, S.E.; Shriner, D.S.; Hoffman, W.A., Jr. The interaction of wet
and dry deposition with the forest canopy. Michigan State University.
Institute of Water Research. Initial draft of the proceedings for the
effects of acid precipitation on ecological systems: Great Lakes region;
1981 April 1-3; Michigan State University, East Lansing, MI; 1981. To be
published by Ann Arbor Science Publishers, Inc., Ann Arbor, MI.
Linzon, S.N. Economic effects of sulfur dioxide on forest growth. J.
Air Pollut. Control Assoc. 21(2):81-86; 1971.
Linzon, S.N. Effects of airborne sulfur pollutants on plants. Nriagu,
J.O., ed. Sulfur in the environment: Part II, Ecological impacts. New
York: John Wiley & Sons; 1978:109-162.
Linzon, S.N.; Temple, P.J. Soil resampling and pH measurements after an
18-year period in Ontario. Drablos, D.; Tollan, A., eds. Ecological
impact of acid precipitation: Proceedings of an international confer-
ence; 1980 March 11-14; Sandefjord, Norway. Oslo-As, Norway: SNSF
Project; 1980:176-177.
Little, P; Martin, M.H. A survey of zinc, lead and cadmium in soil and
natural vegetation around a smelting complex. Environ. Pollut. 3:241-
254; 1972.
Lynch, D.F. Diameter growth of ponderosa pine in relation to the Spokane
pine-blight problem. Northwest Sci. 25:157-163; 1951.
Manning, W.J. Effects of limestone dust on leaf condition, foliar
disease incidence and leaf surface microflora of native plants.
Environ. Pollut. 2:69-76; 1971.
Mayer, R.; Ulrich, B. Input to soil, especially the influence of
vegetation in intercepting and modifying inputs -- a review.
Hutchinson, T.C.; Havas, M., eds. Effects of acid precipitation
on terrestrial ecosystems. New York: Plenum Press, 1980:173-182.
McClenahen, J.R. Distribution of soil fluorides near an airborne
fluoride source. J. Environ. Qual. 5:472-475; 1976.
McClenahen, J.R. Community changes in a deciduous forest exposed to
air pollution. Can. J. For. Res. 8:432-438; 1978.
McFee, W.W.; Cronan, C.S. The action of wet and dry deposition com-
ponents of acid precipitation on litter and soil. Michigan State
University. Institute of Water Research. Initial draft of the pro-
ceedings for the effects of acid precipitation on ecological systems:
Great Lakes region; 1981 April 1-3; Michigan State University, East
Lansing, MI; 1981. To be published by Ann Arbor Science Publishers,
Inc., Ann Arbor, MI.
McLaughlin, S.B., Jr.; Barnes, R.L. Effects of fluoride on
photosynthesis and respiration of some southeast American forest trees.
Environ. Pollut. 8:91-96; 1975.
71
-------
Michigan State University. Institute of Water Research. Initial draft
of the proceedings for the effects of acid precipitation on ecological
systems: Great Lakes region; 1981 April 1-3; Michigan State University,
East Lansing, MI; 1981. To be published by Ann Arbor Science Publishers,
Inc., Ann Arbor, MI.
Miller, P.R. Oxidant-induced community change in a mixed conifer
forest. Naegle, J., ed. Air pollution damage to vegetation. Washing-
ton, DC: American Chemical Society, Advances in Chemistry Series 122;
1973:101-117.
Miller, P.R.; Elderman, M.J., eds. Photochemical oxidant air pollutant
effects on a mixed conifer forest ecosystem. A progress report, 1976.
Corvallis, OR: U.S. Environmental Protection Agency, Office of Research
and Development; EPA-600/3-77-104; 1977. 338 p.
Miller, P.R.; McBride, J.R. Effects of air pollutants on forests. Mudd,
J.B.; Kozlowski, T.T., eds. Responses of plants to air pollution. New
York: Academic Press; 1975:195-235.
Miller, P.R.; Parmeter, J.R.; Flick, B.H.; Martinez, C.W. Ozone damage
response of ponderosa pine seedlings. J. Air Pollut. Control Assoc.
19:435-438; 1969.
Miller, P.R.; Parmeter, J.R.; Taylor, O.C.; Cardiff, E.A. Ozone injury
to the foliage of Pinus ponderosa. Phytopathology 53:1072-1076; 1963.
Mitchell, C.D.; Fretz, T.A. Cadmium and zinc toxicity in white pine, red
maple, and Norway spruce. J. Am. Soc. Hort. Sci. 102:81-84; 1977.
Mudd, J.B. Peroxyacyl nitrates. Mudd, J.8.; Kozlowski, T.T., eds.
Responses of plants to air pollution. New York: Academic Press; 1975a:
97-119.
Mudd, J.B. Sulfur dioxide. Mudd, J.B.; Kozlowski, T.T., eds. Responses
of plants to air pollution. New York: Academic Press; 1975b:9-22.
Nash, T.H.; Sigal, L.L. Sensitivity of lichens to air pollution with an
emphasis on oxidant air pollutants. Miller, P.R., ed. Proceedings of a
symposium on effects of air pollutants on mediterranean and temperate
forest ecosystems; 1980 June 22-27; Riverside, CA. Berkeley, CA: U.S.
Department of Agriculture, Forest Service, Pacific Southwest Forest and
Range Experiment Station; General Technical Report PSW-43; 1980:117-124.
National Research Council. Committee on Biological Effects of Atmo-
spheric Pollutants. Lead: Airborne lead in perspective. Washington,
DC: National Academy Press; 1972. 330 p.
National Research Council. Effects of fluorides in animals. Washington,
DC: National Academy press; 1974.
72
-------
National Research Council. Committee on Medical and Biological Effects
of Environmental Pollutants. Ozone and other photochemical oxidants.
Washington, DC: National Academy Press; 1977a. 719 p.
National Research Council. Committee on Medical and Biological Effects
of Environmental Pollutants. Nitrogen oxides. Washington, DC: National
Academy Press; 1977b. 333 p.
National Research Council. Committee on Medical and Biological Effects
of Environmental Pollutants. Sulfur oxides. Washington, DC: National
Academy Press; 1978. 209 p.
National Research Council. Committee on the Atmosphere and the Bio-
sphere. Atmosphere-biosphere interactions: Toward a better under-
standing of the ecological consequences of fossil fuel combustion.
Washington, DC: National Academy Press; 1981. 263 p.
Newman, J.R. Animal indicators of air pollution: A review and recom-
mendations. Corvallis, OR: U.S. Environmental Protection Agency,
Corvallis Environmental Research Laboratory; CERL-006; 1975. 192 p.
Newman, J.R. Effects of air emissions on wildlife resources. Ann
Arbor, MI: U.S. Fish and Wildlife Service, Biological Services Program,
National Power Plant Team; FWS/0BS-80M0.1; I960. 32 p.
Norton, 5.A.; Hanson, O.W.; Campana, R.J. The impact of acidic precipi-
tation and heavy metals on soils in relation to forest ecosystems.
Miller, P.R., ed. Proceedings of a symposium on effects of air pollu-
tants on mediterranean and temperate forest ecosystems; 1980 June 22-27;
Riverside, CA. Berkeley, CA: U.S. Department of Agriculture, Forest
Service, Pacific Southwest Forest and Range Experiment Station; General
Technical Report PSW-43; 1980:152-157.
Oehme, F.W., ed. Toxicity of heavy metals in the environment. New
York: Dekker; 1978: Part I, 515 p.; Part II, 970 p.
Overrein, L.N.; Seip, H.M.; Tollan, A. Acid precipitation - effects on
forest and fish. Final report of the SNSF-project 1972 - 1980. Oslo-As,
Norway; 1980. 175 p.
Palmer, K.T.; Kucera, C.L. Lead contamination of sycamore and soil from
lead mining and smelting operations in eastern Missouri. J. Environ.
Qual. 9:106-111; 1980.
Parmeter, J.R. Jr.; Bega, R.V.; Neff, T. A chlorotic decline of
ponderosa pine in southern California. Plant Dis. Reptr. 46:269-273;
1962.
Parmeter, J.R., Jr.; Miller, P.R. Studies relating to the cause of
decline and death of ponderosa pine in southern California. Plant Dis.
Reptr. 52:707-711; 1968.
73
-------
Parmeter, J.R.; Uhrenholdt, B. Some effects of pine needle or grass
smoke on fungi. Phytopathology 65:28-31; 1975.
Petersen, L. Podsolization: Mechanisms and possible effects of acid
precipitation. Hutchinson, T.C.; Havas, M.; eds. Effects of acid
precipitation on terrestrial ecosystems. New York: Plenum Press;
1980:223-237.
Reiners, W.A.; Marks, R.H.; Vitousek, P.M. Heavy metals in subalpine
and alpine soils of New Hampshire. Oikos 26:264-275; 1975.
Renwick, J.A.A.; Potter, J. Effects of sulfur dioxide on volatile
terpene emission from balsam fir. J. Air Pollut. Control Assoc.
31(1):65-66; 1981.
Richards, B.L., Sr.; Taylor, O.C.; Edmunds, G.F., Jr. Ozone needle
mottle of pines of southern California. J. Air Pollut. Control Assoc.
18:73-77; 1968.
Ricks, G.R.; Williams, R.J.H. Effects of atmospheric pollution on
deciduous woodland - Part 2: Effects of particulate matter upon stomatal
diffusion resistance in leaves of Quercus petraea (Mattuschka) Liebl.
Environ. Pollut. 6:87-109; 1974.
Roberts, B.R.; Townsend, A.M.; Dochinger, L.S. Photosynthetic response
to SO2 fumigation in red maple. Plant Physiol. 47:30; 1971.
Rosenberg, C.R.; Hutnik, R.J.; Davis, D.D. Forest composition at varying
distances from a coal-burning power plant. Environ. Pollut. 18:307-317;
1979.
Ruhling, A.; Tyler, 6. Heavy metal pollution and decomposition of spruce
needle litter. Oikos 24:402-416; 1973.
Scheffer, T.C.; Hedgcock, 6.C. Injury to northwestern forest trees by
sulfur dioxide from smelters. Washington, DC: U.S. Department of
Agriculture, Forest Service; Technical Bulletin No. 1117; 1955.
49 p.
Schnitzer, M. Effect of low pH on the chemical structure and reactions
of humic substances. Hutchinson, T.C.; Havas, M.; eds. Effects of acid
precipitation on terrestrial ecosystems. New York: Plenum Press; 1980:
203-222.
Shaw, C.6.; Fischer, G.W.; Adams, D.F.; Adams, M.F.; Lynch, D.W.
Fluorine injury to ponderosa pine: A summary. Northwest Sci.
15:156; 1951.
Shriner, D.S. Terrestrial vegetation - air pollutant interactions:
Nongaseous pollutants, wet deposition. Krupa, S.V.; Legge, A., eds.
Proceedings of international conference on air pollutants and their
effects on terrestrial ecosystems; 1980 May 10-17; Alberta, Canada.
New York: John Wiley Interscience ; 1981.
74
-------
Shriner, D.S.; Richmond, C.R.; Lindberg, S.E., eds. Atmospheric sulfur
deposition: Environmental impact and health effects. Ann Arbor, MI:
Ann Arbor Science Publishers, Inc; 1980. 568 p.
Shugart, H.H.; McLaughlin, S.B.; West, DX. Forest models: Their
development and potential applications for air pollution effects
research. Miller, P.R., ed. Proceedings of a symposium on effects
of air pollutants on mediterranean and temperate forest ecosystems;
1980 June 22-27; Riverside, CA. Berkeley, CA: U.S. Department of
Agriculture, Forest Service, Pacific Southwest Forest and Range
Experiment Station; General Technical Report PSW-43; 1980:203-214.
Siccama, T.G.; Smith, W.H. Lead accumulation in a northern hardwood
forest. Environ. Sci. Technol. 12(5):593-594; 1978.
Siccama, T.G.; Smith, W.H.; Mader, O.L. Changes in lead, zinc, copper,
dry weight, and organic matter content of the forest floor of white pine
stands in central Massachusetts over 16 years. Environ. Sci. Technol.
14(1):5456; 1980.
Skelly, J.M. Photochemical oxidant impact on mediterranean and temperate
forest ecosystems: Real and potential effects. Miller, P.R., ed. Pro-
ceedings of a symposium on effects of air pollutants on mediterranean and
temperate forest ecosystems; 1980 June 22-27; Riverside, CA. Berkeley,
CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest
Forest and Range Experiment Station; General Technical Report PSW-43;
1980:38-50.
Skelly, J.M.; Duchelle, S.F.; Kress, L.W. Impact of photochemical oxi-
dant air pollution on eastern white pine in the Shenandoah, Blue Ridge
Parkway, and Great Smoky Mountains National Parks. Proceedings II con-
ference on scientific research in National Parks; San Francisco, CA;
1979.
Smith, R.L. Ecology and field biology. Second ed. New York: Harper
and Row; 1974. 849 p.
Smith, W.H. Air pollution - a 20th century allogenic influence on forest
ecosystems. Miller, P.R., ed. Proceedings of a symposium on effects of
air pollutants on mediterranean and temperate forest ecosystems; 1980
June 22-27; Riverside, CA. Berkeley, CA: U.S. Department of Agri-
culture, Forest Service, Pacific Southwest Forest and Range Experiment
Station; General Technical Report PSW-43; 1980:79-87.
Smith, W.H. Air pollution and forests. Interactions between air con-
taminants and forest ecosystems. New York: Springer-Verlag; 1981.
379 p.
Soholt, L.F.; Wiedenbaum, S. Oil shale: Its development and potential
for air quality effects. Washington, DC: U.S. Fish and Wildlife
Service, Office of Biological Services; FUS/OBS-81/34; Draft; 1981.
62 p.
75
-------
Spurr, S.H.; Barnes, B.V. Forest ecology. Second ed. New York: Ronald
Press; 1973. 571 p.
Stark, R.W.; Miller, P.R.; Cobb, F.W., Jr.; Wood, D.L.; Parmeter, J.R.,
Jr. Photochemical oxidant injury and bark beetle {Coleoptera:
Scolytidae) infestation of ponderosa pine. I. Incidence of bark beetle
infestation in injured trees. Hilgardia 39:121-126; 1968.
Strand, L. The effect of acid precipitation on tree growth. Drablos,
D.; Tollan, A., eds. Ecological impact of acid precipitation: Pro-
ceedings of an international conference; 1980 March 11-14; Sandefjord,
Norway. Oslo-As, Norway: SNSF Project; 1980:64-67.
Strojan, C.L. Forest leaf litter decomposition in the vicinity of a
zinc smelter. Oecologia 32:203-212; 1978a.
Strojan, C.L. The impact of zinc smelter emissions on forest litter
arthropods. Oikos 31:41-46; 1978b.
Suwannapinunt, W.; Kozlowski, T.T. Effect of SOg on transpiration,
chlorophyll content, growth, and injury in young seedlings of woody
angiosperms. Can. J. For. Res. 10:78-81; 1980.
Tairm, C.O.; Cowling, E.B. Acidic precipitation arid forest vegetation.
Oochinger, L.S.; Seliga, T.A., eds. Proceedings of the first inter-
national symposium on acid precipitation and the forest ecosystem; 1975
May 12-16; Ohio State University, Columbus, OH. Upper Darby, PA: U.S.
Department of Agriculture, Forest Service, Northeastern Forest Experiment
Station; 1976:845-856. Available from: NTIS, Springfield, VA; PB-258645.
Taylor, O.C. Importance of peroxyacetylnitrate (PAN) as a phytotoxic
air pollutant. J. Air Pollut. Control Assoc. 19:347-351; 1969.
Taylor, O.C., ed. Oxidant air pollutant effects on a western coniferous
forest ecosystem. Task C report: Study site selection and onsite
collection of background information. Riverside, CA: University of
California, Air Pollution Research Center; EPA-R3-73-043B; 1973a.
189 p.
Taylor, O.C., ed. Oxidant air pollutant effects on a western coniferous
forest ecosystem. Task B Report: Historical background and proposed
systems study of the San Bernardino Mountain area. Riverside, CA:
University of California, Air Pollution Research Center; 1973b. 278 p.
Taylor, O.C. Oxidant air pollutant effects on a western coniferous
forest ecosystem. Task D: Annual progress report, 1973-1974.
Riverside, CA: University of California, Air Pollution Research
Center; 1974. Ill p.
Taylor, O.C., ed. Photochemical oxidant air pollution effects on a
mixed conifer forest ecosystem. Final report. Corvallis, OR: U.S.
Environmental Protection Agency, Office of Research and Development;
EPA-600/3-80-002; 1980. 196 p.
76
-------
Taylor, O.C.; Dugger, W.M., Jr.; Cardiff, E.A.; Darley, E.F. Interaction
of light and atmospheric photochemical products ('smog') within plants.
Nature 192:814-816; 1961.
Taylor, O.C.; Thompson, C.R.; Tingey, D.T.; Reinart, R.A. Oxides of
nitrogen. Mudd, J.B.; Kozlowski, T.T., eds. Responses of plants to
air pollution. New York: Academic Press; 1975:121-139.
Thompson, L.K.; Sidhu, S.S.; Roberts, B.A. Fluoride accumulations in
soil and vegetation in the vicinity of a phosphorus plant. Environ.
Pollut. 18:221-234; 1979.
Treshow, M. Interaction of air pollutants and plant diseases. Mudd,
J.B.; Kozlowki, T.T., eds. Responses of plants to air pollution. New
York: Academic Press; 1975:307-334.
Treshow, M. Interactions of air pollutants and plant disease. Miller,
P.R., ed. Proceedings of a symposium on effects of air pollutants on
mediterranean and temperate forest ecosystems; 1980 June 22-27; River-
side, CA. Berkeley, CA: U.S. Department of Agriculture, Forest Service,
Pacific Southwest Forest and Range Experiment Station; General Technical
Report PSW-43; 1980:103-109.
Treshow, M.; Anderson, F.K.; Harner, F. Responses of Douglas-fir to
elevated atmospheric fluorides. For. Sci. 13:114-120; 1967.
Treshow, M.; Pack, M.R. Fluoride. Jacobson, J.S.; Hill, A.C., eds.
Recognition of air pollution injury to vegetation: A pictorial atlas.
Pittsburgh, PA: Air Pollution Control Association; 1970: D1-D17.
Treshow, M.; Stewart, D. Ozone sensitivity of plants in natural
communities. Biol. Conserv. 5(3):209-214; 1973.
Troedsson, T. Ten years acidification of Swedish forest soils. Drablos,
D.; Tollan, A., eds. Ecological impact of acid precipitation: Pro-
ceedings of an international conference; 1980 March 11-14; Sandefjord,
Norway. Oslo-As, Norway: SNSF Project; 1980:184.
Tyler, G. Heavy metals pollute nature, may reduce productivity. Ambio
1(2):52-59; 1972.
Tyler, G. Heavy metal pollution and mineralization of nitrogen in forest
soils. Nature 255:701-702; 1975.
U.S. Department of Agriculture. Air pollution damages trees. Upper
Darby, PA: Forest Service, Northeastern Area, State and Private
Forestry; 1973. 32 p.
Ulrich, B.; Mayer, R.; Khanna, P.K. Chemical changes due to acid
precipitation in a loess-derived soil in central Europe. Soil Sci.
130:193-199; 1980.
77
-------
Van Hook, R.I.; Harris, W.F.; Henderson, G.S. Cadmium, lead, and zinc
distributions and cycling in a mixed deciduous forest. Ambio 6:281-286;
1977.
Varshney, C.K.; Garg, K.K. Significance of leaf surface characteristics
in plant responses to air pollution. Water Air Soil Pollut. 14:429-433:
1980.
Voigt, G.K. Acid precipitation, forest ecosystems and intensive
harvesting. Leaf, A.L., chairman. Proceedings of symposium on impact of
intensive harvesting on forest nutrient cycling. 1979 August 13-16.
Syracuse, NY: State University of New York, College of Environmental
Science and Forestry; 1979:33-48.
Voigt, G.K. Acid precipitation and soil buffering capacity. Drablos,
D.; Tollan, A., eds. Ecological impact of acid precipitation: Pro-
ceedings of an international conference; 1980 March 11-14; Sandefjord,
Norway. Oslo-As, Norway: SNSF Project; 1980:53-57.
Weinstein, L.H. Fluoride and plant life. J. Occup. Med. 19:49-78;
1977.
Wert, S.L. A system for using remote sensing techniques to detect and
evaluate air pollution effects on forest stands. Proceedings of sixth
international symposium on remote sensing of the environment, 1969;
Volume 2. Ann Arbor: University of Michigan; 1969.
West, D.C.; McLaughlin, S.B.; Shugart, H.H. Simulated forest response
to chronic air pollution stress. J. Environ. Qual. 9(1):43-49; 1980.
Westman, W.E. Opening remarks and summary of panel/audience discussion.
Miller, P.R., ed. Proceedings of a symposium on effects of air pollu-
tants on mediterranean and temperate forest ecosystems; 1980 June 22-27;
Riverside, CA. Berkeley, CA: U.S. Department of Agriculture, Forest
Service, Pacific Southwest Forest and Range Experiment Station; General
Technical Report PSW-43; 1980:215-220.
Whittaker, R.H. Communities and ecosystems. Second ed. New York:
MacMillan Publishing Co.; 1975. 385 p.
Wiersma, G.B.; Brown, K.W. Background levels of trace elements in forest
ecosystems. Miller, P.R., ed. Proceedings of a symposium on effects of
air pollutants on mediterranean and temperate forest ecosystems; 1980
June 22-27; Riverside, CA. Berkeley, CA: U.S. Department of Agri-
culture, Forest Service, Pacific Southwest Forest and Range Experiment
Station; General Technical Report PSW-43; 1980:31-37.
Wiklander, L. Leaching and acidification of soils. Howells, G.,
coordinator. Ecological effects of acid precipitation - workshop pro-
ceedings; 1978 September 4-7; Galloway, U.K. Palo Alto, CA: Electric
Power Research Institute, Energy Analysis and Environment Division; EPRI
EA-79-6-LD; 1979.
78
-------
Wilhour, R.G. The influence of ozone on white ash (Fraxinus americana
L.). University Park, PA: Pennsylvania State University, Center for
Air Environment Studies; Publication 188-71; 1971. 86 p.
Williams, Lloyd, M.M.; Ricks, 6.R. Effects of atmospheric
pollution on deciduous woodland. I. Some effects on leaves of
Quercus petraea (Mattuschka) Leibl. Environ. Pollut. 2:57-68;
1971.
Wood, F.A. Air pollution and shade trees. Proceedings of the 43rd
international shade tree conference; 1967:66-82.
Woodwell, G.M. Effects of pollution on the structure and physiology
of ecosystems. Science 168:429-433; 1970.
79
-------
APPENDIX
-------
APPENDIX
Foliar injury is a readily discernible, often used response variable
in air pollution studies. Visible symptoms commonly are exhibited first
in foliar tissue because leaves are the primary contact sites for pollu-
tants. The following summary table (Table A-l) presents general foliar
symptom and dose-threshold information for acute injury responses to the
various pollutants discussed in this document; Smith (1981)* should be
consulted for a more detailed discussion of symptom development, including
the mechanisms of toxicity involved. The qualifying statement made in
subsection 1.3 regarding interpretation of dose-threshold information is
applicable for the values presented in Table A-l. In addition, a word of
caution should be expressed regarding the symptoms listed; they are often
not specific for individual pollutants [this is especially true for gym-
nosperms (USDA 1973; Kozlowski 1980)], they are mimicked in the field by
other stress factors (such as extremes in temperature, nutrient or water
imbalances, microorganism or arthropod infestation or predation), and in-
terpretation is further complicated by the fact that pollutant mixtures,
and hence interactions, may occur in the field (USDA 1973; Smith 1981).
Therefore, diagnosis of air pollution injury based only on these symptoms
should not be attempted by any investigator not thoroughly familiar with
both the affected species and the variety of potential stress factors
characteristic for a specific area. Supporting color photographs can be
found in Jacobson and Hill (1970) and USDA (1973).
~Citations in the appendix are included with those of the main text.
80
-------
Table A-l. Acute foliar injury symptoms and corresponding
dose thresholds of individual air pollutants.3
Pollutants
Symptoms'5
Dose threshold
Sulfur
dioxide
Nitrogen
dioxide
Ozone
Peroxyace-
tylnitrate
Fluoride
Trace
metals
Acid
deposition
Angiosperms: interveinal
necrotic blotches
Gymnosperms: red-brown
dieback or banding
Angiosperms: interveinal
necrotic blotches similar
to SO2 injury
Gymnosperms: red-brown
distal necrosis
Angiosperms: upper surface
flecks
Gymnosperms: distal necro-
sis, stunted needles
Angiosperms: lower surface
bronzing
Gymnosperms: chlorosis,
early senescence
Angiosperms: tip and margin
necrosis
Gymnosperms: distal necro-
sis
Angiosperms: interveinal
chlorosis, tip and margin
necrosis
Gymnosperms: distal necro-
sis
Angiosperms: necrotic spots
Gymnosperms: distal necro-
sis
0.70 ppm (1820 ug m-3) for 1 hr;
0.18 ppm (468 ug nr3) for 8 hr;
0.08-0.017 ppm (21-44 ug m-3) for
growing season
20 ppm (38 X 103 ug m-3) for 1 hr;
1.6-2.6 ppm (3000-5000 ug m-3)
for 48 hr;
1 ppm (1900 ug m"3) for 100 hr
0.20-0.30 ppm (392-588 ug m-3)
for 2-4 hr; some conifers 0.08
ppm (157 ug m~3) for 12-13 hr
0.20-0.80 ppm (989-3958 ug m"3)
for 8 hr
100 ug g"1 fluoride, dry wt.
basis
Variable, undetermined
pH < 3.0
aAdapted from Smith (1981).
^Symptoms and dose thresholds are for the most sensitive species.
81
-------
GLOSSARY
Abscission - separation of a leaf from a plant by dissolution of the cementing
material between cells in the abscission layer.
Albedo - the portion of solar radiation reflected back into space from the
earth's surface; the reflectivity or brightness of a surface.
Autecology - the study of the interrelationships of individual organisms with
their environment.
Biogeochemical cycles - the movement of chemical elements in the biosphere;
nutrient cycling.
Biomagnification - the concentration of an element at progressively higher
trophic levels of a food chain.
Chlorosis - yellowing in normally green plants resulting from disruptions in
chlorophyll development.
Dendrochronology - the science of dating annual growth rings of woody plants.
Glabrous - lacking hair or pubescence.
Hispid - rough due to the presence of stiff hairs, bristles, or minute spines.
Holistic - the concept that the environment is an interconnected whole.
Interspecific competition - competition between organisms of different species.
Lenticel - a slightly raised area in the bark of a stem or root, consisting of
loosely arranged unsuberized cells; thought to function in gas exchange.
Necrosis - the pathologic death of cells or tissues, especially those in
contact with or associated with living cells.
Physiognomy - the study of form and structure in natural communities.
Primary pollutants - pollutants emitted directly from an identifiable source.
Secondary pollutants - pollutants produced in the atmosphere by reactions
involving primary pollutants and/or other atmospheric constituents.
Serai - (stage) a relatively transitory community in the ecological succession
occuring at a given site; from pioneer to climax types.
82
-------
Synecology - the study of the interrelationships of biotic communities
with their environment.
Systems ecology - the application of systems analysis (mathematical
modeling) procedures to ecology.
Zonal soils - soils developed on level or rolling terrain that corres-
pond, in general, to climatic climax or prevailing climax vegetation.
83
-------
REPORT DOCUMENTATION "EPORT NO- 2-
PAGE FWS/0BS-80/40.6
3. Recipient's Accession No.
4. Title and Subtitle
Air Pollution and Acid Rain, Report 6
The Effects of Air Pollution and Acid Rain on Fish,
Wildlife, and Their Habitats - Forests
5. Report Date
June 1982
7. Author(s)
L. Borghi
8. Performing Organization Rapt. No.
9. Performing Organization Name and Address
Dynamac Corporation
Dynamac Building
11140 Rockville Pike
Rockville, MD 20852
10. Protect/Talk/Work Unit No.
11. ContractCC) or Grant(G) No.
(o 14-16-0009-80-085
(G)
12. Sponsoring Organization Name and Address y
------- |