Biological Services Program
FWS/OBS-80/40.7 Air Pollution and Acid Rain,
JUNE 1982 Report No. 7
THE EFFECTS OF AIR POLLUTION AND ACID RAIN
ON FISH, WILDLIFE, AND THEIR HABITATS
GRASSLANDS
Office of Research and Development jar
U.S. Environmental Protection Agency JffMT
Fish and Wildlife Service
U.S. Department of the Interior
-------
The Biological Services Program was established within the US 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.
Fur wile by tlie Superintendent of Documents, U.S. Government Printing Olliee
Washington. D.C. 20402
-------
FWS/0BS-80/40.7
June 1982
AIR POLLUTION AND ACID RAIN, REPORT 7
THE EFFECTS OF AIR POLLUTION AND ACID RAIN
ON FISH, WILDLIFE, AND THEIR HABITATS
GRASSLANDS
by
M. A. Peterson
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
Kearneysville, WV 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
Fish and Wildlife Service
U. S. Department of the Interior
Washington, DC
-------
DISCLAIMER
The opinions and recommendations expressed in 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 is:
Peterson, M.A. 1982. The effects of air pollution and acid rain on -fieh
wildlife, and their habitats - grasslands. U.S. F1sh and Ulldl fe sJlw
mXo,fo:V"h%Zm- Eastern Energy and Land Use T""'
-------
ABSTRACT
This report on grassland ecosystems is part of a series syn-
thesizing the results of scientific research related to the effects
of air pollution and acid deposition on fish and wildlife resources.
Accompanying reports in this series are: Introduction, Deserts and
Steppes, Forests, Lakes, Rivers and Streams, Tundra and Alpine
Meadows, Urban Ecosystems, and Critical Habitats of Threatened
and Endangered Species.
General aspects of grassland ecosystems relevant to a discussion
of air pollution effects are presented along with a brief introduction
to various other types of ecosystem stresses. The bulk of this
report describes plant, animal and ecosystem responses to air
pollution within the following pollutant categories: photochemical
oxidants, particulates, and acidifying air pollutants. The report
closes with a discussion of relevant topics for future research.
iii
-------
CONTENTS
Page
ABSTRACT iii
FIGURES v
TABLES . v
1.0 INTRODUCTION 1
2.0 GRASSLAND ECOSYSTEMS 2
2.1 Geographical and Historical Overview » 2
2.2 Ecological Overview 6
2.2.1 Flora * 7
2.2.2 Fauna 10
2.2.3 Ecosystem Stresses , . 11
3.0 EFFECTS OF AIR POLLUTION AND ACID RAIN ON WILDLIFE
AND HABITAT OF THE GRASSLAND ECOSYSTEM 14
3.1 Photochemical Oxidants 16
3.1.1 Plant Effects 16
3.1.2 Animal Effects ....... 29
3.1.3 Ecosystem Effects 20
3.2 Particulates 21
3.2.1 Plant Effects 22
3.2.2 Animal Effects 25
3.2.3 Ecosystem Effects 27
3.3 Acidifying Air Pollutants . . 29
3.3.1 Plant Effects . 32
3.3.2 Animal Effects ..... 37
3.3.3 Ecosystem Effects 38
4.0 TOPICS FOR FURTHER RESEARCH 42
4.1 Baseline Studies 42
4.2 Research on Plant Effects .............. 43
4.3 Research on Animal Effects t , 44
4.4 Research on Ecosystem Effects 45
REFERENCES 4B
IV
-------
FIGURES
Number Page
1 Bailey's grassland provinces of the United States ... 3
2 Weighted mean pH of precipitation in the
continental United States (1976-1979) 30
3 Effects of six-week SOo fumigations of varying
concentration on productivity and chlorophyll
content of Oryzopsis hymenoides 35
TABLES
Number Page
1 Features of Bailey's grasslands provinces of
the United States 4
2 Distribution of organic carbon in grassland
ecosystems 8
3 Floral constituents of major grassland associations 9
4 Concentration thresholds for visible ozone
injury to native grasses 18
5 Concentration thresholds for visible ozone
injury to grassland forbs 18
6 Heavy metal concentrations in soils and
vegetation near coal-fired power plants in the
Kaiparowitz basin of Arizona 23
7 Estimated concentrations of selected trace
elements in bluebunch wheatgrass (Agropyron
spicatum) at a distance of three km from a
phosphate-processing facility 23
8 Atmospheric fluoride accumulations in insects of
differing trophic status 27
v
-------
TABLES (continued)
Number Pa9e
9 Comparison of nutrient loss in grassland and
forest soils amended with arsenic 2S
10 Percentage of total leaf area injured by different
concentrations of S02 in two-hour field fumigation
studies of native grassland vegetation 33
11 The distribution of sulfur in producer and detritus
compartments of the grassland ecosystem 41
vi
-------
1.0 INTRODUCTION
This report on grassland ecosystems is one of a series presenting
current knowledge of the effects of air pollution and acid rain on fish,
wildlife, and their habitats. Its purpose is to assist U.S. Fish and
Wildlife Service field biologists in the anticipation or early detection
of air pollution injury in natural grasslands and modified rangelands, and
to identify relevant topics for further research.
This discussion of biotic and ecosystem effects focuses on three
basic groups of air pollutants: the photochemical oxidants, particulate
matter, and the acidifying air pollutants. A detailed description of the
individual pollutants within these categories is found in the introductory
volume of this series along with a discussion of pollutant sources, trans-
port, transformation, and deposition in aquatic and terrestrial ecosys-
tems. Reports in this series summarize current understanding of the ef-
fects of air pollution and acid precipitation within specific types of
ecosystems. Deserts and forests, which form ecotones with the temperate
grassland biome, are discussed in separate reports.
The following chapter briefly describes major geographic, historical,
and ecological aspects of grassland ecosystems that are relevant to an
assessment of air pollution effects. Chapter 3 presents both observed and
potential effects of air pollutants on grassland biota and ecosystem
structure and function. Finally, several lines of research are suggested
to improve and integrate knowledge of air pollution effects in grasslands
and their implications for wildlife management.
-------
2.0 GRASSLAND ECOSYSTEMS
Grasslands may be defined as any region where herbaceous plants are
natural cormtunity dominants and woody vegetation is absent or marginal
(Bailey 1978; Coupland 1979). As discussed below, they are very much a
product of characteristic climate, rainfall, and soil type. Their biotic
composition is greatly influenced by inherent ecosystem properties (for
example, frequent fire or drought) as well as by land-use conversions to
agriculture and livestock grazing. The following section describes the
North American temperate grassland biome and provides information on eco-
system alterations of relevance to the study of air pollution effects in
this region.
2.1 GEOGRAPHICAL AND HISTORICAL OVERVIEW
The temperate grassland biome of North America is located in mid-
continent between the Rocky Mountains of the western United States and the
eastern deciduous and mixed forests (Bailey 1978). It is bordered to the
north by coniferous forest in Canada and to the south by the Chihuahuan
desert of southern New Mexico and western Texas (Bailey 1978). North
American grasslands have been divided into six distinct provinces, as
illustrated in Figure 1. The characteristic land forms, climate, flora
and fauna of each of these provinces are described in Table 1.
Grassland ecosystems in this flat-to-rolling terrain form a gradient
from east to west varying from tall grass prairie to mixed and short grass
prairie in a pattern closely following a gradient of decreasing precipita-
tion from east to west. Grasslands form distinct ecotones with mixed con-
iferous and deciduous forests to the east, west, and north; these include
the western ponderosa pine savanna and the eastern oak-aspen savanna.
Primary factors regulating grassland expansion in these directions are
lowered temperatures and elevated precipitation. Grassland ecotones on
the desert fringe are less distinct, consisting of sagebrush and scattered
short grasses, and reflect the lack of sufficient moisture for abundant
perennial growth.
Important climatic features of grasslands are:
reduced precipitation;
increased evaporation rates;
t frequent wind;
periodic severe drought; and
fire.
2
-------
Division (2610). (Adapted from Bailey 1978)
-------
Table 1. Features of Bailey's grassland provinces of the United States.
Provinces Land Surface Form Climate Dominant Flora Typical Fauna
Prairie Parkland
(2511, 2521)
gently rolling plains, steep
bluffs, border valleys
far north has been glaciated
prairie and deciduous forest
alternate
Elevation:
hot summers and cold winters
frost free from 140 days
(north) to 280 days (south)
Average annual precipitation3:
23-40" {0.6-1.0 m) year
sea 1evel to 1,2001
(370 m)
bunch grasses (bluestem
prairie) in grassland areas
many prairie animals that
are independent of the need
for woody vegetation
few forms are peculiar to
this region
Prairie Bushland
(2521, 2522,
2523)
rolling plains and plateaus
occasionally bisected by
canyons
mesa and butte landscape in
many parts
Elevation: sea level to 3,600'
(1,100 m)
long hot sunmers and short
mild winters
frost free 250-300 days
evaporation exceeds precipi-
tation by a factor of 2 from
flay to October
Average evaporation: 71-79"
(1.8-2.0 m) year
Average annual precipitation3:
20-30" (0.5-0.8 m) year
arid grasslands with shrubs
and low trees singly or in
bunches
N.tf. Texas: xerophytic
grasses (grama, bluestem,
buffalo grass) with mesquite
in open stands
Edwards Plateau: Oak and
juniper mixed with grasses
white-tailed deer, wild
turkey, armadillo
northern limit of Mexican
groud squirrel
quail, bobwhite, hawks and
owls
golden-cheeked warbler
(threatened)
Tall Grass Prairie
(2530, 2531, 2532,
2533)
flat rolling plains with
relief of less than 300'
(91 m)
north of Missouri River:
young glacial drifts and
dissected till plains
south: loess and sand de-
posits with well-developed
drainage
Elevation: 1,000' (305 m) in
east to 2,500" (762 in) in west
drought less frequent and
severe in forested areas than
western portions
Average annual temperature:
N 4Q°F {4SC}, S 65°F (18°C)
E 55°F (13°C), W 60°F (16°C)
Average annual precipitation3:
15" (0.4 m) in northwest to
40" (1.0 m) in east
tall and mixed grasslands:
bunch grasses are conspicu-
ous, sod formers share
dominance
woody vegetation rare
most areas are under
cultivation
bison, antelope, coyotes
jackrabbits and cottontails
where cover is adequate
ground squirrels, prairie
dogs, pocket gophers,
badgers, red wolf
grouse and bobwhite
prairie chicken and black-
footed ferret (endangered)
California
Grassland
(2610)
flat alluvial plain forming
Central Valley of
Cal ifornia
broad, nearly level valleys
bordered by sloping alluvial
fans, slightly dissected
terraces and lower foothills
of surrounding uplands
hot summers and mild winters
(except ne. r coast)
evaporation exceeds precipi-
tation in warmest months
low stream flow: scarcity of
water
Average annual temperature:
once dominated by natural
grass associations: cultiva-
tion, fire and grazing have
eliminated all but relief
stands
dominants were bunch grasses
(similar to mixed grass
prairie)
California grizzly, ante-
lope and wolf have emigrated
mule deer, cottontail, jack-
rabbits, ground squirrels,
mice and kangaroo rats
coyote and bobcat in
adjacent woodlands
-------
Table 1. (Concluded)
Province
Land Surface Form
CI imate
Dominant Flora
Typical Fauna
Elevation:
sea level to 500'
(150 m)
60-67°F (16-19°C), 55°F (13°C)
in north
Average annual precipitation'':
6" (0.7 in) in uplands to 30"
(0.8 m) near coast
introduced annuals include
wild oats, brome, fescue,
barley
San Joaquin kit fox
(endangered)
Great Plains- - rolling plains and table-
Shortgrass Prairie lands of moderate relief
(3110, 3111, 3112,
3113)
plains are flat with
occasional valleys, canyons
and buttes
northern portion: badlands
and isolated mountains
Elevation: 2,500' (762 m) in
central states to 5,000'
(1,676 m) at Rockies
semiarid continental regime
evaporation usually exceeds
precipitation
¦ warm hot summers and cold
dry winter
frost free 100 days in north
to 200 days in Texas
Average annual temperature:
45-60°F (7-16°C)
Average annual precipitation3:
10" (0.3 m) In north to 25"
(0.6 m) in south
shortgrass prairie (steppe):
bunched and sparsely distri-
buted
occasional trees and shrubs:
gradation of cover into
semi desert and modi and
types
buffalograss, sunflower and
locoweed common
former large buffalo herds:
antelope is most abundant
large mammal
mule and white-tailed deer,
jackrabbits, cottontail,
prairie dogs, coyotes
horned lark, lark bunting,
grouse
prairie chicken and black-
footed ferret (endangered)
Palouse Prairie
(3120)
loess-covered basalt table-
lands of moderate to high
relief
uplands are moderately to
strongly dissected; slopes
mostly hilly and steep
major streams have cut deep
canyons
Elevation: 600' (180 m) along
streams to 4,000' (1,220 m)
hot dry sumners and
moderately cool, wet winters
frost free 120-170 days
Average annual temperature:
45-55°F (7-13°C)
Average annual precipitation*5:
18-23" (0.4-0.6 m)
once dominated by prairie
grasses, now under wheat
cul tivation
dominants were bluebunch
wheatgrass, fescue, blue-
grass
Sagebrush and bromegrass
dominance has resulted from
overgrazing and fire
antelope, deer in winter
bobcat, coyote, badgers
and ground squirrels
hawks, owls, sparrows,
flycatchers, warblers,
grouse
Most during growing season
Host In winter
(Adapted from Bailey 1978}
-------
The Rocky Mountains shelter mid-continental grassland regions from
the precipitation of Pacific air masses. The average annual rainfall of
250 to 1000 mm is sufficient to prevent desert conditions yet falls short
of that required for forest growth (Lauenroth 1979). Electrical storms
provoke frequent outbreaks of fire that are essential for the maintenance
and renewal of grassland plant species and for the periodic elimination
of invading woody growth.
The northern Great Plains of the United States are underlain by
masses of unconsolidated sedimentary rocks of which the Fort Union geo-
logical formation is representative. This formation typifies the geologi-
cal parent materials of western grassland soils, e.g., silt and loam allu-
vium derived mainly from wind and water erosion. Soils are characteris-
tically deep, predominantly calcareous and of medium texture. Soil hori-
zons are not as distinct as those in forest ecosystems, yet are generally
much deeper. Grassland soils are characterized by slow to medium rates of
surface water runoff and moderate water permeability. Leaching of nutri-
ents and trace elements from the soil is limited by low rates of water
infiltration, the decreased solubility of minerals in basic soils, and
depressed rates of release from humus (Coupland 1979).
Numerous climatic fluctuations and resultant glaciations have shaped
the grassland ecosystem over the ages, causing continual expansion or re-
cession of the grassland frontiers. Evidence of recent climatic fluctua-
tions in the western United States suggest that the prairie first seen by
European settlers was a uniquely rich and diversified climax community.
A product of a half-century or more of unusually abundant precipitation,
it was perhaps unprecedented in geologic time. Remnants of the original
prairie are presently scattered and few, largely due to conversion to
cropland and rangeland. It is believed, however, than an overall drying
trend, beginning in the late nineteenth century, would have reduced the
range of climax prairie even in the absence of human intervention (Bryson
1980).
Shifts in the pathways of continental air masses, which have occurred
throughout geologic time, have had a large influence on climate. In the
not-too-distant past, these shifts were sufficient to promote rapid eco-
system changes which lasted long enough to affect patterns of human
settlement (Bryson 1980). These climatic variations have exerted a pre-
dominant influence on the nature and extent of historical grassland devel-
opment and are likely to do so in the future.
2.2 ECOLOGICAL OVERVIEW
The biotic components of the grassland ecosystem may be classified
as:
autotrophs (primary producers);
6
-------
heterotrophs (consumers); and
saprotrophs (decomposers).
Detritus, or decaying matter, is the major abiotic component containing
large amounts of organic material in this ecosystem. These components
comprise the trophic pyramid, or the biomass distribution in the eco-
system at a single point in time; although it varies between different
sites, it tends to remain intraseasonally stable in a given location
(French et ak 1979). The trophic pyramid may be determined on the
basis ofTiomass, numerical counts, or the energy content of the
organisms present.
The percentage of organic carbon contained in these ecosystem compo-
nents also reflects the varying contributions of flora and fauna to total
biomass. The distribution of organic carbon among trophic levels in
grasslands is depicted in Table 2. Three quarters of total organic matter
is in some stage of decomposition at any one time, while primary producers
dominate the living biomass. Combined, these values show the large amount
of primary productivity forming the base of the trophic pyramid in grass-
land ecosystems.
Soil microflora are also shown in Table 2 to be influential ecosystem
components. Moreover, the biomass of bacteria, actinomycetes, and fungi
is greater in grasslands than in forested regions; important functions
include (Coupland 1979):
decomposition of dead organic materia);
channeling of energy from the detritivorous food web to the graz-
ing food web;
recirculation of materials within the detritivorous food web; and
symbiotic and non-symbiotic nitrogen fixation.
Patterns of organic carbon distribution emphasize the overriding impor-
tance of decomposer populations and nutrient cycling mechanisms to grass-
land productivity and the trophic webs on which wildlife depend.
2.2.1 Flora
The dominant plant species of tall-grass, mixed-grass, and short-
grass prairies are presented in Table 3. In a given habitat, two or three
species usually comprise more than half of total plant biomass (Coupland
1979). The diversity of remaining species is a function of topographical
variability and subsequent differences in microclimate and microhabitat.
7
-------
Table 2. Distribution of organic
carbon in grassland ecosystems.
Ecosystem Compartment
Percent Organic
Carbon (500 g/m^)
Soil organic matter (detritus)
75
Primary producers (autotrophs)
23
Decomposers (sapotrophs)
2
Consumers (heterotrophs)
1
Adapted from: Lauenroth and Heasley (1980)
Perennial grasses (Graminae) may be categorized into two basic mor-
phological groupings: sod formers and bunch grasses. Bunch grasses grow
in discrete clumps and spread through the propagation of aboveground stems
called tillers. Typical bunch grasses include orchardgrass (Dactylis
qlomerata), crested wheatgrass (Agropyron cristatum), and little bluestem
(Andropogon scoparius). Sod formers form thick mats of vegetation that
spread laterally via rhizomes or underground stems. Kentucky bluegrass
(Poa pratensis) and western wheatgrass (Agropyron smithii) are common
examples. Some of the more common species exhibit both morphological
forms depending on their environment and the vegetative association in
which they occur.
Sedges (Cyperaceae) and perennial forbs, especially the Compositae
and Leguminosae, are also abundant components of a climax prairie.
Goldenrods (Solidago sp.) and asters (Aster sp.) are frequently dominant
forbs. Annual plants, on the other hand, comprise a very small percentage
of natural grassland associations.
Grassland flora occupy three basic strata of the air-soil interface:
the root zone, the ground layer, and the herbaceous layer. Fifty to
eighty percent of total plant biomass is located beneath the surface in
roots and rhizomes, with the proportion of aboveground biomass to below-
ground biomass decreasing with increasing aridity (Lewis 1970). Most
short-grass roots occupy upper soil layers to depths of 30 to 90 cm while
8
-------
Table 3. Floral constituents of major grassland associations.
Tall Grass Association
Lowland
Upland
Mixed Grass Association
Tall dominants
Short dominants
Short Grass Association
Andropoqon qerardi
Elymus canadensis
Panicum virgatum
Sorghastrum nutans
Spartina pectinata
Andropoqon scoparius
Stipa spartea
Agropyron smithii
Bouteloua curtipendula
Koeleria~cristata
§ Qryzopsis sp.
Sporobolus heterolepis
Andropoqon scoparius
Stipa coriTata
Bouteloua graci1 is
Bouteloua hirsuta
Buchloe dactyloides
Bouteloua sp.
Bromus sp.
Buchloe dactyloides
Poa sp.
- big bluestem
- Canadian wild rye
- switchgrass
- Indian grass
- prairie cordgrass
- little bluestem
- needlegrass
- western wheatgrass
- side-oats grama
- junegrass
- Indian rice grass
- prairie dropseed
- little bluestem
- needle-and-thread
grass
- blue grama
- hairy grama
- buffalo grass
- gramas
- cheatgrass or
bromegrass
- buffalo grass
- bluegrass
ta7i-grass roots may penetrate as deep as T80 cm (Couplancf 1979). Tap-
roots of some forbs may reach depths of several meters. The microhabitat
surrounding plant roots is termed the rhizosphere and contains higher
populations of microflora, microfauna, and macroinvertebrates than
adjacent soil (Lewis 1970).
The herbaceous layer consists of the aerial portions of plants and
includes stems, leaves, and reproductive structures. The ground layer is
occupied by plant bases, stolons, propagative tillers, and large amounts
of mulch and decayed matter. Litter decomposition initially proceeds very
slowly, accelerating as compression provides increased contact with min-
eral soil and enhances moisture retention. Up to three years may be re-
quired for effective mineralization of grassland litter.
9
-------
Primary production typically increases in response to increased rain-
fall and temperature; lowest productivity is observed in areas of little
rainfall and elevated temperatures (Lauenroth 1979). Major factors
influencing net primary productivity in grassland flora are (Lewis 1970;
Lauenroth 1979):
solar radiation, through its influence on ambient temperature,
evapotranspiration, and light availability;
moisture, as related to leaf water potential, soil transpiration,
edaphic influences on soil moisture, precipitation fluctuations,
and the effects of overgrazing or fire;
mineral nutrition, including uptake from soil parent material, the
influence of the rhizosphere, nutrient limitations of nitrogen and
phosphorus, and effects of fire and excess salt or heavy metals;
allelochemics, or plant-released biological inhibitors, particu-
larly those preventing natural community succession;
biotic activities, including grazing by domestic and wild herbi-
vores, influences of predation, parasitism, and disease on preda-
tor populations, plant diseases, and nematode consumption of
roots; and
impacts of human population and industrialization, for example,
residential and commercial development, atmospheric pollution,
herbicide and pesticide misuse, and releases of ionizing radia-
tion.
2.2.2 Fauna
Within historic times, faunal diversity in the North American tem-
perate grassland biome has become markedly reduced, largely through human
intervention. Buffalo have been replaced as the dominant herbivores by
managed livestock herds, and predator populations have largely been con-
trolled. Some contemporary grassland species (e.g., the buffalo and
pronghorned antelope) have recovered from near extinction while others
(e.g., the prairie chicken, bald eagle, and black-footed ferret) are
currently threatened or endangered.
Insect species and other invertebrates are particularly numerous
and diversified, playing an important role in the maintenance of prairie
food webs. Belowground populations are of greater significance as only
3-8 percent of total consumption and productivity derives from above-
ground consumers (Scott et^L 1979). Animal populations are character-
ized by grazing and burrowing life habits, as well as a tendency to
aggregate in herds or colonies (Coupland 1979).
10
-------
Grassland wildlife differ greatly in their habitat requirements for
food, water, shelter, and reproductive cover. They may be categorized as
single cover type users, which obtain their life requirements from only
one kind of vegetative cover, or multicover type users, which require more
than one kind of cover to satisfy their needs (U.S. Fish & Wildlife Ser-
vice 1980). The home range, habitat dependencies, trophic status and
other life habits of fauna are all important factors modifying air pollu-
tion injury to wildlife in the grassland ecosystem.
2.2.3 Ecosystem Stresses
The grassland biome of North America has been subjected to numerous
stresses and alterations both before and during its settlement by man.
While natural occurrences of fire and drought have shaped grassland
ecosystems for millenia, the recent activities of man have exerted more
pronounced effects. Grazing, fire protection, and activities leading to
desertification provoke major alterations in the grassland biome that
must be considered as background against which air pollution impacts may
occur.
Remnants of the original prairie are now confined to railroad rights-
of-way and other protected areas, as conversion to cropland has altered
the original grassland character. Agricultural systems are much less con-
servative of energy, nutrients, and moisture than are native climax eco-
systems; annual crop production rapidly utilizes nutrient reserves that
have been accumulating for centuries in fertile prairie soils. Very lit-
tle of the harvested biomass is returned to the system for recycling.
Like human influences described below, these actions result in reduced
ecosystem organization and complexity as well as enhanced local entropy
of the system (Curtis 1971).
The use of natural vegetative cover for livestock grazing has long
been an important economic activity in the American west, yet continuous
research in rangeland management has been required to maintain productive
forage. Grazing pressure in general is known to promote successional
rollbacks in affected areas that destabilize climax communities and favor
the growth of pioneer species (Curtis 1971). As a result of overgrazing
available soil moisture is reduced through increased surface runoff and
evaporation, and through reduced infiltration, leading to xeric conditions
and possibly accelerated wind and water erosion (Lewis 1970). Perennial
plants are weakened by energy losses resulting from the constant removal
of photosynthetic organs and the continual requirement of new growth.
Overgrazing can lead to rapid declines in plant productivity and cover
that encourage the replacement of quality forage with invading herbaceous
annuals and unpalatable, thorny perennials (Curtis 1971). Palatable
grasses and nitrogen-fixing forbs and legumes are among the first plants
to succumb to overgrazing pressure.
Compounding the problem of overgrazing, predator control undertaken
to protect livestock may seriously deplete carnivorous populations while
encouraging overpopulation and excessive grazing by mice, prairie dogs,
11
-------
jackrabbits, and other prey species. The net effect of rangeland grazing
is to revert a highly complex, integrated and energy efficient climax com-
munity to a less organized successional stage (Curtis 1971). Overgrazing
tends to maintain plant communities at the least stable of pioneer stages
and may eliminate the grassland component entirely. As these ecosystem
stresses occur organic matter accumulation, nutrient cycling, and rainfall
retention may all decline as mulch deteriorates and soils are subjected to
increased compaction and erosion. The availability of functional niches
for wildlife may decline and reproductive cover may become scarce.
Fire protection is a relatively recent activity that has restricted
the natural expansion of grasslands. Eastern and western savanna ecotones
depend for their maintenance on periodic fires that remove woody vegeta-
tion and permit the invasion of grassland species. As a result of vigi-
lant fire protection, those portions of the savanna that have not been
brought under cultivation are being increasingly reclaimed by forest spe-
cies, with subsequent changes in wildlife habitat (Curtis 1971).
Chronic drought is a phenomenon of the grassland biome that can dras-
tically alter plant communities and soil characteristics. Associated dust
storms have had devastating effects on wildlife. Plants that were once
abundant may be severely reduced in range if they possess shallow root
systems or are unable to maintain themselves in a dormant state. Some
wildlife species may find new territories opened up to them, while the
home range of others may be reduced.
The devastating drought of the 1930s greatly altered the character of
the grassland biome. Tall-grass prairie reverted to a mixed-grass associ-
ation, the mixed-grass prairie became a short-grass prairie, and the
short-grass association was reduced to the Dust Bowl. Many of the origi-
nal grassland communities have yet to recover. More recently a trend
towards desertification is affecting major portions of the grassland
biome (Council on Environmental Quality 1980).
The desertification process is defined by the Council on Environment-
al Quality (1980) as a serious degradation of the soils, vegetation, and
ecological resiliance of arid and semi-arid lands. It is characterized by
excessive wind and water erosion, shortages of surface water, a lowering
of the groundwater table, and the salinization of existing water re-
sources. Desertification is believed to be caused by the complex inter-
action of increased urban and industrial development, groundwater mining,
poor irrigation practices, neglected soil conservation, overgrazing and
attempts to cultivate marginal lands. Devegetation and the invasion of
brush or desert-like species commonly result and sand dunes or salt crusts
may form (Council on Environmental Quality 1980). The Federal Great
Plains Conservation Program was enacted in 1966 to preserve national soil
resources by promoting the conversion of erosion-prone cropland to grass-
land; focused on only one aspect of this complex phenomenon, it has done
little to prevent desertification from spreading in the grassland biome
(Council on Environmental Quality 1980).
12
-------
Grassland flora and fauna characteristically respond to environmental
stresses of overgrazing, fire, or desertification by increasing or de-
creasing in numbers or biomass. Alterations in the abiotic environment
influence plant adaptivity, as well as inter- and intra-specific competi-
tiveness, and may provoke major shifts in species composition. Any envi-
ronmental factor which diminishes photosynthetic capacity or phloem trans-
port of carbon to roots will suppress productivity by arresting nutrient
uptake from soil; similarly, decreases in root exudate production can al-
ter the composition of the rhizosphere (Lewis 1970). Decreased primary
productivity associated with any of these conditions can reduce decomposi-
tion and nutrient cycling processes. Wildlife populations may, in turn,
be affected by loss of food, shelter, and nesting cover.
The air pollution effects discussed below thus occur within the con-
text of several dynamic processes influencing the structure and function
of grassland ecosystems. Air pollution episodes will rarely occur in the
absence of one or more of these conditions, and may exert an interactive
effect. Little is currently known of the exact nature of air pollutant
interactions with stresses, like drought, or with irrigation and other
management schemes. The combined effects of air pollution with other
stresses may be especially important in areas subject to desert ification
where sustained water supplies for wildlife and man largely depend on the
quality of vegetative cover.
13
-------
3.0 EFFECTS OF AIR POLLUTION AND ACID RAIN ON
WILDLIFE AND HABITAT OF THE GRASSLAND ECOSYSTEM
Injury to grassland flora from air pollution can be visible, as in
changes of normal leaf coloration (e.g., chlorosis), or may be expressed
more subtly by the alteration of physiological processes (e.g., photosyn-
thesis, reproduction). Plant injury by pollutants may also be categorized
as acute or chronic. Acute injuries typically produce visible symptoms
and result from exposure to high concentrations of pollutants over a short
period of time. This type of injury is generally only observed in plants
growing close to pollution sources (Wood and Nash 1976; Dawson and Nash
1980).
Chronic injuries produce more subtle plant alterations and result
from repeated exposures to low-level concentrations of pollutants over a
long period of time. Such injuries generally occur in grassland vegeta-
tion growing near pollution sources. Chronic injuries may be expected to
occur with greater frequency than acute effects, yet they are generally
more difficult to detect. The perennial nature of dominant grasses and
forbs may render them more vulnerable to the cumulative impacts of
chronic air pollution than agricultural crops and other annual species
(Lauenroth and Heasley 1980). Little is known about the potential for
long-range genetic effects from chronic exposures to air pollution.
Plant absorption of air pollutants occurs via two routes:
foliar uptake through leaf stomata; and
root absorption following pollutant deposition in soil.
The nature of uptake and plant response is affected to varying de-
grees by a number of factors present during exposure. The following
biotic and abiotic factors have been found to influence the susceptibility
of vegetation-to air pollutant uptake and expressions of injury (Heck
1968; Ziegler 1975; Guderian 1977; Heck and Anderson 1980):
Biotic Factors
Inherent Genetic Susceptibility - The variable sensitivities of
plant species to air pollution are due to morphological (e.g.,
number and arrangement of stomata) and physiological (e.g., sto-
matal function or detoxification mechanisms) differences. Differ-
ences in patterns of early SO2 metabolism are postulated to
mediate interspecific variations in tolerance to this pollutant;
tolerance results from the capacity to convert the gas to less
toxic sulfate ions (SO4 2*) and reduce rates of turnover in
tissues (Garsed and Read 1977). There is some evidence for the
development of tolerance within the same species when grown in
polluted areas (Horsman and Wellburn 1977). Intraspecific genetic
14
-------
adaptation has permitted some plants to minimize injury caused by
excessive levels of heavy metals; potential toxins may be incor-
porated into cell walls or compensations in enzymatic processes
may take place (Lewis 1970).
Age of Tissue - Dodd et aH. (1978) found a sign ificantly greater
amount of injury in older leaves of western wheatgrass (Agropyron
smithii) following acute exposures to 50^. On the other hand,
Horsman and Wellburn (1977) reported young leaves of the broad-
leaved dock (Rumex obtusifolius), a forb, to be most sensitive to
SO2. Recently matured leaves of ryegrass (Lolium perenne) are
more susceptible to photochemical oxidant injury tnan matured
leaves (Youngner and Nudge 1980). Rapid growth in general enhan-
ces the expression of air pollution injury in plants (Lewis 1970).
t Biotic Associations - Population levels and activities of plant
pathogens, parasites, and beneficial symbionts can be stimulated
or depressed by exposures to air pollution (Treshow 1968; Heagle
1973; Shriner 1978; Shriner and Cowling 1980).
Abiotic Factors
Light - The intensity and duration of the photoperiod affect sto-
matal opening and closure, hence the extent of exposure and the
amount of pollutants absorbed. Common pasture grass (Phleum pra-
tense) has been shown to be more resistant to low-level SO2 ex-
posures during long days with high irradlance; short days and re-
duced light render them more susceptible to injury due to a re-
duced ability to detoxify SO2 by-products that accumulate
(Davies 1980).
Humidity - Plants growing in humid areas tend to be more sensitive
to phytotoxic air pollutants (e.g., SO*, N0X, HF, CI2> O3,
and PAN) than those grown in drier habitats. Humid conditions en-
hance both pollutant uptake (Fowler and Unsworth 1974; McLaughlin
and Taylor 1981) and phytotoxicity (Bennett and Hill 1974; Hill
et al. 1974).
Soil Conditions - Soil water status may influence stomatal activi-
ty, and along with nutrient conditions, can modify plant responses
to air pollution. Low soil fertility tends to enhance the severi-
ty of SO2 effects in ryegrass (Lolium perenne) (Bleasdale 1973).
0 Temporal Influence - Daily variations in ambient air pollution
levels are also an important variable; SO2 concentrations are
generally lower during the day than at night due to higher wind
speeds and greater mixing of the air {McNary 1980). Oxidant con-
centrations tend to peak during hours of maximum irradlance and
decline at nightfall. Periodic climatic fluctuations may augment
the number of different air pollutants mixing and interacting in
ambient air.
15
-------
Acute exposures of grassland wildlife to air pollution may lead to
irritation of the lungs and eyes, the bioaccumulation of trace elements,
or subtle physiological and behavioral alterations. Pollutant avoidance,
or emigration from contaminated areas, is a response which has been ob-
served in both vertebrates and invertebrates (Newman 1980). The effects
of chronic exposures in animals, however, are for the most part indirect
and result from direct impacts on primary producers. Thus, wildlife ef-
fects mostly result from alterations taking place within the entire eco-
system.
Ecosystem exposures to air pollution are greatest near point sources
of trace elements and sulfur oxides. The systemic ,fects of point
sources of air pollution on ecosystems stem fror ae selective removal of
large plant species, plant community simplifica .on, and successional ar-
rest, which in turn lead to reduced nutrient cycling and an accelerated
rate of nutrient efflux from the system (Woodwell 1970). Deteriorating
ecosystem structure favors generalists, or hardy organisms, over more
specialized members of plant and animal associations (Lewis 1970).
3.1 PHOTOCHEMICAL OXIDANTS
The effects of photochemical oxidants on grassland ecosystems have
received scant attention in the scientific literature. The photochemical
oxidant complex has long been associated with large urban areas with high
concentrations of emissions of N0X and other precursors of photochemical
oxidants. Only recently has it been noted that photochemical oxidants
undergo long-range transport in continental air masses (Fankhauser 1976;
Cleveland and Graedel 1979; Worth and Ripperton 1980). Furthermore, the
quantity of oxidant precursors (nitrogen oxides and hydrocarbons) emitted
from anthropogenic sources located in grassland areas is increasing over
time (USEPA 1978).
Oxidant concentrations vary significantly from one location to ano-
ther in response to changes in atmospheric stability and the intensity of
solar radiation. Temporal variations in a given location tend to be more
consistent. On an annual basis, significantly greater oxidant concentra-
tions are observed in summer than in winter; diurnally, lowest values are
usually recorded at night while peak values occur at mid-day. Ozone
(O3) levels in grasslands near Salt Lake Valley commonly average 0.06
ppm over one-hour periods, yet peak values of 0.15 ppm O3, sufficient to
produce visible injury in sensitive plants, have also been recorded; acute
exposures typically occur at concentrations above 0.15 ppm O3 while
chronic exposures stem from lower levels in the range of 0.06 to 0.15 ppm
O^ (Treshow and Stewart 1973).
3.1.1 Plant Effects
Several researchers have documented the effects of acute exposures
of ozone on native grassland vegetation. Treshow and Stewart (1973)
reported that visible responses of leaf-tip chlorosis combined with chlor-
16
-------
otic flecking occurred in native grasses and sedges after experimental
fumigations of 0.15-0.4 ppm O3. Heck and Anderson (1980) found visible
effects from acute ozone exposures to include:
scattered necrotic flecking on both leaf surfaces;
occasional necrotic streaking; and
interveinal chlorosis.
Tingey et aK (1978) observed that these characteristic injuries tend to
concentrate in the region between the leaf tip and the bend in the leaf.
Visible injuries have been induced in rice plants from exposures in the
range of 0.1-0.15 ppm O3; reddish-brown flecks, bronzing, and chlorosis
of leaf blades were typical visible symptoms (Nakamura 1979). Acute ozone
exposures have been shown to produce symptoms of chlorosis in most forbs
and shrubs while some (e.g., Rumex and Veronica sp.) exhibited bronzing
of the leaf surface (Treshow and Stewart 1973). Elevated ozone exposures
are also known to cause premature leaf senescence and abscission in rice
(Nakamura 1979) and a variety of broad-leaved plant species (Pell 1974).
Price and Treshow (1972) exposed individual grassland species for
four hours to ozone concentrations ranging from 0.05 to 0.35 ppm to deter-
mine levels causing visible injury. The lowest ozone exposures producing
visible injury (sensitivity threshold) are presented in Table 4 for six
species of native grasses along with daily exposures at which visible in-
juries persist (acute threshold). Treshow and Stewart (1973) exposed sev-
eral grassland species to average ozone concentrations of 0.15 to 0.4 ppm
for two hours; Bromus tectorum, a widespread dominant of importance as
soil cover, was injured by single two-hour exposures of 0.15 ppm 0-3.
Bromus and Poa species, however, may complete their growth cycles before
oxidant levels reach their usual mid-summer peak (Treshow and Stewart
1973).
Of forty-eight annual and perennial grassland forbs studied by Tre-
show and Stewart (1973), over half exhibited visible injury from two-hour
exposures to 0.3 ppm O3 or less. Concentration thresholds for visible
injury to selected forbs are presented in Table 5. Of seventy grass,
forb, shrub, and tree species studied in a grassland-tree association,
forty-four were injured by two-hour exposures of 0.3 ppm O3 or less
while only five species remained unaffected by 0.4 ppm O3 (Treshow and
Stewart 1973).
Responses of turfgrasses to acute ozone exposures are widely varied,
yet warm-season species are found to be more tolerant than cool-season
species, especially at elevated exposure levels (0.4 ppm O3) (Richards
et aiK 1980; Youngner and Nudge 1980). Nine to fourteen day-old seedlings
were more susceptible to injury from a given concentration than mature
plants, although the susceptibility of a few turfgrasses was shown to
17
-------
Table 4. Concentration thresholds for
visible ozone injury to native grasses.
Native Grass Species
Sensitivity
Threshold3
(ppm)
Acute
Threshold13
(ppm)
Bromus tectorum
Agropyron can mum
Bromus carinatus
Bromus polyanthus
Poa bulbosa
Agropyron spicatum
(cheatgrass)
(wheat grass)
(cheatgrass)
(cheatgrass)
(bluegrass)
(bluebunch
wheatgrass)
0.14-0.15
0.15-0.18
0.18-0.20
0.23-0.25
0.23-0.25
0.30-0.32
0.15-0.18
0.20-0.22
0.22-0.24
0.25-0.27
0.27-0.30
0.32-0.34
Concentration range required to produce visible injury from a single
four-hour exposure
^Concentration range in which visible injury persists under four-hour
daily exposures
(Adapted from Price and Treshow 1972)
Table 5. Concentration thresholds for
visible ozone injury to grassland forbs.
Injury Threshold3
Species (ppm)
Annuals
» Polygonum douglasii (smartweed) 0.25
Perennials
Ambrosia psilostachya (ragweed) 0.40
Cirsium arvense (thistle) 0.40
Helianthus annuus (sunflower) 0.30
Vicia americana (vetch) 0.25
» Taraxacum officinale (dandelion) 0.25
Rumex cri'spus (curlydock) 0.25
> Aster engelmanni (aster) 0.15
Concentration required to produce visible injury from a single two-hour
exposure
(Adapted from Treshow and Stewart 1973)
18
-------
increase with physiological development. An exposure regime of 0.1 ppm
O3 for 7 hours per day caused approximately twice as much visible injury
as a 3.5 hour per day treatment in bluegrass cultivars (Richards et al.
1980).
The subtle effects of chronic oxidant exposures on plants generally
involve changes in photosynthesis, respiration, reproduction, and carbon
allocation. Chronic ozone exposures can cause significant reductions in
plant growth and quality even in the absence of visible effects. Ozone is
known to disrupt the bioenergetic process of plant cells by affecting oxi-
dative phosphorylation pathways in chloroplasts and mitochondria; photo-
synthesis, electron transport, and adenosine triphosphate (ATP) production
are all reduced while plant respiration is increased (Pell 1974). Ulti-
mately, plant productivity and reproductive capacity may be diminished.
The potential long-term effects of chronic leaf injury in grassland
species have been investigated by Price and Treshow (1972). Native
grasses were fumigated over their entire life cycle for five days per week
through the use of a four-hour exposure regime simulating conditions of
elevated oxidant levels (0.15-0.18 ppm O3 for the first hour, 0.28-0.33
ppm in the second and third hours, and 0.18-0.20 ppm in the fourth hour).
The productivity index, or growth potential, of four grasses (Bromus tec-
torum, B^ polyanthus, B. carinatus, and Poa bulbosa) ranged from 70-8&
percent of control values; the productivity index of Aqropyron caninum was
44 percent of control growth capacity, while that of A. spicatum was only
17 percent (i.e., 83 percent reduction in growth potential). Biomass re-
ductions were greatest in B. tectorum (80 percent), least in B. polyanthus
(42 percent) and averaged about 50 percent in other species, relative to
controls.
Decreases in both the number and mass of reproductive structures were
observed in most species studied by Price and Treshow (1972). Reproduc-
tion of B. tectorum and ^ carinatus was completely inhibited while that
of Aqropyron species was reduced by 90 percent in comparison with control
plants. Price and Treshow attributed reduced plant growth to decreased
photosynthetic activity while diminished reproductive potential was caused
by declining energy reserves in the plant. In areas with short growing
seasons, effects induced by reductions in energy storage may be particu-
larly severe.
3.1.2 Animal Effects
Field observations of direct oxidant effects on grassland wildlife
are absent from the scientific literature. Nevertheless, the extrapola-
tion of results obtained in experiments on laboratory animals may lend
insight into possible direct effects of oxidants on wildlife (Lillie 1970;
Kavet and Brain 1974; Newman 1975, 1980; National Research Council 1977).
These studies indicate that oxidants are potential eye and lung irritants
in terrestrial vertebrates.
19
-------
Chronic exposures to ozone are known to diminish pulmonary function
in laboratory animals and predispose them to infection through the sup-
pression of lung macrophages (Kavet and Brain 1974). While the develop-
ment of ozone tolerance has been demonstrated in localized areas of the
lung, immunity to infection cannot be similarly acquired. In addition,
chromosome breakage has been observed in the lung cells of laboratory mice
exposed to 0.2 ppm O3 for five hours (National Research Council 1977).
Chronic ozone exposure may impair the visual and olfactory senses of
animals (Taylor 1973; National Research Council 1977). The effect of this
could be to increase the likelihood of predation for a particular species,
or to otherwise reduce the competitive advantages animals maintain in
their inter- and intra-specific relationships.
Recent studies have demonstrated a genetic basis for tolerance to
acute ozone exposures in wild populations of deer mice from oxidant pol-
luted environments of California (Richkind and Hacker 1980). At ozone
levels of 6.6 ppm for twelve hours, complete mortality was observed in
populations of California deer mice (Peromyscus callifornicus) from low
pollution areas, whereas 56 percent of the populations from polluted areas
survived these exposures. First-generation progeny of the two populations
responded similarly, indicating the genetic inheritance of ozone resis-
tance in chronically-exposed deer mice. Further experiments suggested
genetic variability within the population to be an important factor in the
development of tolerance in individuals.
3.1.3 Ecosystem Effects
The potential ecosystem effects of photochemical oxidants in grass-
lands relate primarily to the differential susceptibility of plant spe-
cies. Oxidant-induced reductions in growth, reproduction, and energy
storage can adversely affect the competitive ability of sensitive plants
and their dominance status within natural communities. For example,
Bennett and Runeckles (1977) showed that the dry weight yield and leaf
area of crimson clover (Trifolium incarnatum) was reduced relative to an-
nual ryegrass (Lolium multiflorum) in cultivated mixtures exposed to 0.09
ppm O3. Similarly, Kochhar et al. (1980) found fescue seedlings to in-
crease in abundance relative to clover following ozone exposure, despite
growth reductions in both species; leachate from ozone-exposed fescue
leaves was shown to inhibit nodulation in clover while the leachate of
unexposed leaves did not.
Grassland ecosystems may be vulnerable to such effects since dominant
species have been reported to be among the most sensitive plants in this
biome (Treshow and Stewart 1973). The demise of these dominants can lead
to alterations in community structure and composition, and to a variety of
functional changes. Although field studies of ecosystem-level impacts in
grasslands are lacking, oxidant-induced reductions of plant density and
diversity have been detailed by Westman (1979) for sagebrush scrublands of
20
-------
the grassland-desert ecotone. In this study, oxidant air pollution was
the variable among 45 different habitat factors that best explained ob-
served effects.
Both visible and subtle plant injuries could cause changes in commun-
ity productivity, competitive interactions, and species composition.
Where dominant plants are most sensitive, marked reductions in the primary
productivity of the ecosystem are likely. Plant cover may decline signif-
icantly if tolerant species are unavailable to occupy niches vacated by
sensitive species. Further effects may be anticipated if inhibited repro-
duction leads to a loss of plant control over microclimate and increased
evaporation or erosion occurs. As a result of reduced growth, productiv-
ity, and cover, the carrying capacity of lands may be decreased for wild-
life and grazing animals alike. The precise effects of oxidants on ani-
mals cannot be predicted. However, wildlife may be adversely affected
through loss of food, moisture and nesting cover, general reductions in
the quality of habitat, or alterations in prey-predator relationships.
Several other potential impacts of oxidant air pollution in the
grassland ecosystem are possible. Excessive accumulations of leaf litter
may result from necrotic injury and accelerated leaf senescence. Nutrient
cycling in the community as well as energy transfers between producer and
consumer trophic levels can be disrupted if large amounts of nutrients
remain bound in undecomposed biomass. Resulting declines in plant vigor
may adversely affect beneficial populations of soil and root organisms,
causing further reductions in decomposition, mineralization, and nutrient-
fixation processes. Plant pathogens and parasites can be similarly af-
fected although the outcome of such changes my be highly variable and
remains uncertain in grasslands.
3.2 PARTICULATES
Atmospheric particulates of anthropogenic origin can elicit a variety
of responses in grassland ecosystems, although the precise nature of many
effects remains unknown. They may affect grassland flora by chronic depo-
sition on plant surfaces or accumulation in soils. Fauna may experience
acute or chronic effects through inhalation, ingestion and subsequent bio-
concentration of the chemicals associated with particulates. Wildlife
populations may be indirectly affected by particulate emissions through
alterations in the quality of habitat and food supplies.
In addition, particulates can adsorb and transport photochemical oxi-
dants, hydrocarbons, and sulfur and nitrogen oxides. A large array of
trace elements have been found preferentially concentrated on the surfaces
of fine particles that pass through emission control devices (Linton et
al. 1976). Because these fine particles remain suspended in the atmos-
phere for up to several days, they can be transported great distances.
21
-------
Elevated exposures occur primarily near point and line sources, such
as smelters, power plants, industrial boilers and roads. The direct and
indirect effects of particulates from power plants have been reviewed by
Dvorak ^t _al_. (1978) in considerable detail. Gough et _al_. (1979) review
the potential toxicity of trace elements on plants and animals alike.
Little scientific information exists on the effects of particulates on
species native to grasslands.
3.2.1 Plant Effects
Although little is known of the effects of specific trace elements on
grassland vegetation, in general, sufficient exposure can be expected to
produce certain visible manifestations of toxicity, such as chlorosis,
necrosis, discoloration, and stunting or deformation of plant parts
(Dvorak et 1978). A wide variety of particulate-induced effects has
been observed in forest ecosystems, and these are detailed in a companion
report of this series.
Particulate deposition in terrestrial ecosystems is reported to clog
the stomata of tree leaves (Ricks and Williams 1974). This action can al-
ter diffusion rates of CO2 and water vapor between the atmosphere and
internal leaf spaces. On the other hand, excessive particulate deposition
may prevent stomates from closing, and in this way enhance SO2 uptake
rates in woody plants (Ricks and Williams 1974).
In extrapolating information from forest species to grassland spe-
cies, some inherent differences between the two ecosystems must be con-
sidered. Particle deposition rates are one of the more striking differ-
ences between these ecosystems. Little and Martin (1974) observed part-
icle deposition rates to be a function of community microtopography; depo-
sition occurred at a higher rate in woodlots, where trees tend to disrupt
wind patterns, than in fields, where the surface is less broken. Further-
more, particles deposited on a grassland site are more susceptible to at-
mospheric re-entrainment due to the lower humidity and precipitation char-
acterizing grasslands, and the greater circulations of wind at the soil
surface. Therefore, the effects of particulates observed by Ricks and
Williams (1974) in woody species might be less likely to occur with com-
parable severity in a grassland community.
The deposition of particulates on plant and soil surfaces can also
introduce potentially toxic trace elements to biota. While some of these
(e.g., zinc, copper, manganese, bolybdenum, boron) are essential to
healthy p7ant growth and development, they may be toxic at excessive
concentrations. The non-essential trace elements (e.g., cadmium, lead,
selenium, nickel) tend to bioaccumulate to varying degrees in grassland
species (Dvorak et al. 1978). Table 6 shows measured concentrations of
three trace metaTs Tn the soil and flora of a grassland community located
near coal-fired power plants in Arizona. For comparison, Table 7 shows
estimated concentrations of six trace elements in bluebunch wheatgrass
(Agropyron spicatum) growing upwind and downwind from an industrial facil-
ity in Idaho.
22
-------
Table 6. Heavy metal concentrations in soils and vegetation
near coal-fired power plants in the Kaiparowitz basin of Arizona.
Metal Concentrations (ppm)
Compartment
Cadmium
Chromium
Zinc
SOIL
0.06
0.54
1.37
VEGETATION
Compositae
Gutierrezia sp. (snakeweed)
0.29
2.57
17.13
Graminae
Agropyron sp. (wheatqrass)
Bouteloua gracilis (blue grama)
Bromus tectorum (cheatqrass)
Oryzopsis hymenoides (Indian rice grass),
Stipa comata (needle-and-thread grass)
0.54
0.86
0.86
0.25
0.03
5.04
5.14
6.43
4.32
0.82
34.44
14.62
31.45
10.19
25.89
(Adapted from Northern Arizona University 1979)
Table 7. Estimated concentrations of selected trace elements
in bluebunch wheatgrass (Agropyron spicatum) at a distance of
three km from a phosphate-processing facility.
Plant Tissue Concentrations5
Trace Element Upwind Downwind
Cadmium 18 78
Fluorine 29b 45b
Selenium 0.3b 0.8°
Uranium 2 5
Vanadium 77 170
Zinc 390 890
appm as ash
bppm dry weight
(Adapted from Severson and Gough 1979)
23
-------
The primary pathway for absorption of most trace elements by plants
is through the roots. As particulate substances tend to accumulate within
the top few centimeters of soil, plants with shallow roots are exposed to
greater concentrations than deep-rooting species. A number of factors de-
termine soil retention capacities and subsequent trace element availabil-
ity to plants. Of these, soil structure, texture, and cation exchange
capacity (CEC) are perhaps the most important. Generally, soils that have
large amounts of organic matter also have a high CEC, hence the capacity
to sorb large quantities of atmospheric particulates. Sandy soils with
low amounts of organic matter and a correspondingly low CEC do not retain
trace elements as well as richer soils (Dvorak et al_. 1978). Grassland
soils typically have a high organic matter content and CEC; therefore they
may be expected to retain a larger proportion of deposited trace elements
than soils of other ecosystems.
Other important factors determining the mechanisms and amounts of
particulate uptake include (Dvorak et al_. 1978):
the chemical properties of deposited trace elements;
the inherent accumulation capacity of specific grassland
flora; and
t the nutritional status of the plant.
Due to the number of factors involved in plant uptake, accumulation rates
and mechanisms relative to a given trace element vary greatly from spe-
cies to species and from place to place. The propensity of a given plant
species to accumulate one or several of the different trace elements
is also highly variable.
Fluoride accumulation and phytotoxicity have both been documented in
grassland flora. Foliar applications are significantly more toxic than
fluoride taken up by roots (Severson and Gough 1979). Subtle effects of
reduced photosynthesis are compounded by visible injuries that commonly
include necrosis of leaf tips and margins (Carlson and Dewey 1971). Vis-
ible symptoms of toxicity usually appear only after weeks or months of
chronic exposure and uptake; concentration thresholds producing pathologi-
cal symptoms are highly variable among plant species. Levels as high as
775 ppm have been reported in living grasses near a fluoride source in
Montana, however tissue concentrations in adjacent herbs, shrubs, and con-
ifers were much higher (Carlson and Dewey 1971). Grasses tend to in-
crease in abundance in response to fluoride exposures due to reduced
competition from more sensitive broad-leaved plants (Treshow 1968).
Lichen species are well-known accumulators of trace elements in at-
mospheric deposition (Little and Martin 1974). The following substances
were documented to decrease in concentration in tissues of Parmelia chlor-
ochroa with increasing distance from a coal-fired power plait! aluminum,
copper, chromium, fluorine, gallium, lithium, magnesium, manganese, sel-
enium, strontium, titanium, uranium, and yttrium (Gough and Erdman 1977).
24
-------
Determinations of ash content indicated that the ash composition of this
lichen reflected accumulations of elements emitted by the power plant;
scanning electron microscopy demonstrated the presence of fly-ash micro-
spheres adsorbed within the thallus. Within 8 kilometers of the plant,
only selenium persisted in concentrations above baseline levels in similar
lichens of the area.
Due to an expected increase in the development and use of fossil
energy reserves in the western U.S., the potential exists for the release
of large amounts of particulates into the grassland ecosystem. In order
to foresee the potential impacts of increased emissions, research is
needed to examine possible effects of specific trace elements on the
characteristic vegetation of grassland communities.
3.2.2 Animal Effects
Acute exposures to atmospheric particulates, particularly fluorides,
have been associated in several studies with severe disease or mortality
in livestock and wildlife populations (Newman 1975, 1980). Symptoms of
fluorosis, a disorder caused by rapid fluoride accumulation which leads to
degradation of the bones and teeth, have been documented in exposed white-
tailed, black-tailed, and wild mule deer populations of the western United
States (Kay ^t al. 1975; Newman and Yu 1976). However, as increased ef-
forts to controT~particulate emissions reduce the incidence of acute pol-
lution, research efforts are focused more and more on the effects of
chronic low-level particulate pollution in wildlife populations.
Whether ingested or inhaled, contaminants from particulate deposition
are often accumulated in animal tissues. Substances ranging from fluor-
ides and trace metals to pesticides and other synthetic compounds may be
concentrated to varying degrees in different body organs. Organisms at
higher levels of the trophic chain may be subject to excessive trace ele-
ment accumulation through the biomagnification of contaminants accumulated
in prey organisms. For example, atmospheric lead has been shown to be
disproportionately concentrated in predators of insects near roadways
(Giles et al. 1973). As major links in the trophic chain, insects of
varying~H"i7e habits may serve as repositories for substances that are sub-
sequently transferred to higher trophic levels (Price jita2. 1974).
In the forest and grassland ecotone of Montana, trace metal accumula-
tion in kidneys and other organs of mice, rabbits and Columbian ground
squirrels have been attributed to lead and cadmium deposition from smelter
operations (Gordon 1969). In the vicinity of a phosphate-processing plant
in Idaho, observed plant concentrations of cadmium and fluoride (Table 8)
were sufficient to cause accumulation of these substances in grazing ani-
mals. Amphibians from the vicinity of a zinc smelter have been reported
to concentrate lead to levels 60.8 times greater than amphibians in a con-
trol area, and cadmium by a factor of 11.5-15.3 (Dmowski and Karolewski
1979). Insectivorous birds of this area were shown to accumulate greater
amounts of lead in the liver than granivorous or omnivorous species.
25
-------
Observations in other ecosystems have shown that small mammals and
invertebrates also accumulate mercury in the vicinity of point sources
(Bull et al. 1977) and lead, cadmium, and zinc near roadways (Quarles et
al. 1973";~Van Hook 1974; Goldsmith and Scanlon 1977; Ireland 1979; ScanTon
1979). In general, biologically essential trace elements (e.g., Co, Cr,
Cu, Mn, Mo) tend not to accumulate in animals as their levels in body tis-
sues can be properly maintained by mechanisms of physiological regulation
or excretion (Schlesinger and Potter 1974). Cadmium poses a significant
threat since it is not excreted from animal bodies. Selenium may become a
more common grassland toxicant as it is a plentiful constituent of western
soils (Dvorak et _al_- 1978).
Trace element accumulation in small mammals largely depends on vari-
ables related to trophic status or position in the food web. Quarles et
al. (1974) found insectivores to accumulate lead at greater rates than
Tferbivores, and granivores to accumulate the least, however other charac-
teristics besides diet determine the degree of accumulation. Among small
mammals, these include metabolic rate, life span, mobility, and the size
and location of the home range relative to sources (Gordon 1969; Quarles
et al. 1974).
Many insect species, including the pollinators, are susceptible to
the bioaccumulation of chemicals associated with deposited airborne par-
ticulates; accumulation is also observed in herbivorous and predatory in-
sects in the vicinity of point and line sources (Price et al_. 1974;
Quarles et aK 1974; Bromenshenk 1975). Pollinators are particularly sus-
ceptible to fluoride accumulation (Lillie 1970; Dewey 1973) as their daily
pollen-gathering activities take them over larger areas than ground-dwell-
ing insects. Soil invertebrates, on the other hand, are able to concen-
trate high levels of available trace metals from polluted soils (Van Hook
1974; Ireland 1979).
Biological monitoring undertaken near coal-fired power plants in Col-
strip, Montana has demonstrated fluoride levels in honey bees 2 to 17
times higher than those found prior to plant operation (Bromenshenk 1979a,
1980a,b). From baseline levels of 5-10 ppm, fluoride concentrations in
bees and pollen were observed to average 154 ppm and 4.3 ppm, respec-
tively, near the plant following four years of operation. Chronic expo-
sures are frequent and large amounts of contaminated pollen may be
collected daily. Measurements of fluoride concentrations in grasshoppers
and bumblebees from the Colstrip area also show the tendency for pollina-
tors to concentrate this element (Table 8).
The accumulation of airborne particulate matter in the lungs of the
eastern meadowlark is another documented biological effect of power plant
emissions near Colstrip, Montana. While lung tissue irritation is the
only confirmed physical effect, observations have suggested that a
gradual migration of the meadowlark population away from emission sources
has taken place (Kern et li» 1980). Particulate burdens in avian lungs
are nevertheless believed to be of practical biomonitoring application
26
-------
Table 8. Atmospheric fluoride accumulations
in insects of differing trophic status.
Tissue Fluoride Concentrations (ppm dry weight)
Organisms Background Near Source
Herbivore
Grasshopper
(Melanoplus sp.) 7.5 31.0
Pol 1inator
Honey bee
(Apis mellifera) 10.5 221.0
Bumble bee
(Bombus sp.) 7.5 406.0
(Adapted from Carlson and Dewey 1971)
(McArn et al. 1974); counts of particulate-laden lung macrophages have
been shown to increase over time and to be inversely related to distance
from the Colstrip power plants (Kern et a/L 1980). The long-term effects
of such accumulations on pulmonary functions are not known.
In sum, very little information is to be found concerning the effects
of trace element emissions on grassland wildlife. This lack of informa-
tion has be^n recognized by several researchers. Among them, Kern and
Lewis (1980) have collected baseline data on the histology of various or-
gans of the deer mouse, Peromyscus maniculatus. In future studies this
information may be compared with data obtained from individuals exposed
to anthropogenic emissions to gain information on the accumulation and
toxicity of various trace elements in grassland fauna.
3.2.3 Ecosystem Effects
At the ecosystem level of biological organizaton, impacts of particu-
late deposition in grasslands stem primarily from alterations in abiotic
components. Surface soils in particular are susceptible to chronic metal
and trace element accumulation near roads (Milberg et al. 1980) and point
sources (Rutherford and Bray 1979). Perennial specvesTioaccumulating
these substances tend to enhance metal levels in soils through cycling of
the decomposition products of unharvested biomass (Dvorak et al_. 1978).
By contrast, harvested annuals of agroecosystems contribute much less
contaminated biomass to soils. In areas of sparse vegetation, enhanced
susceptibility to wind and water erosion can aid in the dispersal of soil
particulate accumulations (Dvorak et _a2. 1978).
27
-------
Soil acidification is an abiotic impact known to occur near point
sources of trace metals and results from emissions of sulfur oxides (Wood
and Nash 1976; Dawson and Nash 1980). In Alberta, Canada, prairie soils
have been found to undergo a pH reduction of one unit every 10 to 20 years
in the vicinity of metal smelters (Nyborg et 1976). Dawson and Nash
(1980) reported soil surface pH near a smelter in Arizona to be two units
lower than in unaffected areas eight miles away. Copper toxicity in com-
bination with low soil pH was found to limit the establishment and growth
of grasses and other herbaceous perennials near the smelter (Wood and Nash
1976). The density of various groups of plant species increased with
distance from the source, following a pattern of declining soil acidity
and exponential reductions in soil concentrations of Cu, Cd, Fe, Pb, and
Zn. Successional rollback to a modified pioneer community was the primary
effect of air pollutants near the smelter. These changes may persist due
to depressed decomposition processes in soils of low pH.
Particulate accumulations can also increase the susceptibility of
soils to nutrient and mineral leaching. Disruptions of nutrient cycling
and energy flow, storage, and transfer through established trophic chains
may result. Increased rates of nutrient loss from terrestrial ecosystems
have thus been postulated as a sensitive indicator of the ecosystem ef-
fects of atmospheric deposition (O'Neill et al. 1977). Accelerated losses
of both calcium and nitrate have been measured in soils treated with
arsenic (Jackson jst _al_. 1977). Table 9 compares arsenic-induced nutrient
losses in forest and grassland soils. Grasslands are shown to have low
susceptibility to this leaching effect. This is largely due to their much
greater cation exchange capacity (CEC), organic matter content, and resul-
tant capacity to adsorb cations. However, long-term accumulations may
exhaust this protection and result in the release of pollutant toxins that
were formerly unavailable to biota (Dvorak £t _al_. 1978).
Atmospheric particulates have the potential to alter the abiotic
environment of grasslands in other ways. They can serve as cloud conden-
sation nuclei, possibly leading to modification of precipitation patterns
over large areas (Marwitz et 1975; Abshire ^t al. 1978; Lewis et al.
1978). Due to the delicate water balance in grasslands, any deviation in
rainfall patterns could result in changes to plant communities, with
potential ramifications for the entire ecosystem.
The direct biotic effects of particulates on plant life may also lead
to ecosystem disruptions. The differential accumulation of these sub-
stances by individual species can contribute to biomagnification in con-
sumer food chains. Certain species, for example, the pollinators and in-
sectivores, may be selectively contaminated, resulting in reductions or
migrations of local populations. The removal of sensitive species from
the community can reduce or eliminate sources of food and habitat for
wildlife; the nature of the effect depends on the specific habitat re-
quirements of each species as well as the importance of sensitive vegeta-
tion to the maintenance of ecosystem integrity.
28
-------
Table 9. Comparison of nutrient loss in
grassland and forest soils amended with arsenic.
Arsenic Treatment (uq/cm?)
0
10
100
Nutrient
Grassland
Forest
Grassland
Forest
Grassland
Forest
Calcium
(ug/ml)
10.6
20.3
12.5
24.7
11.3
29.4
Nitrate-
nitrogen
(ug/i)
20.8
32.4
23.3
48.9
39.9
132.2
(Adapted from Jackson et al. 1977}
3.3 ACIOIFYING AIR POLLUTANTS
The acidifying air pollutants include the primary pollutants, SO2
and NOj, and secondary sulfates and nitrates produced by transformations
of the primary pollutants as they are carried through the atmosphere.
Acidifying air pollutants were once thoughout to be limited to urban areas
and areas near large point sources. It is now recognized, however, that
these pollutants are carried great distances and can affect areas remote
from their sources (Altshuller and McBean 1980).
The secondary acidifying air pollutants are deposited through wet and
dry removal processes collectively referred to as acid deposition (ITFAP
1981). Although the potential effects of the primary gaseous pollutants
are a source of concern in grasslands, acid deposition is not currently
felt to pose an immediate threat to this biome. As shown in Figure 2,
the majority of North American grassland receives precipitation of pH 5.6
or greater. Cooper et al. (1976) reported precipitation in central Texas
to average pH 6.6. ATkaTine rainfall pH is undoubtedly due to a combina-
tion of low ambient levels of atmospheric acids and the neutralizing
effect of alkaline dusts on acids present in ambient air. Some parts
of the biome, notably the Palouse Prairie of the northwest, the Central
Valley of California, mountainous areas of Colorado, southeast Texas, and
states bordering the Mississippi, receive slightly acidic precipitation
of mean annual pH 4.8-5.5 (Figure 2). Limited precipitation sampling in
an industrializing area of western North Dakota yielded a mean pH value
of 4.51 and a range of pH 4.02-5.27 between August and November of 1980
(Angelo and Anderson 1981). Areas of the grassland biome subject to acid
precipitation are generally underlain by highly alkaline soils and soil
29
-------
Figure 2.
Weighted mean pH of precipitation In the continental United States (1976-1979).
(From Wisniewski and Keitz 1982)
-------
parent materials. For this reason, terrestrial and aquatic habitats are
thought to remain unaffected by increased hydrogen ion loadings.
Exceptions include areas of thin soils with rocky outcrops, and habitats
underlain by a sand substrate.
The impacts on grasslands of sulfur oxides have been more thoroughly
investigated than those of nitrogen oxides, photochemical oxidants, and
particulates. This is largely due to a long-term program of range re-
source monitoring in the vicinity of two coal-fired power plants near Col-
strip in southeastern Montana (Preston and Lewis 1978; Preston and Gullett
1979; Preston and O'Guinn 1980; Preston et £]_. 1980). Underway since
1978, this effort comprises:
characterization of background conditions prior to operation of
the power plants, as reviewed by Munshower (1975, 1978) and de-
scribed in detail by Lewis and Lefohn (1976), and Lewis et al.
(1976);
continual monitoring of range resources following the construction
and operation of the two 350 megawatt facilities; and
study of SO? exposures in field plots (Zonal Air Pollution Sys-
tems or ZAPS) and the laboratory to examine specific mechanisms of
pollutant injury in grassland biota (Lee and Lewis 1978; Lee et
al. 1978).
The Colstrip study has integrated data from a number of scientific disci-
plines and, upon completion, will provide an ecosystem-wide characteriza-
tion of the chronic air pollution impacts of coal-fired electric genera-
tion in grasslands.
For purposes of comparison, Altshuller (1973) has suggested a thresh-
old level of 5 ug/m3 (0.0019 ppm) SO2 above which ambient air in areas
far from point sources is thought to be influenced by long-range trans-
port. In the vicinity of Colstrip, Montana, ambient SOg levels have in-
creased from a background concentration of 2.3 ug/m3 (0.0009 ppm) in
1974 to a level of 4.6 ug/m3 (0.0018 ppm) in 1978 (Preston and O'Guinn
1980). Thus, in agreement with patterns! of sulfate transport in North
America, it would appear that most grasslands, with the possible exception
of mid-western ecotones, are not yet subject to Impact from atmospheric
acids transported long distances. Moreoever, the dry deposition of SOg
in grasslands 1s estimated to be two to three orders of magnitude less
than that in a forest canopy (Shreffler 1978). Nevertheless, increased
emissions of sulfur and nitrogen oxides have been forecast for the western
United States (USEPA 1978) and the acidifying effects of these pollutants
may become more widespread in the soils and biota of grasslands.
31
-------
3.3.1 Plant Effects
Many studies have been performed on the effects of acute exposures to
acidifying pollutants, but few of these investigate effects on native
grassland species. Although acute exposures are rarely encountered in
native grasslands, because sources are small and dispersed, these studies
nevertheless may provide useful information concerning injury symptoms and
the relative sensitivities of grassland species.
Tingey jet jah (1978) studied acute, four-hour exposures of species
native to the Northern Great Plains under varying concentrations (0.5 to
4.0 ppm) of SO^, NO?, and SO? and NO? mixtures. All species were
injured following exposure to 2.0 ppm SO?. Injury was observed as
lesions, ranging from light tan to ivory in color, and interveinal streaks
of necrotic tissue. Injury was confined to the leaf tip in young leaves
while older leaves exhibited injury at the bend of the leaf. Hill et aj[.
(1974) sought to determine concentrations of SO? which produces visTFle
injury in grassland plant species; results of tneir work are shown in
Table 10. Indian rice grass (Oryzopsis hymenoides) is shown to be the
most susceptible of this group to visible damage from acute SO? expo-
sures.
Studies of acute exposures also showed nitrogen oxides to be phyto-
toxic, but at concentrations much greater than those required for SO?
injury. Following a four-hour exposure at 4.0 ppm NO?, the only two
species to develop significant injury were blue grama (Bouteloua gracilis)
and prairie junegrass (Koeleria cristata) (Tingey et al. 1978). Injuries
caused by NO? were found to be similar to those resulting from SO?
exposure.
There is little evidence of synergistic effects of these two gases
which are often emitted from the same anthropogenic source. Hill et al.
(1974) fumigated plants with an N0?:S0? ratio of 0.28, found to be
characteristic of levels downwind from a large coal-fired power plant;
concentrations of SO? ranged from 0.5 to 11 ppm. No evidence of syner-
gism was detected at this ratio. Furthermore, Tingey jet al. (1978) re-
ported that mixtures of SO? and NO? did not increase the level of in-
jury over that caused by SO? alone. Studies of British grassland spe-
cies, however, have suggested that long-term fumigations of SO? and
NO combined may be somewhat more toxic than fumigations of the indi-
vidual pollutants (Ashenden 1979).
Studies of chronic exposures, such as those in progress at Colstrip,
are promising tools for assessing the effects of air pollutants in grass-
lands. They show that low-level exposures produce changes in plant physi-
ological or biochemical processes, leading to chronic injuries, which are
much more difficult to detect than injuries resulting from acute expo-
sures. The only consistent visible injury resulting from chronic SO?
exposure is premature leaf senescence (Bleasdale 1973; Heitschmidt et aj_.
1978; Dodd et al. 1979; Rice et _al. 1979; Davies 1980).
32
-------
Table 10. Percentage of total leaf area injured by different con-
centrations of SO2 in two-hour field fumigation studies of native
grassland vegetation.
Average percent injury from SO?
Plant Species 0.5 ppm 1 ppm 2 ppm 4 ppm 6 ppm 10 ppm
Aqropyron caninum - - 0 0 0 78
(wneatgrass)
Aqropyron desertorum - - 20
(crested wheatgrass)
Ambrosia sp. - 0 0 Oil
(ragweec!)
Aster chilensis - 0 0 1 5 -
[aster)
Bouteloua barbata - 0 0 0 0 0
(six-weeks grama
grass)
Bromus gracilis - - 0
(blue grama grass)
Bromus ciliatus - 0 0 0 13 96
(fringed brome)
Bromus inermis - - - 0.6
(smooth brome)
Bromus tectorum
(cheatgrass)
Cirsium undulatum
(thistle)
Gutierrezia sarothrae
(snakeweed")
Hedysarum boreale
(sweet vetch)
Oryzopsis hymenoides
(Ind ian ricegrass)
Poa pratensis
["Kentucky bluegrass)
Stipa occidental is
fneedlegrass)
Viola sp.
[VToTa)
-
-
0
0
0
10
-
0
-
6
14
-
-
-
0
0
21
78
-
-
0
0
40
75
0.2
2
2
17
29
90
-
-
0
0
7
-
-
-
-
-
0
73
25
_
(Adapted from Hill et aj_. 1974)
33
-------
When present in low ambient concentrations, SO? can benefit plant
growth, especially in sulfur-deficient ecosystems (Cowling et _al_. 1973;
Ziegler 1975; Cowling and Lockyer 1976). Within the leaf, SO2 dissolves
to form bisulfate which is oxidized into sulfate, a plant nutrient. An-
thropogenic SO2 may be metabolized preferentially by plants over other
forms of sulfur naturally available in the environment (Garsed and Read
1977). Moreover, if conditions favor stomatal opening, entry of ambient
SO2 will increase pollutant conductance and sustain chronic injury as
long as SO2 loadings do not exceed plant detoxification capacities (Thor
1980). If the SO2 flux into the leaf is greater than the rate of its
conversion and use, accumulation in plant tissues will occur (Schwartz et
al. 1978; Dodd et aj_. 1979; Riceet aj_. 1979, 1980; Lauenroth et al.
1980). Sulfur accumulation in western wheatgrass has been shown to in-
crease linearly in response to either augmented SO2 levels or exposure
times; accumulations are greatest in older tissues (Lauenroth et al.
1980).
Excess sulfur accumulation from chronic exposures to SO2 has been
reported to reduce the chlorophyll content of individual leaves (Lauenroth
and Dodd 1980a,b; Lauenroth and Heasley 1980). Reduction of chlorophyll
levels in leaves of western wheatgrass has been suggested as an indicator
of chronic SO2 exposure (Lauenroth and Dodd 1980a). Other species, how-
ever, demonstrate varying responses in chlorophyll levels, reducing the
reliability of this parameter as an indicator of subtle SO2 injury
(Lauenroth and Dodd 1980b).
Depressed chlorophyll levels have been shown in some cases to lead to
reduced energy capture and photosynthetic production by leaves. Figure 3
depicts the results of research on reductions in both chlorophyll content
and productivity in Indian rice grass (Oryzopsis hymenoides) exposed to
different SO2 concentrations. As shown in tnis figure, productivity
was initially stimulated by low-level SO2 fumigations. Increasing
SO2 concentrations reversed this trend and productivity then declined
as chlorophyll content continued to be reduced.
Such alterations, when combined with premature senescence, produce a
phenological shift toward a dependence on younger leaves to satisfy
photosynthetic needs. According to Lauenroth and Heasley (1980), these
younger leaves have a much greater energy demand than older leaves,
placing a strain on the energy reserves of the plant. Observations of
increased rates of carbon translocation from belowground to aboveground
portions of plants in response to low level exposures support this theory
(Milchunas et a^. 1980a). In addition, measurements of rhizome biomass
over a five-year period showed a decrease in carbon content with
increased period of exposure (Lauenroth and Heasley 1980). Reductions in
net primary productivity accompanying alterations in the apportionment of
plant biomass can decrease competitiveness, leading to changes in species
composition and abundance (Dodd et al_. 1980).
34
-------
SO, concentration (ppm)
Figure 3. Effects of six-week S02 fumigations of varying concentration
on productivity and chlorophyll content of Oryzopsis hytnenoides.
(Adapted from Ferenbaugh 1978; Gaud 1978)
35
-------
Other expressions of plant injury result from the direct effects of
chronic SO2 exposure and sulfur accumulation. Bell and Clough (1973)
have measured several responses in ryegrass (Lolium perenne) exposed to
SO2 levels (0.73 ppm) that produced no visible injury^ In relation to
controls, exposed plants had:
0 41 percent fewer tillers;
$ 45 percent fewer living leaves;
5) percent less dry weight in living leaves;
$ 51 percent less leaf area;
88 percent more dead leaves; and
78 percent greater dry weigfit in dead leaves.
Bleasdale (1973) reported similar changes in ryegrass from continuous ex-
posures to low-level ambient SO2 (0.01-0.09 ppm); plants grown in fil-
tered air weighed 20-135 percent more than their exposed counterparts.
Plant productivity also can be affected by SOjj-induced declines of
beneficial symciont populations, and subsequent root degeneration. The
percent of plant roots with mycorrhizal associations, for example, has
been shown to decrease with increasing sulfur accumulation {Rice et al.
1979, 1980). These alterations may also cause the symbiont to revert to
activities more characteristic of plant pathogens, resulting in detri-
mental effects to the plant.
SO2 exposures may also inhibit reproduction in perennial grasses
by depressing seed germination capacity, germination times, and seed
weights (Rice et al. 1979). Cell division processes in asexual reproduc-
tion are alternately suppressed and enhanced by intermittent SOo expo-
sures, with least activity taking place during times of greatest exposure
(Bleasdale 1973).
The nutritional quality of forage grasses may be altered by SO? ex-
posures (Dodd et jiT_. 1979). Both the crude protein content and dry matter
digestibility of western wheatgrass were significantly reduced by sulfur
accumulations resulting from two-year SO2 fumigations of 0.2 to 0.07 ppm
(Schwartz et aK 1978). Other studies suggest that in vitro digestibility
may not be affected, and the major change in forage quality of western
wheatgrass is limited to an increase in sulfur and ash content (Milchunas
et al, 1981). Potential effects of altered forage quality on ruminant
iTcroflora remain unknown.
Lichen species, known to be sensitive to sulfur dioxide (Skye 1965,
1979; Sundstrom and Hallgren 1973), play an important role in soil reten-
tion in short and mixed grass prairies. Significant increases in the
36
-------
sulfur content of Usnea hirta have been observed with proximity to the
power plants of Colstrip, Montana (Eversman 1980a). Subtle effects on
lichens include (LeBlanc and Rao 1975; Eversman 1979, 1980b,c):
reduced pigment content;
depressed photosynthetic activity;
erratic respiration patterns; and
elevated cell plasmolysis.
Visual symptoms of tissue bleaching have been observed in U. hirta and
Parmelia chlorochroa at SO2 levels as low as 0.03 pm {Eversman 1980c).
To summarize, the following effects of chronic SO2 exposure on
grassland species may be expected (Coughenour 1978; Dodd et a_[. 1979;
Lauenroth and Heasley 1980);
altered patterns of photosynthesis, transpiration and allocation
of photosynthate;
altered rates of growth and senescence;
changes in net primary productivity; and
reductions in the nutritional quality of forage grasses.
These impacts of chronic SO2 exposure may alter ecosystem function-
ing with no apparent change in structure (Coughenour 1978) or they may
lead to a restructuring of ecosystem components by altering the competi-
tive relationships of dominant species and decreasing total plant cover,
especially that of lichens and grasses (Taylor and Leininger 1979; Taylor
et al. 1980).
3.3.2 Animal Effects
The acidifying air pollutants can directly affect vertebrate animals
through irritation of the eyes and respiratory tract (Lillie 1970; Newman
1975, 1980). As with plants, terrestrial vertebrates are prone to acute
or chronic injury from these pollutants. A review of the available liter-
ature yields no information on the acute effects of acidifying air pollu-
tants on grassland vertebrates in the field. However, Chilgren (1978,
1979) has investigated the chronic effects of SO2 exposure in small
mammals of the grassland ecosystem.
Chilgren (1978, 1979) investigated populations of deer mice (Peromy-
scus maniculatus) and prairie voles (Microtus ochrogaster) exposed to
37
-------
median concentrations of SO? ranging from 0 to 0.075 ppm. The Zonal Air
Pollution System (ZAPS) described by Lee and Lewis (1978) and Lee et al.
(1978) were used. Baited traps were visited most frequently by these spe-
cies in areas subject to the least SO2 fumigation. The avoidance of
areas of elevated S0^ concentration was most noticeable among popula-
tions of deer mice, indicating a greater biomonitoring potential for this
species than the prairie vole. Chilgren attributed this avoidance beha-
vior to the irritant nature of SO?, both in gaseous form and adsorbed to
particulates, although pulmonary function appeared to remain physiologi-
cally unaffected.
While the precise effects of chronic field exposures remain uncer-
tain, several indirect effects have been postulated. It has been suggest-
ed that survivability may be decreased either through spontaneous abortion
in response to irritating fumes or by coughing and sneezing reactions that
would tend to attract predators (Chilgren 1978, 1979). Other indirect
effects could arise if accelerated plant senescence were to change the
seasonal distribution of plant cover used by consumers for food or shelter
(Milchunas jrt aj_. 1980b).
A large variety of invertebrate populations may also be affected by
chronic SO? fumigations. Populations of the following insect orders,
which include herbivores, fungivores, and predators, were observed to de-
cline: Acarina, Acrididae, Carabidae, Coleoptera, Collembola, Curculioni-
dae, Lepidoptera, and Pyralidae (Leetham _et _al_. 1979, 1980a,bj. Tardi-
grade populations were observed to decrease as well (Leetham et_ al. 1980c)
yet soil nematodes and rotifers remained unaffected (Leetham et aT.
1980d). Populations of scavenger beetles, essential to the rapid decompo-
sition of carrion or plant remains and the recycling of nutrients, were
also found to decline (Bromenshenk 1979b, 1980c). Observed population
reductions were found to be more severe with increased soil moisture
(Leetham et al. 1980a).
Among aboveground insect populations, grasshopper (Melanoplus san-
quinipes) numbers were observed to decline in response to SO? fumigation
(McNary et al. 1980). Grasshoppers exposed to SO2 over their various
life stages suffered mortality during certain larval instars, yet no mor-
tality was found at any other stage in their life history (Leetham et al.
1980e). Population reductions in aboveground insects are thus presumaFTy
due to emigration from areas of high ambient SO? (Leetham et aU 1980b).
This hypothesis is reinforced by observations tnat feeding grasshoppers
selectively reject western wheatqrass contaminated by excessive sulfur
from controlled SO? fumigations (Leetham ert al_. 1979).
3.3.3 Ecosystem Effects
The effects of acidifying air pollutants in the grassland ecosystem
will depend on the differential susceptibility of plant species and alter-
ations induced in the abiotic environment. Indirect effects on wildlife
38
-------
may also be caused by alterations in the nutritional quality and palata-
bility of contaminated forage. The short-term impacts on grassland com-
munities resulting from the low concentrations of acidifying air pollu-
tants that currently exist in regions containing these ecosystems are ex-
pected to be minimal. However, long-term simulations suggest that more
serious impacts could accompany the projected increases in fossil fuel
combustion in these regions (Heasley et a]_. 1981).
Compared to particulates, gaseous pollutants such as sulfur and nit-
rogen oxides are carried greater distances from point sources before being
deposited, explaining why soil pH measurements showing lowest values are
found at intermediate distances from point sources (Wood and Nash 1976).
As a result, the effects of acidifying gases may be anticipated over
larger areas surrounding point sources than would particulate-related
effects.
The effects of acidifying air pollutants on plant community structure
are similar to those of other pollutant gases, notably the photochemical
oxidants. Acute tissue injury as well as subtle effects leading to re-
ductions in energy storage can alter plant competitiveness, causing shifts
in species composition and decreased community productivity. They may
also affect ecosystem stability by increasing plant susceptibility to
stresses of drought, fire, and grazing common in grasslands (Lauenroth and
Heasley 1980). Consumer and decomposer communities may experience compo-
sition shifts and population declines as a result of alterations in the
plant community. In arid portions of the biome, where leaf diffusion of
SO2 is reduced by fewer numbers of stomates and frequent stomatal clos-
ure, direct effects may be negligible while indirect effects resulting
from soil acidification may assume greater importance (Dawson and Nash
1980).
Soil acidification is the primary abiotic change leading to eco-
system-level impacts. Unlike areas where ecosystem acidification results
from acid deposition, the acidification of grassland soils chiefly results
from direct gaseous sorption; where vegetation is scarce, soils may serve
as a major sink for sulfur and nitrogen oxides (Ferenbaugh _et aj. 1979).
In experimental fumigations of soils with SO2 and NO2, pollutant
sorption is maintained at relatively constant rates for extended time per-
iods (States 1978). Alkaline, calcareous soils from a cool-desert grass-
land remove greater amounts of SO2 than NO2 (Ferenbaugh et jil_. 1979).
Microorganisms are not involved in soil conversion of SOg to sulfate and
organic sulfur; however, nitrifying populations do facilitate the oxida-
tion of sorbed NO2 to nitrate (Ghiorse and Alexander 1976). Soils
brought to saturation by continuous SO2 fumigation are able to sorb
additional quantities following brief recovery periods of no exposure;
sorption is increased in moist soils relative to air-dried soils (Feren-
baugh et aj[. 1979).
39
-------
Reductions in soil microbiota have been shown to result from chronic
SO2 fumigations (McFarlane £t aj. 1979; Lauenroth and Heasley 1980).
This decline in bacterial numbers has been attributed to increased soil
acidity (States 1978). States further reported the dominant fungi of a
shortgrass prairie to respond to SO2 exposures by decreased spore germ-
ination.
Reduced rates of litter decomposition and mineralization can result
from adverse effects on microbial populations and their activities.
Leetham eit _al_. (1980f) documented reductions of 9-17 percent in decomposi-
tion rates of western wheatgrass following exposure to 0.085 ppm SO2 for
five weeks. Similar observations have been reported by Lauenroth and
Heasley (1980), who found depressed decomposition to result directly from
SO2 fumigation rather than sulfur accumulations in plant tissues. Sul-
fur dioxide exposure has also been reported to reduce microbial nitrifica-
tion processes in soils of low pH, yet continuous exposures of 0.5 ppm
SO? showed no similar effects on a loam of neutral pH (Labeda and Alex-
ander 1978). Exposures of this soil to 5 ppm NO2 did, however, inhibit
rates of ammonia decay, increase rates of nitrate formation, and result
in nitrite accumulation in the soil.
Depressed decomposition and mineralization rates will, in turn, cause
reductions of nutrient cycling rates. Nutrients tied up in accumulating
litter remain unavailable for plant uptake. At the same time, soil pools
of nutrients and minerals are gradually depleted (Lauenroth and Heasley
1980). Decreased nutrient availability can result in depressed synthetic
rates of primary producer carbon; consequences may include reductions in
the carrying capacity of habitat, hence lowered populations of consumer
organisms.
Pollutant-induced changes in plants can lead to indirect effects on
consumer communities. Several studies have concluded that an increase in
the sulfur content of plants can reduce the palatability of grasses for
herbivores (Leetham et al. 1979; Lauenroth and Heasley 1980). This ef-
fect, in turn, could reduce herbivore numbers, or cause a shift in grazing
pressure towards more palatable grasses, possibly altering species compo-
s ition.
Through both direct biotic effects and alterations of the abiotic
environment, exposures to the acidifying air pollutants accelerate sulfur
accumulation and transfer among all ecosystem compartments (Lauenroth and
Heasley 1980). Table 11 indicates how additional sulfur is distributed
among the producer and detritus compartments. The highest percentages are
seen to occur in living plant parts and soil litter where sulfur is most
likely to be transferred to herbivorous and detritivorous consumers.
There may be beneficial effects associated with moderate exposures to
acidifying pollutants. Primary productivity may be stimulated by low-
level aerial additions of supplementary nitrogen and sulfur, and slight
reductions of soil pH can render more nutrients available for plant uptake
40
-------
(Wood and Nash 1976; States 1978; Lauenroth and Heasley 1980). However,
as sulfur concentrations increase throughout the ecosystem, organic carbon
levels are likely to increase in the litter compartment at the expense of
producer, consumer, and decomposer populations.
Table 11. The distribution of sulfur in producer
and detritus compartments of the grassland ecosystem.
Ecosystem Compartment
Percent of
Total Sulfur
Producer
Live shoots
Dead shoots
Root translocation
39-54
11-24
4- 7
Detritus
Litter and soil
28-33
(Adapted from Coughenour 1978)
41
-------
4.0 TOPICS FOR FURTHER RESEARCH
Forecasts of increased energy and industrial development in the west-
ern United States underline the need for acquiring ecosystem-specific in-
formation on the effects of air pollution and atmospheric deposition in
grasslands. Parts of this region may be subjected to subtle yet progres-
sive and potentially irreversible impacts from increased loadings due to
the proliferation of point emission sources or the long-range transport of
air pollutants (LRTAP). Monitoring and evaluating potential ecosystem al-
terations is therefore important for both habitat preservation and range-
land protection. As with acid precipitation in sensitive areas of the
United States, the air pollution problem in grasslands encompasses econom-
ic and aesthetic, as well as scientific and managerial issues. The cate-
gories of research outlined below are suggested as a necessary foundation
for acquiring an understanding of air pollution impacts in this biome.
4.1 BASELINE STUDIES
Efforts to discern the exact mechanisms and consequences of air pol-
lutant injury to wildlife and habitat must be predicated on firm knowledge
of existing conditions in grasslands. Of particular relevance are inves-
tigations into the effects of natural ocurrences (e.g., fire, disease, and
drought) and man-induced modifications (e.g., cultivation, irrigation,
grazing, and activities leading to desertification) on native plant and
animal communities. The purpose of this research would be two-fold:
to distinguish air pollution effects from alterations induced by
other sources of impact; and
to determine the nature of potential synergism or antagonism be-
tween the effects of air pollutants, natural, and other stresses.
Similar efforts should concentrate on the characterization of soil
properties, edaphic conditions, and other abiotic factors across the
biome, in relation to their influences on native community composition.
Finally, detailed descriptions of plant and wildlife density and diversity
should be compiled for selected representative areas of the biome.
Further baseline studies should concentrate on documenting the com-
plex biology of grassland organisms and populations. One example would be
an examination of the nutritional quality of dominant forage plants over
their entire range. Another is found in work currently underway at Col-
strip, Montana, to characterize the general histology and background par-
ticulate burdens of the different organs of common grassland vertebrates.
Bioassay organisms should be sought for effective inter-regional com-
parisons of grassland wildlife. The deer mouse (Perom.yscus maniculatus)
might serve a bioindicator function as ft is ubiquitous, throughout the
42
-------
United States. Organisms from several positions in the trophic chain,
which possess similar advantages as bioindicators, should be sought to
provide a more complete picture of grassland ecology. More rigorous tech-
niques, particularly in the analysis of behavioral responses, are needed
to enhance the usefulness of bioindicators.
With respect to the diverse air pollutants discussed in the previous
chapters, studies of their effects on grasslands would profit from further
knowledge gained in the following areas:
Photochemical oxidants
rates of oxidant formation from low but steadily increasing emis-
sions of N0X and hydrocarbons;
ozone decay rates, impaction rates, and distribution within the
ecosystem.
Particulates
detailed characterizations of localized particulate emissions,
including substances adsorbing to particles;
deposition rates and patterns; extent to which grassland biota
are exposed;
effects of accumulation on soil properties and plant-soil inter-
actions.
Acidifying air pollutants
dry deposition velocities, rates, and amounts for S0X and N0X;
transformations in soils and effects on soil properties.
In general, these studies should develop data bases describing present am-
bient pollution levels throughout the biome. Such data will lead to a
better understanding of emission trends and resulting levels of ambient
pollution.
4.2 RESEARCH ON PLANT EFFECTS
Current knowledge of air pollution and acid rain effects on plants is
generally less developed for grasses and other monocotyledons than for
broad-leaved species. Many details remain to be clarified regarding the
relative importance of various uptake mechanisms and factors influencing
uptake, toxicity, and inherent plant susceptibility to pollutant injury,
Stomatal functioning and detoxification mechanisms particularly require
further understanding.
43
-------
Available evidence of pollutant effects on grassland flora would
suggest two basic priorities for future research:
investigation of the effects of reduced litter decomposition and
accelerated soil leaching on primary producers; and
investigation of the subtle effects of chronic air pollution ex-
posures and pollutant accumulation in ecosystem compartments on
plant growth, productivity, and year-to-year maintenance.
Further research is also required to judge the relative phytotoxicity
of ambient pollutant levels in different areas and during different sea-
sons, and to relate this knowledge to potential increases or reductions in
plant productivity. In areas where adverse effects have been observed,
more work is needed to understand pollutant impact on the nutritional
value and palatability of forage vegetation. Research to determine pollu-
tant impacts on plant relations with pathogens, parasites, beneficial
symbionts and other root and soil organisms must be intensified so that
potential repercussions on plant productivity and reproductive success may
be assessed. The above studies should lead to a comprehensive evaluation
of the selective influence of air pollutants on plant competitiveness in
grassland communities. This would facilitate the development of a plant
biomonitoring capacity through which responses of indicator species could
be correlated with various types of pollution and thus aid in the antici-
pation of potential effects on wildlife and the quality of their habitat.
4.3 RESEARCH ON ANIMAL EFFECTS
The exact nature of the responses of grassland fauna to air pollution
exposures is difficult to predict on the basis of the available litera-
ture. The bioaccumulation of trace elements in particulates, for example,
is widely documented for many wildlife species, yet the potential conse-
quences of this response remain, in most instances, poorly understood.
Similarly gaseous pollutants are known to cause eye and lung irritation at
elevated concentrations, but resultant effects on animal performance and
competitiveness are unclear. As with baseline studies of animal popula-
tions, the understanding of air pollution impacts on grassland fauna re-
quires the design and implementation of precise investigative methodology.
Several fruitful avenues of research may be pursued. Dominant modes
of pollutant exposure need to be associated with individual populations
and generalized for various trophic groups. Representative indicator or-
ganisms could be employed to monitor pollutant exposures among these
groups. Potential effects on the competitive status of individual species
also deserve examination. These effects may be examined through compari-
sons of exposed indicator species and their non-exposed counterparts.
44
-------
Dvorak jit a2- (1978) have identified several pressing research needs
related to particulate impacts in animals; information is required con-
cerning:
concentrations of trace elements in animal diets relative to the
food habits of species;
food chain transfers and the bioaccumulation of combustion by-
products;
trace element retention times, excretion rates, and assimilation
rates in individual species;
physiological, biochemical, and synergistic effects of individual
trace elements in the body; and
effects of life-time exposure to low-level concentrations and
pollutant uptake through the ingestion of contaminated vegetation.
Mechanisms of potential disease, toxicity, reproductive effects, and
mutagenicity, related to bioaccumulation in lungs and other tissues,
all require further study.
With respect to the gaseous pollutants, more needs to be known of be-
havioral responses and of factors that modify these responses. Further
understanding of the character and extent of animal migration in response
to ambient pollution would be useful, as would the specification of levels
eliciting widespread migration in species exhibiting this response. The
potential for related impacts on secondary consumers and higher-order car-
nivores, as well as ecosystem productivity in general, remains to be in-
vestigated.
Inquiries into specific animal effects in grasslands will be aided by
systematic evaluations of the habitat requirements, food preferences and
other dependencies of wildlife relative to potential air pollution impacts
in plant communities. This knowledge should be developed in particular
for single cover type users and threatened or endangered species. Such
knowledge will be useful to focus research on the effects of pollutant-
induced plant injury on species inhabiting sub-optimal portions of their
range; effects of reduced habitat quality or availability on animals due
to air pollution may be more noticeable in these areas.
4.4 RESEARCH ON ECOSYSTEM EFFECTS
The ecosystem-level impacts of air pollution are generally less well
known .in grasslands than in other ecosystems, particularly forests and
aquatic systems, however, some information gaps are being filled by cur-
rent research efforts. On the basis of present knowledge, research prior-
ities in grasslands should be directed toward a fuller understanding of
the:
45
-------
accumulation and exchange of air pollutants in the ecosystem, in-
cluding the quantification of deposition, retention, and transfer
rates, as well as patterns of pollutant distribution in biotic and
abiotic components;
effects of pollutant accumulation, especially sulfur and the toxic
trace elements, on decomposition and mineralization processes; and
repercussions of the above on nutrient cycling, primary produc-
tivity, and food chain energetics.
Further knowledge is also needed of the consequences of shifts in
species composition resulting from the selective influence of the various
air pollutants on plant competitiveness. Potential repercussions on the
availability of food, cover, and functional niches for wildlife species
require clarification. The effects of pollutant-induced successional
rollbacks on the quality of habitat need to be documented, especially as
they relate to water availability and the overall carrying capacity of
habitats. With respect to plants and animals alike, attempts should be
made to relate pollutant sensitivity to the inherent tolerance of back-
ground stress (e.g., a species' adaptivity to pollution versus other
stresses) and to quantify biotic sensitivity to pollutants under varying
conditions of natural stress.
Several lines of research should be advanced to assess the ecosystem-
level effects of pollutant-induced animal migrations or population de-
clines. These include studies of:
plant community responses to altered patterns of grazing pressure;
potential increases in the competitive status of certain insect
and prey species; and
alterations in the abiotic properties and biotic composition of
soils in response to reductions in animal acitivites of foraging
and burrowing.
Useful research could also be directed at understanding the long-term ef-
fects of reductions in pollinator populations, especially in relation to
the reproductive success of native plants that depend on this mode of fer-
tilization. Similar research should reveal the long-term effects of air
pollutants on beneficial predatory insects, as well as resultant plant
susceptibility to pest infestation. Potential impacts on nutrient cycling
stability from reductions in the activities of decomposer populations also
require further investigation.
Research is needed to clarify the effects of depressed soil pH, alone
and in conjunction with particulate accumulations, on soil decomposition
and mineralization processes in grasslands. Effects on decomposition and
other vital ecosystem functions should also be studied from an industry-
specific or pollutant-specific point of view as an aid to site-specific
assessments of future facilities in grasslands.
46
-------
More needs to be known of the nature of abiotic factors that can ren-
der certain portions of the grassland ecosystem more susceptible to impact
than others. Pollutant effects under varying conditions of soil moisture,
organic content, mineral nutrition, and cation exchange capacity in par-
ticular require further resolution. Criteria should be developed for
judging and mapping areas of present or potential sensitivity to air pol-
lution impact so that in the future, trends in these areas can be quanti-
fied and monitored. Mapping efforts should also distinguish areas where
pollutants may beneficially increase primary productivity from those where
environmental factors preclude favorable ecosystem responses to low-level
air pollution. Areas subject to nutrient losses from various forms of
contamination should be identified. Comparative studies of findings in
other terrestrial ecosystems may aid the development of sensitivity
mapping and impact monitoring in grasslands.
Ecosystem-level impacts of air pollution in grasslands may generate
socioeconomic impacts. The potential magnitude and degree of reversibil-
ity of these are unknown. Work to relate ecological and economic impacts
may help to discourage over-utilization of range resources, cultivation of
marginal lands, and activities leading to desertification while promoting
rangeland protection and soil and water conservation. In this way con-
tinued research into the effects of air pollution in grasslands will fur-
ther FWS objectives of wildlife protection and habitat preservation by
underscoring the potential fragility of ecosystem components on which the
economic health of the region depends.
47
-------
REFERENCES
Abshire, N.L.; Derr, V.E.; McNice, G.T.; Pueschel, R.; Van Valin, C. In-
tegrated aerosol characterization monitoring, Colstrip, Montana. Preston,
E.M.; Lewis, R.A., eds. The bioenvironmental impact of a coal-fired power
plant, third interim report, Colstrip, Montana. Corvallis, OR: U.S. En-
vironmental Protection Agency, Corvallis Environmental Research Lab.;
EPA-600/3-78-021; 1978:291-320.
Altshuller, A.P. Atmospheric sulfur dioxide and sulfate - distribution
of concentration at urban and nonurban sites in United States. Environ.
Sci. Technol. 7(8):709-712; 1973.
Altshuller, A.P.; McBean, G.A., co-chairman. Second report of the United
States - Canada research consultation group on the long-range transport
of air pollutants. Ottawa: Environment Canada; 1980. 31 p.
Angelo, R.T.; Anderson, K.W. Western North Dakota air quality study.
Bismarck, ND: North Dakota State Department of Health, Management and
Research, Division of Environmental Waste; 1981. 70 p.
Ashendon, T.W. The effects of long-term exposures to SO2 and NO2 pol-
lution on the growth of Dactyl is qlomerata L. and Poa pratensis L.
Environ. Pollut. 18:249-258; 1979.
Bailey, R.G. Description of the ecoregions of the United States. Ogden,
UT: U.S. Department of Agriculture, Fcrest Service; 1978.
Bell, J.N.B.; dough, W.S. Depression of yield in ryegrass exposed to
sulfur dioxide. Nature 241:47-49; 1973.
Bennett, J.H.; Hill, A.C, Acute inhibition of apparent photosynthesis by
phytotoxic air pollutants. Dugger, M., ed. Air pollution effects on
plant growth. Washington, DC: American Chemical Society, ACS Symp. Ser.
No. 3; 1974:115-127.
Bennett, J.P.; Runeckles, V.C. Effects of low levels of ozone on plant
competition. 0. Appl. Ecol. 14:877-880; 1977.
Bleasdale, J.K.A. Effects of coal-smoke pollution gases on the growth of
ryegrass Lolium perenne L. Environ. Pollut. 5:275-285; 1973.
Bromenshenk, J.J. Biological impact of air pollution on insects. Clark,
W.S., ed. Proceedings of the Fort Union Coal Field symposium, Volume 5,
terrestrial ecosystem section; 1975 April 25-26; Billings, MT: Montana
Academy of Sciences; 1975:597-629.
Bromenshenk, J.J. Honeybees and other insects as indicators of pollution
impact from the Colstrip power plants. Preston, E.M.; Gullet, T.L., eds.
The bioenvironmental impact of a coal-fired power plant, fourth interim
report, Colstrip, Montana. Corvallis, OR: U.S. Environmental Protection
Agency, Corvallis Environmental Research Lab.; EPA-600/3-79-044;
1979a:215-239.
48
-------
Bromenshenk, J.J. Responses of ground-dwelling insects to sulfur dioxide.
Preston, E.M.; Gullet, T.L., eds. The bioenvironmental impact of a coal-
fired power plant, fourth interim report, Colstrip, Montana. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental Re-
search Lab.; EPA-600/3-79-044; 1979b:673-722.
Bromenshenk, J.J. Accumulation and transfer of fluoride and other trace
elements in honey bees near the Colstrip power plants. Preston, E.M.;
O'Guinn, D.W., eds. The bioenvironmental impact of a coal-fired power
plant, fifth interim report, Colstrip, Montana. Corvallis, OR: U.S.
Environmental Protection Agency, Corvallis Environmental Research Lab.;
EPA-600/3-80-052; 1980a:72-95.
Bromenshenk, J.J. Fluoride and arsenic concentrations in honey bees near
Colstrip. Preston, E.M.; O'Guinn, D.W.; Wilson, R.A., eds. The bioenvi-
ronmental impact of a coal-fired power plant, sixth interim report, Col-
strip, Montana. Corvallis, OR: U.S. Environmental Protection Agency,
Corvallis Environmental Research Lab.; 1980b: 210-227.
Bromenshenk, J.J. Behavioral responses of saprophagous and necrophagous
beetles exposed to sulfur dioxide. Preston, E.M.; O'Guinn, D.W., eds.
The bioenvironmental impact of a coal-fired power plant, fifth interim re-
port, Colstrip, Montana. Corvallis, OR: U.S. Environmental Protection
Agency, Corvallis Environmental Research Lab.; EPA-600/3-80-052; 1980c:
235-267.
Bryson, R.A. Ancient climes on the Great Plains. Nat. History 89(6):
64-73; 1980.
Bull, K.R.; Roberts, R.D.; Inskip, M.J.; Goodman, G.T. Mercury concentra-
tions in soil, grass, earthworms and small mammals near an industrial
emission source. Environ. Pollut. 12:135-140; 1977.
Carlson, C.E.; Dewey, J.E. Environmental pollution by fluorides in Flat-
head National Forest and Glacier National Park. Missoula, MT: U.S. De-
partment of Agriculture, Forest Service, Forest Insect and Disease Branch;
1971. 57 p. Available from: Supt. Docs., GPO, Washington, DC; 796-468.
Chilgren, J.D. The responses of prairie deer mice to a field SO2 gradi-
ent. Proceedings of the fourth joint conference on sensing of environ-
mental pollutants. Washington, DC: American Chemical Society; 1978:
61-65.
Chilgren, J.D. Small mammal investigations at ZAPS: Demographic studies
and responses to gradient levels of SO2. Preston, E.M.; Gullet, T.L.,
eds. The bioenvironmental impact of a coal-fired power plant, fourth in-
terim report, Colstrip, Montana. Corvallis, OR: U.S. Environmental Pro-
tection Agency, Corvallis Environmental Research Lab.; EPA-60013-79-044;
1979:674-789.
Cleveland, W.S.; Graedel, T.E. Photochemical air pollution in the north-
east United States. Science 204:1273-1278; 1979.
49
-------
Cooper, Jr.; Lopez, J.A.; Oemo, J.M. Chemical composition of acid
precipitation in central Texas. Water Air Soil Pollut. 6:351-359; 1976.
Coughenour, M.B. Grassland sulfur cycle and ecosystem responses to low-
level sulfur dioxide. Fort Collins, CO: Colorado State Univ., Ph.D.
Thesis; 1978. 352 p. Available from: University Microfilms Internation-
al, Ann Arbor, MI.
Council on Environmental Quality. Environmental quality - 1980; the
eleventh annual report of the Council on Environmental Quality. Washing-
ton, DC: Council on Environmental Quality; 1980. 497 p. Available from:
Supt. Docs., GPO, Washington, DC: 335-801/7090.
Coupland, R.T. The nature of grassland. Coupland, R.T., ed. Grassland
ecosystems of the world: Analysis of grasslands and their uses. New
York: Cambridge University Press; 1979:23-29.
Cowling, D.W.; Lockyer, D.R. Growth of perennial ryegrass Lolium perenne
L. exposed to a low concentration of sulphur dioxide. J. Exp. Bot.
27:411-417; 1976.
Cowling, D.W.; Jones, L.H.P.; Lockyer, D.R. Increased yield through cor-
rection of sulphur deficiency in ryegrass exposed to sulphur dioxide.
Nature 243:479-480; 1973.
Curtis, J.T. The modification of mid-latitude grasslands and forests by
man. Detwyler, T.R, ed. Man's impact on environment. New York, NY:
McGraw-Hill Book Co.; 1971:507-521.
Davies, T. Grasses more sensitive to SO? pollution in conditions of
low irradiance and short days. Nature 284:483-485; 1980.
Dawson, J.L.; Nash, T.H. Effects of air pollution from copper smelters
on a desert grassland community. Environ. Exp. Bot. 20:61-72; 1980.
Dewey, J.E. Accumulation of fluorides by insects near an emission source
in western Montana. Environ. Entomol. 2:179-182; 1973.
Dmowski, K.; Karolewski, M.A. Cumulation of zinc, cadmium and lead in
invertebrates and in some vertebrates according to the degree of an area
contamination. Ekol. Pol. 27(2):333-349; 1979.
Dodd, J.L.; Lauenroth, W.K.; Heitschmidt, R.K.; Leetham, J.W. First-year
effects of controlled sulfur dioxide fumigation on a mixed-grass prairie
ecosystem. Preston, E.M.; Lewis, R.A., eds. The bioenvironmental impact
of a coal-fired power plant, third interim report, Colstrip, Montana.
Corvallis, OR: U.S. Environmental Protection Agency, Corvallis Environ-
mental Research Lab.; EPA-600/3-78-021; 1978:345-375.
50
-------
Dodd, J.L.; Lauenroth, W.K.; Thor, 6.L.; Coughenour, M.B. Effects of
chronic low level SO2 exposure on producers and litter dynamics.
Preston, E.M.; Gullet, T.L., eds. The bioenvironmental impact of a coal-
fired power plant, fourth interim report, Colstrip, Montana. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental Re-
search Lab.; EPA-600/3-79-044; 1979:384-493.
Dodd, J.L.; Lauenroth, W.K.; Heitschmidt, R.K. Effects of controlled
SO exposure on net primary production and plant biomass dynamics.
Preston, E.M.; O'Guinn, D.W., eds. The bioenvironmental impact of a coal-
fired power plant, fifth interim report, Colstrip, Montana. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental Re-
search Lab.; EPA-600/3-80-052; 1980:172-184.
Dvorak, A.J.; Lewis, B.G.; Chee, P.C., et al. Impacts of coal-fired power
plants on fish, wildlife, and their habitats. Washington, DC: U.S. De-
partment of the Interior, U.S. Fish and Wildlife Service; Biological Ser-
vices Program; FWS/OBS-78/29; 1978. 261 p. Available from: Supt. Docs.,
GPO, Washington, DC; 753-096/92.
Eversman, S. Effects of low-level SO2 on two native lichen species.
Preston, E.M.; Gullet, T.L., eds. The bioenvironmental impact of a coal-
fired power plant, fourth interim report, Colstrip, Montana. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental Re-
search Lab.; EPA-600/3-79-044; 1979:642-672.
Eversman, S. Observations on two lichen species in the Colstrip area,
1979. Preston, E.M.; O'Guinn, D.W.; Wilson, R.A., eds. The bioenvi-
ronmental impact of a coal-fired power plant, sixth interim report,
Colstrip, Montana. Corvallis, OR: U.S. Environmental Protection Agency,
Corvallis Environmental Research Lab.; 1980a:185-197.
Eversman, S. Responses of two lichen species to low-level SO2.
Preston, E.M.; O'Guinn, D.W., eds. The bioenvironmental impact of a coal-
fired power plant, fifth interim report, Colstrip, Montana. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental Re-
search Lab.; EPA-600/3-80-052; 1980b:136-146.
Eversman, S. Effects of low-level SO2 on two native lichen species;
1979 ZAPS observations and project summary. Preston, E.M.; O'Guinn, D.W.;
Wilson, R.A., eds. The bioenvironmental impact of a coal-fired power
plant, sixth interim report, Colstrip, Montana. Corvallis, OR: U.S. En-
vironmental Protection Agency, Corvallis Environmental Research Lab.;
1980c:198-209.
Fankhauser, R.K. Ozone levels in the vicinity of 33 cities. J. Air
Pollut. Control Assoc. 26(8):771-777; 1976.
Ferenbaugh, R.W. Effects of prolonged exposure of Oryzopsis hymenoides
to SO2. Water Air Soil Pollut. 10:27-31; 1978.
51
-------
Ferenbaugh, R.W.; Gaud, W.S.; States, J.S. Pollutant sorption by desert
soils. Bull. Environ. Contam. Toxicol. 22:681-687; 1979.
Fowler, D.; Unsworth, H.M. Dry deposition of sulphur dioxide on wheat.
Nature 249:389-392; 1974.
French, N.R.; Steinhorst, R.K.; Swift, D.M. Grassland biomass trophic
pyramids. French, N.R., ed. Perspectives in grassland ecology. New
York: Springer-Verlag; Ecological Studies No. 32; 1979:59-87.
Garsed, S.G.; Read, D.J. The uptake and metabolism of 35 SO2 in plants
of differing sensitivity to sulphur dioxide. Environ. Pollut. 13:173-
185; 1977.
Gaud, W.S. Simulating the environmental impact of coal-fired electric
power generation. Proceedings of the fourth joint conference on sensing
of environmental pollutants. Washington, DC: American Chemical Society;
1978:57-60.
Ghiorse, W.C.; Alexander, M. Effect of microorganisms on the sorption and
fate of sulfur dioxide and nitrogen dioxide in soil. J. Environ. Qual.
5(3):227-230; 1976.
Giles, F.E.; Middleton, S.G.; Gran, J.G. Evidence for the accumulation of
atmospheric lead by insects in areas of high traffic density. Environ.
Entomol. 2(2):299-300; 1973.
Goldsmith, C.D.; Scanlon, P.F. Lead levels in small mammals and selected
invertebrates associated with highways of different traffic densities.
Bull. Environ. Contam. Toxicol. 17(3):311-316; 1977.
Gordon, C.C. Effects of air pollution on indigenous animals and vegeta-
tion. U.S. Environmental Protection Agency. Helena Valley, Montana,
area environmental pollution study. Missoula, MT: Univ. of Montana;
1969:95-112.
Gough, L.P.; Erdman, G.A. Influence of a coal-fired power plant on the
element content of Parmelia chlorochroa. Bryologist 80(3):492-501; 1977.
Gough, L.P.; Shacklette, H.T.; Case, A.A. Element concentrations toxic to
plants, animals and man. Washington, DC: U.S. Geological Survey; Bulle-
tin No. 1466; 1979. 80 p. Available from: Supt. Docs., GPO, Washington,
DC; 677-026/57.
Guderian, R. Air pollutionphytotoxicity of acidic gases and its signif-
icance in air pollution control. New York: Springer-Verlag. Ecological
Series No. 22; 1977. 56 p.
Heagle, A.S. Interactions between air pollutants and plant parasites.
Annu. Rev. Phytopathol. 11:365-388; 1973.
52
-------
Heasley, J.E.; Lauenroth, W.K.; Dodd, J.L. Systems analysis of potential
air pollution impacts on grassland ecosystems. International Society for
Ecological Modelling. International symposium on energy and ecological
modelling; 1981 April 20-23; Louisville, KY; (in press) 1981. 10 p.
Heck, W.W. Factors influencing expression of oxidant damage to plants.
Annu. Rev. Phytopathol. 6:165-188; 1968.
Heck, W.W.; Anderson, C.E. Effects of air pollutants on plants. Guthrie,
F.E.; Perry, J.J, eds. Introduction to environmental toxicology. New
York: Elsevier North Holland, Inc. 1980:135-153.
Heitschmidt, R.K.; Lauenroth, W.K.; Dodd, J.L. Effects of controlled
levels of sulphur dioxide on western wheatgrass in a southeastern Montana
grassland. J. Appl. Ecol. 14:859-868; 1978.
Hill, A.C.; Hill, S.; Lamb, C.; Barrett, T.W. Sensitivity of native
desert vegetation to SO2 and to SO? and NO? combined. J. Air
Poll lit. Control Assoc. 24(2): 153-157; 1974.
Horsman, D.C.; Wellburn, A.R. Effect of SO;? polluted air upon enzyme
activity in plants originating from areas with different annual mean
atmospheric SO2 concentrations. Environ. Pollut. 13:33-39; 1977.
Interagency Task Force on Acid Precipitation. National acid
precipitation assessment plan. Draft; 1981. Available from: Supt.
Docs., GPO, Washington, DC: 336-495/7128.
Ireland, M.P. Metal accumulation by the earthworms Lumbricus rubellus,
Dendrobaena veneta, and Eiseniella tetraedra living in heavy metal
polluted sites. Environ. Pollut. 13:201-206; 1979.
Jackson, D.R.; Selvidge, W.J.; Ausmus, B.S. Behavior of heavy metals in
forest microcosms: I. Transport and distribution among components.
Water Air Soil Pollut. 10:3-11; 1978.
Kavet, R.I.; Brain, J.D. Reaction of the lung to air pollutant exposure.
Life Sci. 15(5):849-861; 1974.
Kay, C.E.; Tourangeau, P.C.; Gordon, C.C. Industrial fluorosis in wild
mule and whitetail deer from western Montana. Fluoride 8:182-191; 1975.
Kern, M.D.; Lewis, R.A. Baseline histology of selected organs of the deer
mouse, Peromyscus maniculatus, in Rosebud County, Montana. Preston, E.M.;
O'Guinn, D.W.; Wilson, R.A., eds. The bioenvironmental impact of a coal-
fired power plant, sixth interim report, Colstrip, Montana. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental Re-
search Lab.; 1980:228-273.
Kern, M.D.; Lewis, R.A.; Berlin, M.B. Particulates in the lungs of west-
ern meadowlarks Sturnella neglecta in southeastern Montana. Preston,
E.M.; O'Guinn, D.W.; Wilson, R.A., eds. The bioenvironmental impact of a
coal-fired power plant, sixth interim report, Colstrip, Montana. Corval-
lis, OR: U.S. Environmental Protection Agency, Corvallis Environmental
Research Lab.; 1980:315-330.
-------
Kochhar, M.; Blum, U.; Reinert, R.A. Effects of O3 and (or) fescue on
ladino clover: Interactions. Can. J. Bot. 58:241-249; 1980.
Labeda, D.P.; Alexander, M. Effects of SO2 and NO2 on nitrification
in soil. J. Environ. Qua 1. 7(4):523-526; 1978.
Lauenroth, W.K. Grassland primary production: North American grasslands
in perspective. French, N.R., ed. Perspectives in grassland ecology.
New York: Springer-Verlag; Ecological Studies No. 32; 1979:3-24.
Lauenroth, W.K.; Dodd, J.L. Chlorophyll reduction in western wheatgrass
exposed to sulfur dioxide. Preston, E.M.; O'Guinn, D.W., eds. The bio-
environmental impact of a coal-fired power plant, fifth interim report,
Colstrip, Montana. Corvallis, OR: U.S. Environmental Protection Agency,
Corvallis Environmental Research Lab.; EPA-600/3-80-052; 1980a:197-203.
Lauenroth, W.K.; Dodd, J.L. The impact of sulfur dioxide on the chloro-
phyll content of grassland plants. Preston, E.M.; O'Guinn, D.W.; Wilson,
R.A., eds. The bioenvironmental impact of a coal-fired power plant, sixth
interim report, Colstrip, Montana. Corvallis, OR: U.S. Environmental
Protection Agency, Corvallis Environmental Research Lab.; 1980b:66-73.
Lauenroth, W.K.; Heasley, J.E. Impact of atmospheric sulfur deposition on
grassland ecosystems. Shriner, D.S.; Richmond, C.R.; Lindberg, S.E., eds.
Atmospheric sulfur desposition. Environmental impact and health effects.
Ann Arbor, MI: Ann Arbor Science Publishers, Inc.; 1980:417-430.
Lauenroth, W.K.; Bicak, C.J.; Dodd, J.L. Sulfur accumulation in western
wheatgrass exposed to controlled SO2 concentrations. Preston, E.M.;
O'Guinn, D.W., eds. The bioenvironmental impact of a coal-fired power
plant, fifth interim report, Colstrip, Montana. Corvallis, OR: U.S.
Environmental Protection Agency, Corvallis Environmental Research Lab.;
EPA-600/3-80-052; 1980:147-152.
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.; Lewis, R.A. Zonal air pollution system: Design and perform-
ance. Preston, E.M.; Lewis, R.A., eds. The bioenvironmental impact of a
coal-fired power plant, third interim report, Colstrip, Montana. Corval-
lis, OR: U.S. Environmental Protection Agency, Corvallis Environmental
Research Lab.; EPA-600/3-79-044; 1978:322-344.
Lee, J.J.; Preston, E.M.; Lewis, R.A. A system for the experimental eval-
uation of the ecological effects of sulfur dioxide. Proceedings of the
fourth joint conference on sensing of environmental pollutants. Washing-
ton, DC: American Chemical Society; 1978:49-53.
54
-------
Leetham, J.W.; McNary, T.J.; Dodd, J.L. Effects of controlled levels of
SO2 on invertebrate consumers. Preston, E.M.; Gullett, T.L., eds. The
bioenvironmental impact of a coal-fired power plant, fourth interim re-
port, Colstrip, Montana. Corvallis, OR: U.S. Environmental Protection
Agency, Corvallis Environmental Research Lab.; EPA-600/3-78-021;
1979:723-763.
Leetham, J.W.; Dodd, J.L.; Deblinger, R.D.; Lauenroth, W.K. Arthropod
population responses to three levels of chronic sulfur dioxide exposure in
a northern mixed-grass ecosystem. I. Soil microarthropods. Preston,
E.M.; O'Guinn, D.W.; Wilson, R.A., eds. The bioenvironmental impact of a
coal-fired power plant, sixth interim report, Colstrip, Montana. Corval-
lis, OR: U.S. Environmental Protection Agency, Corvallis Environmental
Research Lab.; 1980a: 139-157.
Leetham, J.W.; Dodd, J.L.; Deblinger, R.D.; Lauenroth, W.K. Arthropod
population responses to three levels of chronic sulfur dioxide exposure in
a northern mixed-grass ecosystem. II. Aboveground arthropods. Preston,
E.M.; O'Guinn, D.W.; Wilson, R.A., eds. The bioenvironmental impact of a
coal-fired power plant, sixth interim report, Colstrip, Montana. Corval-
lis, OR: U.S. Environmental Protection Agency, Corvallis Environmental
Research Lab.; 1980b:158-175.
Leetham, J.W.; McNary, T.J.; Dodd, J.L.; Lauenroth, W.K. Response of
field populations of tardigrades to various levels of chronic, low-level
sulfur dioxide exposure. Preston, E.M.; O'Guinn, D.W., eds. The bioen-
vironmental impact of a coal-fired power plant, fifth interim report,
Colstrip, Montana. Corvallis, OR: U.S. Environmental Protection Agency,
Corvallis Environmental Research Lab.; EPA-600/3-80-052; 1980c:268-271.
Leetham, J.W.; McNary, T.J.; Dodd, J.L.; Lauenroth, W.K. Response of
field populations of soil nematodes and rotifers to three levels of
season-long sulfur dioxide exposure. Preston, E.M.; O'Guinn, D.W.;
Wilson, R.A., eds. The bioenvironmental impact of a coal-fired power
plant, sixth interim report, Colstrip, Montana. Corvallis, OR: U.S.
Environmental Protection Agency, Corvallis Environmental Research Lab.;
1980d:131-138.
Leetham, J.W.; Dodd, J.L.; Logan, J.A.; Lauenroth, W.K. Response of Mel-
anoplus sanguinipes to low-level sulfur dioxide exposure from egg hatch to
adult (Orthoptera: Acrididae). Preston, E.M.; O'Guinn, D.W.; Wilson,
R.A., eds. The bioenvironmental impact of a coal-fired power plant, sixth
interim report, Colstrip, Montana. Corvallis, OR: U.S. Environmental
Protection Agency, Corvallis Environmental Research Lab.; 1980e:176-184.
Leetham, J.W.; Dodd, J.L.; Lauenroth, W.K. Effects of low-level sulfur
dioxide exposure on decomposition of western wheatgrass Agropyron smithii
litter under laboratory conditions. Preston, E.M.; O'Guinn, D.W.; Wilson,
R.A., eds. The bioenvironmental impact of a coal-fired power plant, sixth
interim report, Colstrip, Montana. Corvallis, OR: U.S. Environmental
Protection Agency, Corvallis Environmental Research Lab.; 1980f:43-48.
55
-------
Lewis, O.K. Primary producers in grassland ecosystems. Dix, R.L.;
Beidleman, R.G., eds. The grassland ecosystem: A preliminary synthesis -
supplement. Fort Collins, CO: Colorado State University, Range Science
Department; Science Series No. 2 Supplement; 1970:241-1 - 241-87.
Lewis, R.A.; Lefohn, A.S., eds. The bioenvironmental impact of a coal-
fired power plant, first interim report, Colstrip, Montana. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental Re-
search Lab.; EPA-600/3-76-002; 1976. 107 p. Available from: NTIS,
Springfield, VA; PB-251-162/AS.
Lewis, R.A.; Glass, N.R.; Lefohn, A.S., eds. The bioenvironmental impact
of a coal-fired power plant, second interim report, Colstrip, Montana.
Corvallis, OR: U.S. Environmental Protection Agency, Corvallis Environ-
mental Research Lab.; EPA-600/3-76-013; 1976. 314 p. Available from:
NTIS, Springfield, VA; PB-252-177.
Lewis, R.A.; Preston, E.M.; Glass, N.R. Assessment of ecological impact
from the operation of a coal-fired power plant in the north central Great
Plains. Preston, E.M.; Lewis, R.A., eds. The bioenvironmental impact of
a coal-fired power plant, third interim report, Colstrip, Montana. Cor-
vallis, OR: U.S. Environmental Protection Agency, Corvallis Environmental
Research Lab.; EPA-600/3-78-021; 1978:2-11.
Lillie, R.J. Air pollutants affecting the performance of domestic ani-
mals: A literature review. Washington, DC: U.S. Department of Agricul-
ture, Research Service; Agriculture Handbook No. 380; 1970. 109 p.
Available from: Supt. Docs., GPO, Washington, DC; 0-448-268.
Linton, R.W.; Low, A.; Natusch, D.F.S.; Evans, C.A.; Williams, P. Surface
predominance of trace elements in airborne particles. Science 191:852-
854; 1976.
Little, P.; Martin, M.H. Biological monitoring of heavy metal pollution.
Environ. Pollut. 6:1-19; 1974.
Marwitz, J.D.; Veal, D.L.; Cooper, W.A. Possibilities of climate modifi-
cation by large power plants. Clark, W.S., ed. Proceedings of the Fort
Union Coal Field symposium, Volume 5, terrestrial ecosystem section; 1975
April 25-26; Billings MT: Montana Academy of Sciences; 1975:631-635.
McArn, G.E.; Boardman, M.L.; Munn, R.; Wellings, S.R. Relationship of
pulmonary particulates in English sparrows to gross air pollution. J.
Wildl. Dis. 10:335-340; 1974.
McFarlane, J.C.; Rogers, R.D.; Bradley, D.V. The effect of SO2 on soil
microorganism activity. Preston, E.M.; Gullet, T.L., eds. The bioenvi-
ronmental impact of a coal-fired power plant, fourth interim report, Col-
strip, Montana. Corvallis, OR: U.S. Environmental Protection Agency,
Corvallis Environmental Research Lab.; EPA-600/3-79-044; 1979:377-383.
McLaughlin, S.B.; Taylor, G.E. Relative humidity: Important modifier of
pollutant uptake by plants. Science 211:167-169; 1981.
56
-------
McNary, T.J. Temporal variation in SO? concentrations on ZAPS during
1979. Preston, E.M.; O'Guinn, D.W.; Wilson, R.A., eds. The bioenviron-
mental impact of a coal-fired power plant, sixth interim report, Colstrip,
Montana. Corvallis, OR: U.S. Environmental Protection Agency, Corvallis
Environmental Research Lab.; 1980:1-9.
McNary, T.J.; Leetham, J.W.; Lauenroth, W.K.; Dodd, J.L. Response of
rangeland grasshopper populations to controlled levels of SO2. Preston,
E.M.; O'Guinn, D.W., eds. The bioenvironmental impact of a coal-fired
power plant, fifth interim report, Colstrip, Montana. Corvallis, OR:
U.S. Environmental Protection Agency, Corvallis Environmental Research
Lab.; EPA-600/3-80-052; 1980:272-278.
Milberg, R.P.; Lagerwerff, J.V.; Brower, D.L.; Biersdorf, G.T. Soil lead
accumulation alongside a newly constructed roadway. J. Environ. Qual.
9( 1):68; 1980.
Milchunas, D.G.; Lauenroth, W.K.; Dodd, J.L. The effects of SO2 on 14C
translocation in western wheatgrass. Preston, E.M.; O'Guinn, D.W.;
Wilson, R.A., eds. The bioenvironmental impact of a coal-fired power
plant, sixth interim report, Colstrip, Montana. Corvallis, OR: U.S. En-
vironmental Protection Agency, Corvallis Environmental Research Lab.;
1980a:27-42.
Milchunas, D.G.; Lauenroth, W.K.; Dodd, J.L.; McNary, T.J. Effects of
SO2 exposure with nitrogen and sulfur fertilization on the growth of
Agropyron smithii Rydb. Preston, E.M.; O'Guinn, D.W.; Wilson, R.A., eds.
The bioenvironmental impact of a coal-fired power plant, sixth interim
report, Colstrip, Montana. Corvallis, OR: U.S. Environmental Protection
Agency, Corvallis Environmental Research Lab.; 1980b:96-114.
Milchunas, D.G.; Lauenroth, W.K.; Dodd, J.L. Forage quality of western
wheatgrass exposed to sulfur dioxide. J. Range Manage. 34(4):282-285;
1981.
Munshower, F.F. Monitoring the range resource in the vicinity of Col-
strip, Montana. Clark, W.S., ed. Proceedings of the Fort Union Coal
Field Symposium, Volume 5, terrestrial ecosystem section; 1975 April
25-26; Billings, MT: Montana Academy of Sciences; 1975:1-17.
Munshower, F.F.; DePuit, E.J.; Neuman, D.R. The effects of stack emis-
sions on the range resource in the vicinity of Colstrip, Montana: Pre-
operational description of the range ecosystem. Bozeman, MT: Montana
State University, Animal and Range Sciences Department; Research Report
No. 126; 1978. 196 p.
Nakamura, H. Investigation on injury to rice plants from photochemical
oxidants. Bull. Nat. Inst. Ag. Sci. 30:1-68; 1979.
National Research Council. Committee on Medical and Biological Effects
of Environmental Pollutants. Ozone and other photochemical oxidants.
Washington, DC: National Academy Press; 1977. 719 p.
57
-------
Newman, J.R. Animal indicators of air pollution: A review and recommen-
dations. 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-80/40.1; 1980.
Newman, J.R.; Yu, M. Fluorosis in black-tailed deer. J. Wild!. Dis.
12:39-41; 1976.
Northern Arizona University. Environmental impact studies of the Navajo
and Kaiparowits power plants, final report, 1 June 1975 - 31 May 1976.
Flagstaff, AZ: Northern Arizona Univ., Environmental Impact Studies;
1979. 308 p.
Nyborg, M.; Crepin, J.; Hocking, D.; Baker, J. Effect of sulfur dioxide
on precipitation and on the sulfur content and acidity of soils in
Alberta, Canada. Dochinger, L.S.; Seliga, T.A., eds. Proceedings of the
international symposium on acid precipitation and the forest ecosystem;
1975 May 12-15; Ohio State University, Columbus, Ohio. Upper Darby, PA:
U.S. Department of Agriculture, Forest Service, Northeastern Forest Ex-
periment Station; 1976:767-778. Available from: NTIS, Springfield, VA;
PB-258645.
O'Neill, R.V.; Ausmus, B.S.; Jackson, D.R.; Van Hook, R.I.; Van Voris, P.;
Washburne, C.; Watson, A.P. Monitoring terrestrial ecosystems by analysis
of nutrient export. Water Air Soil Pollut. 8:271-277; 1977.
Pell, E.J. The impact of ozone on the bioenergetics of plant systems.
Dugger, M., ed. Air pollution effects on plant growth. Washington, DC:
American Chemical Society, ACS Symp. Ser. No. 3; 1974:106-114.
Preston, E.M.; Gullet, T.L., eds. The bioenvironmental impact of a coal-
fired power plant, fourth interim report, Colstrip, Montana. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental Re-
search Lab.; EPA 600/3-79-044; 1978. 931 p.
Preston, E.M.; Lewis, R.A., eds. The bioenvironmental impact of a coal-
fired power plant, third interim report, Colstrip, Montana. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental Re-
search Lab.; EPA-600/3-78-021; 1978. Available from: NTIS, Springfield,
VA; PB-280-326/AS.
Preston, E.M.; O'Guinn, D.W., eds. The bioenvironmental impact of a coal-
fired power plant, fifth interim report, Colstrip, Montana. Corvallis,
OR: U.S. Environmental Protection Agency, Corvallis Environmental
Research Lab.; EPA-600/3-80-052; 1980. 360 p.
Preston, E.M.; O'Guinn, O.W.; Wilson, R.A., eds. The bioenvironmental
impact of a coal-fired power plant, sixth interim report, Colstrip, Mon-
tana. Corvallis, OR: U.S. Environmental Protection Agency, Corvallis
Environmental Research Lab.; 1980. 330 p.
58
-------
Price, H.; Treshow, M. Effects of ozone on the growth and reproduction
of grasses. Proceeding International Clean Air Conference; 1972 May
15-18; Melbourne, Austrialia; 1972:275-280.
Price, P.W.; Rathcke, B.J.; Gentry, D.A. Lead in terrestrial arthropods:
Evidence for biological concentration. Environ. Entomol. 3(3):370-372:
1974.
Quarles, H.D.; Hannawalt, R.B.; Odum, W.E. Lead in small mammals, plants,
and soil at varying distances from a highway. 0. Appl. Ecol. 11(3):937-
949; 1974.
Rice, P.M.; Pye, L.H.; Bo Id i, R.; O'Loughlin, J.; Tourangeau, P.C.;
Gordon, C.C. The effects of "low level SO2" exposure on sulfur accumu-
lation and various plant life responses of some major grassland species
on the ZAPS sites. Preston, E.M.; Gullett, T.L., eds. The bioenviron-
mental impact of a coal-fired power plant, fourth interim report, Col-
strip, Montana. Corvallis, OR: U.S. Environmental Protection Agency,
Corvallis Environmental Research Lab.; EPA-600/3-79-044; 1979:494-591.
Rice, P.M.; Gordon, C.C.; Tourangeau, P.C.; Pye, L. Mycorrhizal associa-
tion and root characteristics in western wheatgrass fumigated with sulfur
dioxide. Preston, E.M.; O'Guinn, D.W., eds. The bioenvironmental impact
of a coal-fired power plant, fifth interim report, Colstrip, Montana.
Corvallis, OR: U.S. Environmental Protection Agency, Corvallis Environ-
mental Research Lab.; EPA-600/3-80-052; 1980:120-135.
Richards, G.A.; Mulchi, C.L.; Hall, J.R. Influence of plant maturity on
the sensitivity of turfgrass species to ozone. J. Environ. Qual. 9(1):
49-53; 1980.
Richkind, K.E.; Hacker, A.D. Responses of natural wildlife populations
to air pollution. 0. Toxicol. Environ. Health 6:1-10; 1980.
Ricks, G.R.; Williams, R.O.H. Effects of atmospheric pollution on decid-
uous woodland - Part two. Effects of particulate matter upon stomatal
diffusion resistance in leaves of Quercus petraea (Mattuschka) Liebl.
Environ. Pollut. 6:87-109; 1974.
Rutherford, G.K.; Bray, C.R. Extent and distribution of soil heavy metal
contamination near a nickel smelter at Coniston, Ontario. 0. Environ.
Qual. 8(2):219-222; 1979.
Scanlon, P.F. Lead contamination of mammals and invertebrates near high-
ways with different traffic volumes. National Research Council. Animals
as monitors of environmental pollution. Washington, DC: National Academy
of Sciences; 1979:200-208.
Schlesinger, W.H.; Potter, G.L. Lead, copper, and cadmium concentrations
in small mammals in the Hubbard Brook Experimental Forest. Oikos
25(2):148-152; 1974.
59
-------
Schwartz, C.C.; Lauenroth, W.K.; Heitschmidt, R.K.; Dodd, J.L. Effects of
controlled levels of sulfur dioxide on the nutrient quality of western
wheatgrass. 0. Appl. Ecol. 15:869-874; 1978.
Scott, J.A.; French, N.R.; Leetham, J.W. Patterns of consumption in
grasslands. French, N.R., ed. Perspectives in grassland ecology. New
York: Springer-Verlag; Ecological Studies No. 32; 1979:89-105.
Severson, R.C.; Gough, L.P. Environmental implications of element emis-
sions from phosphate-processing operations in southeastern Idaho. Wash-
ington, DC: U.S. Geological Survey; Professional Paper No. 1083; 1979.
20 p. Available from: Supt. Docs., GPO, Washington, DC; 677-026/55.
Shreffler, J.H. Factors affecting dry deposition of SO2 on forests and
grasslands. Atmos. Environ. 12:1497-1503; 1978.
Shriner, D.S. Effects of simulated acidified rain on host-parasite in-
teractions in plant diseases. Phytopathology 68:213-218; 1978.
Shriner, D.S.; Cowling, E.B. Effects of rainfall acidification on plant
pathogens. Hutchinson, T.C.; Havas, M., eds. Effects of acid precipita-
tion on terrestrial ecosystems. New York: Plenum Press; 1980:435-442.
Skye, E. Botanical indications of air pollution. Acta Phytogeogr. Suec.
50:285-287; 1965.
Skye, E. Lichens as biological indicators of air pollution. Annu. Rev.
Phytopathol. 17:325-341; 1979.
States, J.S. Effect of atmospheric pollutants on the microbial decompo-
sition process of an acid ecosystem. Proceedings of the fourth joint
conference on sensing of environmental pollutants. Washington, DC:
American Chemical Society; 1978:54-56.
Sundstrom, K.R.; Hallgren, J.E. Using lichens as physiological indicators
of sulfurous pollutants. Ambio 2(1-2):13-21; 1973.
Taylor, J.E.; Leininger, W.C. Plant community changes due to low level
SO2 exposure. Preston, E.M.; Gullet, T.L., eds. The bioenvironmental
impact of a coal-fired power plant, fourth interim report, Colstrip, Mon-
tana. Corvallis, OR: U.S. Environmental Protection Agency, Corvallis
Environmental Research Lab.; EPA-600/3-79-044; 1979:610-641.
Taylor, J.E.; Leininger, W.C.; Hoard, M.W. Plant community structure on
ZAPS. Preston, E.M.; O'Guinn, D.W., eds. The bioenvironmental impact of
a coal-fired power plant, fifth interim report, Colstrip, Montana. Cor-
vallis, OR: U.S. Environmental Protection Agency, Corvallis Environmental
Research Lab.; EPA-600/3-80-052; 1980:216-234.
60
-------
Taylor, O.C., ed. Oxidant air pollution effects on a western coniferous
forest ecosystem. Task B report. Riverside, CA: Univ. of California,
Air Pollution Research Center; 1973.
Thor, G.L. Photosynthesis in western wheatgrass exposed to chronic SO?
air pollution. Fort Collins, CO: Colorado State University, M.S. Thesis;
1980. 71 p.
Tingey, D.T.; Bard, L.; Field, R.W. The relative sensitivity of selected
plant species to several pollutants singly and in combination. Preston,
E.M.; Lewis, R.A., eds. The bioenvironmental impact of a coal-fired power
plant, third interim report, Colstrip, Montana. Corvallis, OR: U.S. En-
vironmental Protection Agency, Corvallis Environmental Research Lab.;
EPA-600/37 8-021; 1978:508-513.
Treshow, M. The impact of air pollution on plant populations. Phyto-
pathology 58:1108-1113; 1968.
Treshow, M.; Stewart, D. Ozone sensitivity of plants in natural communi-
ties. Biol. Conserv. 5(3):209-214; 1973.
U.S. Environmental Protection Agency. National air quality, monitoring
and emissions trends report, 1977. Research Triangle Park, NC: Office
of Air, Noise and Radiation; EPA-450/2-78-052; 1978. 102 p.
U.S. Fish and Wildlife Service. Terrestrial habitat evaluation criteria
handbook. Big Sandy Creek, Texas; 1980. 344 p. Available from: Office
of Biological Services, Western Energy and Land Use Team, Fort Collins,
Colorado.
Van Hook, R.I. Cadmium, lead and zinc distributions between earthworms
and soils: Potentials for biological accumulation. Bull. Environ.
Contam. Toxicol. 12(4):509-512; 1974.
Westman, W.E. Oxidant effects on Californian coastal sage scrub. Science
205:1001-1003; 1979.
Wisniewski, J.; Keitz, E. Acid rain deposition patterns in the conti-
nental United States. Water Air Soil Pollut. (in press); 1982.
Wood, C.W.; Nash, T.H. Copper smelter effluent effects on Sonoran desert
vegetation. Ecology 57:1311-1316; 1976.
Woodwell, G.M. Effects of pollution on the structure and physiology of
ecosystems. Science 168:429-433; 1970.
Worth, Ripperton, L.A. Rural ozone - sources and transport.
Pfafflin, O.R.; Ziegler, E.N., eds. Advances in environmental science and
engineering. New York: Gordon and Breach Science Publishers; 1980:150-
170.
61
-------
Youngner, V.B.; Nudge, F.J. Air pollution oxidant effects on cool-season
and warm-season turfgrasses. Agron. J. 72:169-172; 1980.
Ziegler, I. The effect of SOo pollution on plant metabolism. Residue
Rev. 56:79-105; 1975.
62
-------
5027? -IQ1
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
FWS/QBS-80/40.7
4. Title and Subtitle
Air Pollution and Acid Rain,
The Effects of Air Pollution
Wildlife, and Their Habitats
Report 7
and Acid Rain
- Grasslands
on Fish,
7. Author(s)
A. Peterson
9. Performing Organization Name and Address
Dynamac Corporation
Dynamac Building
11140 Rockville Pike
Rockville, MD 20852
12. Sponsoring Organization Name and Address US Department Of the
Interior, Fish and Wildlife Service/Office of Bio-
logical Services; Eastern Energy and Land Use Team,
Route 3 Box 44, Kearneysvilie, WV 25430
3. Recipient's Accession No.
5. Report Date
June 1982
8. Performing Organization Rept. No.
10. Project/Task/Work Unit No.
11. Contract(C) or Grant(G) No.
(O 14-16-0009-80-085
------- |