Biological Services Program
FWS/OBS-80/40.9 Air Pollution and Acid Rain,
JUNE 1982 Report No. 9
THE EFFECTS OF AIR POLLUTION AND ACID RAIN
ON RSH, WILDLIFE, AND THEIR HABITATS
DESERTS AND STEPPES
Office of Research and Development
U.S. Environmental Protection Agency
Fish and Wildlife Service
U.S. Department of the Interior
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The Biological Services Program was established within the U.S. Fish and
Wildlife Service to supply scientific information and methodologies on key
environmental issues that impact fish and wildlife resources and their supporting
ecosystems.
Projects have been initiated in the following areas: coal extraction and
conversion; power plants; mineral development; water resource analysis, including
stream alterations and western water allocation; coastal ecosystems and Outer
Continental Shelf development; environmental contaminants; National Wetland
Inventory; habitat classification and evaluation; inventory and data management
systems, and information management.
The Biological Services Program consists of the Office of Biological Services in
Washington, D.C., which is responsible for overall planning and management;
National Teams, which provide the Program's central scientific and technical
expertise and arrange for development of information and technology by contracting
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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.
I,* _ by the Superintendent of Document*. U.S. Government I'rlntlnR Office
WuxhlnRton. O.C. 20402
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FWS/0BS-80/40.9
June 1982
AIR POLLUTION AND ACID RAIN REPORT 9
THE EFFECTS OF AIR POLLUTION AND ACID RAIN
ON FISH, WILDLIFE, AND THEIR HABITATS
DESERTS AND STEPPES
by
Edward N. Mirsky
Dan Harper
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
Kearneysvilie, 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
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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-XD581 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:
Mirsky, E.N. 1982. The effects of air pollution and acid rain on fish,
wildlife, and their habitats - deserts and steppes. U.S. Fish and Wildlife
Service, Biological Services Program, Eastern Energy and Land Use Team,
FWS/OBS-80/40.9. 38 pp.
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ABSTRACT
This report cm desert and steppe 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. Accompany-
ing reports in this series are the following: Introduction, Forests,
Lakes, Rivers and Streams, Tundra and Alpine Meadows, Urban Ecosystems,
Grasslands, and Critical Habitats of Threatened and Endangered Species.
This report describes the features of desert and steppe ecosystems
which determine the sensitivity of these ecosystems to air pollution.
Data related to the effects of air pollutants on biota and whole ecosys-
tems are reviewed. The data come from both field and laboratory studies.
Some general information based on studies in other ecosystems is included.
Suggestions are made for areas of further research.
In general there has been less concern for the effects of air pollu-
tants on the biota of deserts and steppes than for those of other ecosys-
tems. Much of the concern for, and research on, air pollution in desert
and steppe ecosystems is related to fossil fuel powered electric gener-
ating plants.
In the reports of this series, a simplified classification of air
pollutants has been used. Within this framework air pollutants fall into
the categories of photochemical oxidants, acidifying air pollutants, or
particulates, as described in detail in the introductory report of the
series.
i i i
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CONTENTS
Page
ABSTRACT 111
FIGURES i . . *
TABLES V
1.0 INTRODUCTION 1
2.0 ECOSYSTEM OVERVIEW 2
2.1 Ecosystem Geography and Characteristics 2
2.2 Types of Air Pollutants ...» 2
2.3 Susceptibility of Soils to Acid Deposition 7
3.0 EFFECTS OF ACID RAIN AND AIR POLLUTION ON FISH
AND WILDLIFE OF THE DESERT AND STEPPE ECOSYSTEMS 10
3.1 Effects on Individuals and Populations 10
3.1.1 Effects on Fish 10
3.1.2 Effects on Wildlife 11
3.1.3 Effects on Plants 17
3.2 Ecosystem Effects 21
3.2.1 Effects on Plant Diversity
and Productivity 21
3.2.2 Microbial Effects . 24
3.2.3 Aquatic Ecosystems * . . 26
4.0 SUMMARY AND TOPICS FOR FURTHER RESEARCH 2d
4.1 Summary Facts 29
4.2 Research Needs 30
4.2.1 Physicochemical Effects 30
4.2.2 Effects on Individuals 31
4.2.3 Effects on Habitats * . . . . 31
4.2.4 Effects on Ecosystems 31
4.2.5 Integrated Program of Study 31
REFERENCES 32
iv
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FIGURES
Number Page
1 Deserts, steppes, and California chaparral
as defined by Bailey 3
2 Regional distribution of acid rainfall 8
3 SO2 and NO? uptake by air-dried
desert soil 26
TABLES
Number Page
1 Features of Bailey's desert and steppe provinces 4
2 Responses of wildlife to air emissions 12
3 Effects on animals of exposure to selected air
pollutants 13
4 The major biological systems of animals affected
by selected air emissions H
5 Effects of selected air emissions on animal
behavior 15
6 Plant species and exposure concentrations used in
greenhouse experiments 18
7 Productivity of desert and arid lands 2?
8 Sulfur and nitrogen dioxide uptake by desert soil
under various conditions of moisture content and
sterility 27
v
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1.0 INTRODUCTION
As part of a series of reports discussing the effects of air pollu-
tion and acid deposition on fish, wildlife, and their habitats, this docu-
ment reviews research related to deserts and steppes of the southwestern
United States. Companion reports in this series review the effects of air
pollution on forests and grasslands, therefore, these aspects of the
steppe are not reviewed in this document. The California chaparral mixes
with the American desert towards the eastern edge of the Los Angeles
basin. Information on the long-term effects of exposure to photochemical
air pollution in this area is included to augment information on deserts
and steppes. The objective of the report is to provide a document that
will assist the U.S. Fish and Wildlife Service, and others, in the antici-
pation, identification, and evaluation of air pollution damage to deserts
and adjacent steppes, and to identify relevant topics for further re-
search.
This paper reviews data which indicates that animals and plants (in-
cluding lichens) may be adversely affected by exposure to photochemical
air pollutants and acid deposition. Acid rain has been recorded in the
Mexican Highlands Shrub Steppes of Arizona, and oxidizing air pollution
impinges on the areas of the American desert nearest the Los Angeles air
basin. Statistical evidence suggests a causal relationship between pollu-
tion levels and the abundance and distribution of California chaparral and
desert vegetation. Although existing ambient concentrations of pollutants
are below the threshold for detection of adverse effects, the potential
for harm has been demonstrated and monitoring is needed to detect change
before effects become irreversible.
The next section (Section 2) of this report reviews pedological and
geological features of deserts and steppes which play an important role in
determining the extent of air pollution damage. Section 3 reviews the
available research concerning the effects of air pollution on fish and
wildlife in deserts and steppes. The section is divided into two parts;
the first of these deals with the effects on individuals and populations
and the second reviews effects at the ecosystem level of organization.
The final section of the report (Section 4) summarizes the most important
findings and suggests areas where further research into the effects of air
pollution within desert ecosystems is likely to be most productive.
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2.0 ECOSYSTEM OVERVIEW
2.1 ECOSYSTEM GEOGRAPHY AND CHARACTERISTICS
The deserts and steppes of the southwestern United States lie south
of the Rocky Mountains (Bailey 1978). These deserts are divided into the
Chihuahuan Desert Province of southern New Mexico and western Texas, and
the American Desert Province of California, Arizona, Nevada, and Utah
{Figure 1). The American Desert includes the Mojave, Colorado, and Son-
oran Deserts. Steppes include the Mexican Highlands Shrub Steppe Pro-
vince, which lies between the American Desert on the west and the Chihua-
huan Desert on the east, and the Colorado Plateau Province in Arizona, New
Mexico, and Utah. Steppes also include the Intermountain Sagebrush
Province, or Great Basin, which extends north from the American Desert,
encompassing most of Nevada and portions of Utah, California, Idaho,
Oregon, and Washington. These provinces and their characteristic
land-surface forms, climate, flora and fauna are presented in Table 1.
2.2 TYPES OF AIR POLLUTANTS
Because the focus of these reports is on the effects of air pollution
and acid deposition, a simplified classification of air pollutants has
been adopted throughout the series. Pollutants affecting wildlife re-
sources have been classified into three categories: photochemical oxi-
dants, acidifying pollutants, and particulates. The introductory volume
of the series discusses this classification scheme and presents a summary
of pollutant origins, atmospheric transport, transformation, and deposi-
tion. The following paragraphs present information on the pollutants
relevant to the review of their effects on desert and steppe ecosystems.
The photochemical oxidants are secondary pollutants produced by com-
plex chemical reactions involving the primary pollutants, notably nitrogen
oxides and hydrocarbons (U.S. EPA 1978). The major oxidants of concern
are ozone, peroxyacetylnitrate (PAN), and aldehydes such as formaldehyde.
Of these, ozone is the most toxic and is also the most abundant (National
Research Council 1977a). As a result, ozone toxicology is the best ap-
proximation of the toxicology of the entire photochemical oxidant complex.
PAN is actually the most abundant of a group of similar compounds, but it
is the only member of the group which occurs in concentrations high enough
to cause injury to plants and animals. Peak concentrations of ozone in
urban areas range from 0.2 to 0.3 ppm, while average rural concentrations
rarely exceed 0.3 ppm; the corresponding figures for PAN are peak urban
concentrations from 0.05 to 0.2 ppm with rural maximum concentrations
seldom greater than 0.003 ppm (U.S. EPA 1978).
Urban oxidant plumes may extend as far as 160 km or more downwind
(U.S. EPA 1978). In Southern California this results in oxidant transport
across much of the American Desert. Similar transport is expected from
Phoenix, Tucson, and other urban centers of the southwest.
2
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Intermountain
Sagebrush
CO
American Desert' t
Mexican Highlands
Shrub Steppe
Colorado Plateau
Chihuahuan Desert
Figure 1. Deserts, steppes and California Chaparral as defined by Bailey (1978)
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Table 1. Features of Bailey's desert and steppe provinces.
Province
Land-surface Form
CIimate
Dominant Flora
Typical Fauna
Chihuahuan
Desert
(3210)a
166,000 km2
American
Desert
(3220)a
200,700 km2
• permanent streams:
Rio Grande River,
Pecos River
• undulating plains with
elevations near 1,200 m
some isolated mountains
rise to 1,500 m
• wash dry most of year,
fill with rain runoff
• basins drain into playa
lakes that are dry dur-
ing rainless periods
• extensive dunes of silica
sand and a few of gypsum
sand
• some isolated buttes of
blackish lava
• arid; torrential summer
storm July through Octo-
ber; northern part of
province receives winter
rains
• average annual tempera-
ture range 10-18°C (50-
65°F); winters include
brief periods of tempera-
tures below freezing
• includes Mojave and
Colorado deserts
• permanent streams:
Colorado River and
large tributaries
its
• extensive gently undu-
lating plains with iso-
lated buttes. Elevations
range from -85 m to
1,200 m in valleys and
basins, and 3,400 m in
mountains
• arid: rain in winter;
summer storms in Arizona
and California east of
Colorado river
• average annual precipita-
tion 50-250 mm (2-10 in),
610 mm (25 in) in moun-
tains
t average annual temperature
15-24 C (60-75°F)
• creosote bush covers great
areas especially on gravel fans
• short grass grows in associa-
tion with shrubs in many places
• on deep soils, mesquite is
often the dominant plant
• on rocky slopes ocotillo is
abundant
• on slopes leading down to the
Rio Grande the ceniza shrub
domintes
• cottonwoods and other trees grow
beside rivers
• pinyon pine and juniper on rocky
outcrops on Stockton Plateau in
western Texas
t oak and juniper woodlands at
higher elevations and pine and
oak at highest elevations
• sparse cacti and thorny shrubs
are conspicuous
• creosote bush covers extensive
areas
¦ mesquite grows in soft sand
• paloverde, ocotillo, saguaro,
and bitterbrush are found on
deep slopes
• Joshua trees are prominant
toward the northern margin of
the province
• predators: coyote, bobcat,
golden eagle, great horned owl,
red-tailed hawk, ferruginous
hawk
• large herbivores: pronghorn
antelope, mule deer, white-
tailed deer, collared peccary
• small herbivores: black-tailed
jackrabbit, desert cottontail,
kangaroo rat, wood rat, and
other rodents; scaled quail,
Ganbel's quail, bobwhite quail,
and numerous small birds
• predators: desert kit fox,
coyote, western spotted skunk,
red-tailed hawk, prairie falcon,
roadrunner, and rattlesnake
• large herbivores: desert mule
deer, peccary, desert bighorn
sheep
• small herbivores: desert tor-
toise, Gambel's quail, kangaroo
rat, and other small mammals
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Table 1. Continued
Province
Land-surface Form
Climate
Dominant Flora
Typical Fauna
Mexican
highlands
shrub steppe
(3140)®
45,325 km?
plains range in eleva-
tion from about 1,200 m
to 2,100 m; high moun-
tains to 2,700 m
seraiarid, most rain in
summer
average annual temperature
13-2rc (55-70°F)
periods of extremely cold
weather may occur
• at higher elevations pinyon,
pines, and juniper are prominent
• soils near playas are alkali;
quantity decreases with distance
from lake producing a zonation
of vegetation according to tol-
erance for salts
• four life belts occur: desert
belt at lower elevations from
the American desert to the
Santa Catalina Mountains of
Arizona; plants include i
saguaro, creosote bush, palo-
verde
• arid grassland belt over most
of the high plains; tall grass
and short grass (grana) are
abundant
predators: coyotes, golden
eagle, great horned owl, and
hawks
large herbivores: mule deer
pronghorn antelope
and
small herbivores: scaled quail,
Gambel's quail, jackrabbit,
cottontail, kangaroo rat, and
other rodents
Colorado
Plateau
(P3130)a
245,300 km2
• plateau tops range from
1,500-2,100 m
• in some areas volcanic
mountains rise 300-900 m
above the plateau
cold winters and hot
summer days
annual average tempera-
tures 4-13°C
average precipitation is
about 500 mm (20 in)
mostly in winter, but
thunderstorms in summers
• submontane belt covers most of
the hills and lower slopes of
mountains; oaks and some juniper
are present
• montane belt at higher elevations
dominated by pines and oaks;
douglas and white fir occur on
sheltered upper slopes of Santa
Catalina Mountains
• lower elevations of grasslands
with sagebrush dominant over
extensive areas; several kinds
of cacti and yucca are common
« cottonwoods and other trees
along permanent streams
• woodland zone is most exten-
sive; open stands of pinyon
pine and several species of
juniper
• predators: mountain lion,
coyote, and bobcat
• large herbivores: pronghorn
antelope and elk
• small herbivores: cliff chip-
munk, jackrabbit, cottontai,
and small rodents and birds
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Table 1. Concluded
Province
Land-surface Farm
CIimate
Dominant Flora
Typical Fauna
« pine and fir are dominant in
snountains
Intermountain • numerous separate in-
Sagebrush
(3130)a
526,806 km11
terior basins, few of
which drain to the sea
• accumulation of alkaline
and saline salts in
lower parts of many
basins
• streams are rare and
few are permanent
• many steep mountains
• summers hot; winters
moderately cold
• average annual temperature
4-13°C (40-55°F)
• average precipitation
125-500ram (5-20 in);
almost no rain in summer
except in mountains
• sagebrush dominates at lower
elevations; other plants in-
clude shadscale, fourwing
saltbrush, rubber rabbitbrush,
spiny hopsage, and horsebrush,
all of which tolerate alkali
• communities dominated by
greasewood or saltgrass where
salt concentration is very
high
• ponderosa pine on lower and
more exposed mountain slopes,
Douglas-fir on higher, shel-
tered slopes; subalpine fir and
Englemann spruce in subalpine
belt; few mountains high
enough to support alpine
vegetation
• few large mammals live in
province
• predators: mountain lion,
bobcat, kit fox, badger
• large herbivores: mule deer
• small herbivores: ground
squirrels, jackrabbits,
kangaroo mice, wood rats
aNumbers refer to identification of provinces by Bailey
(Adapted from Bailey 1978}
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The acidifying air pollutants include the primary gaseous pollutants
which react witn water to form acids. The most important of these are the
oxides of sulfur and nitrogen which react to form sulfuric and nitric
acids. These reactions can take place either in the atmosphere or in the
biotic and abiotic components of ecosystems. When the transformations
take place in the atmosphere, the resulting acids can be deposited hun-
dreds of kilometers from the source of pollution, as discussed in the in-
troductory report of this series. Because of the long range aspect of
acid deposition, there is growing concern about the sensitivity of remote
areas, once considered unaffected by air pollution. The susceptibility of
soils in desert and steppe ecosystems is discussed in more detail below.
The acid products of atmospheric transformations can be removed from
the atmosphere through either wet or dry deposition processes. The form-
er, usually referred to as acid precipitation, are associated with rain,
snow, hail, sleet, and fog. Dry deposition, expected to be especially
relevant in desert ecosystems, is much more difficult to measure, and con-
sequently much less is known about this mode of acid deposition. In
either form the acids may directly affect plants and animals, although
much more is known about indirect effects on wildlife brought about
through changes in habitat, for example alterations in the pH of soils and
surface waters. Changes in soil acidity, in turn, may lead to other ef-
fects such as increased mineral leaching resulting in soil impoverishment.
Particulate air pollutants are solid particles or liquid droplets
suspended in the atmosphere and range in composition from single elements
to complex chemicals and in size from clusters of molecules to visible
dust partic?es. Included in this category are the metaTs, su?fates, trace
elements, and organic micropollutants. In the arid deserts and steppes,
the effects of particulate pollution are difficult to study because of the
frequent strong winds characteristic of these regions, generating high
background levels of dust. For that reason, there is little known about
the effects of particulates in the desert and they will not be treated in
detail in this review.
The burning of fossil fuels is a major source of air pollution in
desert and steppe ecosystems. These pollutants may be transported long
distances and ultimately deposited in even the most remote areas of the
southwest (Fetb 1967; Craig 1971; Blumenthal et al. 1974; Hoffler et al.
1979).
2.3 SUSCEPTIBILITY OF SOILS TO ACID DEPOSITION
Areas of the United States where acid rainfall has been recorded are
identified in Figure 2. In the regions covered by this report only the
Mexican Highlands Shrub Steppe receives acid rainfall. The impact of
acid precipitation is determined largely by the chemical and physical
characteristics of the soil and rock. Limestone has essentially infinite
acid-neutralizing (buffering) capacity because of the large amount of
7
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00
San Francisco
Portland'
Los Angeles
pH greater than 5.5
m pH between 5.0 and 5.5
H pH between 4.0 and 5.0
pH less than 4.0
Figure 2. Regional distribution of acid rainfall.
(From USEPA 1980)
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free carbonate present (Hendrey et al. 1980). No impact is expected on
soils, streams, or lakes underlain By or receiving runoff from soils with
free carbonate present. Rock of intermediate buffering capacity such as
sandstones, shales, and many volcanic types have little or no free car-
bonate present. However, due to the presence of other buffering agents,
such as aluminum and iron hydroxides, silicates, etc., they are only
slightly affected by acid rain. Predominately igneous rocks, such as
granite and quartzite, which yield acidic products as they weather, pos-
sess minimal or no buffering capacity and in areas underlain by these
types of rocks the effects of acid deposition can be severe.
Desert soils are primarily aridisols and entisols, both of which have
accumulations of calcium carbonate. Soils of the Colorado Plateau Steppe
(including the Kaiparowits Basin) are moderately alkaline (average pH 7.8-
8.9f and may show high onsite variability (e.g., pH 6.5-9.2 in pinyon-
juniper woodlands) (Northern Arizona University 1979). Soluble carbonates
in the soil (0.56-3.45%) provide high buffering capacity to neutralize the
effects of deposited acids. Similarly the heavy accumulation of alkaline
and saline salts in the low portions of the Great Basin (Bailey 1978) can
be expected to render these areas insensitive to the effects of acid
deposition.
In the Mexican Highlands Shrub Steppe (Mule Mountains, Arizona) gran-
ite and limestone soils have representative pHs of 6.1 and 7.8, respec-
tively (Wentworth 1981). The pH of the granite soils falls within the
range considered ideal for agricultural purposes (see, for example, Brady
1974).
These observations suggest that except for granites and noncalcareous
sandstones, desert and steppe soils are capable of neutralizing the impact
of wet or dry acid deposition.
9
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3.0 EFFECTS OF ACID RAIN AND AIR POLLUTION ON FISH
AND WILDLIFE OF THE DESERT AND STEPPE ECOSYSTEMS
This section is divided into two parts. The first reviews findings
concerning individual species and populations. The second part reviews
effects which may be expected at the ecosystem level.
3.1 EFFECTS ON INDIVIDUALS AND POPULATIONS
The purpose of this section is to review the available information
on the toxic effects of air pollution on fish, wildlife, and plants, and
to identify plants and animals that may be adversely affected themselves
or may indirectly cause adverse effects in others.
3.1.1 Effects on Fish
Acid deposition has been implicated in the decline or elimination of
fish populations in lakes and streams of the eastern United States and
Canada (Beamish 1976; Beamish and Harvey 1972; Schofield; 1976; see re-
ports on Lakes, and on Rivers and Streams in this series). In the Ameri-
can Desert only one study has been found related to fish. Lee and Gerking
(1980) studied survival and reproductive performance of the desert pupfish
(Cyprinodon n. nevadensis) in the laboratory under conditions of increased
acidity (decreased pH). The spring from which the laboratory stock was
collected is naturally basic with a pH of 8.3. A number of findings
emerged from the study:
• The 96-hour LC50 f°r the species was pH 4.56. The LC50 is the
concentration at which 50% of the individuals in the test popula-
tion are killed.
• Egg production was significantly reduced at every pH level tested
below the control level (pH 8.3). At pH 7, there was a 61% reduc-
tion in the number of eggs laid. No eggs hatched below pH 6, and
egg laying virtually ceased at pH 5 (0.8% of control level).
• The percentage of fertile eggs that hatched declined to 50% at
pH 7.
• Reproductive performance did not fully recover to control levels
when the fish were placed in more favorable conditions after expo-
sure to low pH values. Furthermore, acclimation did not occur;
the longer the exposure to acid conditions, the greater the detri-
mental effect upon the exposed fish.
• Larvae are less tolerant to acid conditions than adults. The
larval 96-hour LC50 is pH 4.72.
10
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Tolerance, in general, has two components: a genetically determined
capacity to survive within a range of a parameter (in this case pH), and
an ability to vary the tolerance range as a result of previously experi-
enced conditions (acclimation). Acclimation did not occur in C. n. neva-
densi s. There is evidence, however, that the various isolated populations
of Cyprinodon have differentiated in time (Miller 1950; Brown and Feldmeth
1971)1 Each population of desert pupfish may have a different minimum pH
for successful reproduction and a limit for survival corresponding with
the natural waters they inhabit.
3.1.2 Effects on Wildlife
A review of the experimental toxicology of photochemical oxidants was
conducted by the National Research Council (1977 a,b). These studies gen-
erally used commercially bred stains of laboratory animals to assess the
potential hazards of the individual pollutants, often at concentrations
higher than those in ambient air. Nevertheless, they provide a prelimin-
ary indication of the hazards to terrestrial mammals that could occur in
the desert. It should be pointed out that laboratory rodents are only
distantly related to native species of the United States. In the labora-
tory, the closest phylogenetic relative of the deer mouse (Peromyscus
spp.), for example, is the hamster; laboratory mice and rats are very
closely related to each other; and guinea pigs are distantly removed from
both groups.
Studies on laboratory animals tend to examine the effects of single
pollutants at high concentrations. In nature, however, organisms are ex-
posed to a mixture of pollutants. In spite of these shortcomings, it is
worth noting that a number of responses of wildlife to gaseous and partic-
ulate emissions have been reported. The effects of air emissions on dom-
estic and laboratory animals and wildlife (but not desert animals specifi-
cally) have been reviewed by Newman (1979, 1980). In general, the sever-
ity of the effects, acute or chronic, depends on the specific pollutant,
its concentration, the pathway of entry into the body, and the duration of
exposure. The effect will also vary with the age, sex, reproductive con-
dition, nutritional status, and general health of the organism at the time
of exposure. The nature of the physiological and ecological responses to
air pollutants are shown in Table 2, and Table 3 summarizes the effects of
specific pollutants on birds and mammals. The most commonly affected sys-
tems are the respiratory, central nervous, and gastrointestinal systems
(Table 4). The first signs of effects of air emissions on wildlife are
usually observed in behavior (Table 5). Abnormal behavior may range from
lethargy and gasping to muscle tremors and paralysis.
A recent study by Richkind and Hacker (1980) indicates that chronic
exposure of small mammal populations to air pollution can favor the survi-
val of genetically resistant individuals. In their work, Richkind and
Hacker used the California deer mouse (Peromyscus californicus), close
relatives of which are abundant throughout southwestern deserts. The
California deer mouse differs from its desert relatives in at least one
11
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Table 2. Responses of wildlife to air emissions.
Ecological responses
Physiological responses
Change in population numbers
Change in spatial distribution
Change in appearance
Change in birth rate
Change in death rate
Abnormal behavior
Changes in blood chemistry or
physiology
Changes in cellular enzymes
Changes in energy requirements for
normal activities
Change in growth rates
Change in genetic resistance
Lowered resistance to natural
environmental stress and neurologic
effects
Teratogenic, mutagenic, or carcin-
ogenic effects
(Adapted from Newman 1980)
12
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Table 3. Effects on animals of exposure to selected air pollutants.
Selected air pollutants
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Changes in population numbers
Changes in blood chemistry of physiology
Changes in cellular enzymes
Changes in externa) appearance
Change in population distribution
Change in death rate (in free
living animals)
Change in birth rate
Change in growth rate
Change in genetic resistance
Abnormal behavior
Physiological changes observed in
autopsy and histological analysis
Lowered resistance to natural
environmental stress
Residue accumulation in body tissue
Teratogenic, mutagenic, or carcinogenic
effects
• •
• • •
• • • •
I I
I I I
• • • •
• •
• •
• •
• I •
¦ •
• •
• I
• I
• •
I I I I •
• •••••
• • •
• I
• • •
• •
Particulates refer to unidentified pollutants.
(Adapted from Newman 1980)
-------
Table 4. The major biological systems of animals affected by selected
air emissions.
Upper
Selected Central Circu- Gastroin- Pul- Respir- Skeletal
air emissions Eyes nervous latory testinal Hepatic monary atory Renal & dental
Arsenic • •
Barium $ •
Beryllium t
Cadmium I >1
Carbon monoxide |
Chromium i i~
Fluoride
Hydrocarbons > >
Hydrochloric acid t $ '
Hydrogen sulfide t I I
Iron •_
Lead < t
Manganese t t
Mercury t I t
Molybdenum 9
Nickel t
Nitrogen dioxide t •
Particulatesa >
Phosphorus >
Photochem. oxid. $ t $
Selenium I I
Sulfur dioxide t
Vanadium I ft
Zinc i
Particulates refer to unidentified pollutants
(Adapted from Newman 1980)
-------
Table 5. Effects of selected air emissions on animal behavior.
Selected air emissions
Observed abnormal behavior
Arsenic
Incoordination of gait, muscular paralysis
Barium
Incoordination of movements, twitching, tremors, muscular paralysis
Beryllium
Temporary lethargy in dogs
Carbon monoxide
Incoordination of gait and movements, reduced apptetite in chickens, impairment of
learned activities in rats
Chromium
Stiffness, loss of appetite
Fluoride
laaeness, stiffness, weakness
Hydrocarbons
DUziness, fatigue, loss of appetite
Hydrogen sulfide
Lethargy, gasping
Lead
Bellowing, roaring, staggering about with rolling eyes, frothing of mouth, grinding
of teeth, ataxia, maniacal excitement, lethargy, loss of appetite, delerium
Manganese
Lethargy, tremors
Mercury
Incoordination of movements, paralysis, anorexia, lethargy, blindness
Molybdenum
Stiffness in legs and back
Phosphorus
Restlessness, nervousness
Selenium
Abnormal movement and posture, fear, nervousness, opisthotonus
{Adapted from Newman 1980)
-------
significant respect; i.e., it builds nests on the ground. So, unlike
desert mice, which come out of their subterranean nests when the sun has
set, the California mouse may be exposed at the maximum concentration to
those pollutants that reach their highest levels during the daylight
hours. The following effects were observed:
• Deer mice trapped in areas of Los Angeles with low ambient air
pollution are significantly (P £0.02) more sensitive to ozone
(6.6 ppm for 12 hours) than are mice trapped in areas with high
pollution (100% versus 44% mortality, respectively). The exact
ages of these mice are not known; however, their survival in the
field is believed to be less than one year.
• A genetic basis for this sensitivity is indicated, as laboratory-
born progeny of field-trapped mice show the response pattern of
their parents. Inbred deer mice are much more sensitive to the
lethal effects of ozone than their randomly bred parents or wild
grandparents. The major difference between these groups is the
degree of inbreeding and thus genetic variability. Small popu-
lations in nature may have reduced genetic variability.
• Young mice (less than one year old) are more sensitive than older
mice to the lethal effects of ozone. This is particularly strik-
ing for mice and their offspring trapped on low-pollution areas
(89% versus 52% mortality, respectively).
Species differ in sensitivity to the lethal effects of ozone (Nation-
al Research Council 1977a) and nitrogen dioxide (National Reseat Council
1977b).
Unusual wildlife including disjunct populations exhibiting genetic
variability that may be of scientific interest, are found in the deserts
of the southwest. Some may be particularly susceptible to impact from
anthropogenic pollutants. One example is the spadefoot toad (Scaphiopus
hammoudi and Scaphiopus couchi). Spadefoot toads are adapted to breed in
ephemeral pools that form after heavy rain. Reproduction and embryonic
development are stimulated by rain. The song of males, which serves to
attract females, may be heard within one hour after rain begins. Devel-
opment from egg to tadpole to small hopping toadlet takes only 9.5 days.
An increase in acidity of the pools could result
in development abnormalities and embryo death.
Desert populations of Couch's spadefoot (Scaphiopus couchi) spend six
months or more of each year burrowed in sand. Studies of Arizona desert
populations of spadefoot toads indicate that, at least in some desert
soils, the toads can extract enough water osmotically to avoid significant
dehydration or increases in the concentrations of electrolytes in the body
fluid. An increase in the acidity of the soil could upset this balance
of osmotic forces away from the toad.
16
-------
The importance of soil osmotic forces has been documented in the des-
ert iguana (Dipsosaurus dorsalis) of the American Desert (Muth 1980).
Eggs hatch normally at environmental water potentials between -50 and
-1500 kPA and between 28° and 38°C. Thus, the soil environment imposes
constraints on the timing of egg laying and the location of suitable sites
for egg burrows, ultimately affectinq the qeoqraphical range and abundance
of the desert iguana.
3.1.3 Effects on Plants
The construction of electric generating stations in deserts and the
use of sulfur-containing fuels has prompted studies of time-dosage effects
of sulfur dioxide and nitrogen dioxide separately and in combination.
Thompson et aJL (1980) studied 10 species of plants, 5 perennials and 5
annuals, native to the American Desert and their response to SO2 and
NO2. Plants were grown in pots and fumigated in open-top plastic green-
houses from 0900 to 1400 hours, 5 days per week (25 hours/week). Three
levels of sulfur dioxide, three levels of nitrogen dioxide, three treat-
ments with the combined fumigants, and an untreated control were used
(Table 6). The perennials were fumigated for 16 weeks in 1977 and 32
weeks in 1978. The annuals were treated for 8-17 weeks, depending on the
species. The data suggest the following.
a. Individual species differ in the responses to fumigation. Among
perennials, Larrea was the most sensitive. Chilopsis, Encelia,
and Ambrosia showed intermediate sensitivity, and Atriplex was
resistant. Fumigation of perennials with sulfur dioxide at 2.0
ppm or nitrogen dioxide at 1.0 ppm (level I in Table 6) caused
extensive foliar injury. The combined fumigants have additive
effects in some species, but no suggestion of synergism was noted.
At the lowest concentrations, tested, these fumigants stimulated
lateral growth of Encelia and increased the dry weight of Atri-
plex.
Among the annuals, Chaenactis was the most sensitive; PIantaqo,
Erodium, and Phacelia were very sensitive; and Baileya was tne
least sensitive^ STT annuals experienced extensive reduction of
growth at 2.0 ppm sulfur dioxide and ultimately died. At 0.67 ppm
sulfur dioxide severe injury occurred with some of the plants
dying. Nitrogen dioxide at 1.0 ppm was less injurious than sulfur
dioxide at high concentrations and the addition of nitrogen diox-
ide to sulfur dioxide apparently had an antagonistic effect. Low
concentrations of the fumigants stimulated lateral growth in En-
cel ia, increased dry weight in Plantago, and increased flowerTng
in Baileya.
b. Annual species of plants were more severely affected than peren-
nials. Greater sensitivity among annuals was evidenced by the
complete death with some treatments and extensive injury at lower
fumigation levels.
17
-------
Table 6. Plant species and exposure concentrations
used in greenhouse experiments.
Plant Species
Pollutant Concentration (ppm)
Duration
(weeks)
Level
S02 N02
SO2 + NO2
1977
1978
PERENNIALS
Larrea divaricata
Chilopsis linearis
Encelia farinosa
Ambrosia dumosa
Atriplex canescens
I
II
III
2.0 1.0
0.67 0.33
0.22 0.11
(2.0, 1.0)
(.67, .33)
(.22, .11)
16
32
ANNUALS
Baileya pleniradiata
Plantago insularis
Phacelia crenulata
Erodium cicutarium
Chaenactis carphoclinia
same as above
17
17
17
16
12
12a
ga
8a
aSecond crop
(Adapted from Thompson et al. 1980)
18
-------
c. A variety of measurable effects were observed. Signs of toxicity
produced by sulfur dioxide and nitrogen dioxide included:
• leaf-tip burn and other areas of necrosis
• small and chlorotic newly formed leaves
• leaf and lateral branch drop
• reduced plant growth
• reduction in seed production
• reduction in the number of influorescences per plants and at
high concentrations complete lack of flower formation
• reduced survival
An important finding was the severe reduction in seed production and
flowering in annuals and perennials. Seed production by Ambrosia was re-
duced at all treatment concentrations, with the greatest loss (96%) in the
high sulfur dioxide plus nitrogen dioxide fumigation (2.0 ppm SO2 + 1.0
ppm NO2). Even at the lowest concentration of the combined fumigants
(0.22 ppm SO2 +0.11 ppm NO2), there was a 61% reduction in seed pro-
duction.
At the highest combined concentration of sulfur dioxide plus nitrogen
dioxide there was a complete lack of flower formation in Encelia. At the
lowest concentration of the combined fumigants, there was a 63% reduction
in the number of influorescences per plant. The observed reduction in
survival, seed production, and flower production could be a threat to spe-
cies' survival.
Hill et al. (1974) tested the effects of sulfur dioxide and a combi-
nation of sulfur dioxide and nitrogen dioxide on 87 plants in the Colorado
Plateau near the Four Corners Power Generating system located in the
northwest corner of New Mexico. Plants were fumigated in situ in portable
chambers for 2 hours with a mixture of sulfur dioxide (0.5 - 11. ppm) and
one-third as much nitrogen dioxide (0.16 - 3.6 ppm). This mixture approx-
imated the ratio of sulfur dioxide to nitrogen dioxide measured down-wind
from a coal-fired electrical generating station. Their results indicate
that concentrations that caused no harm during most years could cause in-
jury in a year with high rainfall. When injury occurred, it appeared
within a few days.
The increased injury to plants experienced during years with high
rainfall by Hill et a^. (1974) is consistent with laboratory results of
McLaughlin and Taylor (1981); they found that foliar uptake was enhanced
two- to three-fold for sulfur dioxide and three- to four-fold for ozone by
an increase in relative humidity from 35% to 75%. Desert plants may thus
absorb a significantly greater influx of pollutants when relative humidity
is high.
The effects of prolonged, continuous exposure to sulfur dioxide at
concentrations that do not cause any apparent external injury, but which
may have physiological effects in plants, were studied in the region
around the Four Corners Power Station (Northern Arizona University 1979).
19
-------
Such long-term physiological effects might reduce the chance of survival
and reproduction of plants. The desert grass Oryzopsis h.ymenoides was
selected as an experimental subject. Hill et _al_. (1974) had found this
species to be the most sensitive to sulfur dioxide (0.5 ppm, 2 hours) in
their acute toxicity study. The results of fumigation for 6 weeks demon-
strated a statistically significant decrease in chlorophyll content of the
plant at a sulfur dioxide concentration of 0.063 ppm; a decrease in pro-
ductivity, measured as mg dry wt per plant, and necrotic lesions on the
leaves of fumigated plants were observed at 0.125 ppm.
The implications of these studies are that the emissions of sulfur
dioxide and nitrogen dioxide from electrical generating stations could
cause injury to some desert plants if concentrations were high enough and
sustained for long periods. Typical exposure levels near electrical power
stations are maximum hourly concentrations of 0.04 - 0.07 ppm sulfur diox-
ide and one-half to one-third these levels of nitrogen dioxide (Thompson
et a[. 1980). High levels persist during static weather conditions. The
effects of these emissions on desert vegetation, particularly over the
course of several years, is not known. However, the 0.063 ppm used by
Northern Arizona University (1979) and the 0.22 ppm used by Thompson et
al. (1980) are sufficiently close to that value to warrant further moni-
toring and scientific investigation. This is particularly true since
Larrea, the most abundant perennial in many areas of the desert, was the
perennial most affected by sulfur dioxide and nitrogen dioxide.
In a study of smelters in Arizona, Dawson and Nash (1980) documented
effects on plant communities in semi-arid areas which could be attributed
to airborne effluents. The investigators studied metal concentrations
and levels of pH in the soil, sampled perennial and annual plant commu-
nities, and tested soil toxicity using a bioassay procedure. The results
of these tests were compared for points at different distances from the
smelter. An area for 10 km around the smelter had concentrations of
copper well above background levels. Decreases in copper concentration
with increasing distance from the source and a similar pattern of de-
creasing soil acidity were observed. The soil acidity was attributed to
SO2 emissions. Tests of soil toxicity showed that the least toxic soils
were those farthest from the smelter. The toxic effect involved both the
copper and the acidity. In separating the effects, it was found that at
pH 4, plant growth was depressed regardless of copper concentrations;
however, the effects of high copper concentrations were not uniform but
depended on the soil pH. The results of the plant sampling corresponded
to the toxicity tests. Close to the smelter, grasses, spring annuals,
forbs, some small shrubs and succulents were reduced in number. Large
shrubs were unaffected.
Dawson and Nash (1980) pointed out that, since the effects of aerial
deposition were concentrated in the upper layer of soil, shallow plants
were more seriously affected than deeper rooted plants. They pointed out
the difference between their observations and those of SO2 damage in
forest communities and suggested that in arid regions the indirect
effects of soil acidification by SO2 may be more important than the
direct affects of this pollutant on plants.
20
-------
3.2 ECOSYSTEM EFFECTS
The object of this section is to review the potential effects of air
pollution at the ecosystem level of biological organization. Monitoring
is needed to measure both baseline conditions and changes in the total
system. Changes in an ecosystem occur most often as (1) changes in the
amount of green plant material produced over one year's growing season
(primary production), (2) changes in the number (density) and kinds (div-
ersity) of plants and wildlife, and (3) changes in the rates or products
of microbial processes (O2 uptake, CO2 evolution, change in soil nu-
trient content). All of these parameters are useful for monitoring eco-
system change.
3.2.1 Effects on Plant Diversity and Productivity
Although the effects of air pollution on ecosystems will depend on
specific characteristics of the affected site, it is instructive to com-
pare the quality and quantity of plant resources in polluted and relative-
ly pristine sites. Primary productivity rates for a variety of desert
ecosystems are shown in Table 7. The results point out the importance of
obtaining site-specific data. In general, annual productivity rates de-
pend on (1) the length of the growing season, (2) the availability of
moisture, and (3) soil fertility.
Westman (1979) compared the number of plant species and foliar cover
in sites of high oxidant levels with floristically comparable sites of low
oxidant levels in arid lands at the margins of the desert where desert and
California Chaparral (coastal sage scrub) intermix. The dominant plants
of the coastal sage scrub have soft leaves that drop during periods of
drought. The plants are shallow-rooted and typically 0.5 - 2.0 m tall.
Coastal sage scrub is found at lower elevations, generally below 500 - 900
m, on the coastal and interior sides of the coastal mountain ranges.
Prevailing winds in the area are westerly, particularly during the
summer when photochemical oxidant formation is greatest. Direct measure-
ments of pH have shown the rain in the Los Angeles basin to have been
acidic as early as 1959, and the precipitation-weighted mean pH of rain-
fall in Pasadena was 4.06 (range, 2.78-5.33) from February, 1976, to Sep-
tember, 1977 (also see Figure 2). Oxidants are blown inland to the moun-
tains and through the mountain passes to the desert. Eleven sites in re-
gions of high mean annual oxidant concentrations were compared with eleven
floristically comparable clean air sites. The clean air sites were in San
Diego County and northern Baja California and included several strongly
desert-influenced sites. The mean annual oxidant concentrations from 1963
to 1977 at these sites were 0.04 0.03 ppm (X +_ S.D.). The more polluted
sites were desert margin areas of the eastern Los Angeles and Riverside
basins. Oxidant concentrations at these sites averaged 0.18+0.03 ppm.
21
-------
Table 7. Productivity of desert and arid lands.
Net primary productivity (dry g/m^/y)
Ecosystem
average
range
Productivity
of specific
ecosystem
Extreme desert, rock, sand and icea
3
0-10
Desert and semidesert scrub3
Desert on tropical coalesced
soi1sb
Desert grasslandc
Saline and alkali soil formations
in deserts"
Desert on tropical desert soils'3
Desert on subtropical desert
soi 1 sb
Desert on clayey tracts amid
sand patches'3
Desert on alfiso 1 soils (pH 8.2)b
90
0-250
22
24-29
45
90
90
90
197
Mountain desert
Desert highland soils'3
Brown mountain semidesert'3
Mountain aridisol'3
157
291
1,200
Savanna13
900
200-2,000
Desert like savanna*3
403
Temperate grasslands'3
600
200-1,500
Desert steppe*3
Dry and desert steppe on
mollisol soils'3
Dry steppeb
Steppified desert on aridisolb
493
493
896
1,000
a Whittaker (1975)
" Golden ert al. (1979)
c Northern Arizona University (1979)
22
-------
The results indicate that the more polluted sites, which include
desert and coastal sage flora, have:
• Lower mean number of plant species
• More individuals of the predominant species
• Decreased total foliar cover.
Two lines of evidence indicate that the observed effects are due to
longterm continuous pollution:
• Statistical analysis of 43 habitat variables at 67 sites over the
geographic range of coastal sage scrub indicates that the single
strongest direct cause of the decline in foliar cover is the in-
creased mean annual concentration of oxidants;
§ Statistical analysis also Indicated that the decline in coastal
sage flora was not due to the effect of desert flora (e.g., com-
petition or toxins).
In a later study of the factors influencing the distribution of spe-
cies within coastal sage scrub, air pollution was identified as a strong
predictor (Westman 1981). Present pollutant levels of oxidants are corre-
lated with a decrease in the abundance of Salvia apiana, a dominant shrub,
and Mirabilis californica, a perennial herlT Rowever, oxidants and nitro-
gen dioxide were correlated with an increase in abundance of Schismus bar-
batus, an introduced grass. Nitric oxide was correlated with an increase
in the abundance of Artemisia californica and Eriogonum fasci'cu latum, both
dominant shrubs.
As noted by Westman (1981), statistical evidence can only suggest a
causal relationship between pollution levels and the abundance of native
plants. No laboratory or field fumigation studies with oxidants on Cali-
fornia Chaparral species have been published. Damage to conifers by oxi-
dants in the coastal ranges of southern California has been documented
(Miller and McBride 1975, see also the report on forest ecosystems in this
series).
The effects of air pollution from smelters on the distribution of
desert vegetation have also been studied. Wood and Nash (1976) observed
species diversity, density, and cover to be inversely related to levels
of copper, cadmium, lead, iron, and zinc in soils. Metal concentrations
were highest in soils near the smelter where some annuals, herbaceous
perennials, grasses, cacti, and shrubs were greatly reduced in number.
Sulfur dioxide, also emitted from the smelter, was observed to acidify
soils near to and at intermediate distances, (3-6 km) from the smelter
(Wood and Nash 1976; Dawson and Nash 1980).
23
-------
Increased acidity of the surface soil within a radius of 8 km from
the smelter was attributed to gaseous adsorption of sulfur dioxide. The
combined effects of acidity and elevated metal concentrations in increas-
ing the toxicity of the soil provide the most likely explanation for the
suppression of native plant communities observed near the smelter.
Sulfur dioxide fumigation of eight desert lichen species from the
Four Corners region revealed that in the hydrated condition they were sen-
sitive to sulfur dioxide in an 8 hour exposure at 0.5 ppm (1430 ug/m3);
however, they were insensitive when dehydrated (Marsh and Nash 1979). Due
to the aridity of desert climates the lichens are probably rarely moist
and hence are infrequently susceptible to sulfur dioxide injury. The
authors found that although the power station in the Four Corners area had
been in operation for over 10 years, no marked gradients in species compo-
sition or lichen cover were evident in relation to the location of the
power station. These findings are consistent with the fumigation results
described above, since the mean annual sulfur dioxide concentration in the
Four Corners region typically ranges from 0.0006 to 0.0009 ppm (17.16-
25.74 ug/m3), with the highest 4 month average being 0.0012 ppm (34.32
ug/m3) (Marsh and Nash 1979).
3.2.2 Microbial Effects
Air pollution can produce changes in microbial populations or in the
functions of microbial communities. Microbial activities are associated
with the weathering of stone (Hansen 1980), the decomposition of organic
matter and the mineralization of nutrients that accumulate on or under the
surface of the soil, the fixation of atmospheric nitrogen (cyanobacteria
and algae), the transfer of water and minerals to plant roots (fungi), and
agents of plant and animal disease (fungi and bacteria).
Little is known about the decomposition of plant litter in deserts
and the organisms involved in that process; however, changes in microbial
populations caused by air pollution could affect decomposition and nutri-
ent cycling desert ecosystems. In the Chihuahuan Desert, Santos and Whit-
ford (1981) and Santos et al. (1981) found that prostigmatid mites were
the most abundant animal? o7 the microarthropod fauna. In contrast, orba-
tid mites are dominant in other ecosystems and feed on dead plant materi-
al. This relationship raised questions concerning the role of prostigma-
tid mites in decomposition. Since significant quantities of plant litter
are buried in the desert, studies were carried out to examine the differ-
ences in buried and surface litter decomposition and the relative contri-
butions of bacteria, fungi, and microarthropods to litter decomposition.
In a series of fumigation experiments with an insecticide, a fungi-
cide, an insecticide and fungicide combination, and a nematicide, insecti-
cide and fungicide combination, arthropods were eliminated, leaving bac-
teria. The loss of organic matter from surface litter in a three month
period (August to October) was 57.4 + 7.7%. This was significantly higher
24
-------
than loss from buried litter for that period. The loss of organic matter
from surface litter was attributed to termites. Decomposition of buried
litter in the Chihuahuan Desert for the six month growing season was
56.6%. The initial stages of buried litter decomposition appear to be via
bacteria. Bacteria are grazed upon by nematodes; nematodes and nematode
eggs are fed on by prostigmatid (more precisely, tydeid) mites. Thus, in
desert ecosystems, microarthropods affect litter decomposition by a pre-
viously undescribed mode--preying on free-living nematodes.
Analysis of microbial communities in the Colorado Plateau Steppe
(Kaiparowits Plateau) revealed a relationship between the decomposers and
the primary producers in the desert (Northern Arizona University 1979).
The species composition of soil fungi is functionally adapted to the
aboveground vegetation. This suggests that indirect effects on the vege-
tation may occur subsequent to directs effects on the soil microorganisms.
Soil fumigation studies of representative composite soil samples have
been performed with sulfur dioxide or sulfur and nitrogen dioxides com-
bined at concentrations both approximating and exceeding those predicted
to result from stack gas emissions from the Navajo Generating Stations
(States 1978). Sandy loam soils adsorbed a large percentage of both sul-
fur dioxide and nitrogen dioxide flowing at a constant rate over and
through the soil matrix. A constant adsorption rate was maintained for
extended periods of time (Figure 3). Soils wetted to moisture holding
capacity (field capacity) showed accelerated adsorption rates for sulfur
dioxide compared to dry soils (Table 8). Chemical and biological charac-
teristics monitored in the fumigated soils showed only minor changes at
0.5 ppm, the concentration expected at the study site. Changes in soil
acidity and the number of bacteria present were restricted to the upper
few millimeters of the soil. A decrease in fungal number and spore germi-
nation was noted with the increase in acidity; however, little change was
noted in overall microbial community structure and microbial decomposition
activity (Northern Arizona University 1979).
The soil in the Kaiparowits region is dry most of the year due to a
high evaporation rate, low water holding capacity, and low annual precipi-
tation. Therefore, acid soil problems, such as aluminum toxicity or cal-
cium deficiency, would not be expected (Clarkson 1965, 1966).
Computer simulation incorporating this effect suggested that detri-
mental changes in microbial populations would occur in the soil surface
directly exposed to stackgas impingement from coal-fired electrical gener-
ating stations. However, experimental effects were detected only at 0.5
ppm, the maximum concentration expected at ground level. The effects did
not appear to be long lasting, despite the rapid adsorption of the gases
by the soil. The alkaline nature of the soils apparently buffers it
against a change in acidity (Northern Arizona University 1979).
25
-------
0-5
E
CL
;0-4 -
Z
Ld
3
H 0-3 H
0-2 -
z
o
I—
<
Qi
Ui
u
z
o
O 0
O X
o x
ox»*
% *
% **
°°o0
°Ooo
oo
» empty chamber
« N0a
o S02
I
10
20
30
TIME (mln)
—r-
40
—r~
50
!
60
Figure 3. S02 and N02 uptake by air-dried desert soil
(From States 1978)
26
-------
Table 3. Sulfur and nitrogen dioxide uptake by desert soil under
various conditions of moisture content and sterility.
Sulfur Dioxide nitrogen Dioxide
Effluent Effluent
Concentration Uptake Concentration Uptake
(PP«0 (ppm)
Soil Condition
Initial
Rate
Final (ug/tir/cm3)
%
Initial
Final
Rate
(ug/hr/cm3)
%
Air-dried
1.00
0.57
0.54
43
1.00
0.65
0.40
31
Air-dried
0.50
0.27
0.30
47
0.50
0.29
0.26
39
Air-dried
0.25
0.15
0.13
42
0.25
0.17
0.12
33
Oven-dried
0.50
0.32
0.24
37
0.50
0.26
0.32
47a
Field capacity
0.50
0.19
0.39
63>>, c
0.50
0.40
0.14
21
Autoelaved
0.50
0.28
0.27
44
0.50
0.26
0.31
46
Significant at 0.05 level
^Significant at 0.01 level
cEquilibrium uptake not established at one hour
(From Northern Arizona University 1979)
-------
These results should be considered tentative until a long-term moni-
toring program is conducted to obtain more definitive data on the effects
of atmospheric pollutants on arid ecosystems. Higher ambient concentra-
tions of atmospheric pollutants than were used in the model could have
deleterious effects on desert plants (Ferenbaugh 1978), and increased
acidity in the soil due to an extended period of exposure could adversely
effect decomposition processes (Northern Arizona University 1979).
Little is known about the nitrogen and the sulfur cycles in the des-
ert. Soils can remove a larqe percentage of the sulfur dioxide (44-63%)
and nitrogen dioxide (21-34%) from the air (Ferenbaugh et £l_. 1979). How-
ever, microorganisms may not be directly involved in the adsorption of
either of the gases from the air (Ghiorse and Alexander 1976; Smith and
Mayfield 1978). Monitoring changes in soil mineral availability and con-
tent resulting from increased acidity could help assess the impact of air
pollution on desert ecosystems. This is true regardless of whether the
changes are due to disruption of physicochemical mechanisms in the soil
or to the effects on the metabolism of microorganisms present in the soil.
This approach is very sensitive to changes and could warn of impending
impacts on an ecosystem, before they can be measured as changes in popula-
tion parameters, such as litter invertebrate biomass, density, or diver-
sity (O'Neil et 1977; Jackson et aK 1977). Observation of changes
in soil mineral content may help to identify detrimental changes before
they reach the level of disruption of the total ecosystem.
3.2.3 Aquatic ecosystems
There are no observations of the effects of air pollution and acid
deposition on bodies of water in deserts and steppes reported in the lit-
erature. Among living organisms, changes in composition and abundance of
fish populations, insects, and microscopic life in the water or closely
associated with the bottom have been reported (see the reports on Lakes
and on Rivers and Streams in this series).
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4.0 SUMMARY AND TOPICS FOR FURTHER RESEARCH
In this report, the current knowledge of the effects of air pollution
and acid rain on fish, wildlife, and their habitats in deserts and steppes
of the southwest has been reviewed. The understanding is rudimentary at
best. In this section the knowledge of air pollution impacts on these
ecosystems is summarized and topics for further research are suggested.
4.1 SUMMARY FACTS
The following points summarize what is known about the effects of
air pollution on desert and steppe ecosystems, based on the available
literature reviewed in this report:
1) The alkalinity characteristic of most of the soils in the desert
and steppe ecosystems suggests that, except for granites and non-
calcareous sandstones, these soils are capable of neutralizing the
impact of wet and dry acid deposition.
2} The desert pupfish (Cyprinodon n. nevadensis) is highly suscepti-
ble to changes in pH. The lower limit for successful reproductive
performance is pH 7, and the limit for survival was 4.6. Desert
springs from which the stock were taken, however, have a pH of
8.3.
3} In greenhouse experiments individual desert plant species
differed in tlieir response to SO2 and NO?. In addition
annual species of desert plants were more severely affected by
SOg and NO? than perennials.
4) In experimental fumigations in open-top greenhouses the symptoms
of SOg and NO2 toxicity in desert plants included:
• leaf-tip burn and other areas of necrosis;
• newly formed leaves were small and chlorotic;
• leaf and lateral branch drop;
• reduced plant growth;
• reduction in seed production;
• reduction in the number of influorescences per plants and at
high concentrations complete lack of flower formation; and
• reduced survival.
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5) Concentrations of SO2 and NO2 that are considered fairly harm-
less most years in arid environments can cause plant injury in a
year with high rainfall due to increased adsorption of the gases.
Desert plants may adsorb significantly more pollutants when the
relative humidity is high.
6) Emissions of SO2 and NO2 similar to those of the Four Corners
Power plant could cause injury to some desert plants resulting
from chronic exposure even if concentrations are not high enough
to cause apparent, external injury.
7) Suppression of native plant communities and reduced species
density and diversity have been observed in the vicinity of metal
smelters in arid regions. These effects were attributed to
increased soil toxicity resulting from a combination of copper
deposition and increased soil acidity caused by SO2 emissions.
The most important effects of SO2 in arid regions may be
indirect, resulting from increasing soil acidity.
8) Desert sites that are more polluted have:
• a lower mean number of plant species;
• more individuals of the predominant plant species; and
t decreased total foliar cover.
9) Exposed wildlife may show physiologic, neurologic, and genetic
effects in individuals and reduced birth and growth rates in pop-
ulations.
10) Acid deposition may have an impact on soil microorganisms and
their functions, leading to long-term effects on the ecosystem if
the soil pH is significantly altered.
4.2 RESEARCH NEEDS
The avail able data is not sufficient to determine the types of
changes that can occur in the deserts and steppes as the result of air
pollution and acid rain. Additional research as outlined below is needed.
4.2.1 Physicochemical Effects
Data should be collected to serve as the basis for a monitoring pro-
gram. Soils, rock formations, and water bodies should be characterized
according to susceptibility to acid deposition (i.e., pH, free carbonates,
iron and aluminum hydroxides and silicates, etc.). In addition, a moni-
toring program should be established in sensitive regions to identify
changes that could be hazardous to fish and wildlife.
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4.2.2 Effects on Individuals
Species particularly susceptible to impact from air pollution should
be identified, and a list of species which can serve as indicator species
to monitor the effects of anthropogenic pollution should be drawn up.
Particular attention should be given to organisms that are endangered or
of scientific or commercial value, and to vegetation which provides essen-
tial food or shelter for wildlife, particularly rare and endangered wild-
1 ife.
4.2.3 Effects on Habitats
A program should be established to determine what impact, if any, air
pollution and acid deposition damage to individual species of desert
plants or animals would have on other individuals in the habitat.
4.2.4 Effects on Ecosystems
Data should be gathered on the effects of air pollution on microor-
ganisms and microbial activity, particularly activity associated with the
carbon, nitrogen, and sulfur cycles and organic matter decomposition.
4.2.5 Integrated Program of Study
An integrated program of study is needed to monitor the effects of
air pollution and acid precipitation in deserts. Evaluation criteria
should be developed, and existing methods should be evaluated and ranked,
flew methods should be developed where current protocols are inadequate.
Test procedures should involve laboratory tests, laboratory simulation of
natural environments and field studies. Confirmation of laboratory stud-
ies by periodic field monitoring is required. A program of monitoring the
effects of air pollution might profitably include systems models to help
guide research activities (see U.S. Department of the Interior 1978).
Procedures for estimating the socioeconomic impact of anthropogenic
pollution should be included in this program.
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50272 -10)
REPORT DOCUMENTATION report no. | 2.
PAGE FWS/OBS-80/40.9
3. Recipient's Accession No.
4. Title and Subtitle
Air Pollution and Acid Rain, Report 9
The Effects of Air Pollution and Acid Rain on Fish,
Wildlife and Their Habitats - Deserts and Steppes
5. Report Date
June 1982
G.
7. Author(s)
Mirsky, E. N., D. Harper
8. Performing Organization Rept. No.
9. Performing Organization Name and Address
Dynamac Corporation
Dynamac Building
11140 Rockville Pike
Rockville, MD 20852
10. Project/Task/Work Unit No.
11. Contract(C) or Grant(G> No.
to 14-16-0009-80-085
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