6EPA
United States
Environmental Protection
Agency
Environmental Research
Laboratory
Corvallis OR 97330
EPA-600 3-79-045
April 1979
Research and Development
Oxidant Air Pollution
Impact to the
Forests of Eastern
United States
A Literature Review
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are
1. Environmental Health Effects Research
2 Environmental Protection Technology
3, Ecological Research
4 Environmental Monitoring
5. Socioeconomic Environmental Studies
6 Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8. "Special" Reports
9 Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aguatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-79-045
April 1979
OXIDANT AIR POLLUTION IMPACT TO THE
FORESTS OF EASTERN UNITED STATES -
A LITERATURE REVIEW
by
John M. Skelly
J. Wi11iam Johnston
Department of Plant Pathology and Physiology
Virginia Polytechnic Institute and State University
Blacksburg, VA 24061
CC71142-J
Project Officer
Raymond G. Wilhour
Terrestrial Systems Division
Corvallis Environmental Research Laboratory
Corvallis, Oregon 97330
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
-------
DISCLAIMER
This report has been reviewed by the Corvallis Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
-------
FOREWORD
Effective regulatory and enforcement actions by the Environmental Pro-
tection Agency would be virtually impossible without sound scientific data on
pollutants and their impact on environmental stability and human health.
Responsibility for building this data base has been assigned to EPA's Office
of Research and Development and its 15 major field installations, one of
which is the Corvallis Environmental Research Laboratory (CERL).
The primary mission of the Corvallis Laboratory is research on the
effects of environmental pollutants on terrestrial, freshwater, and marine
ecosystems; the behavior, effects and control of pollutants in lake systems;
and the development of predictive models on the movement of pollutants in the
biosphere.
The forests of the eastern United States are a valuable natural resource
providing timber production, recreation, wildlife habitat and watersheds.
This resource is increasingly threatened by photochemical oxidants which are
transported great distances in phytotoxic concentrations from populated areas
to the rural forest environment. This report attempts to describe the real
and potential impacts of photochemical oxidants on eastern forest ecosystems.
Information of this kind is necessary to assure full assessment of the cost/
benefits of EPA's air pollution control strategies as well as input for the
Prevention of Significant Deterioration legislation.
Thomas A. Murphy
Director, CERL
-------
ABSTRACT
This report presents a review of past studies that have attempted to
delineate measurable and/or possible impacts of photochemical oxidants on the
forests of Eastern United States. Sources of oxidant precursors and subsequent
long distance transport phenomena are reviewed and documented. A brief his-
torical treatment of eastern white pine responses to air pollutants is followed
by an up-to-date evaluation of current air pollution measurements and asso-
ciated impacts.
Potential threats to eastern forest tree species are reviewed through a
comparison of various fumigation studies in laboratory and field situations.
The concept of hidden injury is discussed as being a possible major impact
problem facing analysis of real losses.
The authors present evidence that would suggest that many forest tree
species indigenous to the eastern United States may already be detrimentally
impacted by previous high oxidant episodes. They further suggest that even
more drastic and only long term reversible effects to the forest ecosystem
will follow a trend of increasing oxidant air pollution in many major forested
regions of this area of the United States.
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TABLE OF CONTENTS
Foreword iii
Abstract iv
List of Tables vi
1. Introduction 1
2. Conclusions 3
3. Photochemical Oxidant Air Pollution in the Eastern
United States 4
The photochemical oxidants 4
Incidence of ozone in the air of the Eastern United
States 4
4. Diseases of Eastern White Pine Caused by Ozone 8
Needle blight of eastern white pine 8
Chlorotic dwarf disease 11
Symptomatology of white pine needle blight 11
5. Impact of the Photochemical Oxidants on Forest Vegetation 13
Response of forest vegetation to PAN 13
Response of forest vegetation to the nitrogen oxides 13
Relative sensitivity of the species 13
Sensitivity variation within species 16
Factors affecting sensitivity to 0., 16
Growth response of forest vegetation to 0, 17
Response of forest vegetation to pollutant mixtures 18
Community and ecosystem effects 19
Literature Cited 20
-------
TABLES
Number Page
1. Chronological Listing of Four Parameters Related to Air
Pollution Emissions for the Period 1900 to 1970 in the
U.S. and Virginia 2
2. A Comparison of Various White Pine Needle Blights
According to Hepting/Berry, Linzon, Costonis, and
Dochinger 9
3. Sensitivity of Tree Species to N0? 14
4. Relative Sensitivity of Trees to Ozone 15
VI
-------
INTRODUCTION
Air pollution has been recognized as a threat to forest productivity for
more than one hundred years (Stoeckhardt, 1871). It was generally assumed
that the importance of air pollution was restricted to the immediate vicinity
of industrial complexes. Impacts, therefore, were considered to be local in
nature. The pre-1950 air pollution research dealt primarily with the effects
of industrial stack gases and fumes (primarily S02) on crops and woodlands.
Several reviews that summarize the literature dealing with the effects of
industrial emissions on forests are available (Scurfield, 1960; Hepting,
1964, 1966, 1968; Keller, 1968; Knabe, 1971).
More recently a new threat to forest productivity has been recognized.
Increased levels of air pollution have resulted from increased use of auto-
mobiles and demands for electrical power since the 1940's (Table 1) (Nicholson,
1977). In the early 1950's several researchers determined that photochemical
oxidant air pollution was causing damage to a number of plant species in the
Los Angeles Basin (Middleton et al. , 1950; Haagen-Smit et al., 1952). Damage
to eastern white pine (Berry, 1961; Berry and Ripperton, 1963) and ponderosa
pine (Miller, 1973) was shown to be caused by 03, the major component of
photochemical oxidant air pollution. Since that time, interest concerning
the impacts of photochemical oxidants on forests has increased.
It is now known that air pollution problems are not restricted to metro-
politan environments. Even relatively remote mountainous areas of the east
are adversely affected (Hayes and Skelly, 1977). The potential for damage to
forests is great. The land areas affected probably include the entire
United States east of the Mississippi River. Far too little is known of the
photochemical oxidant impact on eastern forests to make reliable estimates of
dollar losses.
The impact may go far beyond mere dollar value reductions. Irreversible
changes in the structure and function of forest ecosystems that go unnoticed
at the present may have profound effects on our way of life in the future.
There is presently an urgent need to study the effects of photochemical
oxidants on the eastern forests before deleterious changes take place. The
post mortem approach to research (Treshow, 1968) may prove to be inadequate
in protecting our forest resources.
The purpose of the present report is to provide a summary of the avail-
able literature that is pertinent to a study of photochemical oxidant air
pollution effects to the forests of eastern United States. Sections dealing
with the gases involved in plant damage, the etiology of the diseases of
white pine that are caused by oxidant air pollution, and the known effects of
the photochemical oxidants on forest vegetation are included.
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TABLE 1. CHRONOLOGICAL LISTING OF FOUR PARAMETERS RELATED TO AIR POLLUTION EMISSIONS FOR THE PERIOD 1900 to 1970
IN THE U.S. AND VIRGINIA
Populationa
in 1 ,000's
Value Added to
Manufactured Goods b
In Mill ions of Dollars
Product of Electric
Power Using Fuels by Public
Utilities in 1,000,000 KWH
Motor Vehicle
Registrations
In 1,000's
Year
U.S.
VA
U.S.
VA
U.S.
VA
Year
U.S.
VA
1975
70
65
60
55
50
45
40
35
30
25
20
15
10
05
1900
212
204
194
180
165
151
139
132
127
123
115
106
100
92
83
76
References
References
C Data
d D-.C-.
,000
,879
,303
,671
,275
,684
,928
,122
,250
,077
,829
,461
,546
,407
,822
,094
: U.S.:
: U.S.:
was compiled
n r
5,032
4,648
N/A
3,964
N/A
3,319
N/A
2,678
N/A
2,422
N/A
2,309
N/A
2,062
N/A
1,854
: 1975
: 1973
405,225 (1973) 6
300,228 4
226,940 3
153,999 2
135,023 1
89,750 1
N/A 1
24,487
18,553
18,601
25,668
23,842
9,286
8,160
6,019
4,647
(85), 1900-1970 (83); Virginia:
(85), 1900-1970 (83); Virginia:
from the monthy publication of the U.S
T me
f etc \ i nne i mn /no1*, n~ -i--, x^^, '
,197.0 (1972)
,921.5
,573.6
,433.0
,827.0
,326.5
,051.6 (1947)
376.3 (1939)
247. Of
366. 41
274. 8f
228. 2T
108.7 (1914)
94.2 (1909)
65.2 (1904)
49.3
1975 (12),
1972 (84),
1,512,603
1 ,282,254
851,341
603.342
433,678
233,115
I 142,431
94,700
56,915
59,922
39,653
23,644
N/A
N/A
e N/A
N/A
1900-1970 (83)
1900-1970 (50)
. Federal Power Commission
34
27
22
17
8
5
3
1
entitled:
,078
,838
,577
,068
,493
,536
.056
,724
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Production
1975
1970
1965
1960
1955
1950
1945
1941
1931-1940
1921-1930
1911-1920
1906-1910
of Electrical
133,727
108,407
90,358
73,869
62,689
49,162
31,035
34,894
278,294
119,199
38,809
1,230
Energy in
3,172
2,577
2,039
1,534
1,327
984
607
583
4,257
3,003
434
7
the U.S.
Division of Motor Vehicles, Commonwealth of Virginia for the years 1955-1975.
£
Where data was not available for a given year, the most recent data is presented as shown.
Where actual data was not available for a given year, data presented represents an average of the previous and subsequent years.
Value added by manufacturer: This figure is derived by subtracting the cost of the materials, supplies, fuel, purchased electricity,
and contract work from the value of shipments for products manufactured plus receipts for services rendered. The result of this
calculation is then adjusted by the addition of value added by merchandising operations (the difference between the sales value and
cost of merchandise sold without further manufacture processing or assembly) plus the net charge in finished goods and work-in-process
inventories between the beginning and end of the year (50).
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CONCLUSIONS
Photochemical oxidant air pollution presents a formidable threat to the
continued productivity of the forests in the eastern United States. Sensitive
species have been identified. Little is known about the factors that affect
plant sensitivity in the forest and preliminary greenhouse fumigation studies
have shown that 03 may reduce the growth of seedlings. Knowledge of the
growth impact on mature trees is lacking. Potential photochemical oxidant
impacts on the population and plant community level have been discussed, but
field data are lacking.
In general, very little is known of the actual impact of photochemical
oxidant air pollution on the forests of the eastern United States. Data are
needed that will identify and quantify actual impacts in the forest. Of
critical concern are the effects of photochemical oxidants on forest produc-
tivity. Specific areas of needed research include:
1) Determination of background pollutant levels so that adequate and
realistic air quality standards can be established.
2) Continued dose-response studies that are designed to measure plant
responses to pollutants as they occur in the ambient air.
3) Determination of the actual impact of photochemical oxidants on tree
growth in the forest.
4) Continued breeding of important tree species for pollutant toler-
ance.
5) Continued study on the feasibility of establishing bioindicator
systems that will allow for estimation of growth impacts.
6) Development of techniques that will identify changes in plant
communities and allow for prediction of the effects of any measured
change.
The only real solution to pollution is abatement. The prospects for
abatement of photochemical oxidant air pollution are remote, at best.
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PHOTOCHEMICAL OXIDANT AIR POLLUTION IN THE EASTERN UNITED STATES
THE PHOTOCHEMICAL OXIDANTS
The photochemical oxidants include ozone (03), the peroxyacyl nitrates,
of which peroxyacetyl nitrate (PAN) is the most important, and the nitrogen
oxides (NO, N02, NO ). These compounds occur in polluted air as a result of
photochemical reactions involving primary pollutants or direct emissions. The
sources of photochemical oxidants (Wood, 1968) and their reactions (Stephens,
1969) have been discussed.
Ozone is the most widespread and important photochemical oxidant (Hegges-
tad, 1969). The oxides of nitrogen and peroxyacyl nitrates are rarely found
in the ambient air of the eastern United States and are therefore considered
to be of little importance. There are, however, reports that implicate the
nitrogen oxides (Skelly et al., 1972) and peroxyacyl nitrates (Pearson et al.,
1974) as phytotoxicants in the eastern United States.
Ozone occurs through natural processes involving transport from the
stratosphere, lightning, or photochemical generation from natural precursors
(Rasmussen and Went, 1965) or through photochemical generation from precursors
of anthropogenic origin (primary pollutants). Photochemical generation from
anthropogenic precursors are thought to be the most important source of 03.
The nitrogen oxides occur primarily through processes that involve high
temperature combusion of fossil fuels such as internal combustion engines or
stationary fossil fuel consuming power plants. Other sources include the
manufacture of nitric acid, nitrated propellants, nitrogen fertilizer and
nylon intermediates (Wood, 1968).
The peroxyacyl nitrates are formed almost exclusively from the photo-
chemical reaction of unsaturated hydrocarbons with oxides of nitrogen.
There are natural sources of precursors for each of the above mentioned
pollutants. Nitrogen oxides (Robinson and Robbins, 1970) and hydrocarbons
capable of photochemical reactions resulting in 03 (Rasmussen and Went, 1965)
and PAN (Stephens and Scott, 1962) are known. For purposes of setting air
pollution standards, reliable estimates of the natural background concen-
trations of the photochemical oxidants are needed but to date, such estimates
are not available.
INCIDENCE OF OZONE IN THE AIR OF .THE EASTERN UNITED STATES
During the 1950's air pollution was generally considered to be a problem
of large metropolitan areas or industrial sources. However, interest in air
pollution in rural areas increased after the discovery that atmospheric oxi-
-------
dants were found to be the cause of several plant disorders whose etiology was
previously unknown. Richards et al. (1958) and Heggestad and Middleton
(1959) demonstrated the causal relationships between oxidants and grape
stipple and tobacco weather fleck, respectively. Monitoring studies were
conducted at several rural areas in the U.S. and Canada beginning in the early
1960's.
Leone et al. (1962) measured oxidant (reported as 03) concentrations
during September and October, 1960 at three rural sites in New Jersey.
Oxidant concentrations occurred during periods of high barometric pressure and
the site nearest a large industrial-urban complex had the highest pollution
levels.
In a similar study, Cole and Katz (1966) measured oxidant concentrations
near Lake Erie in southern Ontario during the summer of 1960 and 1961. The
highest maximum oxidant concentrations were above 10 pphm during both years.
The occurrence of oxidant concentrations high enough to cause flecking of
tobacco leaves was associated with the presence of high pressure systems.
During 1966 and 1967 Costonis and Sinclair (1969a,b) measured oxidant
concentrations at rural sites in central New York. The highest 4 hr mean
oxidant concentration was 5.2 and 8.5 pphm in 1966 and 1967, respectively.
Oxidant concentrations were measured from June 6 - July 6 at a rural site
in Pocohantas County, West Virginia in 1961 (Berry and Ripperton, 1963) and
near Asheville, North Carolina in 1962 (Berry, 1964a). The highest sustained
oxidant concentrations in West Virginia and North Carolina were 6.5 and 4.2
pphm, respectively. In a later study Costonis (1971) measured oxidant concen-
trations in the Pisgah National Forest in western North Carolina during the
summer of 1969. He recorded a maximum sustained oxidant concentration of 4
pphm.
The studies that were conducted in urbanized regions recorded higher
maximum oxidant concentrations than those in the relatively remote moun-
tainous areas of West Virginia and North Carolina. The low oxidant concen-
trations measured at remote West Virginia and North Carolina sites may have
represented the natural background levels of oxidants at that time.
Recent studies have demonstrated the impact of urban pollution on down-
wind sites. Cleveland and Kleiner (1975) showed that rural areas downwind of
the Phi ladelphia-Camden urban complex often had higher 03 concentrations than
the city. Ozone concentrations often exceeded the national ambient air
quality standard (NAAQS) at rural and urban sites. Cleveland et al. (1976)
showed that 03 concentrations in Connecticut and Massachusetts were highest
when the wind came from the New York City area, and were often higher than the
03 concentration in New York City. These studies demonstrated the transport
of 03 and/or its precursors from urban sources to rural, downwind areas.
Stasiuk and Coffey (1974) and Coffey and Stasiuk (1975) point out that 03
concentrations at rural and urban sites reach maximal values on the same days.
This implies a common source of either 03 or its precursors. Therefore, the
cities could not be responsible for the high ozone concentrations measured
-------
simultaneously throughout the state. They suggest that 03 or its precursors
result from natural phenomena such as photochemical generation from natural
precursors or transport from the stratosphere.
Several investigators have shown that sites remote from urban centers
often experience 03 concentrations above the NAAQS. Hayes and Skelly (1977)
correlated high oxidant (above the NAAQS, 8 pphm for 1 hr) concentrations in
the mountains of western Virginia with winds from the north and northeast.
They concluded that 03 or its precursors were transported from the urban
northeast corridor and Lake States into Virginia where they became entrapped
within a stagnant high pressure system. Their interpretation of the results
of the 1975 episode was supported by Husar et al. (1977). The maximum oxidant
concentrations in the mountains of western Virginia were above 15 pphm during
1976 and 1977 (Skelly, 1977). Oxidant concentrations during July, 1977 in
western Virginia were above the NAAQS 30 percent of the time (Skelly and
Johnston, 1978). They used 4 pollution monitoring sites established through-
out the Blue Ridge and Southern Appalachian Mountains of Virginia. During
1977 they reported several oxidant pollution episodes with respect to inten-
sity, duration and impact to the forest vetatation in the area. During May,
218 hr above the NAAQS were recorded with the episode extending from May 12-
20. During July 14-24 a similar episode with a peak of 16.6 pphm 03 was
recorded and the NAAQS was exceeded at least 30% of the actual time at all 4
sites. They suggested that there was strong meterological evidence that the
system that originated the episode had traveled from the midwest portion of
the United States. Galloway and Skelly (1978)pub!ished a report that demon-
strated that sulfates also increased during this same peak episode period.
Severe restrictions in visibility were also noted.
Wolff et al. (1977) found that the movement of 03 concentrations above
the NAAQS into new areas coincided with the movement of high pressure systems.
They suggested a process involving long distance transport of 03 or its
precursors as the mechanism responsible for the occurrence of high 03 concen-
trations at sites from urban sources.
Vukovich et al. (1977) associated high 03 concentrations in the eastern
U.S. with slow moving high pressure systems. The highest 03 concentrations
within these systems were found on the back side of the high pressure system,
corresponding with the air parcel that would be expected to have the longest
residence time within the system. It was suggested that the high 03 concen-
trations in the eastern United States were due to the injection of 03 pre-
cursors into the system and the long residence time allowed for the accumu-
lation of 03. The precursors were thought to be of anthropogenic origin.
In general, the 03 measured at rural sites may result from local sources
if urban areas are close, from a few miles away in an urban plume or from
several hundred miles away by long range transport in a slow moving high
pressure system.
Comparison of the early oxidant measurements of Berry and Ripperton
(1963), Berry (1964a), and Costonis (1971) with the more recent measurements
of Hayes and Skelly (1977), Skelly et al. (1977), Skelly (1977), and Skelly
-------
and Johnston (1978) may indicate a dramatic increase in oxidant concentrations
at rural sites remote from urban areas. Recently reported oxidant levels have
been two to three times higher in the 1975-1977 period than those reported by
Berry and Ripperton (1963) at similar sites in the southern Appalachians. The
trend of increasing oxidant air pollution, if it continues, will present an
increasing challenge to the productivity of the forest resources of the east.
Wood (1968) predicted that photochemical air pollutants will continue to be of
major concern beyond the year 2000.
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DISEASES OF EASTERN WHITE PINE CAUSED BY OZONE
NEEDLE BLIGHT OF EASTERN WHITE PINE
The determination that needle blight of eastern white pine was caused by
exposure to 03 was provided by several interesting etiological studies. More
than fifty years passed from the first report of the disease symptoms until
proof of cause and effects was established. The fact that symptoms of needle
blight were present around the turn of the century (Dana, 1908) indicate that
air pollution problems are not new. A complete review of this topic has been
prepared by Gerhold (1977) and more recently by Nicholson (1977). Table 2
presents a review of the past white pine studies (Nicholson, 1977).
The diseases of eastern white pine (Pinus strobus L. ) called needle
blight, white pine blight, semimature-tissue needle blight (SNB), tipburn,
emergence tipburn, post-emergence chronic tipburn, post-emergence acute
tipburn, and others were puzzling to forest pathologists for years. Needle
blight of eastern white pine was first described by Dana (1908) in New Hamp-
shire. Other early reports of its occurrence include Spaulding (1909) in New
York and New England and Faull (1922) in southern Ontario. Later reports
included large areas of the southeastern United States (Toole, 1949) and
Maryland (Walker, 1946). The disease has been reported throughout the range
of eastern white pine.
The symptoms of needle blight were described as a reddening of the
needle tips followed by a progressive dieback (Dana, 1908; Spaulding, 1909;
Faull, 1922; Gussow, 1928; Spaulding and Hansbrough, 1943; Walker, 1946;
Baldwin, 1954). The symptomatic trees were scattered randomly within white
pine stands.
The investigators attributed needle blight to a number of possible
causes. Faull (1922) reported that needle blight was worse on trees of
greater than 6 inch diameter. The feeder roots of unhealthy trees were often
dead and the disease was not transmitted by fusion of healthy and blighted
branches. Drought was believed to play a role in the disease. Gussow (1928),
however, suggested that excess water was the cause. Hudson (1944) demon-
strated that excess water killed the mycorrhizae. This resulted in reduced
root vigor and tipburn from drought stress. Deuber (1931) also suggested
drought as the cause of needle blight. Swingle (1944) discounted the role of
water stress, either in excess or drought, because diseased trees were found
among the healthy trees.
Toole (1949) found that several fungicides had no effect on the needle
blight disease. He suggested that the causal agent was a root aphid or a
virus. However, the lack of graft transmission reported by Faull (1922)
seemed to discount the possibility of viral infection.
8
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TABLE 2. A COMPARISON OF VARIOUS WHITE PINE NEEDLE BLIGHTS ACCORDING TO HEPTING/BERRY, LINZOfl, COSTONIS, AIID DOCHINGER
Researcher
Study Area
Diagnostic
Terminology
Needl es
Affected
Time of
Obvious
BI ighting
Margin:
Healthy vs.
Diseased
Tissue
Fungal
Fruiting
Bodies
Mottl ing
Needle
Shedding
Onset
Color of
Lesions
Cause
Remarks
References
Hepting/Berry
West Virginia, Tennessee
Bi fusel la
Blight
Current
In Spring on
1 Yr. old
Needles
Sharp
Large
Black
None
Sometimes
in 1 yr.
old needles
Sudden
Black
Stromata
Bi fusel la
Linearis
Usually
Strikes
Singl e
Trees
35
, North Carol ina
Brown Spot Emergence
Tnpburn
Current
Current
In Spring on In Summer
1 yr. old when newly
Needles Emerging
Sharp
Small
Black
Discrete
Spotting
Profuse in
Spring
Gradual
Chlorotic
Processing
to Brown
Scirbhia
Acocola
Resin Drop
Usually
Found on
Lesion
35, 67
Sharp
None
None
None
Sudden
Reddish-
Brown to
Brown
to Grayish
03
Widespread
Problem
In Eastern
U.S.
4, 35
Post Emer-
gence
Chronic
Tipburn
Any
Usually
Current
Any
Season
Indefinite
None
Common
Profuse in
2nd yr
needl es
Gradual
Reddish-
Brown to
Brown
to Grayish
Unknown
Probably
Oa and S02
Gen.
Chlorosis
Then Emerg.
Tipburn
6, 34
Post Emer-
gence
acute
Tipburn
Any
Any
Season
Usually
Sharp
None
None
Sometimes
Sudden
Brown
Necrosis
S02 and
chlorine
Assoc. with
Indus.
Areas in
TN
6, 34
Semimature
Needle
Current
Late June t
Mid-August
Sharp
None
Common
Profuse in
2nd yr
needles
Sudden
Pink Chang-
ing to
Orange-Red
Probably
03 and
SO,
Cause
Never
Proven to
be 03 and
S02
15, 47, 49
Linzon
Ontario, Canada
Ozone
Damage
Current
° S™-
Sharp
None
None
Not
discussed
Sudden
Pale Green
to Bronze
to Orange-
Brown
03
03 Cone.
Used where
60 pphm for
2 H
47, 49
Sulfur
Dioxide
Any
Any
Season
Usually
Sharp
None
Very SI ight
Only in
Chronic
Exposures
Profuse in
2nd yr.
needl es
Sudden
Gray Green
to White
to Reddish-
Brown
S02
Assoc. with
Point
Sources
43, 47, 49
Costonis
New York
Needle
Blight
Current
Early Summer
Sharp
None
Common
Profuse in
2nd yr
needl es
Sudden
Silver to
Yellow-Pink
to Yellow-
Brown
03 and/or
S02
After 72 H.
03/S02 dam-
age was the
same
13, 14, 15
Dochinger
Ohio
Chlorotic
Dwarf
Current
Early Summer
Gradual
None
Common
Profuse in
2nd yr.
needles
Sudden
Yellow
03 and S02
Trees reach
2'-4r tall
maximum
21, 25
Chart format taken from Hepting and Berry (35).
-------
Following a review of the literature and the results of a survey of
needle blighted trees in New Hampshire, Baldwin (1954) observed that a small
proportion of the trees was affected and eastern white pine was the only
species exhibiting symptoms. The injured trees were randomly scattered
within stands in many soil and moisture conditions. He concluded that needle
blight was associated with drought from the previous year.
Linzon (1960) made a detailed description of the progression of needle
blight symptoms. He found that the dieback did not begin at the needle tips,
as previously reported. Rather, the first symptoms were faint, pinkish spots
on the stomata-bearing surfaces of the semimature tissue of elongating needles.
The spots became orange-red and then spread toward the needle tip. New injury
from subsequent disease attacks first appeared in the semimature tissue and
spread distally. He concluded that the disease was related to unfavorable
environmental conditions and was genetically controlled.
Grafting studies further supported the contention that the disease was
not communicable (Berry, 1961; Linzon, 1969; Berry and Hepting, 1964). In
each experiment the four combinations of healthy and diseased scion and stock
were tested. Diseased scion remained diseased and healthy scion remained
healthy, regardless of root stock. It was concluded that the disease was
genetically controlled.
Studies of diseased trees transplanted from areas of high disease inci-
dence to areas of low disease incidence further indicated the abiotic nature
of the disease, and implicated atmospheric constituents as the probable cause
(Berry, 1961). Symptomatic trees moved from an area of high disease incidence
(Marlington, West Virginia) to an area of low disease incidence (North Caro-
lina) exhibited no symptoms of disease in the second year after transplanting.
Symptomatic trees dug up and put back in the same hole, or moved 20 miles to
another location remained symptomatic.
Ozone was shown to be the causal agent of needle blight when Berry
(1961) induced symptoms on sensitive trees by fumigating them with 10 pphm 03
for 2 hr. The symptoms were identical to those seen on sensitive trees
injured in ambient air. Trees that were not sensitive outdoors were not
injured in the artificial fumigations.
The fact that 03 caused emergence tipburn (or needle blight) was con-
firmed in the studies reported by Berry and Ripperton (1963). Sensitive
ramets from a single parent enclosed in chambers supplied with air from which
03 was removed (Mn04 and activated charcoal filters) were protected from
injury. Sensitive ramets from the same parent grown in ambient air were
injured. Fumigations using 03 doses similar to those measured in the field
caused injury symptoms identical to those observed in the field.
That 03 was the causal agent of emergence tipburn was further substan-
tiated by Costonis and Sinclair (1969a,b). High ambient oxidant levels
preceded the appearance of symptoms by one or two days. Needle retention on
sensitive trees was greater on branches that were bagged and supplied with
filtered air than on branches that were not bagged. Interaction of ozone and
two fungi, Lophodermium pinastri and Aureobasidium pullulans were not found
(Costonis and Sinclair, 1972).
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CHLOROTIC DWARF DISEASE
Another puzzling problem for forest pathologists was the chlorotic dwarf
disease of eastern white pine. Swingle (1944) described the symptoms as
stunted roots, greenish-yellow to yellow stunted tips and premature needle
drop. He recognized the similarities between the chlorotic dwarf and needle
blight diseases of eastern white pine.
The grafting experiments of Dochinger and Seliskar (1965) demonstrated
that the chlorotic dwarf disease was a genetically controlled trait. Dochinger
and co-workers demonstrated that the chlorotic dwarf disease was caused by an
interaction of 03 and S02 (Dochinger 1964, 1968; Dochinger and Heck, 1969;
Dochinger and Seliskar, 1970; Dochinger et al., 1970). In the experiments
reported in these papers, ramets from chlorotic dwarf trees were injured more
by simultaneous exposure to 03 and S02 (both at 10 pphm) than the sum of
injury to trees exposed to 03 or S02 separately. The chlorotic dwarf disease
is another manifestation of the high sensitivity of some eastern white pines
to air pol1ution.
SYMPTOMATOLOGY OF THE WHITE PINE NEEDLE BLIGHTS
Differentiating the causes of the various needle blights of eastern white
pine can be difficult. Faull (1922) stated that needle blight could be
distinguished from S02 damage only on the current year needles. He observed
that needle blight symptoms occurred only on needles emerging from the buds.
In contrast, S02 damage occurred on older needles, although the current year
needles were most sensitive.
Hepting and Berry (1961) and Linzon (1960, 1966, 1967 a,b) discussed the
symptom differences that would aid in diagnosis of the specific causal agents.
Hepting and Berry (1961) discussed five common blight syndromes of
eastern white pine. Two of the diseases were caused by fungi, Bifusella
1inearis and Scirrhia acicola, and were easily diagnosed by fruiting bodies.
The other three, emergence tipburn (ET), post emergence chronic tipburn
(PECT), and post emergence acute tipburn, were thought to be caused by air
pollutants although proof at that time (1960) was lacking. Emergence tipburn
symptoms, proven to be caused by 03 (Berry, 1961; Berry and Ripperton, 1963),
were distinguished from PECT in that only the current year needles were affec-
ted and there was a sharp line of demarcation between the injured and uninjured
tissue. In PECT the symptoms could appear on older needles and there was a
zone of chlorosis between the necrotic and healthy tissue. The cause of PECT
was believed to be a chronic-type of S02 injury. Post emergence acute tipburn,
thought to be associated with industrial pollutants (S02 or chlorine), also
affected needles of all ages.
Linzon described the symptoms of a disease he called semimature-tissue
needle blight (SNB). His studies included a description of the symptoms
(Linzon, 1960) and histological examinations of injured tissues (Linzon 1962,
1966). The tissue most sensitive to SNB coincided with that part of the
needle where suberization of the endodermis was occurring. Injury first
appeared as faint, pinkish spots adjacent to stomata in the semimature tissue
(Linzon, 1966).
11
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In other studies, Linzon (1967a,b) attempted to distinguish between
injury caused by 03, S02, and SNB injury. The SNB-type injury seems to be the
same as the ET reported by Berry and Hepting (1964). However, Linzon (1967b)
did not believe that SNB and 03 injury were the same. He fumigated SNB sensi-
tive trees with high 03 concentrations (40-60 pphm) and found them to be
insensitive. If SNB is not caused by 03, its cause remains unknown.
Because of the similarites between 03 and S02 induced needle blights of
eastern white pine it is difficult to determine the cause of a particular
outbreak of disease on the basis of symptoms alone. At present, monitoring of
pollutants is usually necessary to determine the cause of a particular outbreak
of eastern white pine needle blight. Further complications arise when 03-S02
interactions are considered.
Studies have been conducted to determine the feasibility of developing
eastern white pine lines for use in a bioindicator system for the major air
pollutants (Berry.. 1964b, 1973, 1974). A reliable bioindicator system would
lessen the requirements for expensive monitoring equipment.
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IMPACT OF THE PHOTOCHEMICAL OXIDANTS ON FOREST VEGETATION
RESPONSE OF FOREST VEGETATION TO PAN
There has been only one major report in the literature that deals with
the response of forest vegetation to peroxyacetyl nitrate (PAN). Drummond
and Wood (1970) exposed 29 tree species to concentrations of PAN ranging
between 10 and 20 pphm for 8 hr. They observed no injury on any of the
species tested. However, Pearson et al. (1974) reported PAN-type injury on
tomato in southwestern Ontario during 1972 and 1973. The potential for PAN
damage to forest vegetation exists.
RESPONSE OF FOREST VEGETATION TO THE NITROGEN OXIDES
Van Haut and Stratman (1967) ranked 60 forest and shade tree species
according to their sensitivity to short-term N02 exposures. Twenty-five of
these species are presented in Table 3. The most sensitive species were
Betula pendula, Mai us sp. , Pyrus sp. , Larix decidua, and J_._ leptolepis.
Nitrogen dioxide concentrations in the ambient air of the eastern United
States rarely reach phytotoxic levels and when N02 concentrations are high,
other pollutants are usually present. Resulting plant injury is therefore
most commonly from pollutant combinations, rather than from exposure to N02
alone.
Nicholson (1977) studied the effect of N02 and 03 singly and in combina-
tion on 12 clones of eastern white pine collected from ramets located near an
industrial source of N02 and S02. He found that clonal sensitivity to the
pollutant combination of 03 + N02 or 03 alone followed the field observations.
N02 alone had little or no effect at the concentrations and exposure times
used. Kress (1978c) used several levels of exposure to N02 alone and in
combination but no injury was observed on loblolly pine when only N02 was
used at concentrations up to 10 pphm for 6 hrs per day for 28 consecutive
days.
RELATIVE SENSITIVITY OF THE SPECIES
Reports are available that list tree species according to their 03
sensitivity (Dochinger, 1964; Davis and Gerhold, 1976). Table 4 presents a
ranking of tree sensitivity to ozone and is reproduced from David and Gerhold
(1976). The usefulness of relative sensitivity lists was discussed (Davis
and Gerhold, 1976). They caution against placing a great dependence on
relative sensitivity rankings. The plant material (source, age, etc), cri-
teria for ranking (injury, growth), and the methods of study (exposure cham-
ber, ambient air) may play an important role in the results of the experi-
ments.
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TABLE 3. SENSITIVITY OF TREE SPECIES TO N02>
Sensitive
Intermediate
Tolerant
Betula pendula
Malus
Larix decidua
Larix leptolepis
Broad leaved trees
Acer platinoides
Acer palmatum
Ti1 la cordata
Ti1ia platyphyllous
Conifers
Picea pungens glauca
Picea alba
Chamecyparis lawsoniana
Abies homolepis
Abies pectinata
Robinia pseudocacia
Carpinus betulus
Faqus silvatica
Sambucus
Ginko biloba
Ulmus scabra
Fagus si 1vatica
atropurpurea
Quercus robur
Taxus baccata
Pinus austriaca
Pinus montana
nughus
Taken from Van Haut and Stratman (1967).
The relative 03 sensitivity of species in the following groups have been
determined: conifers (Davis and Wood, 1972 - 18 species; Berry, 1971 - 3
species); deciduous trees (Davis and Wood, 1968 - 22 species; Wood and Davis,
1969; Wood, 1970 - 16 species; Wood and Coppolino, 1972 - 20 species); woody
ornamentals (Davis and Coppolino, 1974; Wood and Coppolino, 1971), and woody
shrubs and vines (Davis and Coppolino, 1976). In the reports mentioned
above, species were classified as sensitive, intermediate or tolerant on the
basis of their sensitivity to an 8-hr exposure to 25 pphm 03.
Jensen (1973) determined the relative sensitivity of nine deciduous tree
species on the basis of height growth during a five-month chronic 03 fumiga-
tion (8 hrs daily for 5 days per week). The rank of only three of the nine
species tested were in agreement with the rankings of Wood and Davis (1969).
The ranking discrepancies between the two studies illustrate the problems
encountered when attempting to compare results of studies using different
plant material, methods, and criteria for ranking.
Trees found to be relatively sensitive to 03 in separate studies include
Fraxinus americana (Wilhour, 1970) and Populus tremuloides (Karnowsky, 1976).
14
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TABLE 4. RELATIVE SUSCEPTIBILITY OF TREES TO OZONE*
Sensitive
Ailanthus altissima
Amelanchier alnifolia
Fraxinus americana
Fraxinus pennsylvanica
Gleditsia triacanthos
Juglans regia
Larix decidua
Liriodendron tulipifera
Pinus banksiana
Pinus coulteri
Pinus jeffreyi
Pinus nigra
Pinus ponderosa
Pinus radiata
Pinus taeda
Pinus virginiana
Platanus occidental is
Populus maximowiczii X
Trichocarpa
Populus tremuloides
Quercus alba
Quercus gambelii
Sorbus aucuparia
Syringa X chinensis
Intermediate
Acer negundo
Cercis canadensis
Larix leptolepis
Libocedrus decurrens
Liquidambar styraciflua
Pinus attneuata
Pinus contorta
Pinus echinata
Pinus elliotii
Pinus lambertiana
Pinus rigida
Pinus strobus
Pinus sylvestris
Pinus torreyana
Quercus cocci nea
Quercus palustris
Quercus velutina
Syringa vulgaris
Ulmus pavirfolia
Resistant
Abies balsamea
Abies concolor
Acer grandidentatum
Acer platanoides
Acer rubrum
Acer saccharum
Betula pendula
Cornus florida
Fagus sylvatica
Ilex opaca
Juglans nigra
Juniperus occidental is
Nyssa sylvatica
Persea americana
Picea abies
Picea glauca
Picea pungens
Pinus resinosa
Pinus sabiniana
Pseudotsuga menziesii
Pyrus communis
Quercus imbricaria
Quercus macrocarpa
Quercus robur
Quercus rubra
Robinia pseudoacacia
Sequoia sempervirens
Sequoiadendron giganteum
Thuja occidental is
Tilia americana
Tilia cordata
Tsuga canadensis
Taken from Davis and Gerhold (1976).
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Trees found to be relatively tolerant of 03 in separate studies include Acer
saccharum (Hibben, 1969a,b), Acer rubrum (Townsend and Dochinger, 1974),
Quercus rubra and Cornus florida (Hibben, 1969b) and "Golden Delicious"
apples (Kender and Spierings, 1975). Several Platanus species and Ulmus
americana seedlings from several seed sources were slightly to moderately
injured by exposure to 20 pphm 03 for 3 hr (Santamour, 1969). Pinus nigra, P.
densiflora and P_. thunbergii were shown to be more sensitive to a pollution
episode in New Jersey than other species such as Pinus strobus (Brennan and
Davis, 1967).
Kohut and Krupa (1978) determined the sensitivity of several herbaceous
plants of the north central U.S. forests. They listed a group of plants that
are found native in the forests of the North Central region that were also
sensitive to 8 and 15 pphm 03 for only 4 hrs. These plants are also native to
the forested areas of the north and southeastern portions of the United
States. The sensitive plants listed were wild buckwheat (Polygonurn convo-
vulus), chicory (Cichonium intybus), daisy (Chrysanthemum leucanthemum),
mustard (Brassica kaber) and ribes (Ribes sp.). Other work by Skelly (1977,
unpublished) has identified 03 typical symptoms on clematis (Clematis sp.) in
the Shenandoah National Park of Virginia.
In studies of pollution damage to plants in New York City, Hibben (1969c)
found oxidant-type injury on Pinus strobus, Syringa vulgaris, Ginko biloba,
and several species of Ulmus. Wood (1971) found ozone-type stippling on
American basswood, tree of heaven, a Prunus sp., Carolina silverbell, English
oak, European mountain ash, flowering dogwood, grape, hawthorne, mulberry, and
rhododendron in Philadelphia.
SENSITIVITY VARIATIONS WITHIN SPECIES
The intraspecific variations in sensitivity for many plants have led
several researchers to propose breeding for air pollution tolerance as a
measure to control air pollution damage to plants. Gerhold (1977) has reviewed
the literature pertinent to the subject of forest tree breeding for air
pollution resistance. Studies involving the differential resistance of woody
plants to 03 include Scotch pine (Gerhold and Palpant, 1968; Demeritt et al. ,
1971), American elm (Santamour, 1969; Karnowsky, 1974, Kress 1978b), English
holly (Brennan and Leone, 1970), a hybrid poplar (Wood and Coppolino, 1972),
eastern white pine (Houston and Stairs, 1972, 1973; Houston, 1974), trembling
aspen (Karnowsky, 1976, 1977), azalea (Gesalman and Davis 1977), and loblolly
pine (Kress, 1978a,b). In addition to uses in breeding for tolerance, the
intraspecific variation in pollutant sensitivity may aid in developing a
viable bioindicator system for detection of air pollutants (Berry, 1964, 1973;
Kress and Skelly, 1977).
FACTORS AFFECTING SENSITIVITY TO 03
Environmental factors that may affect the sensitivity of forest vegeta-
tion to 03 have not been adequately studied. Heck (1968) provided a general-
ized review of the factors that affect the sensitivity of plants to air
pol1ution.
16
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In experiments with Virginia pine (Pinus virginiana) Davis and Wood
(1973a,b) found that high relative humidity (85%), high pre- and post-exposure
temperature (32 C), low exposure temperature (10 C), dark pre-exposure, and
light post-exposure treatments favored injury from exposure to 25 pphm 03 for
4 hr.
In similar experiments with white ash, Wilhour (1970) found that high
pre-exposure, exposure and post-exposure relative humidity (80%) and high pre-
and post-exposure temperature (27 C) and low exposure temperature (16 C)
favored injury from exposure to 25 pphm 03 for 4 hr. Fertilization increased
the sensitivity of white ash seedlings. Fertilization of eastern white pine
has been reported to alleviate air pollution damage (Spaulding and Hansbrough,
1943; Dochinger, 1964; Cotrufo and Berry, 1970; Cotrufo, 1974; Will and
Skelly, 1974).
SORPTION OF AIR POLLUTANTS BY VEGETATION
There is evidence that vegetation is a major sink for air pollutants
(Hill, 1971; Bennett and Hill, 1973). Differential rates of 03 sorption by
nine shade tree species and four seed sources of red maple were reported
(Townsend, 1974). The rate of 03 sorption was not necessarily related to the
species sensitivity. Sorption by herbaceous plants has been shown to be
greater than for selected trees (Thorne and Hanson, 1972).
GROWTH RESPONSE OF FOREST VEGETATION TO 03
The growth responses of forest vegetation to air pollutant stresses have
received little attention. Because of size restrictions of plants for use
during pollutant exposure studies most of the available reports deal with
seedlings.
Growth reductions of seedlings in response to 03 exposures have been
reported for American elm and Platanus species (Santamour, 1969) and eastern
white pine (Feder and Perkins, 1977). Jensen (1973) found that height growth
of sycamore, sugar maple, silver maple, black walnuts, green ash, and red
maple was reduced by chronic exposure to 30 pphm 03 (8 hr per day, 5 days per
week for 6 months). The height growth of yellow poplar, white ash, and
European black alder was not affected. Jensen and Dochinger (1974) found that
chronic exposure of hybrid poplar cuttings to 15 pphm 03 (8 hrs per day, 5
days per week, 6 weeks) caused reductions in height and dry weight. Acute
exposure to 100 pphm 03 for 2 hr caused extensive injury but no height or dry
weight reduction.
Growth reductions may be due to the loss of leaf area available for
photosynthesis (visible injury) or disruptions of metabolism that may include
photosynthesis, respiration, or the patterns of photosynthate utilization.
Botkin et al. (1971, 1972) found that exposure of branches of eastern white
pine saplings to 50 pphm 03 (or higher concentrations) for 4 hr caused suppres-
sion of net photosynthesis.
Barnes (1972a) found that chronic exposure of slash, pond, western,
white and loblolly pine seedlings to 5 or 15 pphm 03 usually caused depressed
17
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rates of photosynthesis. The effect was more consistent with exposure to 15
pphm 03. In addition, he found evidence of a photosynthesis stimulation
after continuous exposure of slash, pond, and loblolly pine to 5 pphm 03 for
36 days.
Barnes (1972b) found that chronic exposure of eastern white, shortleaf,
slash; and pond pine seedlings to 5 pphm 03 caused increases of soluble
sugars and ascorbic acid. He postulated that these effects may represent an
impairment of polysaccharide synthesis. Barnes and Berry (1969) discussed
the relationship between carbohydrate and ascorbic acid levels and tipburn
sensitivity of eastern white pine.
Wilkinson and Barnes (1973) found differences in the pattern of 14C02
fixation after exposure of eastern white and loblolly pine seedlings to 5
pphm 03 for 10 minutes. The major effect of the 03 exposures was to divert
photosynthate from soluble sugars to other products.
RESPONSE OF FOREST VEGETATION TO POLLUTANT MIXTURES
The interaction of air pollutants in causing plant damage has received
considerable attention in recent years. Reinert et al. (1975) reviewed the
literature dealing with pollutant interactions. The interaction of 03 and
S02 in causing injury to tobacco was the first reported synergistic air
pollutant interaction (Menser and Heggestad, 1966). Shortly thereafter
Dochinger and co-workers determined that the chlorotic dwarf disease of
eastern white pine was caused by the synergistic interaction of 03 and S02
(Dochinger, 1968; Dochinger and Heck, 1969; Dochinger and Seliskar, 1970;
Dochinger et al., 1970). Banfield (1972), Jaeger and Banfield (1970) and
Houston (1974) reported greater-than-additive effects of 03-S02 mixtures on
eastern white pine. Costonis (1973) reported less-than-additive effects of
03-S02 mixtures on eastern white pine. Greater-than-additive effects of 03-S02
mixtures have also been observed on trembling aspen (Karnowsky, 1976) and
'Golden Delicious' apples (Kender and Spierings, 1975).
Kress (1972), Kohut (1972), and Kohut et al. (1976) studied the inter-
action of 03 and PAN on hybrid poplar. Kress (1972), using sequential expo-
sure, usually found greater-than-additive effects. Kohut (1972) and Kohut et
al. (1976), using simultaneous exposures, found greater-than-additive,
additive and less-than-additive effects in different replications of the same
experiment.
Hill et al. (1974) reported an additive effect of S02 and N02 on selec-
ted native desert species and trembling aspen. Skelly et al. (1972) sugges-
ted that N02 in combination with S02 was causing injury to eastern white
pine. The growth of eastern white pine (Stone and Skelly, 1974; Phillips et
al., 1977a), loblolly pine (Phillips et al. , 1977b), and yellow poplar
(Stone and Skelly, 1974) near a N02-S02 source was reduced. Nicholson
(1977) reported greater-than-additive injury effects on eastern white pine
from Oo-NOo mixtures.
18
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Kress and Skelly (1976, 1977) and Kress (1978 a,b,c,d) have provided
the first reports of forest tree response to a three-pollutant interaction.
They found that exposure of loblolly pine Pi nus taeda L. and American syca-
more Platanus occidental is L. seedlings to combinations of 03, S02, and N02
caused greater height growth reductions than exposure to any of the two
pollutant combinations. The pollutant concentrations used in all the treat-
ments were 14 pphm S02, 10 pphm N02, and 5 pphm 03 and exposures lasted 6
hours per day for 28 consecutive days. In addition to visual injury, several
height measurements were taken on both species in order to determine the
effect of the pollutants on terminal growth. Significant growth reductions
of 26% and 21% were observed in loblolly pines exposed to the 03 + S02 and
the S02 + N02 + 03 treatments, respectively. When all three pollutants were
combined, the resultant foliar injury was significantly different from that
of the 03 treatment, however, it was not significantly different from that
of the 03 + S02 treatment. Results using sycamore showed that foliar injury
was not a reliable indicator of sensitivity under these experimental condi-
tions since no treatment was consistently significantly different from any
other. Treatment with all three pollutants produced a 45% and 25% growth
reduction on sensitive and tolerant lines, respectively. This was especially
important because no significant foliar symptoms were observed in either
case. Significant growth reductions were also observed in the 03 + S02
treatment where 34% and 17% growth reductions were observed on the sensitive
and tolerant lines, respectively. Again, no significant foliar symptoms
were observed.
COMMUNITY AND ECOSYSTEM EFFECTS
Several authors have outlined the potential effects of photochemical
oxidant air pollutants on forest ecosystems. Miller (1973) and Miller and
McBride (1975) described the results of the rather extensive San Bernardino
Mountain studies in southern California. In that area the decline of pon-
derosa pine has led to undesirable changes in the plant community and forest
ecosystem. Similar changes are possible if not already occurring in the
eastern United States.
Treshow (1968) discussed the ways that air pollution could cause changes
in plant populations and plant communities. The values of a baseline ap-
proach to air pollution research were outlined. Sinclair (1969) discussed
air pollution as a selective force in forests. Not only will the pollutants
select individuals and species through natural process, but selection of
trees by man through tree breeding and planting will also affect the future
composition of the forests.
Smith (1974) defined three classes of potential air pollution impacts
on forests. In a Class I relationship the pollution load is low and vegeta-
tion will remain unaffected, and play a role as a sink for air pollutants.
In a Class II relationship there may be subtle plant population and plant
community changes caused by the predisposition of sensitive species to other
abiotic stresses. Much of the eastern United States is probably in a Class
II situation at the present time. In a Class III relationship the pollutant
load is high and impacts on vegetation are obvious. At the present time,
Class III situations are encountered only around industrial point sources of
pollution.
19
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and respiration of pines. Environ. Pollut. 3:133-138.
Barnes, R. L. 1972b. Effects of chronic exposure to ozone on soluble sugar
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Botkin, D. B. , W. H. Smith, and R. W. Carlson. 1971. Ozone suppression of
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29
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-79-045
4. TITLE AND SUBTITLE
Oxidant Air Pollution Impact to the Forests of
Eastern United States—A Literature Review
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO
John M. Skelly and J. William Johnston
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Dept. of Plant Pathology and Physiology
Virginia Polytechnic Institute and State University
Blacksburg, VA 24061
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory--Corvallis
Office of Research and Development
U.S. Environmental Protection Agency
Corvallis, Oreaon 97330
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
April 1979
6. PERFORMING ORGANIZATION CODE
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
CC71142-J
13. TYPE OF REPORT AND PERIOD COVERED
literature review
14. SPONSORING AGENCY CODE
EPA/600/02
15. SUPPLEMENTARY NOTES
Project Officer: Raymond G. Wilhour, 503-757-4634 (FTS 420-4634)
Corvallis. Or 97330
16. ABSTRACT
This report presents a review of past studies that have attempted to delineate measur-
able and/or possible impacts of photochemical oxidants on the forests of Eastern
United States. Sources of oxidant precursors and subsequent long distance transport
phenomena are reviewed and documented. A brief historical treatment of eastern white
pine responses to air pollutants is followed by an up-to-date evaluations of current
air pollution measurements and associated impacts.
Potential threats to eastern forest tree species are reviewed through a comparison of
various fumigation studies in laboratory and field situations. The concept of hidden
injury is discussed as being a possible major impact problem facing analysis of real
losses.
The authors present evidence that would suggest that many forest tree species indige-
nous to the Eastern United States may already be detrimentally impacted'by previous
high oxidant episodes. They further suggest that even more drastic and only long
term reversible effects to the forest ecosystem will follow a trend of increasing
oxidant air pollution in many major forested regions of this area of the United States
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
air pollution
photosynthesis
photochemical oxidants
b. IDENTIFIERS/OPEN ENDED TERMS
Eastern forests
forest vegetation
white pine
COSATI Held/Group
o6/F
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report/
UNCLASSIFIED
21. NO. OF PAGES
36
20. SECURITY CLASS ITMs page I
UNCLASSIFIED'
22. PRICE
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