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OCR for page 141
Air Pollution Impacts on Forests
in North America
ANN M. BARTUSKA
U.S. Forest Service
U.S. Department of Agriculture
No other impact of air pollution has so mobilized public concern in
North America as has the effect on forests. During the 1980s, funding
for air-pollution research on forests increased tenfold. "Acid rain" was the
primary issue early in the 1980s when effects on lakes and streams were
the focus; now, as concern increases about effects on forests, studies are
focusing on acidity (sulfur and nitrogen) in association with photochemical
oxidants (especially ozone) and other gases. This chapter presents our
current understanding of the impact of air pollution on the productivity
and health of forests in various parts of North America, and discusses the
major uncertainties still remaining in this area of research. This chapter
will not review the substantial literature dealing with effects near major
point sources of sulfur dioxide or fluoride (e.g., smelters), but instead will
concentrate on regional air pollution.
EFFECTS OF AIR POLLUTION ON FORESTS:
CASE STUDIES
Forest decline is a term used to refer to a general decrease in health
and vigor leading to tree mortality over a large geographic region. Declines
are not new phenomena, and have been widely reported in the literature.
Some declines are caused by a complex interaction of multiple abiotic and
biotic factors (Marion, 1981~. Others are caused by only one or two ca-
sual factors (Benoit et al., 1982~. A classic example was the dieback of
birch which occurred between 1930 and 1950 in southeastern Canada and
the northeastern United States. In this example, higher than average soil
temperatures in summer apparently resulted in extensive root mortality.
The weakened trees were subsequently attacked by foliar and bark-boring
141
OCR for page 142
142
ECOLOGICAL RISKS
~ -I- ~
~4..
Expbnation me\ '
· pH at Sample Site \
~ Line of Equal pH Value ~ J
FIG-ORE 1 The 1986 distribution of precipitation-weighted pH (NAPAP, 1986~.
insects Armillarea mellea and various viruses leading to widespread mor-
tality. Clearly, there was a multiplicity of causes. Whether atmospheric
deposition plays a role in forest decline can only be assessed within the
context of the numerous other stress factors that affect forests.
While there have been numerous studies on the effects of a specific
air pollutant on a specific plant, the complex nature of declines can only be
assessed through an intensive, multilevel investigation of the community at
risk. Due to this complexity, it is not surprising that we have few clear-cut
examples of regional declines where air pollution has been a contributory
factor (Figures 1 and 2~. In only two cases has air pollution been implicated
as a cause of damage: the mixed conifer forests of the San Bernardino
mountains of southern California and the Eastern white pine (Pinus strobes
L.) in eastern North America. A third and more recent decline red spruce
(Picea rubens Sarg.) at high elevations in the eastern United States has
been suggested as being due to atmospheric deposition in association with
natural causes. Finally, recent growth reductions in southern pines has led
to speculation that regional air pollution is a primary cause. These four
cases will be discussed in detail below (Figure 3~.
San Bernardino Mountains
Foliar damage to a variety of western conifers was observed in the San
Bernardino Mountains of southern California in the early 1970s. These
OCR for page 143
HUA"V EFFECTS ON THE TERRESTRIAL ENVIRONMENT 143
,
}-—~
~ ~~ '
W~'. ,1
.
to l
·4
·42
Nor
· 65 i;: ~ ~
Am,
FIGURE 2 Average of maximum 7-hour daily mean concentration (ppb) of O3 during
1984 growing season at selected rural sites in the United States (NAPAP, 1987~.
Me
~ ~ _SoUthem
FIGURE 3 Areas where air pollution is suspected to impact forest trees.
Mortem
White Poe
Spruce-flr
effects provoked an extensive interdisciplinary study of this mixed conifer
forest ecosystem (Miller et al., 1977; Miller, 1983~.
Eighteen vegetation study sites were established along a geographical
gradient of visible injury in the San Bernardino Mountains. The frequency
and intensity of visible injury in the forest types occupying the transect was
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144
ECOLOGICAL RISES
monitored from 1973 to 1976. The five forest types identified along this
gradient include: ponderosa pine (fin us ponderosa Dougl. ex Laws.~;'pon-
derosa pine/white fir (Abies concolor [Gord. & Glend.] Lindl. ex Hildebr.~;
ponderosa pine/Jeffrey pine (R je~reyi Grev. & Balm.; Jeffrey pine/white
fir; and Jeffrey pine.
The symptoms visible on these species are very characteristic of what is
termed "typical symptoms of ozone exposure," and include chlorotic mot-
tling, necrotic tipburn progressing from the tip to the base, and premature
needle abscission (Miller et al., 1982~. The trees showing the most visible
injury were ponderosa -pine and Jeffrey pine. The symptoms on these trees
appeared to worsen in degree and magnitude over time, i.e., some of the
trees showing chlorotic symptoms in 1973 showed symptoms of necrosis by
1976, and a few of the trees showing necrosis and needle drop in 1973 were
dead by 1976. Overall, the accumulated mortality of ponderosa pine and
Jeffrey pine varied with forest type, but ranged from 0 to 6% for the 18
plots from 1973 to 1978. Average accumulated mortality rates by type were
4% for ponderosa pine, 4% for ponderosa pine/white fir, 6% for ponderosa
pine/Jeffrey pine, 1% for Jeffrey pine/white fir, and 0%~ for Jeffrey pine
(Taylor, 1980~.
The visible symptoms and mortality were associated with decreased
photosynthetic capacity, suppressed radial growth,' and reduced nutrient
retention and availability. There was also evidence of decreased cone and
seed production, increased litter accumulation, and increased infestation
by pests and pathogens such as the pine beetle (Dendroctonus brevicomus)
and root rot-caused by Comes annosus. The long-term effects expected
for this system result in shifts from a pine overstory to a self-perpetuating
ozone-tolerant community of oak and shrub species.
The evidence is strong for ozone as the agent causing foliar injury and
other types of injury. The San Bernardino National Forest (SBNF), which
is located ' et the east end of the South Coast Air Basin (including Los
Angeles), has been exposed to increasing annual dosages of air pollutants
from heavy urban and industrial development over the last three to four
decades. Photochemical oxidants have been carried by marine air currents
to the mixed conifer forests since at least the early 1950s, when signs of
injury were detected in ponderosa pine. As human population growth in
the Basin has continued, both pollutant concentrations and the extent of
the affected geographic area has increased (Miller, 1977; Taylor, 1980~.
Thirteen air monitoring sites accompanied the vegetation study sites
along the geographical gradient of visible foliar injury (Miller, 1983~. The
natural background ozone (03) concentration in the study areas was 30
to 40 parts per billion (ppb); this concentration is comparable to that
in other mountainous regions in the United States. The first signs of
injury-of ponderosa pine needles were associated with a 24-hour average
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HUAL4N EFFECTS ON THE TERRESTRIAL ENVIRONMENT
145
O3 concentration exceeding 50 to 60 ppb during the months of May
through September. When the average ranged from 100 to 120 ppb,
injury to sensitive species such as ponderosa pine was severe and ecosystem
functions were affected (Miller, 1983~. More recently, Peterson et al.
(1987) demonstrated a significant decrease in Jeffrey pine growth north of
Los Angeles in the Sierra Nevadas of California. This growth decrease
has been linked to o7.one exposure and the appearance of visual damage
symptoms, and is alarming due to the high aesthetic value of the area.
Eastern White Pine
Needle-blight injury on Eastern white pine has been reported for
decades; however, it was not determined until the 1960s that the injury was
caused by ozone (Berry and Hepting, 1964~. The conditions of Eastern
white pine in areas of the southeastern United States mimic those of
western conifers in the San Bernardino Mountains. In addition to the
symptoms being similar, the short-term effects on the biological, chemical,
and physical properties of the trees appear to be analogous.
Foliar injury was visible on Eastern white pines in the Blue Ridge
Mountains of southern Virginia (Skelly et al., 1972; Stone and Skelly, 1974;
Phillips et al., 1977a,b; Benoit et al., 1982~. The pines showed typical
ozone symptoms which varied in intensity within the species. Trees were
classified as sensitive, intermediate, or tolerant based on needle length,
needle retention, and presence of foliar injury. Eleven, 67, and 22% of
the white pines surveyed were rated sensitive, intermediate, and tolerant,
respectively (Skelly et al., 1979~.
Nine Eastern white pine trees were sampled in Tennessee, three in
each sensitivity class, and cored for radial growth analysis. Similar growth
trends were found in the pines of tolerant and intermediate class, while
a steady decline in growth rate (approximately 70~o over 15 years) was
observed in pines of the sensitive class (McLaughlin et al., 1981~. This
study also detected altered allocation of carbon, resulting in a reduction
of photosynthate to the boles and roots. Radial growth decline was also
evident in the trees sampled in the Blue Ridge Mountains and was corre-
lated to changing local air quality (Benoit et al., 1982~. Skelly and Stone
(1972) also noted a 66% decrease in height growth. The rate of decline
of these white pine will be furthered by bark beetle infestation and root
disease such as Verticicladiella procera (Skelly et al., 1983~.
McLaughlin et al. (1982) suggest the following sequence of events and
conditions afflicting Eastern white pine in the southeastern United States:
1. premature senescence and loss of older needles at the end of the
growing season
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146
ECOLOGICAL RISKS
2. reduced storage capacity in the fall and resupply capacity in the
spring to support new needle growth;
3. increased reliance of new needles on self-support during growth;
4. shorter new needles resulting in lower gross photosynthetic pro-
ductivity;
5. higher retention of current photosynthate by foliage resulting in
reduced availability of photosynthate for external usage (including repair
of chronically stressed tissues of older needles);
6. premature casting of older needles.
The net result of this condition is a reduction in the total amount of
photosynthesizing tissue and carbohydrates available for growth and main-
tenance. This sequence of events was derived from continuous observation
of Eastern white pine (Pious strobes) in the Cumberland Plateau region of
eastern Tennessee. Perhaps more importantly, these stages also are appear-
ing in loblolly pine following ozone exposure, and may reflect a common
pattern of tree response.
Concentrations of ozone in the study areas of the Blue Ridge Moun-
tains repeatedly reached 40-60 ppb, with peak episodes ranging from 100
to 200 ppb (Skelly et al., 1983~. Foliar injury occurred most frequently
on Eastern white pine and milkweed and was absent on characteristically
insensitive species. The observations of foliar injury corresponded with
periods when ozone concentrations were the highest. The Eastern white
pines that did not show visible injury did appear to exhibit growth effects
(Skelly et al., 1983~.
High-Elevation Red Spruce
Although evidence of injurer has been recorded in high-elevation
spruce-fir forests throughout the eastern United States, the patterns of
symptom expression vary a great deal, and the linkage to air pollution is
uncertain. In the northern Appalachian forests, Siccama et al. (1982) noted
a reduction in density of all size classes of red spruce in higher elevational
zones (>760 m) in the Green Mountains of Vermont. Similar observations
on the decline of spruce in the Adirondacks were reported by Raynal et
al. (1980), as well as in the White Mountains of New Hampshire, where a
decline in number and basal area of this species was noted (Siccama et al.,
1982~.
The major visible foliar symptoms are loss of needles from the tips
of the branches and from the apex of the crown, without the pronounced
chlorosis indicating nutrient deficiency and with only slight macroscopic
structural damage, i.e., necrotic spotting on the older foliage (Friedland et
al., 1984a). Field and microscopic observations indicate that cold and/or
winter moisture stress are responsible for the loss of the young foliage
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HURON EFFECTS ON THE TERRESTPL4L ENVIRONMENT
147
(Friedland et al., 1983b). Mature red spruce showed foliar loss from the
tips of the crowns down and from the tips of the branches inward, similar to
foliar loss exhibited on younger trees (Friedland et al., 1984a). Balsam fir
(Abies balsamea [L.] Mill.) appears vigorous in that the symptoms of stress
and necrosis exhibited by the spruce have not yet been noted. However,
measurement of average annual increment on balsam fir shows a decrease
similar to that of spruce (Siccama et al., 1982~. The symptoms cited above
are typical of declining red spruce in the northern Appalachians.
The spruce-fir forests of Camels Hump in the Green Mountains of
Vermont show the decline symptoms typical of the northern region. Camels
Hump is comprised of a complex of schist overlain by glacial till. On the
lower slopes (< 750 m), northern hardwoods with occasional conifers are
found. The upper slopes (750-1,210 m) are primarily red spruce-balsam fir,
with occasional white birch (Betula papynfera var. cordifolia). The upper
slopes are characterized by shallow acid till and very acidic Spodosols
or Histosols (pH in H2O 3.04.5~. Average annual rainfall is 1,200-2,000
mm, increasing with elevation, and there is prolonged contact with cloud
moisture (70-120 days per year). Visible characteristics of decline include
the loss of younger foliage, severe frost damage (i.e., browning of foliage),
and damage to needles at the cellular level, including to the chloroplasts
and tonoplasts, which is typical of the damage to high-elevation spruce-fir
in the north.
The decline of red spruce, which is a long-lived, shade-tolerant species,
is not the anticipated pattern based on its known ecological strategies and
former abundance. Significant in the assessment of this decline is the fact
that the pattern is recorded for both larger trees (30 m in height) as well as
saplings (2 m in height in the substrate). Equally important is the fact that
these symptoms occur throughout all the elevational gradients and across
all age and size classes (Siccama et al., 1982~.
In the southern Appalachians (i.e., Virginia, North Carolina, and
Tennessee), some of the spruce-fir forests are in a severe state of decline
(Bruck, 1984~. Here, symptoms include the loss of older foliage, proceeding
from the inner to outer portions of the crowns. Chlorosis on the needles is
apparent. Also, the appearance of epicormic branches has been noted on
both the red spruce and the Fraser fir (Abies Easers [Pursh] Poir.) on the
branches and stems.
Mount Mitchell is located in western North Carolina and the first
symptoms of decline in the south were noted here (Bruck, 1984~. At
2,038 m, it is the highest peak in the eastern United States and in the
Appalachians. The bedrock is Precambrian metamorphic, gneiss and schist,
with fine granitoid layers. Slopes of 20-60% are common, but some flat
areas occur as draws and on crests. Where soils have coarse textured,
parent material and a stable surface, Spodosols may be likely; where soils
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148
ECOLOGICAL RISKS
are of medium textured parent material with unstable substrates, Umbrepts
are likely. The climate is characterized by high precipitation: 1,800 mm
throughout the year with extensive periods of cloud cover and relatively
high input of total precipitation from cloud moisture.
The survey of Mount Mitchell in 1984 showed that trees aged 45-85
years, primarily red spruce, averaged 75-90% defoliation characterized by
loss of the oldest needles, often leaving a chlorotic tuft of needles at the
branch ends. Most trees at or above 1,900 m exhibited some form of growth
reduction beginning in the early 1960s. The spruce stands below 1,800 m
also have begun to show signs of defoliation. Foliar analyses of needles
collected during the survey showed no unusual concentration of macro-
or micronutrients or trace elements. However, anticipated decreases of
nitrogen (N) content with flush age for red spruce were not observed.
Instead, N content of the 1983 needles was actually greater than the 1984
or 1982 needles (Bruck, 1984~.
More recent surveys completed in 1985 and 1986 have shown contin-
ued deterioration of the spruce-fir stands in the Mount Mitchell area. A
concomitant study of cloud and rain chemistry in the area is showing sign-
ficantly greater deposition of pollutants than at lower elevations; however,
cause and effect cannot be attributed to any specific factories) at this time.
Another important factor is the extensive Fraser fir mortality through-
out the southern Appalachians due to the balsam woolly adelgid (Adelges
piceae Ritz). The loss of fir has significantly altered the microclimate of
these sites as the crown has broken up, increasing light penetration to the
forest floor. Whether this structural change has affected the red spruce is
still conjectural; however, it is an important natural stress factor which must
be considered (Bartuska and Medlarz, 1986~. Recent hypotheses suggest
that air pollution in the region is acting as a predisposing stress on Fraser
fir, increasing the fir's susceptibility to adelgid attack (Hain and Arthur,
1985~. However, the link is circumstantial at present, and underscores
the point that high elevation ecosystems are subject to many co-occurring
stresses. Therefore, it may not be reasonable to expect that one factor can
be isolated as the ultimate cause of mortality.
Southern Pines
Of the various case studies discussed in this chapter, the role of air
pollution in the southern commercial forest region (specifically, Piedmont
and Coastal Plain) of the United States is the most uncertain, but also
the most important with regard to potential economic impact. Data from
ten-year remeasurements of Forest Inventory and Assessment (FIA) plots
in Alabama, Georgia, South Carolina, and North Carolina indicate that
there has been a decrease in the rate of diameter growth in some portions
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HUMAN EFFECTS ON THE TERRESTRIAL ENVIRONMENT
149
of the southern pine region (Sheffield et al., 1985). These U.S. Department
of Agriculture Forest Survey data suggest that commercially important
loblolly (Pinus taeda L.), shortleaf (Pinus echmata Mill.), and slash pine
(Pinus ellipse Engelm.) forests in the Piedmont and low elevation mountain
regions of these states grew less rapidly by about 16-20% in diameter
during the past ~ to 10 years than during the previous 10 years. Shortleaf
pine also showed a decrease in growth in the Coastal Plain, although loblolly
and slash pine showed a volume increase of 17% and 49%, respectively.
The cause of the growth reduction has been attributed to increased
hardwood competition, loss of the `'old field condition," an increase in pine
mortality due to pine-beetle outbreaks, and the natural aging of stands.
However, in evaluating any of these factors, air pollution can not be
ignored. The average growing season rainfall pH is < 4.6, with events as
low as pH 3.6 (NADP, 1988~. Perhaps of greater importance with respect to
southern forests, the Piedmont and Mountain regions of the southeastern
United States showed higher hourly O3 levels than most other regions
(Lefohn and Pinkerton, 1988~. The influence of these air pollution factors
on tree or forest response is still unknown and is being studied extensively.
RECENT FINDINGS AND UNCERTAINTIES
Prom 1985 to the present, significant research efforts have been un-
derway to study the effects of atmospheric deposition and ozone exposure
on forest species, with support from federal and state agencies, forest in-
dust~y, and other institutions. While much of the data from this research is
still being evaluated, some significant advances in understanding have been
made. The purpose of this section is to provide some more recent research
results which perhaps bring us closer to evaluating the link between air
pollution and forest health.
Western Conifers
While the San Bernardino forests of southern California have long
been known to be impacted by air pollution as described earlier in this
chapter, recent research also is focusing on other areas which are, or have
the potential to be, at risk. These areas are: Puget Sound in Washington
State; the Sierra Nevada in California; and the Front Range of the Colorado
Rockies.
Sites in the southern Sierra Nevada have shown recent reduced
growth rates from increment core analysis and visible ozone damage. Re-
duced growth was an isolated occurrence among sites; the region as a whole
showed no growth decline for ponderosa pine.
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150
ECOLOGICAL RISKS
· Comparative analysis of cloud water and rainfall indicates that
clouds can have 3-10 times more hydrogen (H+), nitrate, and sulfate than
precipitation in many parts of the western United States. These results are
consistent with similar observations on cloud water chemistry in the eastern
part of the country.
Spruce-Fir
.
Measurement and analysis of increment cores collected from dom-
inant and codominant red spruce and balsam fir trees at permanent plot
locations throughout New York and New England have documented that
there has been a significant decline across the region in the rate of indi-
vidual tree growth since about 1960 for red spruce, and since about 1970
for balsam fir; however, all other major forest tree species are currently
growing at rates that equal or exceed the rates prior to 1960 (Hornbeck et
al., 1987~.
While these analyses initially focused on the general question of growth
reduction without attempting to answer questions of cause, recent analyses
of both red spruce and balsam fir data have indicated that the declines
should have been expected due to a natural stand growth phenomena.
Stands of red spruce and balsam fir growing at elevations below 700 m
are experiencing reduced growth as would be expected because of natural
factors of stand development. Although atmospheric deposition impacts
on growth rate cannot be completely ruled out by these analyses, the
involvement of such pollutants must be considered minimal. This position
is now widely accepted by other scientists, many of whom continue to
corroborate these findings with other data.
· A field study at Whitetop Mountain, Virginia, confirmed that wet
acidic deposition leaches basic cations from red spruce foliage. A compar-
ison of cloud water and throughfall chemistry showed that there was an
exchange of incoming H+ ions with foliar cations, mainly Ca2+ and Mg2+.
This leaching increased as cloud pH decreased. In addition, a depletion of
NH4+ in throughfall appeared to indicate the occurrence of direct foliar
nitrogen uptake.
The significance of these results is unclear. Foliar leaching is a normal
process that usually occurs to some extent. It has not been determined
whether the leaching losses observed here are excessive with respect to
internal nutrient balances. Additional research is needed to better quantity
nutrient leaching and to determine its significance as related to growth and
productivity.
Controlled laboratory and field studies have not demonstrated a
significant ozone effect on red spruce seedlings, although ozone stress
may alter winter hardiness. In contrast, exposure to sulfate acidic mist
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HUMAN EFFECTS ON THE TERRESTRI24L ENVIRONMENT
151
produced foliar symptoms rapidly on red spruce seedlings. Results indicate
that spruce is particularly vulnerable to injury from acidic mist when sulfate
concentrations are high, and there are repeated opportunities for drying of
liquid on foliage.
· Recent hypotheses have suggested that a primary mechanism of pol-
lutant impact on red spruce is through an alteration in the cold-hardening
process, leading to increased winter injury. Several studies are ongoing, so
that these data are only preliminary; however, results to date indicate that
most hardiness is strongly negatively influenced by acid mist treatments.
Further research is needed to better define the linkage between acidic
deposition and winter damage.
Southern Pines
· A dendrochronological analysis of over 2,000 increment cores from
dominant and codominant naturally regenerated loblolly pine trees on
typical Piedmont sites in North Carolina, South Carolina, and Georgia
has led to the conclusion that these trees are growing today at less than
two-thirds the annual rate that equivalent trees in stands on the same
sites were growing 35 years ago. Analysis of the data using a modeling
technique that allowed for the quantitative analysis of the impact of various
stress factors on growth, including site, quality, stand-density changes, and
climatic impacts revealed that an additional unexplained reduction in
radial growth remained.
· A number of coordinated projects have demonstrated that families
of loblolly pine (Pinus taeda) differ significantly in response both to simu-
lated acid rain and to ozone, although the differences were most striking for
ozone. An examination was made of 100 half-sib families of loblolly pine,
selected for superior growth under ambient conditions, from throughout
the southern commercial pine region. There were significant differences
in response to acidic rain and to ozone among these families. Response
to acidic rain treatments (pH 3.5, 4.3, and 5.2) was variable; some exper-
iments showed negative effects, others showed positive, while still others
showed no effect at all. In a two-year field study, the acid treatment affect
did not appear until 18 months with rain exposure, at which point growth
stimulation due to the pH 3.5 treatment was measured. These results
emphasize the need for long-term research under controlled conditions to
better quantify responses to acid deposition.
· In contrast, loblolly pine response to ozone was significant after
only 6 months. Higher concentrations of ozone resulted in decreased height
and diameter growth. These same saplings showed marked reduction in
photosynthetic capacity and quantum yield. Similar studies with slash
(Pinus elliotii) and shortleaf (fin us echinata) pines are showing responses
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152
ECOLOGICAL RISKS
after eight months of treatment, consistent with the loblolly pine response.
Further evaluation of the mechanism of impact is ongoing and must be
expanded to include trees at all stages of development, from seedling to
mature tree. There appears to be a strong link between ozone exposure
and changes in carbon fixation and allocation. The net effect appears
as a reduction in productivity without visible symptoms a response only
detectable with long-term repeated measurements.
CONCLUSION
Our knowledge concerning the impact of regionally dispersed (as op-
posed to locally dispersed) air pollutants on forest ecosystems clearly is
incomplete. Improving this knowledge base is complicated by an absence
of visible symptoms in many cases. The ability to perform research which
links physiological or nutritional changes with grown appears to be a
more useful approach to evaluating air pollution impacts on trees in the
short-term. Ultimately, the response which society should consider is forest
growth and productivity changes, which can only be detected with long-term
measurements.
A major challenge will be in providing sufficient information in the
short term to assist policy makers in the decision process, coupled with
the understanding that only through long-term studies wid uncertainty be
reduced. Because multiple causal factors are probably involved in the
response, the general public, policymakers, and scientists must recognize
that if a large number of interactive factors contribute to a widespread
change in forest conditions, even a well-funded research program may not
produce a definite cause-and-effect relationship in forest ecosystems. We
may have to be satisfied with a substantial body of circumstantial evidence
with which to make decisions.
Acknowledgement
Sections of this document have been adapted from the Forest Response
Program (FRP) Plan, the 1987 FRP Annual Report, the briefing document
on the FRP prepared for the EPA Science Advisory Board, and the 1989
FOP Accomplishments Report. The contributions of the FRP management
are appreciated.
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HUMAN EFFECTS ON THE TERRESTRL4L ENVIRONMENT
153
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Representative terms from entire chapter:
eastern white
