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FOREST APPLICATIONS OF BIOMARKERS
IN SOUTHEASTERN FORESTS
Robert L. Anderson
Plant Pathologist
USDA Forest Service, R-S
Ashevile, NC 2XX06
ABSTRACT
Air pollution symptoms on sensitive tree species have long
been recognized as a way to assess air pollution damage. In
1974, the USDA Forest Service reported that forests in the
southeastern United States were being affected near point sources
and may be affected over large areas. Eastern white pine was
viewed as a classic biomarker. Clones of different sensitivity
were propagated and planted out as survey tools. Many of the
more sensitive clones have died. The National Park Service has
used biomarkers such as milkweed and eastern white pine to
survey for air pollution injury in southeastern National Parks since
1983. In 1986, a survey was made of the Piedmont of Georgia,
South Carolina, and North Carolina, using existing biomarkers such
as cherry. It showed that sensitive plants were widely distributed,
but were more common around sources of pollution. In 1986,
eastern white pines were used as biomarkers for a survey of
portions of Virginia, North Carolina, South Carolina, Georgia,
Tennessee, and Kentucky. Surveys of wilderness areas in South
Carolina and Virginia have also been made using biomarkers.
Lichens have also been used as biomarkers. The European system
of crown density classification has been evaluated and modified for
use on loblolly and shortleaf pines. Surveys using the crown vigor
system are being developed.
Injury to vegetation by phytotoxic levels of ozone, fluoride, sulfur dioxide, and
other pollutants has been reported in the southeastern United States for a number of
years. Much of the reported injury has been associated with industrial sources. In some
cases, the injury has produced severe symptoms on sensitive vegetation miles from the
source. The symptoms are more common around point sources and in areas where
meteorological or topographical conditions inhibit pollutant dispersal (Davis, 1970~.
Ozone is a pollutant that is a product of photochemical reactions of a number of
pollutants originating from a number of sources, such as automobiles. Whereas
pollution-caused symptoms from most point sources usually occur in a limited area ozone
occurs over a wide area. In 1974, the USDA Forest Service (Loomis, 1974) reported that
forests in the southeastern United States were being affected near point sources and may
be affected over large areas. We now know that ozone does cause injurious effects on
105
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106
forest trees at concentrations that occur on a regional scale in the Southeast (Woodman,
1986).
A number of forest tree species or plants commonly found in association with the
plant species are more sensitive to pollutants such as ozone (Skelly et al., 1988~. Several
of these more sensitive species, such as eastern white pine, blackberry, black cherry,
sweetgum, ragweed, white ash, milkweed, and poison ivy, show symptoms of ozone while
located next to more resistant species, such as oak, that do not show any visible
symptoms. These more sensitive plants are referred to as bioindicators or biomarkers.
These plant species offer an opportunity to assess the relative incidence of pollutant
injury in a given area. By looking at the biomarkers in a geographic area and comparing
them to the same species in another area, one can assess whether the damage is more
severe in one area as compared to another, and from year to year. However, estimates
on impact or the level of pollutants required to cause the symptoms cannot be easily
made. Another use is to select biomarkers that are sensitive to certain levels of
pollutants and plant them in the field. These biomarkers can then be roughly correlated
with the amount of pollutants required to cause the noted injury.
A number of factors must be considered when using biomarkers. Injury to leaves
from air pollutants is easily confused with mimicking symptoms caused by factors such as
temperature and soil moisture extremes, mites, certain insects and fungi, viruses, salt
application, herbicides, fertilizers, and the list continues. Also, the use of biomarkers
requires that the plants be examined at a point when symptom expression is at its
maximum, but fall colors have not started. This normally means that the surveys have to
be conducted from mid-July until the start of fall colors. In spite of the limitations,
biomarkers have been used for a number of years in the southeastern United States to
assess air pollution incidence.
Eastern white pine has been viewed as a biomarker since 1964 (Berry, 1964~. Berry
selected clones of eastern white pine that would detect low levels of oxidants, sulfur
dioxide, or fluorides. By using the sensitive clones, the pollutant could be identified, as
well as a rough estimate made of the concentration. Of the 1,428 seedlings Berry
screened, 53 were sensitive only to oxidants, ~ to sulfur dioxide, and 14 to fluorides.
Only 4.5°h were tolerant to all three types of pollutants. Selections from these clones
were planted in portions of Tennessee, Kentucky, Virginia, and North Carolina in the
1 960s. Many of the plantings have been lost for a number of reasons. The few that do
remain have a story to tell. The clones more sensitive to ozone are for the most part
dead. The intermediate clones are still alive but show substantial growth reductions
when compared to resistant selections. The USDA Forest Service at Asheville, N.C., has
continued to propagate the eastern white pine biomarkers selected by Berry. Recently,
clonal plants were provided to the National Park Service, Virginia Polytechnic Institute,
and Penn State. Additional material is being propagated at this time for use in
controlled pollutant studies.
Other biomarkers, such as milkweed and tulip poplar, occur over a very large
geographic area and lend themselves to use in surveys. In 1983-84, the National Park
Service used milkweed to conduct biomarker surveys on a number of parks in the
southeastern United States (Bennett and Stalte, 1985~. They found the milkweed surveys
were useful to identify areas with higher levels of ozone. For a number of years they
have used eastern white pine as a biomarker. The Park Service has established
permanent plots in a number of parks and from 1984-87 recorded the amount of chlorotic
mottling on eastern white pine. This helps identify "hot spots" and can be used to
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107
compare incidence from year to year. In general, the percentage of trees with some
damage has been high, but the severity has been low. They have also used chlorotic
mottling to survey for damage on slash pine in the Everglades National Park. Hardwood
biomarkers, such as tulip poplar and cherry, were used to survey several Park Service
battlefields in northern Virginia (Davis and Bennett, 1985~. They found the incidence of
ozone damage on the biomarkers to be very common, with the degree of injury varying
by location. The Park Service has also used the presence or absence of lichen and
biochemical analysis of the lichen to assess air pollution injury (personal communication,
J. Bennett).
In 1986, the USDA Forest Service used eastern white pine as a biomarker to
survey for ozone symptoms in the natural range of white pine in Georgia, South Carolina,
North Carolina, Virginia, Tennessee, and Kentucky (Anderson et al., 1988~. They found
the ozone symptoms of chlorotic mottling and tip burn to occur throughout the range,
but the symptomatic trees were more common around areas of urban development. About
23% of the stands surveyed had some symptomatic trees. Trees with ozone symptoms had
49% less volume than symptom-free trees.
In 1985, the Southeastern Forest Experiment Station reported a growth loss in
loblolly pine in the Piedmont of Georgia, North Carolina, and South Carolina. Chevone,
Chappelka, and Brown (1986) used biomarkers to survey for ozone injury in the area
showing growth loss. Plots were established in the vicinity of pine growth plots so
correlations could be made. They found that typical ozone injury was common on the
biomarkers throughout the survey area, varied geographically, and was more pronounced
around urban areas. They theorized that the damage on the biomarkers may be severe
enough to cause a growth loss in loblolly pine.
In 1986-87, the USDA Forest Service made a survey of two class-one wilderness
areas: Bull Island in South Carolina and the James River Face Wilderness Area in
Virginia. Both of these biomarker surveys found the percent of plants with ozone
symptoms to be low and the severity on the symptomatic plants to be slight. The data
show that ozone damage was low in these years, but should be used with caution because
ozone is highly variable from year to year.
All of these surveys used plants that are sensitive to pollutants. There are several
benefits to these kinds of surveys:
1. The damage is relatively easy to see and evaluate.
2. The surveys use native plants that are part of the area's ecology.
3. The data permit comparisons of injury over time and geographic areas.
4. Data collection is relatively inexpensive and can be done in a short time.
However, there are several disadvantages:
1 ~' ~ ~ . . ..
2
3.
4.
5.
6.
1nere are a number ot mimicking symptoms that can confuse the observations.
The biomarkers may vary in their genetic sensitivity to the pollutant.
Some pollutants are highly variable from year to year.
Normally, the surveys have to be done in a 2- to 4-week period.
The concentration of pollutants cannot be determined.
Normally, impact cannot be determined from the data.
In addition to the biomarkers, a European system rates the crowns of trees for
foliage loss. The USDA Forest Service (Anderson and Belanger, 1986) has evaluated this
system on shortleaf and loblolly pine in the South. They found that by estimating the
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foliage loss and measuring crown width, the relative growth rate of a tree could be
accurately estimated.
SUMMARY
Biomarkers can provide valuable information on presence or absence of injury,
relative severity of injury, type of pollutant, geographic variation, and seasonal variation,
yearly variation. However, there are problems with mimicking symptoms, plant genetics
variation, climatic variations, long-term exposure in a given area, etc. As any tool, they
should be used with their limitations in mind.
REFERENCES
Anderson, R.L., and R.P. Belanger. 1986. A crown rating method for assessing tree
vigor of loblolly and shortleaf pines. In: Proceedings of the Fourth Biennial
Southern Silvicultural Research Conference, Atlanta, Gal, Nov. 4-6. Pp. 538-543.
Published by USDA Forest Service, Southwestern Forest Experiment Station,
General Technical Report SE-42, Asheville, NC.
Anderson, R.L., and others. 1988. Occurrence of air pollution symptoms (needle tip
necrosis and chlorotic mottling) on eastern white pines in the southern
Appalachian Mountains. Plant Disease Reporter 72~2~: 130-132.
Bennett, J.P., and K.W. Stalte. 1985. Using vegetation biomonitors to
assess air pollution injury in National Parks: milkweed survey. National Park
Service, Air Quality Division, Denver, CO, Natural Resources Report Series No.
85-1.
Berry, C.R., and G.H. Hepting. 1964. Injury to eastern white pine by
unidentified constituents. For. Sci. 10~1~:1-13.
Chevone, B.I., A.H. Chappelka, and H.D. Brown. 1986. Survey for ozone injury on
sensitive plant species on or near natural loblolly pine stands in Georgia,
South Carolina, and North Carolina. Cooperative Research Agreement #29-206,
USDA Forest Service, National Vegetation Survey. Raleigh, NC. p. 26.
Davis, D.D. 1970. Air pollution and southern forests. Forest Farmer 10:6-~.
Davis, D.D., and J.P. Bennett. 1985. Evaluation of air pollution injury to
vegetation in four mid-Atlantic National Park Service areas. Center for Air
Environment Studies No. 756-85. National Parlc Service, Air Quality Division,
Denver Colorado. Pp. 72.
Loomis, R.C. 1974. Evaluation of air pollution effects in the South. USDA Forest
Service. Forest Pest Management, Atlanta, GA. Report #75-1-4. p. 27.
Skelly, I.M., and others. 1988. Diagnosing injury to eastern forest trees. National
Acid Precipitation Assessment Program, Forest Responses Program, Vegetation
Survey Cooperative. Published by Agric. Information Service, College of
Arizona~ Pennsylvania State University, State College, PA. p. 122.
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Woodman, I.N. 1986. Air pollution and forest productivity: a critical issue for
foresters. In: Proceedings of Atmospheric Deposition and Forest Productivity,
Fourth Regional Technical Conference, Appalachian Society of American
Foresters, Raleigh, NC, Jan. 29-31. Pp. 1-~.
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Representative terms from entire chapter:
white pine
