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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 4.5h 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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108 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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109 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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