Introduction: The Southern Commercial Forest Research Cooperative.- Section 1. Characterization of the Condition of Southern Commercial Forests.- 1.Southern Pine Forests of North America.- 2.Soils, Geomorphology, and Land Use of the Southeastern United States.- 3.Air Quality and Atmospheric Deposition in Southern U.S. Forests.- Section 2. Abiotic and Biotic Stress Factors on Southern Pine Forests.- 4.Response of Loblolly Pine to Moisture and NutrientStress.- 5. An Overview of Responses of Southern Pines to Airborne Chemical Stresses.- 6.Biotic Agents of Stress in the South.- 7. Interactive Effects of Air Pollutants with Abiotic and Biotic Factors on Southern Pine Forests.- Section 3. Growth and Physiological Effects of Regional Air Pollutants on Southern Pins.- 8. Atmospheric Deposition and Soil Resources of the Southern Pine Forest.- 9. Atmospheric Nitrogen Deposition and the Mycorrhizae of Southern Commercial Forest Trees.- 10. Growth Response of Southern Pines to Acidic Precipitation and Ozone.- 11. Physiological and Biochemical Effects of Air Pollutants on Southern Pines.- Section 4. Impacts of Atmospheric Deposition and Ozone on Southern Commercial Pines: A Synthesis of Epidemiological and Mechanistic Studies.- 12. Synthesis and Conclusions from Studies of Southern Commercial Pines.

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Impact of Air Pollutants on Southern Pine Forests

In response to unexplained chronic outbreaks of southern pine beetle in loblolly pine forests in Stewart and Chattahoochee Counties, Georgia, the U.S. Geological Survey and the Georgia Forestry Commission conducted a 3-year study to determine whether acidic deposition could explain the pattern of infestation. There were no significant differences in total acidic deposition between areas of high infestation in Stewart County and low infestation in adjacent Marion County. The annual rate of total atmospheric sulfur deposition in the highly infested area was 6.0 kilograms per hectare per year. This rate represents significant pollutant loading; however, it is somewhat lower than previously published estimates for the southern Piedmont and Coastal Plain physiographic provinces. There is no indication of significant local point sources. The annual rate of total atmospheric nitrogen deposition in the highly infested area was 5.9 kilograms per hectare per year which is comparable to previously published estimates. Ambient air-quality measurements indicated that sulfur dioxide and ozone concentrations were comparable to typical values in rural areas of the southeastern United States. Ozone concentrations were high enough to constitute a chronic stress on sensitive loblolly genotypes. However, the limited data available do not indicate that there is a spatial correlation between ozone concentration and southern pine beetle infestation. Comparisons of soil properties that could be influenced by chronic acidic deposition between paired, infested and uninfested plots in Stewart County indicated that there were no significant differences that could explain 1 susceptibility to infestation. Site conditions throughout the study area are marginal for economic production of loblolly pine because of low soil fertility and a tendency towards conditions of drought because of the common occurrence of sandy surface soils. County general soil maps indicate that the area of highest infestation contains a higher abundance of soils containing a subsurface horizon that is partially cemented and restrictive to rooting, when compared with areas of low infestation. Loblolly pine in the study area is growing under multiple, interacting stresses; and it is hypothesized that cumulative effects of these stresses are greater in the most highly infested areas. INTRODUCTION In 1992, unexplained chronic infestations of southern pine beetle (SPB), Dendroctonus frontalis Zimm. (Coleoptera: Scolytidae), infestations in loblolly pine (Pinus taeda L.) in Stewart and Chattahoochee Counties, Georgia (fig. 1), caused concern to commercial and private foresters. Infestations of SPB are common throughout the range of indigenous and planted loblolly pine in the southeastern United States; however, the pattern of persistence and severity in the northwestern Coastal Plain Province of Georgia was unprecedented in 1992. Commercial and private foresters requested assistance from the Georgia Forestry Commission (GFC) to determine whether acidic deposition was related to the SPB infestations. The GFC was conducting an ongoing statewide Forest Health

Assessment of potential role of atmospheric acidic deposition in the pattern of southern pine beetle infestation in the northwestern coastal plain of Georgia, 1992-95

HALE B., RYAN D., ORMROD D. P. and ALLEN O. B. An integrated statistical approach to estimating plant responses to sequential and concurrent gaseous pollutants. BIOTRONICS 22, 35-46, 1993. Controlled environment studies of plant response to multiple environmental stresses frequently have physical (such as chamber space) and analytical (such as experimental design and data summary) limitations. This study demonstrates the use of an efficient, integrated statistical approach in evaluating rutabaga (Brassica napus L. ssp. rapifera (Metzg.) Sinsk cv. Laurentian) and cabbage (Brassica oleracea L. var. capitata cv. Market Prize) shoot growth responses to sulphur dioxide (S02) followed by ozone (03) at acute doses. The approach combines analysis of covariance, an incomplete factorial experimental design, polynomial dose response functions and a reduced-rank regression procedure to the comparison of functions. Young plants were exposed to S02 on one day followed by 0 3 on the next day. Growth responses to sequential exposure were compared with previously reported growth responses to concurrent exposure to the same doses. Rutabaga growth was sensitive to both gases in both exposure regimes, whereas cabbage growth was sensitive to only S02 in the sequential exposure. Rutabaga leaf area and shoot fresh weight responses to sequential exposures followed the same pattern as concurrent responses, and their magnitudes following sequential exposures were approximately 60% of the concurrent responses. Rutabaga shoot dry weight and cabbage shoot fresh and dry weight, and leaf area responses to the sequential exposures were different in both magnitude and pattern from responses to the concurrent exposures. The importance of this work lies in the method for quantification and comparison of plant response to pollutant mixtures, in different exposure patterns. Using a suite of off-the-shelf statistical techniques, plant response to sequential versus concurrent exposure has been mathematically generalized over a broad range of pollutant mixture concentrations. Particularly for the purpose of environmental risk assessment, this integrated statistical technique has broad application to controlled environment studies of plant response to multiple stresses.

D.P. Ormrod

Papers

Co-occurrence patterns of gaseous air pollutant pairs at different minimum concentrations in the united states∗