Ecological Risks Perspectives from Poland and the United States (1990) / Chapter Skim
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Air Pollution Impacts on Forests in North America
Air Pollution Impacts on Forests in North America
Pages 141-154
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From page 141... ...
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.
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From page 142... ...
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.)
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From page 143... ...
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.
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From page 144... ...
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~.
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From page 145... ...
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.
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From page 146... ...
Concentrations of ozone in the study areas of the Blue Ridge Mountains 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.
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From page 147... ...
The upper slopes (750-1,210 m) are primarily red spruce-balsam fir, with occasional white birch (Betula papynfera var.
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From page 148... ...
Another important factor is the extensive Fraser fir mortality throughout the southern Appalachians due to the balsam woolly adelgid (Adelges piceae Ritz)
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From page 149... ...
RECENT FINDINGS AND UNCERTAINTIES Prom 1985 to the present, significant research efforts have been underway to study the effects of atmospheric deposition and ozone exposure on forest species, with support from federal and state agencies, forest indust~y, and other institutions. While much of the data from this research is still being evaluated, some significant advances in understanding have been made.
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From page 150... ...
Measurement and analysis of increment cores collected from dominant 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 individual 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.
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From page 151... ...
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.
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From page 152... ...
CONCLUSION Our knowledge concerning the impact of regionally dispersed (as opposed to locally dispersed) air pollutants on forest ecosystems clearly is incomplete.
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From page 153... ...
1977b. Eastern white pine exhibits growth retardation lay fluctuating air pollutant levels: Interaction of rainfall, age, and symptom expression.
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From page 154... ...
197Z Symptom expression of Eastern white pine located near a source of oxides of nitrogen and sulfur dioxide. Plant Disease Reptr.
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