amounts of pollution that might affect park resources. The Park Service now finds itself in a difficult position because legislators and residents are not convinced, without more conclusive data, that the threat is real.

In Great Smoky Mountains National Park, considerable research on threats and mitigation is under way. For example, research has addressed the high-elevation spruce and fir forests of the southern Appalachians. These unique, island-like ecosystems at the summits of the highest peaks are rich in rare northern vascular plants and southern endemic plant species. The balsam woolly adelgid, an introduced pest insect, has caused nearly complete mortality of Fraser fir, a southern endemic tree, and is causing great structural change within the forest. Research to establish the pattern and cause of mortality is assessing remnant groves of mature fir, the protection of the gene pool through seed collections and tissue culture, and the efficacy of spraying infested trees with an environmentally benign fatty acid. Several rare bryophytes and lichens occur only on the bark of the Fraser fir. In the short term, research will help managers decide whether it is necessary to manage these elements of biologic diversity directly. Research also has addressed fuel loads and the risk of fire in these stands, as well as successional patterns of recovery.

Other research on the influence of acid deposition in Great Smoky Mountains National Park has focused on the spruce-fir ecosystem because acid deposition is greater at higher elevations than it is in low-lying areas. Research has shown unusual reductions in red spruce growth on some sites. These systems are long lived and the mineralization of organic matter is a slow process, so a better understanding of mineral cycles will require additional years of work. The results of the research, however, could help NPS prevent the addition of new sources of pollution in its airshed and suggest the development of other strategies for protecting biological diversity.

Science programs in several national parks, including Great Smoky Mountains National Park, Sequoia-Kings Canyon National Parks, and Rocky Mountain National Park have been important in the National Acid Precipitation Assessment Pro-

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