CONCERNS FOR THE FORESTS OF THE APPALACHIANS IN A SCENARIO OF
POSSIBLE CLIMATE CHANGE

John M. Skelly, Department of Plant Pathology, The Pennsylvania State University, University Park, PA 16802.

At the outset of this paper it is important to understand that current evidence indicates that the forests of the Appalachian Mountains are very healthy and productive; indeed forests across the whole of the eastern United States and southeastern Canada continue to be in excellent condition. It is also important to understand that the author perceives the threats of present day air pollution and perhaps associated issues related to climate change to be of concern to the continuing health and productivity of the Appalachian forests. As a significant part of this conference, it is certainly proper to pause and take stock of the well being of the Appalachian forest....and to consider its future. However a word of caution may also be appropriate. Let us all apply a sense of balance to our concerns while considering the future forests of the Appalachian Mountains We should all keep in mind our current excellence of Forestry Sciences, management skills and general knowledge while continuing to hold high expectations for forest health as we move into the next millennia and beyond.

Forests have always been subject to many natural interactions with their environments and habitats; endemic forest pathogens, insects and natural abiotic stressors all play a significant role in the changing of the forest. Most recent evidence of such cataclysmic natural events may be found in the wake of the far inland paths of recent hurricanes in the southeastern Appalachians and following a 1998 devastating ice storm in northern New England and southeastern Canada. Long term changes result from such cataclysmic natural events in our forests...they are expected and well documented.

Other events which are not so predictable and natural also have introduced havoc, destruction, and long term changes to the natural forests of the Appalachian Mountains. Perhaps none has been as dramatically evidenced as the destructive blight of the American Chestnut following the accidental introduction of the pathogen in 1904 into the New York Zoological Gardens. Simply put, by 1936 100% of the commercial value of the American chestnut was lost and the value of the eastern forest as we know it today was reduced by 50%. The forest was changed by this introduced pathogen for many generations of foresters, naturalists, and landowners alike. Chestnut blight is a disease which ably serves as just one example of what an introduced organism is capable of inciting by way of forest responses and long-term change. White pine blister rust, Dutch elm disease, and dogwood anthracnose serve as continuing examples of diseases caused by introduced pathogens into our forest species with no long-term genetically developed resistances. Introduced insects such as the gypsy moth, balsam wooly adelgid, and most recently the hemlock wooly adelgid serve as just a few of the examples on the entomological side of the more sordid past and continuing calamities for numerous Appalachian forest tree species. Following their respective introductions, many of these pathogens and insects have remained so very destructive in the Appalachian forests with non-relenting virulence and aggressiveness that it becomes very difficult to determine if their levels of destructiveness have been influenced in any measurable way by changing climatic scenarios and/or pollutant loadings. When compared to the total destructiveness of any of these introduced causal factors, any direct and/or indirect influence of climate change or pollution depositions would have to be quite large to be detectable.

Similarly, many known and very-well-understood forest species declines are likewise present within the Appalachian forests; a few examples would include oak decline, sugar maple decline, ash dieback, hickory decline, and attacks of conifers by various bark beetles. Each of these have a well described scenario of causal agents which may collectively drive the tree (species) into a downward decline spiral leading to eventual losses of the species at specific sites. Once again, linkages to climatic change and/or pollutant loadings will be difficult but careful investigation of etiologies and associations with more regional scale inputs may be discernable.

It is also important to understand that change and tree death are common within forests as a natural processes; forest advance from thousands of seedlings per acre through to a hundred or less at mature canopy closing. Other less desirable changes have been directly the result of human activities across much of the Appalachian forests. Accidentally introduced disease inciting pathogens and destructive insects have brought about tremendous changes to forest tree species compositions; at many sites the loss of major (e.g. American chestnut, oaks, maple, beech) and minor species (dogwood, butternut) have been documented. In addition, the Appalachian forest has been directly influenced by introduced exotic weed tree species, previous logging practices such as high grading, severe land use changes and numerous other forest management factors. In light of these changes it may be more tentative to suggest that the forests of the Appalachians are truly "healthy". However, for those tree species that are currently occupying the available growing space within the Appalachian Mountains, their respective overall health condition is excellent as a whole. Growth of our current forest far exceeds current demand for timber and related forest products.

Future considerations must take into account possibilities and probabilities of climate change on the numerous interactions noted above. Changes within endemic populations of pathogens and insects in their relative importance (destructiveness) within natural forests would be noteworthy as a connection to climate change and/or pollution loading. Subtle changes in insect or biotic pathogen life cycles may bring about such noticeable effects. Similarly, forest species responses to their environments may result in altered sensitivity to abiotic stressors such as freeze tolerance, droughts, or site wetness. Newly developing nutrient requirements by faster growing plants (ie, increasing CO2) may be followed eventually by mineral deficiencies of the same site. Increasing CO2 has, in a relatively few studies, been shown to ameliorate responses to ambient tropospheric ozone air pollution. Such investigations provide an interesting twist to how we might look at pollutant interactions. Effects of climate change to biodiversity, species competition, site utilization, metabiotic relationships, and many other forms of natural forest species interactions are all subject to intensive and important long-term studies.

Forest management practices may slowly change in order to meet the changing climatic scenarios. Through the continuing use of sound forest sciences at all levels of forest biology and forest management, it is likely that such long term climate induced changes (should they occur in a noticeable fashion) will most probably be understood (and utilized where appropriate) in such a manner as to insure continuation of excellent forest health and productivity for future generations.

Additional reading:

Canadian Forest Service. 1993. Helping Forests Stay Healthy: The Forest Insect and Disease Survey. Cat. No. F042-201/1993E, Hull, Quebec.

Millers, I., Allen, D.C., Lachance, D. 1992. Sugar maple crown conditions improve between 1988 and 1990. U.S.D.A. Forest Service NA-TP-03-92.

Nash, B.L., D.D. Davis and J.M. Skelly. 1992. Forest health along a wet sulphate/pH deposition gradient in north-central Pennsylvania. J. Environ. Tox. and Chem. 11: 1095-1104.

Skelly, J. M., Davis, D. D., Merrill, W., Cameron, E. A., Brown, H. D., Drummond, D. B., and Dochinger, L. S. (eds.) 1987. Diagnosing Injury to Eastern Forest Trees. USDA-For. Ser., Veg. Survey Res. Coop. and Penn State Univ., University Park, PA. 122 p.

Skelly, J.M. 1989. Forest decline versus tree decline: The pathological considerations. Env. Monit. Assess. 12:23-27.

Skelly, J.M. 1990. On the importance of etiological accuracy during surveys to determine forest condition. World Resources Review 2:250-277.

Skelly, J.M., and Innes, J.L. 1994. Waldsterben in the forests of Europe and eastern North America: Fantasy versus reality? Plant Disease 78:1021-1032.