PARENT SESSION
Oral Session # 4: Forest Ecology I: Diversity, Suppression, and Release.
Presiding: B Schamp
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 103.

The effect of forest edges on tree growth rates.

McDonald, Robert^*,1, Urban, Dean¹, ¹ Duke University, Durham, NC

ABSTRACT- Forest fragmentation is a common process occurring in forests worldwide that has been shown to have important implications for tree species composition and abundance. In particular, the effects of forest edges on microclimate are often profound, usually resulting in increased light available to plants along the forest edge. Using dendrochronological techniques, we assessed the effect of forest edges on the growth rate of 4 species that are common in the North Carolina Piedmont: Acer rubrum, Liriodendron tulipifera, Liquidambar stryacifula, and Pinus taeda. Transects from the forest edge into the forest interior were established on more than 60 forest edges in the Duke Forest (Durham, NC), incorporating edges of varying aspect and ages. Within a transect, all stems greater than 10cm were cored, and their spatial position and species recorded. For each transect, a set of environmental and edaphic variables were measured, including soil texture and nutrient values, and percent canopy closure. All transects were located in a GIS system, and land cover data classified from a time-series of Thematic Mapper images were used to assess the age of each edge. All four species had significant increases in growth rates within 5 meters of an edge (P < 0.05 in all cases), but the effect did not appear to deeply penetrate into the forest interior. However, the increase in growth rate near edges explains a substantially smaller portion of the variance than edaphic or other types of explanatory variables. There is an indication of possible interactions between soil texture and the effect of forest edges on tree growth rate. Overall, this increased growth rate may prove to be quite an important effect for some applications, since analyses of land-cover maps for the region suggest a substantial percentage of trees are within 10 meters of an edge.

Key words: forest fragmentation, edge effects, growth rate, dendrochronology