PARENT SESSION
Oral Session 8: Forest Ecology I: Dynamics and Succession.
Presiding: A Fiala and D Kashian
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room B 117.

Edge effects in old growth forests.

Reemts, Charlotte^*,1, Ellair, Darin¹, Murphy, Peter¹, ¹ Michigan State University, East Lansing, MI

ABSTRACT- Edge effects are one of the most important factors influencing forest fragments. The width of the edge depends on its aspect, the fragment's disturbance history, and the age of the edge. We studied changes in vegetation at the northern and southern edges of a small (9.7 ha), undisturbed, old-growth beech-maple forest fragment in southern Michigan. Toumey Woodlot is surrounded by pasture and has been a fragment for more than 100 years. Nationally recognized for its value, Toumey offers a unique opportunity to study well-developed edges in a mature, old-growth forest. We counted trees and seedlings using 6 transects (3 each on the northern and southern edges) that extended 100m from the edge into the forest. Leaf area index (LAI) was measured using leaf litter collected after the autumn leaf fall. While there were no trends in the size of trees with distance from the edge, shade tolerance of woody species (ranked on a 5 point scale) was significantly greater (p<0.0001) on the northern edge for trees (N: 4.94±0.097; S: 4.59±0.33) and seedlings (N: 4.85±0.098; S:4.61±0.22). On the southern edge, tolerance increased towards the fragment core (trees: p<0.0001, R²=0.71; seedlings: p<0.0001, R²=0.64); no such trend was evident on the north edge. LAI was higher in the northern edge (=0.05) at distances less than 50m from the edge; beyond 50m, the northern and southern edges were indistinguishable (N:5.92±0.45m²/m²; S: 5.14±0.46m²/m²). Our data show that edge effects on the northern edge extend only 5m into the forest, while the edge in the south reaches up to 40m into the forest. However, the width of the edge depends greatly on the characteristic used to measure it. Of the measures we used, LAI was most sensitive to edge effects.

Key words: edge effects, aspect, forest fragmentation, beech-maple forest