PARENT SESSION
Oral Session #6: Disturbance Ecology of Forests: Fire, Patterns. Presiding: R. DeFries.
Monday, August 6, 2001. 8:00 AM to 12:00 PM. Hall of Ideas F.
Effects of multiple human-induced disturbances of forest composition and nitrogen dynamics in northern hardwood forests.
LATTY, ERIKA1, CANHAM, CHARLES2, MARKS, PETER3, 1 2 3
ABSTRACT- We examined structural and functional characteristics of old-growth and second-growth forests that had been exposed to an introduced pathogen and elevated nitrogen deposition. Vegetation surveys indicated few structural differences between old-growth forests in the Adirondacks, New York and nearby forests that were selectively logged 80-100 years earlier. In northern Maine, the smaller basal area of second-growth, 20 m2.ha-1, relative to the old-growth stands, 32 m2.ha-1, indicated that forest structure had not recovered from logging that occurred 60-80 years ago. Overall, tree composition was similar among forests with contrasting histories in New York, and differences in composition and structure were more pronounced in the Maine forests. These data were synthesized with results from a series of comparative studies conducted in old-growth, logged, and logged then burned forests in the Adirondacks to examine the importance of persistent legacies of forest history on present forest functioning. Bark and foliar nitrogen concentrations, and the total nitrogen and carbon content of the soil were all greatest in the old-growth stands. Symptoms of beech bark disease, a disease resulting from an introduced pathogen complex, were positively correlated with nitrogen concentrations of bark from American beech trees (Fagus grandifolia), and old-growth forests contained the greatest number of beech trees acutely infected with disease. This research suggests that novel anthropogenic disturbances, like nitrogen saturation and introduced pests, may have greater effects on future forest dynamics than modest logging.
KEY WORDS: disturbance, old-growth, second-growth, beech bark disease