PARENT SESSION
Symposium #5: Forest edges: unifying concepts and key research needs..
Organized by: CR Nelson and J Chen
Monday, August 5. 1:00 PM to 3:45 PM. Crystal Ballroom, TCC.
Biogeochemical Edge Effects on Nitrogen and Carbon Retention in Fragmented Oldgrowth Forest.
HAYES, TOM*,1,2, SWANSON, ALAN3, D'ANTONIO, CARLA1, GRIFFITHS, ROBERT2, 1 University of California, Berkeley2 Oregon State University, Corvallis3 Montana State University, Bozeman
ABSTRACT- Our research addresses the long-term impact of clearcut edges on biogeochemical processes affecting carbon and nitrogen retention within fragmented old-growth Douglas-fir/western hemlock forests in the Wind River Experimental Forest, near Carson, Washington. In addition to quantifying the magnitude and depth of influence of edge effects on ecosystem processes, our research seeks broader application to conservation and experimental design, using a mechanistic approach. Along 360-m gradients spanning clearcut to forest at 9 sites, long-term monitoring of edge effects integrates microclimate, above-ground structure, litter fall, decomposition, and nitrogen dynamics. Abrupt changes in height and structure at edges induce increased microclimatic variability in adjacent forest, which, in turn, alters rates of nitrogen and carbon cycling. Field and laboratory assays reveal increases in litter decomposition and nitrogen availability in near-edge (0-30 m from edge) forest, and higher rates of litter fall and soil organic matter storage within far-edge (30-120 m) forest, relative to interior forest (more than 120 m). Abiotic structural effects, by modulating microclimatic variability, change the complex biotic interactions involved in nutrient cycling in forest within 120 m of edges. Due to such interactions, nitrogen and carbon pool sizes and process rates, and net ecosystem production, vary in a nonlinear manner with distance into forest from edge. Mixed-effects models most precisely quantify depth of influence for over 100 microclimate and biogeochemical variables.
KEY WORDS: old-growth forest, edge effects, biogeochemistry, microclimate