Document: ERI-3-93-6

Carbon cycling on the edge.

HOFFA, E.A.* and M.E.HARMON

Oregon State University, Corvallis, OR 97331 USA ¹

Abstract:
Analyses of carbon dynamics at the landscape and regional scale usually do not consider spatial interactions. This is based on the notion that carbon dynamics can be modeled within patches that are then added up to predict landscape or broader scale dynamics (i.e., an additive approach). We reexamined this assumption by first identifying the temporal and spatial scales where spatial interactions (the transfer of material from one place to another) strongly influence carbon dynamics. We then used a forest process model to estimate the effect of forest edges on processes (shading, mortality, decomposition) that influence carbon cycling. We found that processes that vary in a nonlinear manner across edges cause carbon dynamics at broader resolutions to depart from an additive estimate. Processes that vary in a linear manner across edges may be obvious at the scale of a forest stand, but become less evident at broader scales given that they tend to be averaged out. In addition to the way process rates change along edges, we found that landscape age structure and the disturbance regime control the degree edges influence carbon dynamics. At low and high elevation sites, shading effects and growth rates at edges increased carbon storage by 2-9% for the entire stand compared to stands with no edge effects. In contrast, carbon storage was reduced when mortality effects at edges were considered. Finally, we report how landscape metrics such as the fractal dimension might be used to estimate the effect of forest edges on carbon dynamics at broad scales.

Keywords: carbon, edges, modeling, scale, landscape, disturbance

This abstract is being presented at: 4:30 PM in session:
Oral Session #52: Carbon Storage in Ecosystems.