HR: 0830h
AN: B41C-0910    [PDF]
TI: Carbon and Nitrogen Pools in Oregon Cascades Forests Over a Successional Gradient
AU: * Cairns, M A
EM: cairns.michael@epa.gov
AF: Western Ecology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, 200 SW 35th Street, Corvallis, OR 97333 United States
AU: Lajtha, K
EM: lajthak@science.oregonstate.edu
AF: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331 United States
AB: In a study to examine impacts of successional and disturbance history on N export from 20 headwater stream systems in the west central Cascades of Oregon, a region of low anthropogenic N inputs, watersheds of differing ages showed a number of significant difference in nutrient export. In order to determine the mechanistic factors driving these differences, we measured soil solution and mineral soil C and N, forest floor and coarse woody detritus biomass, C and N in 12 plots categorized into 4 different classes of successional development. In streamwater, DON ranged from 24% to 51% of TDN in the youngest and oldest watersheds, respectively. In soil solution, %DON did not vary with succession, and was 40-75% of TDN. Although ammonium concentrations were very low in streamwater, ammonium was 25-59% of TDN in lysimeter samples and also did not vary with time since disturbance. The C content and C:N ratio of the forest floor was significantly higher in the youngest plots, most likely due to post-harvest residue and slash. Although there were 2-fold differences in the C content of the mineral soil, these differences were not related to disturbance history. Even with these sharp differences in both forest floor and mineral soil C contents as well as C:N ratios among plots, no measure of N export -- not soil solution, not stream flow -- was significantly related to forest floor, down wood, or mineral soil characteristics. This is most likely because forest floor C:N ratios (54-126:1) all greatly exceed the C:N ratios reported to allow significant leakage.
DE: 1615 Biogeochemical processes (4805)
DE: 1803 Anthropogenic effects
SC: Biogeosciences [B]
MN: 2003 Fall Meeting