HR: 1340h
AN: B43A-0255    [Abstracts]
TI: CO2 Production and Efflux Across Riparian/Hillslope Transitions in the Tenderfoot Creek Experimental Forest, Montana
AU: * Pacific, V J
EM: vpacific@montana.edu
AF: Department of Land Resources and Environmental Sciences, Montana State University, 334 Leon Johnson Hall PO BOX 173120, Bozeman, MT 59717 United States
AU: Riveros, D A
EM: driveros@montana.edu
AF: Department of Land Resources and Environmental Sciences, Montana State University, 334 Leon Johnson Hall PO BOX 173120, Bozeman, MT 59717 United States
AU: McGlynn, B L
EM: bmcglynn@montana.edu
AF: Department of Land Resources and Environmental Sciences, Montana State University, 334 Leon Johnson Hall PO BOX 173120, Bozeman, MT 59717 United States
AU: Welsch, D
EM: dwelsch@frostburg.edu
AF: Department of Geography, Frostburg State University, 211 Gunter Hall, Frostburg, MD 21532 United States
AU: Epstein, H
EM: hee2b@virginia.edu
AF: Department of Environmental Sciences, University of Virginia, 291 McCormick Road PO BOX 400123, Charlottesville, VA 22904 United States
AB: The spatial and temporal controls on soil CO₂ production and efflux have been identified as an outstanding gap in our understanding of carbon cycling. We investigated the primary driving factors and their variability over space and time of soil CO₂ concentration and efflux across environmental gradients in the 550 ha Stringer Creek watershed, Little Belt Mountains, Montana. We collected measurements of soil temperature, soil moisture, C:N ratios, CO₂ efflux, and soil air CO₂ concentrations at two depths (20 cm and 50 cm) at 32 locations across riparian/hillslope transitions in a high elevation mountain watershed in the northern Rocky Mountains. We found that aspect exerted a large control on soil CO₂ concentration and efflux as western aspects had larger CO₂ concentrations and efflux than eastern aspects. We also found that riparian landscape positions showed greater variability in soil CO₂ concentrations and efflux than hillslope landscape positions. In addition, we installed and collected hourly data from groundwater monitoring wells at over half of the sampling locations in order to determine the effect of groundwater fluctuations on soil CO₂ concentration and efflux. We found a large increase in soil CO₂ concentration and efflux as riparian landscape positions changed from saturated to unsaturated conditions. We also examined the diurnal variation in soil CO₂ concentrations and efflux and found that both CO₂ concentrations and efflux reached their maximum during the late afternoon. We conclude that environmental gradients related to catchment topography in soil moisture and soil temperature led to CO₂ concentration and efflux heterogeneity through space and time. We suggest that controlling variables such as riparian versus hillslope landscape position, aspect, differences in C:N ratios, and groundwater fluctuations are the primary controls on heterogeneity in CO₂ concentration and efflux across riparian/hillslope transitions.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
SC: Biogeosciences [B]
MN: Fall Meeting 2005