HR: 08:45h
AN: B21D-04    [Abstracts]
TI: Soil CO2 Efflux Variability in Complex Terrain: Towards Estimation of Watershed-Level Rates
AU: * Riveros-Iregui, D A
EM: diego.riverosiregui@myportal.montana.edu
AF: Department of Land Resources and Environmental Sciences. Montana State University, 334 Leon Johnson Hall, 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, Bozeman, MT 59717, United States
AU: Pacific, V J
EM: vincent.pacific@myportal.montana.edu
AF: Department of Land Resources and Environmental Sciences. Montana State University, 334 Leon Johnson Hall, Bozeman, MT 59717, United States
AU: Epstein, H E
EM: hee2b@virginia.edu
AF: Department of Environmental Sciences. University of Virginia, 291 McCormick Rd., Charlottesville, VA 22904, United States
AU: Welsch, D L
EM: dwelsch@frostburg.edu
AF: Department of Geography. Frostburg State University, 211 Gunter Hall, Frostburg, MD 21532, United States
AB: Soil CO₂ efflux is a primary component of ecosystem respiration and a key determinant of net ecosystem production (NEP). One obstacle to understanding/predicting the heterogeneity of soil CO₂ efflux is the variability in patterns of soil physical and biogeochemical processes imposed by topography, particularly in complex terrain. Extrapolating from single- or multiple-point measurements to watershed-scale efflux estimates requires an understanding of the spatial variability of environmental variables (e.g. soil temperature, vegetation, substrate, soil physical properties). Additionally, soil CO₂ efflux can vary at hourly, daily, and seasonal time scales as a result of the interaction among these variables, including the lateral redistribution of soil water. We examined the relationships between topographically-derived indices (e.g., upslope accumulated area, topographic indices, radiation indices) and the space/time variability of soil CO₂ efflux to explore the concept of biogeochemically similar areas (BSAs) for estimating watershed-scale soil CO₂ efflux. We suggest that characteristic dynamics of BSAs can be used to extrapolate from benchmark data collection locations to larger areas of the landscape and indicate watershed-level response to changes in soil temperature, soil water content, and precipitation. We use both discrete and continuous field-based observations of soil CO₂ efflux from a 380-ha watershed in the Tenderfoot Creek Experimental Forest (TCEF), a montane conifer forest characteristic of sub-alpine ecosystems of the northern Rocky Mountains. These observations, in association with terrain analysis and process-based understanding, are used to characterize and quantify the spatial and temporal variability of soil CO₂ efflux. Based on efflux measurements collected during two growing seasons (2005, 2006), there was moderate correlation between upslope accumulated area and rates of soil CO₂ efflux across 18 diverse upland areas of the watershed (r²=0.37). However, this correlation improves significantly when analyzing efflux rates along single toposequences in moderately sloping SE aspects (r²=0.82) and steeper NW aspects (r²=0.96). Our results suggest that BSA analysis can facilitate estimation of watershed- level soil CO₂ efflux rates and their integration with other measures of C flux (e.g. NEP). As such, BSAs offer potential to improve process understanding and quantitative assessment and modeling of watershed scale soil CO₂ efflux in complex terrain.
UR: http://watershed.montana.edu/hydrology/Carbon_project.htm
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1813 Eco-hydrology
DE: 1866 Soil moisture
SC: Biogeosciences [B]
MN: 2007 Fall Meeting