HR: 09:15h
AN: B21D-06    [Abstracts]
TI: Net Ecosystem Exchange in a Forested Montane Watershed: Trends and Trials in Complex Terrain.
AU: * Muth, D J
EM: djm7f@virginia.edu
AF: University of Virginia Department of Environmental Sciences, 291 McCormick Rd., Charlottesville, VA 22904, United States
AU: Epstein, H
EM: hee2b@virginia.edu
AF: University of Virginia Department of Environmental Sciences, 291 McCormick Rd., Charlottesville, VA 22904, United States
AU: Emanuel, R
EM: emanuelre@appstate.edu
AF: Montana State University Land Resources and Environmental Science, 334 Leon Johnson Hall, Bozeman, MT 59717, United States
AU: Mcglynn, B
EM: bmcglynn@montana.edu
AF: Appalachian State University Department of Geology, 572 Rivers Street, Boone, NC 28708, United States
AU: Welsch, D
EM: dwelsch@frostburg.edu
AF: Frostburg State University Department of Geography, Gunter Hall 101 Braddock Road, Frostburg, MD 21532, United States
AB: Recent years have seen increased study of the land-atmosphere exchange of mass and energy as measured by the eddy covariance technique. Because these results have yielded significant promise, offering the opportunity to integrate small-scale heterogeneities at the ecosystem level, an increasing number of researchers have begun employing the method in montane areas typical of the Rocky Mountains. Problematically, these areas can exhibit complex terrain and tall canopies, introducing the need for a more complete treatment of the mass balance equation to account for advective flows and storage terms brought on by atmospheric stability. Promisingly, a variety of data filtering, modeling, and measurement techniques have shown potential in alleviating some these concerns. Because high altitude forests have shown considerable carbon sequestration potential and may be particularly susceptible to climate change scenarios affecting temperature, moisture, and snowpack accumulation, it is important that eddy covariance measurements continue in these non-ideal settings so that methodologies can be refined, and ecosystem-level mass and energy cycling dynamics can be evaluated. To this end, a 40-meter tower outfitted to FLUXNET specifications was erected over a lodgepole pine-dominated system in the Tenderfoot Creek Experimental Forest, Montana. Initial results indicate that on particularly stable nights (u_×<0.1), subcanopy concentrations of CO₂ became elevated to ~100ppm above levels measured on sufficiently turbulent nights (u_×>0.4). Resultant turbulent flux, as shown by the unfiltered eddy covariance system, exhibit nocturnal carbon emissions that are much larger in times of high turbulence, and much smaller in times of low turbulence. The difference can be an order of magnitude. Presumably, this is due to understory-atmosphere decoupling in times of stability. In order to account for underestimation of nocturnal ecosystem respiration, data were conservatively filtered, excluding measurements under a friction velocity (u_×) of 0.4 m/s. Resultant data gaps were filled with nocturnal respiration measurements obtained from soil and leaf chambers, and compared to nighttime eddy flux measurements obtained in sufficiently turbulent conditions. The results show that this forest is a substantial carbon sink at a rate of 350 g C/m2/yr, and indicate the promise of continuing these studies in complex terrain.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0400 BIOGEOSCIENCES
DE: 0428 Carbon cycling (4806)
DE: 0438 Diel, seasonal, and annual cycles (4227)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting