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Climate-related research activities at the Loch Vale WEBB site

Carbon Cycling studies

Landscapes at northern latitudes and high elevations account for a significant percentage of the Earth's land surface. Soils in many of these landscapes have been identified as important sources and sinks of atmospheric CO2 that maybe particularly sensitive to climate change [Oechel et al., 1997] Wetlands are the largest natural source of CH4 to the atmosphere, and northern and high-elevation wetlands may account for a third of this natural source [Moosavi and Crill, 1996]. Understanding of carbon sources and sinks in these landscape types is needed to reduce uncertainties about the North American carbon budget and underlying processes controlling carbon dynamics.

As much as half of northern latitude and high-elevation landscapes are snow covered for most of the year; yet, most attention has been focused on soil gas emissions in these environments during the growing season. Mast et al. [1998] measured CO2 and CH4 fluxes through snowpacks in Loch Vale to investigate processes controlling the exchange of gas between the soil and atmosphere during winter. The snowpack insulated soils from cold midwinter air temperatures allowing microbial activity to continue through the winter. Subalpine soils were net sources of CO2 through the winter, whereas saturated soils were net emitters of CH4 and dry soils were net CH4 consumers. Winter accounted for 8 to 23% of annual soil CO2 flux and 12 to 58% of the CH4 flux. These results indicate that soil gas fluxes during winter are significant and should be included in annual carbon budgets for seasonally snow-covered terrains.

Wickland et al. [1999; 2001] expanded this research by developing annual budgets for gas exchange in a subalpine wetland system in Loch Vale. Annual respiration and CH4 emission were modeled by applying the flux-temperature relationships to a continuous soil temperature record. Gross photosynthesis was modeled using a hyperbolic equation relating gross photosynthesis, photon flux density, and soil temperature. Modeled annual flux estimates indicate that the wetland was a net source of carbon gas to the atmosphere during the 3-year study period. This contrasts with estimates from an age-dated peat core, which indicate the wetland has been a sink of carbon for the past 7,100 years. Wickland et al. [2001] suggested the switch from sink to source may indicate these wetland systems are sensitive to even minor variations in climate.

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