The temperature increases that some global climate models predict for the coming centuries may lead to an increase in the thaw season of boreal soils. An increase in thawing of these boreal soils will change soil respiration, soil water availability, and soil microbial activities, potentially affecting both carbon and water cycles in these forests. Due to the large extent of this region, boreal forest carbon and water are extremely important potential components of the global carbon and water budgets. In a warmer biosphere, fluxes to the atmosphere of CO2 from the soil will be influenced by altered soil-plant interactions, soil moisture properties, and meteorological conditions. Populations of methanogens and methanotrophs in different soil horizons may also be affected in a warmer climate, potentially altering atmospheric concentrations of this important greenhouse gas. To better predict the effects of these changes on global carbon and water cycles, we need to better understand the relationships between soil gas fluxes and moisture availability. This requires incorporating the effects of moisture availability and low soil temperatures on water flow and soil air filled porosity into water and soil CO2 and CH4 flux models. This study is performed in conjunction with on-going investigations in a Long-Term Ecological Research area at two sites in Alaska where 0.10ha rainout shelters have been constructed. I am measuring soil moisture, water potential, and CO2 and CH4 fluxes and profile concentrations, as well as continuously monitoring tree water use and meteorological variables both in and out of the shelters. I am comparing the changes in water uptake and soil CO2 and CH4 fluxes with fluctuating temperatures and depth of thaw with those estimated by two prognostic equations. The project will be useful for both carbon and water cycle modeling efforts. This relationship between water availability and soil gas fluxes under different precipitation regimes is important because of the potentially great effects changes in soil temperature and seasonal depth of thaw may have on the boreal hydrologic and carbon cycles.

Sharon Billings 
Duke University
Nicholas School of the Environment
Durham, NC, USA 
 
Alaska address: 
Sharon Billings
P.O. Box 85174 
Fairbanks, AK 99708 
ftvbs@aurora.alaska.edu