Soil carbon dioxide fluxes and profile concentrations in two boreal forests

Because a large fraction of the world's carbon exists in the soil of boreal forests, understanding how soil temperature and moisture affect soil respiration is vital for predicting soil response to climate change. We measured soil respiration and CO2 concentrations within soils of floodplain and upland forests in interior Alaska from 1996 to 1997. At each site, a 0.10-ha-area shelter was constructed that prevents summer precipitation from infiltrating into the soil. Measurements of soil profile CO2, soil respiration, soil temperature, and soil moisture were made inside (treatment) and outside (control) the sheltered areas through two growing seasons and the winter of 1996-1997. Sheltered soils had decreased profile concentrations and surface flux of CO2. At the upland control site, individual flux rates ranged from 0.10 to 0.95 g.m(-2).h(-1) in the summer and at sites under the shelter from 0.10 to 0.53 g.m(-2).h(-1) Rates at the floodplain control site ranged from 0.11 to 1.45 g.m(-2).h(-1) and under the shelter from 0.11 to 0.55 g.m(-2).h(-1). Fick's Law could predict surface CO2 flux when the CO2 concentration gradient within the profile accurately represented the soil surface gradient and biological sources and sinks of the gas did not overwhelm flux calculations.