Effect of Soil Water Content on Carbon Dioxide Flux at a Sparse-Canopy Forest in the Canadian Boreal Ecosystem

摘要

The relationship between soil moisture and ecosystem-level carbon budget was investigated for a BERMS (Boreal Ecosystem Research and Monitoring Sites) site in Saskatchewan, Canada, using eddy covariance flux measurements obtained during 2001 and 2002.The site was located in a young jack pine stand (Finns banksiana Lamb.) characterized by a sparse low canopy. The site was harvested in 1994 and young trees from ages one year to ten years were regenerating naturally. Total ecosystem respiration (R_(ec)) at the site was sensitive to volumetric soil water content (VWC), and increased exponentially with VWC and soil temperature in warm seasons. Under daytime light-saturated conditions, gross primary production (GPP) had a positive linear correlation withVWC, with enhancement occurring under high soil temperatures. In contrast to GPP and R_(ec) individually, net ecosystem CO_2 exchange (NEE) was less sensitive to VWC. Under VWC > 0.03, the VWC-dependence was hardly detectable for NEE, irrespective of temperature range.