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 (Pinus 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 (Rec) 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 with VWC, with enhancement occurring under high soil temperatures. In contrast to GPP and Rec individually, net ecosystem CO2 exchange (NEE) was less sensitive to VWC. Under VWC > 0.03, the VWC-dependence was hardly detectable for NEE, irrespective of temperature range.
