Wintertime CO2 evolution from a boreal forest ecosystem

We investigated wintertime ecosystem activity and CO2 efflux over three winters (1 November–28 February 1997–2000) in a boreal Scots pine stand in Finland. During the three winters the cumulative wintertime CO2 efflux measured with continuously operating soil chambers directly from the soil surface was between 103 and 144 g m–2, and between 240 and 330 g m–2 when measured by an eddy covariance method or estimated from the soil sample endogenous CO2 production. The flux measured directly from the soil surface is probably an underestimation due to the ice formation within the chamber. Photosynthesis was found to be active also during winter and metabolic activity was found to show extrapolated zero at –5 °C to –10 °C.