High soil carbon efflux rates in several ecosystems in southern Sweden

Soil C effluxes were measured at five forest stands with different vegetation and a meadow in southeastern Sweden (57¡5«N, 16¡7«E). Exponential regressions of soil respiration against air and soil temperatures were used to model soil respiration at forests stands. For the meadow, a light response curve with gross primary production (GPP) against PAR and a cubic regression with GPP against air temperature were used to model GPP. Soil water content limited soil respiration in all ecosystems but spruce where the limitation appeared only at high soil water content. In the forest ecosystems, the forest floor vegetation was scarce and its C uptake had no significant effect on soil C effluxes. Annual soil respiration in all sites was between 2.05 and 4.34 kg CO2 m–2 yr–1, which is large as compared with that reported in many other studies. Annual GPP of meadow was between 1.81 and 1.99 kg CO2 m–2 yr–1, which gives a NEE between 1.39 and 2.41 kg CO2 m–2 yr–1, i.e. a significant loss of C