Carbon fluxes in coniferous and deciduous forest soils

Our aims were to identify responsible factors for the site-to-site variability in soil CO2 efflux and to assess the sources of soil CO2 of different forest types on a regional scale. Soil CO2 effluxes were measured over 1-4 years in four coniferous and three deciduous forests of Bavaria, Germany, and related to climate, soil properties and forest productivity. Total belowground carbon allocation (TBCA) was assessed using soil CO2 effluxes and aboveground litterfall. Additionally, CO2 production of organic layers was examined over 10 months under constant conditions in an incubation experiment. Annual soil CO2 effluxes were not different among the forest sites, but predicted effluxes at a given temperature of 10A degrees C revealed some significant differences and correlated with the phosphorous stock of the organic layers. The incubation study indicated 50% faster decomposition of organic layers from deciduous than from coniferous forests. TBCA related to soil CO2 efflux was smaller in the deciduous than in the coniferous forests. The ratio of TBCA to soil CO2 efflux was positively correlated with the C stock of organic layers. Our results suggest that marked differences in site characteristics have little impact on soil CO2 effluxes at the regional scale, but the contribution of soil CO2 sources varies among the forest types.