Soil respiration and carbon pools across a range of spruce stand ages, Eastern Tibetan Plateau

To understand the effects of reforestation on soil carbon (C) dynamics, we measured soil carbon dioxide (CO2) effluxes and soil C pools in dragon spruce (Picea asperata Mast.) stands of various ages (22-, 47- and 68-year-old dragon spruce plantations, and a 150-year-old primeval coniferous forest) in the eastern Tibet Plateau. The soil respiration rate of all the stands increased from March, followed by a peak in late July to August with temporal fluctuations, and then dramatically declined in September. The annual total soil CO2 effluxes (Rtot), soil heterotrophic CO2 effluxes (Rh), and soil autotrophic CO2 effluxes (Ra) were higher in the 22- (1004, 656 and 348 g C m−2 year−1, respectively) and 150-year-old stands (1070, 712 and 358 g C m−2 year−1, respectively), and lower in the 47- (792, 543 and 249 g C m−2 year−1, respectively) and 68-year-old stands (952, 607 and 345 g C m−2 year−1, respectively). The soil total organic carbon (TOC), easily oxidizable organic C (EOC), microbial biomass C (MB...