Annual soil CO₂ efflux in a wet meadow during active layer freeze–thaw changes on the Qinghai-Tibet Plateau

Abstract

Soil CO₂ efflux from an ecosystem responds to the active layer thawing depth (H) significantly. A Li-8100 system was used to monitor the CO₂ exchange from a wet meadow ecosystem during a freeze–thaw cycle of the active layer in a permafrost region on the Qinghai-Tibet Plateau. An exponential regression equation ($F_{\text{soil\, flux}} = 1.84e^{0.023H} + 5.06\,R^{2} = 0.96$) has been established on the basis of observed soil CO₂ efflux versus the thawed soil thickness. Using this equation, the total soil CO₂ efflux during an annual freeze–thaw cycle has been calculated to be approximately 8.18 × 10¹⁰ mg C. The results suggest that freeze–thaw cycles in the active layer play an important role in soil CO₂ emissions and that thawed soil thickness is the major factor controlling CO₂ fluxes from the wet meadow ecosystem in permafrost regions on the Qinghai-Tibet Plateau. It can be concluded that with active layer thickening due to permafrost degradation, massive amounts of soil carbon would be emitted as greenhouse gases, and the permafrost region would become a carbon source with a positive feedback effect on climate warming. Hence, more attention should be paid to the influences of the active layer changes on soil carbon emission from these permafrost regions.