Annual variation of temperature sensitivity of soil organic carbon decomposition in North peatlands: implications for thermal responses of carbon cycling to global warming

Abstract

Temperature sensitivities of microbial respiration and dissolved organic carbon (DOC) production were investigated by using a novel method, thermal gradient (2–20°C) temperature bar, in two typical peatlands (bog and fen) in North Wales, UK over 12 months. The study indicated that temperature sensitivity of soil organic carbon decomposition in North peatlands was regulated not only by temperature but soil water content, dry–rewet event and phenologies. Potential decreases of Q10 (CO2) with increasing soil temperature were confirmed in both peatlands, but Q10 (DOC) increase with increasing soil temperature in both bog and fen sites. These results imply, if other factors such as the so-called CO2 fertilization effect are simultaneously taken into account, that the feedback of global warming induced CO2 release from peatlands to climate change may be overestimated in current biogeochemical models. However, global warming might have been nonlinearly accelerating DOC thermal production, and therefore it helps explaining the causes of remarkable increase of DOC in surface water in the Northern Hemisphere during last several decades.