Biogeochemical processes and response to climate change recorded in the isotopes of lacustrine organic matter, southeastern Qinghai-Tibetan Plateau, China

• Rate of organic matter decomposition is reflected by isotopes.
• Organic matter mineralization closely links with climate change.
• The study region would become a net source of greenhouse gas.

Large amount of labile organic matter sequestered in Qinghai–Tibetan Plateau (QTP), the highest plateau in the world. However, large uncertainties remained in the response of biogeochemical cycling to climate change due to the lack of spatial and temporal resolution of climatic and ecosystem records in the plateau. Here, we present the stable carbon (δ13C) and nitrogen (δ15N) isotope records from Muge Co, a lake in the southeastern QTP, in order to investigate the response of biogeochemical processes to climate change. In this record, changes in δ13C and δ15N values were more likely to reflect the rate of organic matter decomposition in the catchment and within the lake, while early diagenesis, changes in organic matter sources and aquatic primary productivity may only play an insignificant role. The trend of the greenhouse gases efflux index (GGEI) based on the δ13C and δ15N records is similar to that of other archives which record the organic matter mineralization, and that of climate change records from the eastern QTP and the adjacent regions, with higher GGEI values indicating a higher degree of decomposition of organic matter is associated with a warmer and wetter climate, and vice versa.