Permafrost carbon-climate feedback in high-altitude ecosystems: evidence from the Tibetan Plateau

Abstract:

Permafrost carbon-climate feedback has received particular interest from the global change research community. However, current evidence is mainly derived from high-latitude ecosystems, with little known about high-altitude ecosystems. In this study, we examined permafrost carbon-climate feedback in alpine grasslands on the Tibetan Plateau from the following three aspects. First, we evaluated soil carbon stock in the top 3 meter by conducting a large-scale soil survey across the study area during the summer of 2013-2014. We found that Tibetan grassland soils store 10.4 Pg C in the upper 3 meter, ~40% larger than previous estimation in the top 1 meter. Second, we examined large-scale patterns of temperature sensitivity of soil carbon decomposition in alpine ecosystems by conducting laboratory incubation experiments, and found that greater temperature sensitivity occurred in those soils with more recalcitrant components. Third, we explored the responses of carbon cycling processes in alpine grasslands to climate warming by conducting OTC experiments. We found that experimental warming stimulated ecosystem respiration, but also increased gross primary production, and thus led to the net carbon accumulation. Overall, these three lines of evidence demonstrate that carbon cycle in high-altitude ecosystems is very sensitive to climate warming.