Modeling the carbon dynamics of alpine grassland in the Qinghai-Tibetan Plateau under scenarios of 1.5 and 2 °C global warming

Abstract Alpine grassland occupies two-thirds of the Qinghai-Tibetan Plateau (QTP). It is vital to project changes of this vulnerable ecosystem under different climate change scenarios before taking any mitigation or adaptation measures. In this study, we used a process-based ecosystem model, driven with output from global circulation models under different Representative Concentration Pathways (RCPs), to project the carbon dynamics of alpine grassland. The results showed the following: 1) Vegetation carbon (C) on the QTP increased by 22–38 gC m −2 during periods of 1.5 and 2 °C warming under different RCPs when compared to the baseline period (1981–2006), while soil C increased by 85–122 gC m −2 . 2) The increases of vegetation C and soil C at the period of 1.5 °C warming were about 15 gC m −2 and 40 gC m −2 smaller than those at the period of 2 °C warming, respectively; increase of C was greater for alpine meadow than for alpine steppe. 3) Precipitation, radiation, and permafrost changed significantly and showed heterogeneous spatial patterns, and caused heterogeneous response of C dynamics. For alpine meadow in regions transformed from permafrost to seasonally frozen soil with medium annual precipitation (200–400 mm), vegetation C and net primary production decreased by 18.7 gC m −2 and 3.1 gC m −2 per year during 2 °C warming under RCP 4.5, respectively. This decrease can be attributed to the disappearing impermeable permafrost. Different from previous studies that indicated an unfavorable response of alpine grassland to climate warming, this study showed a relatively favorable response, which is mainly attributed to CO 2 fertilization.