Soil C mineralization and temperature sensitivity in alpine grasslands of the Qinghai-Xizang Plateau

Aims Currently, the temperature sensitivity of soil carbon (C) mineralization and the factors that control it are the focus of studies on soil C cycle and global climate change. The main objectives of this study were to: (1) in- vestigate the effects of temperature and land-use (fenced grassland vs. grazing grassland) on soil C mineralization and its temperature sensitivity (Q10) in the grasslands of Qinghai-Xizang Plateau and (2) determine the relation- ships of the rate of soil C mineralization with soil properties (e.g. soil organic carbon content (SOC), soil total ni- trogen content (STN)). Methods Eleven pairs of plots (fenced sites vs. grazing sites) were selected along an east-west transect in northwest of Qinghai-Xizang Plateau. Soil samples were collected at a depth of 0-20 cm, to measure soil C min- eralization rates under a temperature gradient (i.e. 5, 10, 15, 20, and 25 °C) in laboratory. Data for soil C miner- alization rate on the 7th day and 56th day, respectively, were used to assess the short- and long-term effects. Important findings Soil C mineralization rates declined from east to west on fenced sites, but varied slightly on the grazing sites. Soil C mineralization rates increased significantly with increasing incubation temperature, and were strongly related to SOC and STN; higher the SOC and STN, greater the accumulative soil C mineralization. Q10 showed no apparent spatial pattern along the east-west transect, and was not susceptible to land-use with av- erage Q10 values of 1.83 and 1.86 on the fenced sites and the grazing sites, respectively. Moreover, Q10 was not correlated with either SOC or STN. Findings in this study provide new insights on the responses of soil C miner- alization and its temperature sensitivity to land-use change on the Qinghai-Xizang Plateau, contributing important information for evaluating soil C sequestration and its response to warming scenarios in this region.