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) investigate 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 relationships of the rate of soil C mineralization with soil properties (e.g. soil organic carbon content (SOC), soil total nitrogen 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 mineralization rates under a temperature gradient (i.e. 5, 10, 15, 20, and 25 °C) in laboratory. Data for soil C mineralization 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 average 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 mineralization 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.