2.3 Data calculation and analysis
In total, we combined 106 sites both from literature and field sampling ranging from large temperature and precipitation gradients covering the main grassland types in China. We divided the soil layer into four groups, 0–10, 10–20, 20–30 and 30–100 cm. Most root biomass was located in the surface soil (0–10 cm), then decreased along the soil profile (10–20 and 20–30 cm), while only a little root biomass was in the deep soil (30–100 cm). In addition, the soil data from most documents were also collected according to these soil layers. The soil samples belonged to six vegetation types (temperate meadow, temperate typical steppe, temperate desert steppe, alpine meadow, alpine steppe and alpine desert steppe) according to the dominant species, temperature and moisture conditions. According to the duration of GE, we divided all the sites into short- (≤5 years), medium- (5–15 years) and long-term (≥15 years) periods. The RPC following GE were calculated with the following formula: RPC (%) = (soil pHGE − soil pHgrazing)/soil pHgrazing × 100%. The rates of RCC, RNC, RAC and RBC changes following GE were calculated by using a similar formula to that of RPC.
We determined the differences in soil pH between grazed and GE grasslands for all samples and in each soil layer using pairedt -test. Differences in RPC between soil layers, durations of GE and dominant species were analysed by one-way ANOVA and LSD tests. The relationships of RPC to MAP, MAT, RCC, RNC, RAC and RBC were determined by Pearson correlation analysis.