Effects of grazing on soil organic carbon stocks in the revegetated grasslands on the Loess Plateau, China

Abstract

Grazing is an important driving factor for soil carbon sequestration in grasslands. The objective of this study was to clarify the effects of grazing and its intensity on soil organic carbon stocks (SOCS) in the revegetated grasslands in the Loess Plateau region. With the grasslands excluded from grazing ＞20 years as the control, we investigated the SOCS in the 0-20 cm soil layer in three grazing intensities in the west, middle, and east of wind-water erosion crisscross region and the water erosion region. The intensity of grazing in the study was represented by the number of goat dung in the sampling sites, which included 0-10, 10-20, and more than 20 goat dung·m-2, respectively. Results showed that grazing significantly affected SOCS in the 0-20 cm soil layer in the west of crisscross region, 0-10 cm soil layer in the east of crisscross region, and 0-5 cm soil layer in the water erosion region. There was no significant effect in each soil layer in the middle of crisscross region. Only in the west of crisscross region, the SOCS in the grazing intensity of 0-10 and ＞20 goat dung·m-2 significantly decreased by 34.8%-50.9%, whereas the SOCS in each grazing intensity was not different from that in the enclosure in the other three regions. The SOCS was mainly affected by grazing intensity in the east of crisscross region and by soil physical and chemical properties and (or) litter biomass in the other three regions. In conclusion, grazing intensity of 10-20 goat dung·m-2 did not affect SOCS in the 0-20 cm soil layer in the revegetated grassland on the Loess Plateau, China.