放牧对黄土高原退耕草地土壤有机碳储量的影响

放牧是影响草地土壤碳固存的重要因素。本研究选取黄土高原水蚀风蚀交错区西部、中部、东部地区及水蚀区,以各区20年以上退耕封禁地为对照,分析3个放牧强度下(羊粪球密度分别为0～10、10～20、>20 ind·m^-2)退耕草地0～20 cm土层土壤有机碳储量的分布特征,研究放牧及其强度对退耕草地土壤固碳效应的影响。结果表明: 放牧对交错区西部0～20 cm、东部0～10 cm,水蚀区0～5 cm土层土壤有机碳储量有显著影响,对交错区中部各土层均无显著影响;羊粪球密度0～10、＞20 ind·m^-2强度的放牧使交错区西部0～20 cm土层土壤有机碳储量显著降低了34.8%～50.9%,而在其他3个区域,放牧对有机碳储量的影响较退耕封禁地差异不显著。在交错区东部,放牧强度是影响退耕草地土壤有机碳储量的主要因素,而其他3个区域有机碳储量主要受土壤理化性质和(或)枯落物生物量的影响。羊粪球密度10～20 ind·m^-2强度的放牧对各区域退耕草地0～20 cm土层土壤有机碳储量无显著影响。

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

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.