Effects of grazing and fencing on soil microorganisms and enzymes activities

This research was conducted in the temperate semidesert ecosystems of Alxa Plateau, and studied the effects of grazing and fencing on soil microbial biomass carbon, nitrogen and soil enzymes activities, aiming to provide scientific basis for restoration and reconstruction of degraded temperate semideser ecosystems. The results showed that: (1)There was no significant difference on microbial biomass carbon between fencing and grazing lands, but soil microbial biomass nitrogen in fencing land was significantly higher than that of grazing lands, which caused soil microbial carbon and nitrogen ratio in fencing lands was significantly lower than that of grazing lands. Soil microbial carbon and nitrogen contents in surface layer (0-10 cm) was higher than those of subsoil (10-20 cm) in fencing lands and grazing lands, respectively; (2) Urease and alkaline phosphatase activities of the surface layer in fencing lands were higher than the grazing. For the subsoil, alkaline phosphatase activities in fencing lands was also higher than that of grazing，while urease activities in fencing lands was significantly lower than that of grazing. For the soil saccharase activities, the subsoil in the fencing lands was significantly higher than the grazing lands，and there was no difference among the surface layers. In addition, the variation of the three enzymes activities in different soil layers under fencing and grazing conditions was inconsistent; (3) The relationships between soil microbial biomass (C and N) and enzyme activities in fencing lands and grazing lands are different. Under fencing conditions, there is a significantly positve correlation between soil microbial biomass carbon and urease activities, while a significant negative correlation was found between soil microbial biomass carbon and saccharase activities. However, under grazing conditions, soil microbial biomass carbon and nitrogen were significantly negative correlated with soil urease activities, and significantly positive correlated with soil saccharase and alkaline phosphatase activities. Furthermore, soil microbial carbon and nitrogen ratio showed a significantly positive correlation with soil urease activities under grazing conditions.