Effects of grazing and mowing on extractable carbon and nitrogen in typical grassland of Inner Mongolia, China.

Abstract

Relying on a long term field manipulated grazing experiment of typical grassland in Inner Mongolia, China, we investigated the responses of soil organic carbon, total nitrogen, extractable carbon and nitrogen, and microbial biomass carbon and nitrogen to livestock grazing and grass mo-wing. The results showed that grazing decreased extractable organic carbon by 11.4%-37.1%, while mowing increased extractable organic carbon by 5.8%. Grazing and mowing increased extrac table nitrogen by 10%-340% and 10%-240%, respectively. Grazing intensity less than 6.0 sheep·hm-2 favored the maintenance of microbial biomass carbon, and heavy grazing intensity, i.e. , 7.5 and 9.0 sheep·hm-2, decreased microbial biomass carbon. Mowing consistently increased microbial biomass carbon and nitrogen by 31.0% and 9.8%, respectively. Path analysis showed that soil organic carbon, extractable total nitrogen and total nitrogen were the dominant controls of microbial biomass carbon with soil organic carbon and total extractable nitrogen as the direct influencing factors. Soil pH, extractable organic carbon, soil organic carbon and total extractable nitrogen were the dominant controls of microbial biomass nitrogen with soil organic carbon and total extractable nitrogen as the direct factors. Mowing, light grazing and moderate grazing were beneficial to maintaining or improving soil function, and heavy grazing would cause soil degradation.