放牧和刈割对内蒙古典型草原土壤可提取碳和氮的影响

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

依托内蒙古典型草原的长期野外放牧控制试验,探讨了放牧和刈割对土壤有机碳、全氮、可提取碳和氮、微生物生物量碳和氮的影响.结果表明:放牧使可提取有机碳降低11.4%~37.1%,而刈割使可提取有机碳升高5.8%.放牧和刈割分别使可提取氮升高10%~340%和10%~240%.放牧强度不高于6.0 sheep·hm^(-2)的条件下有利于维持甚至增加微生物生物量碳,而重度放牧(7.5和9.0 sheep·hm^(-2))则减少微生物生物量碳.刈割处理下微生物生物量碳和氮分别升高31.0%和9.8%.通径分析表明,放牧处理下微生物生物量碳的主要影响因素是有机碳、可提取全氮和全氮,其中直接影响因素是有机碳和可提取全氮;微生物生物量氮的主要影响因素是土壤pH、可提取有机碳、有机碳和可提取全氮,其中直接影响因素是有机碳和可提取全氮.刈割及轻度和中度放牧有利于维持或改善土壤功能,重度放牧将引起土壤退化.

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 mowing. 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 extractable nitrogen by 10%-340% and 10%-240%,respectively. Grazing intensity less than 6. 0sheep·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 p H,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.