不同放牧强度对大针茅草原土壤全土及轻组碳氮储量的影响

Effects of Different Grazing Intensities on Total and Light Fraction Organic Carbon and Nitrogen Storages of Soil in Stipa Grandis Steppe

以内蒙古大针茅典型草原不同放牧强度样地为研究对象,采用野外取样和室内测试相结合的研究方法,研究土壤全土和轻组碳氮含量与分布特征,分析不同放牧强度对土壤全土和轻组碳氮养分的影响。结果表明：（1）不同放牧强度只对0—10cm土层有机碳、全氮含量影响差异显著。随着放牧强度的增加,各土层土壤有机碳、全氮含量均呈先增加后减少趋势,在轻度放牧区（LG）或中度放牧区（MG）达到最高。0—40cm各土层轻组碳氮含量分别在0.20～2.89g/kg和0.01～0.22g/kg之间波动。（2）不同放牧强度0—40cm土壤全土碳氮储量差异明显,分别表现为LG〉MG〉CK（对照区）〉HG（重度放牧区）和MG〉LG〉HG〉CK,0—40cm土壤轻组碳氮储量均表现为LG〉CK〉MG〉HG。相对于土壤有机碳,轻组有机碳对不同放牧强度的响应更敏感,不同放牧强度间变化幅度较大,轻度放牧有助于土壤碳氮的积累。（3）随着放牧强度的增加,0—40cm平均轻组碳氮分配比例均呈先增加后减少趋势,LG区比例最高,MG和HG区比例较低。不同放牧强度土壤轻组碳分配比例均高于轻组氮。（4）研究区土壤全土碳氮含量、轻组碳氮含量之间均呈极显著正相关关系（P〈0.01）,土壤轻组碳氮之间具有更好的耦合关系。

In order to analyze the effects of different grazing intensities on soil carbon and nitrogen nutrients,soil total and light fraction organic carbon and nitrogen contents,and their distribution characteristics under different grazing intensities in Stipagrandis steppe were measured through field investigation and laboratory experiment.The main research results were as follows：（1）The effects of different grazing intensities on soil organic carbon and nitrogen contents were only significantly different in 0—10cm soil layer.With the increasing grazing intensity,soil organic carbon and nitrogen contents increased at first and then decreased,and reached the maximum in light or moderate grazing plots in all soil layers.In 0—40cm soil layer,light fraction organic carbon and nitrogen contents were fluctuated within 0.20—2.89g/kg and 0.01—0.22g/kg,respectively.（2）The total organic carbon and nitrogen storages in soil under different grazing intensities in 0—40cm soil layer were significantly different,with the former listing in the following order：LG〉MG〉CK〉HG,and the latter listing in the following order：MG〉LG〉HG〉CK.The light fraction organic carbon and nitrogen storages in 0—40cm soil layer listed as follows：LG〉CK〉MG〉HG.Compared with soil total organic carbon content,light fraction organic carbon content was more sensitive to different grazing intensities,which showed more significant variation under different grazing intensities.Light grazing was contributed to the accumulation of soil organic carbon and nitrogen contents.（3）With the increasing grazing intensity,the average proportions of light fraction organic carbon and nitrogen increased at first and then decreased in 0—40cm soil layer,which werethe highest in light grazing area and lower in moderate and high grazing areas.The proportion of soil light fraction organic carbon was always higher than that of soil light fraction organic nitrogen under different grazing intensities.（4）There were very significant positive correlations（P〈0.01）between soil total carbon and nitrogen contents and between soil light fraction organic carbon and nitrogen contents,and better coupling relationship was observed between soil light fraction organic carbon and nitrogen contents.