短期放牧对昭苏草甸草原土壤轻组及颗粒碳氮的影响

Effects of Short-period Grazing on Soil Light Fraction and Particulate Carbon and Nitrogen in Zhaosu Meadow Steppe

为了更好地揭示放牧下草地土壤有机质早期响应机制,采用野外控制放牧试验,设置对照（0头牛/hm2）、轻牧（0.38头牛/hm2）、中牧（0.64头牛/hm2）、重牧（0.94头牛/hm2）4个处理,结合室内常规分析,研究放牧对昭苏草甸草原土壤轻组组分及颗粒组分碳氮含量、轻组碳氮含量、颗粒碳氮含量的影响。结果表明：与对照比,放牧3年后0-10cm土层轻组组分碳（185.26~203.62mg/kg）、氮（15.86~18.20mg/kg）含量及颗粒碳氮比（7.68~8.01）,10-20cm土层轻组碳氮比（11.55~11.96）、颗粒碳（18.42~19.26g/kg）、氮（2.65~2.75g/kg）含量及颗粒碳分配比例（50.23%~51.97%）均出现明显降低（P〈0.05）,依次降低2.8%~11.6%,3.2%~15.7%,4.6%~8.6%,1.9%~5.3%,9.6%~32.7%,30.9%~33.3%,28.7%~31.1%,而0-10cm土层颗粒碳分配比例（74.54%~81.01%）及轻组碳分配比例（7.78%~12.08%）则出现明显增加（P〈0.05）,依次增加16.0%~26.1%,10.3%~71.3%;轻牧、中牧、重牧间0-30cm土层土壤轻组组分及颗粒组分碳氮含量、轻组碳氮含量、颗粒碳氮含量、轻组及颗粒碳氮比差异不显著（P〉0.05）,但基本在轻度或中度下出现极值;相关分析表明,随着放牧强度增加,0-10cm土层轻组碳含量呈降低趋势,颗粒碳分配比例呈增加趋势;初步认为0-10cm土层轻组组分碳氮含量、颗粒碳氮比、轻组碳分配比例、颗粒碳分配比例,10-20cm土层轻组碳氮比对放牧较为敏感,可作为衡量本区域土壤有机碳早期变化指标。

In order to better reveal the response mechnism of rangleland soil organic matter to grazing in early stage,the influence on soil carbon and nitrogen content of light fraction component,particulate component,the light fraction,the particulate under no grazing（0cattle/hm2）,light grazing（0.38cattle/hm2）,moderate grazing（0.64cattle/hm2）and heavy grazing（0.94cattle/hm2）condition in Zhaosu meadow steppe by fieldcontrolled grazing experiment and laboratory analysis was studied.The result showed that compared with no grazing,the soil carbon（185.26~203.62mg/kg）,nitrogen（15.86~18.20mg/kg）content of light fraction component of 0-10 cm,carbon-nitrogen ratio of the particulate of 0-10cm（7.68~8.01）,light fraction carbon-nitrogen ratio of 10-20cm（11.55~11.96）,particulate carbon（18.42~19.26g/kg）and nitrogen（2.65~2.75g/kg）content of 10-20 cm,the particulate carbon distribution ratio of 10-20cm（50.23%~51.97%）significantly decreased after 3years grazing（P〈0.05）,those respectively decreased by 2.8%~11.6%,3.2%~15.7%,4.6%~8.6%,1.9%~5.3%,29.6%~32.7%,30.9%~33.3%,28.7%~31.1%,but the particulate carbon distribution ratio of 0-10cm（74.54%~81.01%）and light fraction carbon distribution ratio of 0-10cm（7.78%~12.08%）significantly increased（P〈0.05）,those increased by 16.0%~26.1%,10.3%~71.3%.There was basically no significant effect on carbon and nitrogen content of light fraction component,particulate component,the light fraction,the particulate and carbon-nitrogen ratio of the light fraction in 0-30 cm soil layer and the particulate among no grazing,light grazing,moderategrazing and heavy grazing（P〉0.05）,and extreme value basically emerged at light grazing or moderate grazing condition.Correlation analysis showed that the content of light fraction carbon in 0-10 cm soil layer decreased,and that of the particulate carbon distribution ratio increased with the increase of grazing intensity.Carbon and nitrogen content of light fraction component,carbon-nitrogen ratio of the particulate,light fraction and the particulate carbon distribution ratio of 0-10 cm soil layer,carbon-nitrogen ratio of light fraction of 10-20 cm soil layer was sensitive to grazing,which could be used early indicators of soil organic carbon dynamics in study region.