【摘要】 以阿拉善左旗境内贺兰山中段 (西坡 )及其山前地带主要草地类型为研究对象 ,分析了不同草地类型土壤有机碳 (SOC)的分布特征及其与气候因子、植被特征和土壤特性的关系。结果表明 :土壤有机碳含量随海拔高度的降低而逐渐降低 ,其垂直分异规律是 :山地荒漠草原沿土壤剖面依次降低 ,高山草甸、草原化荒漠和沙砾质草原化荒漠 0～ 2 0 cm与 2 0～ 40 cm土层差异不显著 ,但高于 40～ 60 cm土层。 0～ 2 0 cm和 2 0～ 40 cm土层土壤有机碳含量与年降水量、植被盖度、草地生产力、土壤含水量和<0 .0 5mm颗粒含量呈极显著正相关 ,与年均温、土壤 p H值呈极显著负相关 (P<0 .0 0 1)。偏相关分析显示 ,影响 0～ 2 0 cm土层有机碳含量最主要的因素是植被盖度、草地生产力和年降水量 ,而影响 2 0～ 40 cm土层有机碳含量的最主要因素是草地生产力和植被盖度。放牧与围封对荒漠草地土壤有机碳含量有显著影响 ,在重度放牧下 0～ 2 0 cm土壤有机碳含量明显低于轻、中度放牧处理 (P<0 .0 5) ;重度退化草地围封 3 a后土壤有机碳含量比自由放牧草地显著增加。研究区沙砾质草原化荒漠区 0～ 2 0 cm土层土壤有机碳含量在 15a持续过度放牧后下降了 2 5.2 %。更多还原

【Abstract】 This study analyzed soil organic carbon content (SOC) in major types of grassland along the middle range of Helan mountain in Alex,Inner Mongolia. Factors affecting carbon distribution such as annual precipitation, temperature, plant cover and productivity, soil water content,<0.05mm particle content and soil pH were also monitored. Results indicate that soil organic carbon content declined with a decrease in Altitude according to the following order: alpine meadow >mountainous desert steppe>steppe desert>Gobi steppe desert.In the mountainous desert, soil organic carbon content showed a decline along the vertical soil profile. In the Alpine meadow,steppe desert and Gobi steppe desert, soil organic carbon content showed no difference between the 0～20cm and 20～40cm soil layers, but SOC was higher in these layers than in the 40～60cm layers. Soil organic carbon in the 0～20cm and 20～40cm layers was positively correlated with annual precipitation,plant cover, plant productivity, soil water content, and<0.05mm particle content (P<0.001),and negatively correlated with average temperature and soil pH(P<0.001).The most important factors affecting SOC in the 0～20cm soil layers, were plant cover (C), plant productivity (B) and annual precipitation(AP), and their relationship can be described as follows: SOC=0.0209C+0.00389B+0.00337AP-0.486 (R~2=0.995). To the 20～40cm soil layers, SOC was mostly affected by productivity and plant cover: SOC=0.0117B+0.00831C-0.0294(R~2=0.984).Among the environmental factors,soil water content (W), and average temperature (T) affected SOC in the 0～20cm layers the most: SOC=0.0526W-0.314T+2.632(R~2=0.956),with W being positive and T negative.To the 20～40cm soil layer, SOC was mostly affected by average temperature(T) and annual precipitation(AP): SOC=-3.622T-0.107AP+49.082 (R~2=0.977). Grazing and exclusion also affected SOC significantly. heavy grazing reduced SOC more than medium and light grazing (P<0.05) through it’s effects on plant cover and productivity,Three years after the heavily grazed pasture was excluded from grazing, SOC was significant higher than in the pastures that had been freely grazed, In steppe desert, SOC was 0.247%±0.0541%, because of over grazing, SOC decreased 25.2% in 15 years.更多还原