中文摘要：

采用颗粒大小的物理分组方法,测定了贺兰山（西坡）不同海拔具有代表性的8个样地的草地土壤颗粒有机碳和颗粒有机氮含量,并且分析了土壤颗粒碳、氮分配比例与植被特征及环境因子的关系。结果表明,土壤颗粒碳、氮含量随海拔的降低而显著降低,随土层深度的增加而降低;在4个植被类型中,二者在高山草甸最高,在草原化荒漠最低。土壤颗粒碳、氮分配比例随海拔的降低表现出先降低后升高的趋势,在高山草甸最高,山地荒漠草原最低。土壤颗粒碳、氮分配比例与植被盖度、地上生物量、年均降水量呈极显著的正相关关系,与年均温呈极显著的负相关关系。

英文摘要：

The physical fractionation method was used to measure the contents of soil particulate organic carbon（POC） and particulate organic nitrogen（PON） in eight grassland sites along an elevation gradient on the Helan Mountain,Inner Mongolia.The relationships of POC,PON and their proportion with vegetation characteristics and environmental factors were analyzed.Both POC and PON declined significantly with altitude and with soil depth.Meanwhile,POC and PON changed significantly among vegetation types.The proportions of POC and PON reduced considerably with the altitude from 2 940 to 1 820 and 1 700 m.Among the four vegetation types,proportions of both POC and PON were the highest in the alpine meadow and lowest in the desert steppe.The proportions of POC and PON had significant positive correlations with vegetation cover,aboveground plant biomass and mean annual precipitation,but a significant negative correlation with mean annual temperature.