中文摘要：

对不同沙化程度高寒草甸植被特征、土壤理化性质及土壤微生物数量进行调查分析,结果表明：1）随着沙化程度的加剧,植物多样性指数、地上/地下生物量、土壤含水量及浅层土壤有机质、全氮、速效磷含量呈逐渐下降趋势,植物优势度、pH 值呈增加趋势;深层土壤有机质、全氮、速效磷在轻度沙化样地上达到最高值.2）在不同沙化程度的土壤中,细菌数量最多,之后依次为放线菌、固氮菌、真菌;微生物在轻度沙化样地中的数量比其他3个样地都大.3）以土壤深层速效磷作为控制因子,偏相关关系分析显示,土壤微生物总量及土壤细菌数量变化与地上植物丰富度指数、植物生物量、地下生物量呈极显著负相关关系,而与植物地上/地下生物量之比呈极显著正相关关系;固氮菌数量与地上生物量呈显著相关关系,而真菌数量与地下生物量呈显著相关关系;除地上/地下生物量之比与土壤微生物数量之间呈正相关关系外,其余植被特征值与土壤微生物数量之间均呈现负相关关系.

英文摘要：

In recent years,desertification has been a serious threat to the alpine meadow ecosystem in the Maqu County of Gansu Province.To evaluate the effects of desertification on alpine meadow soil and vegetation,four types of plots with different grades of desertification were established in 2012.The vegetation characteristics, soil physico-chemical properties,and abundance of soil microbes were measured and analyzed in August 2013. At the same time,the relationship between the vegetation characteristics and soil microorganisms was ana-lyzed.The results showed that the plant diversity index,soil moisture content,soil organic matter,total nitro-gen (N),and available phosphorus (P)decreased as the degree of desertification intensified,and the plant dominance index and pH value increased conversely.The deep-soil organic matter,total N,and available P showed the highest values in the lightly desertified plots.Bacteria were the most abundant soil microorganisms in all plots,followed by actinomycetes,fungi,and then nitrogen-fixing bacteria.The lightly desertified plots had the largest number of microbes.A partial correlation analysis showed that the total quantities of soil micro-organisms and bacteria were negatively related to above-ground plant richness index,plant biomass,and below-ground plant biomass,but positively related to the above-ground/below-ground biomass ratio.There were sig-nificant correlations between the abundance of nitrogen-fixing bacteria and aboveground plant biomass,and be-tween the abundance of fungi and below-ground plant biomass.The quantity of soil microorganisms was posi-tively related to the above-ground/below-ground biomass ratio,but negatively related to all of the other meas-ured vegetation characteristics.