中文摘要：

以宁夏荒漠草原典型植物柠条（Caragana korshinskii）、沙蒿（Artemisia ordosica）、短花针茅（Stipa breviflora）和蒙古冰草（Agropyron mongolicum）群落为研究对象,分析不同植物群落不同土层深度（0-5、5-10和10-15cm）土壤活性有机碳组分土壤微生物量碳（MBC）、可溶性有机碳（DOC）和易氧化有机碳（EOC）特征及其与土壤酶（蔗糖酶、脲酶、碱性磷酸酶和过氧化氢酶）活性之间的关系。结果表明：（1）4种典型植物群落土壤SOC、MBC、EOC含量均随土层深度的增加而减少,且表层（0-5cm）土壤显著高于亚表层（5-10cm）和深层（10-15cm）土壤（P〈0.05）,而土壤DOC含量随土层深度的增加呈先增加后减少的趋势。在同一土层深度,灌木（柠条和沙蒿）群落土壤活性有机碳组分含量高于禾本科植物（短花针茅和蒙古冰草）。（2）4种典型植物群落土壤酶（蔗糖酶、脲酶、磷酸酶和过氧化氢酶）活性整体上随土层深度的增加而降低,局部土层深度表现出波动性;同一土层不同植被群落土壤酶活性未表现出一定的变化规律。（3）4种典型群落土壤活性有机碳各组分除DOC外,其余均与SOC呈显著正相关关系,与土壤酶活性、微生物量熵以及有机碳活度具有一定的相关关系,表明土壤活性有机碳不仅依赖于总有机碳,也与土壤酶活性密切相关。

英文摘要：

In this study,we selected four typical communities：Caragana korshinskii,Artemisia ordosica,Stipabrevifloraand Agropyron mongolicumin desert steppe of Ningxia as the research objection,by analyzing the distribution characteristics of soil LOC fractions：microbial biomass carbon（MBC）,dissolved organic carbon（DOC）,and easy oxidation organic carbon（EOC）at different soil depths（0-5,5-10and10-15cm）in different community types,in order to probe into the relationship between soil LOC fractions and soil enzyme（invertase,urease,alkaline phosphatase and catalase）activities.Results show that：（1）the soil SOC and MBC,EOC content in four typical communities declined with the increasing of soil depth,which in surface layer（0-5cm）were significantly（P〈0.05）higher than that in deep soil（5-10 and 10-15cm）,whereas DOC content increased fristly and then decreased with the increasing of soil depth.In the same depth,the soil LOC fractions in shrub（C.korshinskii and A.ordosica）were higher than that in herbs（S.brevifloraand A.mongolicum）;（2）The soil enzymes（invertase,urease,alkaline phosphatase and catalase）of four typical communities generally showed a declined trend with the increasing of soil depth,fluctuate appeared at local depth of soil,but at same layer,the soil enzyme activities did not presented the same distributioncharacter in different community types.（3）The soil LOC fractions of four typical communities except for DOC,other indicators were showed significant（P〈0.05）correlation with SOC,and has a certain correlation with soil enzyme activities,microbial biomass entropy and organic carbon activity,which indicated that soil LOC fractions not only depend on the total organic carbon（TOC）,but also closely related to soil enzyme activities.