Abstract: The temperate desert steppe in Jingtai County of Gansu province degraded seriously because of human activity and climate,etc.In order to reveal the change of supplying level of soil nutrients under grazing disturbance,the relationship between soil enzymes and fertilities in grasslands with different grazing intensities were analyzed.The results show that the water content,total nitrogen,available nitrogen,organic matter,and available phosphorus of soil in each depth declined while the soil bulk density increased along with the increased grazing intensities.Soil available potassium of each layer showed the trend of low-high-low-high along with the grazing intensity increasing.The content of all indices except for soil bulk density and pH reduced along with increased soil depth(P<0.01).The soil in grazing area was of weak alkalescence.The activity of catalase and alkaline phosphatase had a rising trend in 0～10 cm depth with increased grazing pressure while the activities of three soil enzymes in other soil layers showed LG>MG>CK>HG which was the same as the main soil fertilities.Generally,there were no obvious differences of three enzymes among soil layers except for exceptional layer(P>0.05).Significant(P<0.05) or very significant(P<0.01) correlation were detected by correlation analysis among three soil enzymes or between soil enzymes and the main soil fertilities indicating the soil enzymes could characterize the soil fertility status.Principal component analysis had the same result that the activities of three soil enzymes correlated well to the main soil fertilities and could be the indicators of the status of grassland degradation and restoration.

Key words: Temperate desert steppe, Grazing intensity, Soil fertility, Enzyme activity, Principal component analysis

摘要： 为揭示放牧扰动下土壤养分供给水平的变化,对温性荒漠化草原不同放牧强度下土壤酶活性与肥力因子的关系进行了研究。结果表明:除对照区外,随放牧强度的增加,土壤容重增大;各层土壤含水量、全氮、速效氮、有机质和速效磷均随放牧强度的增加而下降,且随土层深度的加深含量递减;各层土壤速效钾则随放牧强度的增加表现"低-高-低-高"的变化趋势,随土层深度的增加含量递减(P<0.01);放牧区土壤呈弱碱性;除0~10 cm土壤过氧化氢酶和碱性磷酸酶随放牧强度的增加有增加趋势外,其他各层土壤3种酶活性均为LG>MG>CK>HG,与土壤主要肥力因子表现出相同的变化趋势,除个别土层外,3种酶土体层次间差异不明显。相关分析表明,土壤3种酶间、3种酶与土壤主要肥力因子间相关显著(P<0.05)或极显著(P<0.01),说明土壤酶可以用来表征土壤肥力状况;主成分分析同样得出土壤脲酶、碱性磷酸酶和过氧化氢酶活性与土壤肥力之间具有良好的相关性,可以用来指示草原退化与恢复状况。

关键词: 温性荒漠化草原, 放牧强度, 土壤肥力, 酶活性, 主成分分析