中文摘要：

采用时空替代法,对石羊河下游不同年限（1,2,3,4,5,8,15,24和31a）退耕区次生草地自然恢复过程中群落特征和土壤过氧化氢酶、蔗糖酶、脲酶、磷酸酶活性及分布进行了调查与分析。结果表明,在退耕31a的次生草地植被自然演替过程中,9个样地的所有样方中出现34种植物,植被群落由一年生草本植物为建群种,多年生草本与个别灌木植物为伴生种,逐渐演替为单一的灌木群落,并表现出较强的连续性与递进性。此外,不同年限退耕区次生草地0-10cm,10-20cm,20-30cm及30-40cm土层中土壤酶活性均存在较大差异;土壤酶活性随土层深度的增加呈现减小趋势,并且表层土壤酶活性在4个层次的总酶活性中占有较大比例。随着退耕区次生草地演替时间的增加,土壤酶活性总的趋势与物种丰富度和多样性指数一样,随着退耕区次生草地植被的恢复呈波动式下降,土壤酶活性与植被的恢复是一个互动过程,它们之间存在着互相回馈的响应。另外,土壤酶活性的变化是极其缓慢的过程,并且与退耕最后一年种植的农作物存在相关性。

英文摘要：

Community characteristics and soil catalase, sucrase, urease and phosphatase activity and distribution in the natural recovery process of vegetation on secondary grassland of abandoned land area of different eras （1, 2,3,4,5,8,15,24,31 a） in the downstream of Shiyang river were investigated and analyzed by the method use space instead of time. The results indicate that 34 species of plant can be found in the 9 investigation samples during 31 a succession after abandoned. The vegetation communities of annual herbaceous as constructive species and Perennial herbaceous with individual bush plants as associated species gradually succession to single shrub community. Strong continuity and graduality showed in the process of succession. Besides, most of the soil enzyme from different depth （0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm） of abandoned lands of different eras show significant differences （P〈0.01） on the activity. The soil enzyme activity decreased with the increase of soil depth, and that of surface occupies a large proportion in the total enzyme activity of the 4 layer. With the time of succession increased, the general trend of soil enzyme activity declined in a fluctuant way same as that of species richness and diversity index. Soil enzyme activity and vegetation restoration is an interactive process with a feedback between them. Furthermore,the change of soil enzyme activity is slow, and has correlation with crops grew the last year.