中文摘要：

采用时空互代法,以黄土丘陵区不同林龄人工刺槐林为研究对象,以坡耕地和天然侧柏林为对照,分析植被恢复过程中土壤酶的演变特征。结果表明：坡耕地种植刺槐林后,土壤脲酶、蔗糖酶、磷酸酶、过氧化氢酶随林龄逐渐增加,纤维素酶呈波动式变化,50年后较坡耕地分别增加160.2%,281.8%,541.6%,92.6%,73.8%,但仍低于天然侧柏林,多酚氧化酶较坡耕地降低39.1%,淀粉酶则先降低后升高。相关性表明,脲酶、碱性磷酸酶、蔗糖酶、过氧化氢酶和多酚氧化酶与土壤养分因子相关性较强,可以作为评价土壤质量的生物学指标。土壤酶指数在刺槐生长前期较坡耕地显著增大,随后趋于稳定,25年后随林龄不断升高,50年时达到最大值,但仅为天然侧柏林的63.2%。侵蚀环境下的坡耕地由于人为活动干扰,土壤酶活性较低,种植刺槐林后,土壤酶活性显著提高,土壤质量显著改善,但要恢复到该区演替顶级群落的水平,还需要很长时间。

英文摘要：

In this paper,the effects of Robinia pseudoacacia plantation at different ages on soil enzyme activity was studied in loess hilly region using a method of time-space mutual substitution,slope cropland and Platycladus orientalis forest were selected as references.The results showed that urease,phosphatases,saccharase and catalase activities in the soil were increased significantly with increase of years,however cellulase fluctuated dramatically.In 50 years,activities of the enzymes increased by 160.2%,281.8%,162.2%,92.6%,73.8% respectively,compared to the slope cropland,but still lower than that in P.orientalis forest.Soil polyphenol oxidase was decreased by 39.11% and amylase was increased in the early years and then declined with time.The significant relationships were observed between soil urease,phosphatases,sucrase,cellulase,catalase,polyphenol oxidase activity and nutrient factors,therefore the enzymes could be used as biological indicators for assessing soil quality.SEI（soil enzyme index） increased at the early stage,followed by a relatively stable stage for 10 to 25 years,after then it continued to increase and reached to the maximum in the 50 years.But it was still lower than that of P.orientalis forest.It is concluded that low soil enzyme activity of slope cropland under erosive environment,owing to human cultivation activities,was improved greatly after planting the R.pseudoacacia forests,but it needs a longer time to reach to the level of P.orientalis forest,the climax community in this region.