中文摘要：

以黄土高原延河流域森林区3种典型植物群落为研究对象，研究了3种植物群落土壤团聚体中有机碳的含量、组分及土壤酶活性，分析了有机碳与酶活性的关系。结果表明：（1）3种植物群落，土壤团聚体各种形态有机碳和酶活性均表现为0-10 cm土层含量高于10-20 cm土层，辽东栎群落0-10 cm土层土壤多酚氧化酶活性却低于10-20 cm土层。（2）土壤团聚体有机碳含量在植物群落间表现为：辽东栎群落〉人工刺槐群落〉狼牙刺群落，酶活性在植被群落间的高低表现则不一致。土壤有机碳含量和酶活性在团聚体间均表现为随团聚体粒级的增大而增大，或先增大再减小的趋势。（3）蔗糖酶、纤维素酶以及β-D葡糖苷酶活性与各种形态有机碳均呈显著的正相关关系，多酚氧化酶和过氧化物酶与有机碳含量相关性不显著。（4）辽东栎群落和狼牙刺群落土壤团聚体蔗糖酶、纤维素酶、以及β-D葡糖苷酶活性在团聚体中表现为：｜〈0.25 mm团聚体｜ 〉 ｜2-0.25 mm团聚体｜ 〉 ｜5-2 mm团聚体｜ 〉 ｜〉5 mm团聚体｜，其多酚氧化酶和过氧化物酶以及人工刺槐群落各种土壤酶活性均表现为2-0.25 mm粒级团聚体中最大。（5）β-D葡糖苷酶活性增大，能促进土壤各种有机碳含量增加；土壤蔗糖酶活性和β-D葡糖苷酶活性的提高有助于土壤活性有机碳含量增加；土壤多酚氧化酶活性的增大，有利于土壤腐殖质碳的积累。

英文摘要：

Three different plant communities typical of the forest region of the Yanhe River watershed in the Loess Plateau were selected as subjects in study to explore effects of vegetation community on content and composition of organic carbon and activities of soil enzymes in soil aggregates, and relationships between organic carbon and enzyme activities, Results show that in all the three soils, regardless of vegetation community, soil aggregates in the 0-10 cm soil layer were higher than those in the 10-20 cm layer in content of organic carbon regarless of fraction and in activity of all soil enzymes, except for ployphenol oxidase, which was higher in the 10-20 cm soil layer than in the 0-10 cm soil layer under the Quercus liaotungensis community; that in terms of soil organic carbon content in soil aggregates the vegetation communities displayed an order of Quercus liaotungensis community 〉 Robinia pseudoacacia community 〉 Sophora viciifolia community, while the three vegetation communities did not show any consistent trend in soil enzyme activity, and the content of organic carbon and the activity of oil enzymes increased with increasing particle size of soil aggregates or increased first and then declined afterwards; significant positive relationships were observed of the activities of sucrase, cellulase and β-D-glucosidase with soil organic carbon of all forms, but no such relationships were of the activities of ployphenol oxidase and peroxidase with soil organic carbon; that in the soils under the Quercus liaotungensis and Shrub Sophora communities, the fractions of soil aggregates displayed an order of ｜〈0.25 mm｜ 〉 ｜2-0.25 mm｜ 〉 ｜5-2 mm｜ 〉 ｜〉5 mm｜ in activities of sucrase, cellulase and β-D-glucosidase, but the fraction of 2-0.25 mm aggregates was the highest in activities of loyphenol oxidase and Peroxidase in both of the soils and in the soil under Black Locust community the fraction was the highest in activities of all the soil enzymes; and that higher activity of soil β-D-glu