中文摘要：

为揭示集约经营对毛竹林土壤固氮细菌群落特征的影响,采用变性梯度凝胶电泳（DGGE）和荧光定量PCR技术,分析集约经营0（CK）、10、15、20、25年毛竹林土壤固氮菌群落结构和丰度的变化规律,并探讨了影响土壤固氮菌群落的主要环境因素.结果表明：毛竹林集约经营导致土壤pH下降而速效养分积累;集约经营初期（10年）和后期（25年）土壤固氮细菌的群落结构与对照相似,而中期的15年和20年则与对照差异较大.固氮菌多样性指数和丰度均呈现先减少后增加的趋势,经营15年时达到最小值;土壤固氮细菌表现出对集约经营干扰的抵抗和恢复反应.冗余分析表明,土壤速效钾、水解氮、硝态氮和铵态氮的含量与固氮菌群落结构的变化有较强的相关性,表明集约经营措施导致了土壤固氮细菌短期的变化,但长期而言,不会对土壤固氮细菌产生不良影响.

英文摘要：

Denaturing gradient-gel electrophoresis and real-time quantitative PCR（ q PCR） were employed to determine the effects of intensive management on soil N2-fixing bacteria in a moso bamboo（ Phyllostachys heterocycla） plantation. Soil samples were collected from the moso bamboo stands receiving 0（ CK）,10,15,20,and 25 years of intensive management. It was found that intensive management caused a strong decrease in soil p H but a general increase in soil available nutrients. The structure of the N2-fixing bacterial communities in the soils having received 10 and 25 years of intensive management were quite similar to that from the CK; however,those from 15 and20 years of intensification differed from the CK. With increasing time of intensive management,the abundance and diversity of the nif H gene at first decreased and then increased,with the minimum values being observed after 15 years of intensive management,indicating the eventual resiliency of N2-fixing bacteria to disturbance induced by intensive management. Redundancy analysis indicated that soil available potassium,available nitrogen,nitrite nitrogen,and ammonium nitrogen were more closely related to the changes of N2-fixing bacterial community structure compared with the other soil indices measured. In conclusion,the soil N2-fixing bacterial community was negatively affected by intensive management in the short term,but could recover in the long term.