中文摘要：

【目的】揭示连作大豆主要生育时期根际土壤微生物群落结构及土壤酶活性变化，为大豆连作障碍提供理论依据。【方法】利用磷脂脂肪酸（phospholipid fatty acid，PLFA）分析方法对连作大豆根际土壤微生物群落结构进行定量分析，同时进行土壤微生物生物量和土壤酶活性的测定。【结果】大豆重迎茬使土壤PLFA总量、土壤微生物生物量碳含量、土壤脲酶和转化酶活性均显著降低，真菌和细菌PLFAs比例显著增加，土壤过氧化氢酶活性无显著变化。不同连作年限及生育时期对土壤微生物及酶活性的影响均不同，与作物品种、根系分泌物和残茬腐解物的数量和种类密切相关。相关分析表明，土壤PLFAs总生物量与土壤微生物生物量碳和土壤脲酶活性呈现显著正相关，与转化酶和过氧化氢酶活性无显著相关性。【结论】大豆重迎茬使土壤微生物群落结构和土壤酶活性发生改变。大豆连作障碍是大豆根际土壤微生态系统和环境因子等综合作用的结果。

英文摘要：

[Objective] The objective of the experiment was to determine the effects of continuous and alternate cropping on microbe community structures and soil enzyme activities in soybean, and to provide a scientific basis for the obstacles of continuous cropping of soybean. [Method] Rhizosphere soils of different growth stages was used to characterize the community structure of soil microbe based on phospholipid fatty acid （PLFA） method, and the contents of soil microbial biomass carbon and enzyme activities were determined. [ Result ] In the soils of alternate and continuous cropping, the total PLFAs biomass, the microbial biomass carbon contents, the activities of urease and invertase all decreased, and the ratios of fungi and bacteria were enhanced, and the activities of catalase had no significant difference among the treatments. There were different influences on microbial and soil enzymes activities in different years of continuous cropping and growth stage, which closely related with the number and type of root exudates and straw decomposing matter. The correlation analysis showed that there was a positive relationship significantly between the total PLFAs biomass and microbial biomass carbon content and the activity of soil urease. There was no relationship between the total PLFAs biomass and the activity of soil catalase and invertase. [ Conclusion] The microbial community structures and enzyme activities were changed by continuous and alternate soybean. The obstacles of continuous soybean were the result of the comprehensive effect of soil micro-ecological system and environmental factor.