长期施肥制度对稻田土壤反硝化细菌群落活性和结构的影响

以中国科学院桃源农业生态试验站长期定位施肥试验为平台,研究了3种长期施肥制度(对照不施肥-CK,化学施肥-NPK,化学施肥+有机肥-NPKOM)下土壤反硝化速率的差异.同时,以硝酸还原酶基因(narG)作为反硝化细菌的功能标志物,分析了施肥对反硝化细菌群落结构和多样性的影响.结果表明,长期施用有机肥的土壤反硝化速率,反硝化菌多样性都高于对照和施用化肥处理.从3个处理的土壤样品中共获得35个narG基因的可操作分类单元(OTU)主要分布在两个簇,与变形菌门(Proteobacteria)和放线菌门(Actinobacteria)的反硝化细菌有一定的亲缘关系,均为首次从土壤中克隆.Shannon多样性指数显示,NPKOM处理的narG基因多样性最高,CK处理次之,NPK处理最低.LUBSHUFF软件对narG基因群落组成的分析显示,施有机肥后含narG基因的细菌群落组成与CK之间有显著性差异(P<0.05),而化肥(NPK)没有产生显著影响.实验结果为进一步研究亚热带地区水稻土反硝化作用及反硝化功能菌提供了重要的依据.

Activity and composition of the denitrifying bacterial community respond differently to long-term fertilization

The objective of this study was to explore the long-term effects of organic and inorganic fertilizers on activity and composition of the denitrifying communities in paddy soil. The soil samples were collected from the following treatments: CK (no fertilizer), NPK (nitrogen, phosphorus and potassium fertilizers) and NPKOM (NPK plus organic matter), which were established in 1990. The activity was measured in terms of potential denitrification rate and narG gene was used as the functional marker of the denitrifying community. The results showed that the potential denitrification rate was higher in plot treated with organic fertilizer than in those with mineral fertilizer and no fertilizer, and this finding was positively correlated to soil organic matter content, MBC, and MBN. Totally 35 OTUs were obtained and identified as narG from the three treatments. Recovered narG sequences were mainly grouped in two clusters and related to narG gene of the denitrifiers from Proteobacteria and Actinobacteria.The LUBSHUFF statistical analyses demonstrated that narG gene library of NPKOM treatment was significantly different from CK, while no significant difference was found between NPK and CK, NPK and NPKOM treatments. It inferred that the combined application of chemical and organic fertilizers remarkably influenced the community composition of narG-containing bacteria.