不同植被恢复模式下呼伦贝尔沙地土壤反硝化细菌nirK基因组成结构和多样性研究

本研究选取呼伦贝尔沙地5种植被恢复模式(单播冰草、单播羊柴、单播柠条、冰草+柠条和冰草+柠条+羊柴+披碱草)为研究对象,以完全退化的沙地为对照,采用分子生物学技术分析了土壤反硝化细菌nirK基因组成结构和多样性,并探讨了与土壤理化因子的相关性。结果表明,土壤反硝化细菌nirK基因组成存在明显差异。单播羊柴模式土壤反硝化细菌nirK基因多样性指数最高,其次为单播冰草和单播柠条,而两种混播模式最低,这5种植被恢复模式均显著高于对照裸地。序列和系统发育分析结果表明,所获得的nirK基因片段与NCBI数据库中的nirK基因的相似度在81%~99%之间,分别归属于苍白杆菌属、根瘤菌属及不可培养的细菌,其中与不可培养细菌相关的片段占到总数的50%以上。典范对应和相关分析结果表明,速效磷、pH、全氮、全磷和含水量对反硝化细菌的影响均达到显著水平,且5种理化因子间均具有极显著相关性,说明这5种理化因子相互关联,共同对反硝化细菌nirK基因组成变化起到决定作用。

Community structure and diversity of soil denitrifying bacteria of the nirK gene type under different vegetation restoration patterns in the Hulunbeier Sandy Land,Inner Mongolia

We selected five vegetation restoration methods including mono-planting of Caragana korshinskii (UC), Agropyron cristatum (UA), and Hedysarum fruticosum (UH), mixed-planting of Agropyron cristatum and Hedysarum fruticosum (AC) and of Agropyron cristatum, Hedysarum fruticosum, Caragana korshinskii, and Elymus nutans (ACHE) to analyze the community structure and diversity of nirK-type soil denitrifying bacteria and their relationships with the soil physical and chemical factors. Bare land was used as a control (CK). There are significant differences in the composition of the soil nirK-type denitrifying bacteria. The Shannon index of the nirK gene is the highest under UH, followed by under UA, UC, AC and ACHE, and the lowest in CK with significant differences between the five methods. The sequence and phylogenetic analysis showed that the similarity of the nirK fragments to the nirK genes registered in GenBank was between 81% and 99%, and that they were mainly from Ochrobactrum, Rhizobium, and some other unidentified bacteria. These bacterial species accounted for more than 50% of the total fragments. Canonical correspondence and correlation analyses showed that the soil available phosphorus, pH, total nitrogen, total phosphorus and soil moisture had significant effects on the denitrifying bacterial communities, and there were very significant correlations among these five soil physical and chemical factors. It is suggested that interactions between the five soil physical and chemical factors played a decisive role in the population changes of the nirK-type denitrifying bacteria.