呼伦贝尔沙地不同植被恢复模式土壤氨氧化细菌群落结构及多样性

Community Structure and Diversity of Soil Ammonia-oxidizing Bacteria Under Different Vegetation Restoration Patterns in Hulunbeier Sandy Land, Inner Mongolia, China

采用PCR-DGGE技术和克隆测序分析方法,对不同植被恢复模式下呼伦贝尔沙地土壤氨氧化细菌群落结构、多样性及与土壤理化因子的相关性进行探讨。结果表明,5种植被恢复模式土壤氨氧化细菌16S rRNA基因Shannon指数均显著高于对照(裸地),其中柠条(Caragana korshinskii)+冰草(Agropyron cristatum)(AC)模式下Shannon指数最高,其他依次为单播柠条(UC)、单播冰草(UA)、柠条+羊柴(Hedysarum fruticosum)+冰草+披碱草(Elymus nutans)(ACHE)和单播羊柴(UH),各植被恢复模式不同程度地提高了土壤氨氧化细菌的多样性。系统发育分析结果表明,对照(裸地)土壤氨氧化细菌群落由亚硝化螺菌属的Cluster 2和Cluster 3组成,而5种植被恢复模式土壤氨氧化细菌群落由亚硝化螺菌属的Cluster 3和亚硝化单胞菌属的Cluster 6组成,植被恢复改变了土壤氨氧化细菌群落结构组成。土壤理化性质测定结果表明,5种植被恢复模式在不同程度上提高了土壤各项理化指标。典范对应分析结果表明,pH值、有机质(OM)、全氮(TN)、全磷(TP)和土壤含水量(SM)对氨氧化细菌群落结构组成的影响均达到显著水平(P<0.05),相关性分析发现pH值、OM、TN、TP和SM各指标之间均具有极显著相关性(P<0.01),说明植被恢复过程中土壤氨氧化细菌群落结构组成的变化是土壤各项理化因子相互关联、共同作用的结果。

Grassland desertification seriously threatens economic and social sustainable developments. How to control grassland desertifica-tion, and even to restore and reconstruct grassland has been paid much attention to. Vegetation restoration is considered to be a very effec-tive solution. Nitrogen cycling plays important role in the vegetation restoration process. Microbial ammonia oxidation is the first and often rate-limiting step of nitrification, a fundamental process in nitrogen cycling. It is, therefore, important to understand the relationship be-tween vegetation and the community structure and diversity of soil ammonia-oxidizing bacteria during the restoration process. Here we in-vestigated the 16S rRNA gene diversity, phylogeny of soil ammonia-oxidizing bacteria and their correlations with the soil physical and chemical factors in Hulunbeier sandy land of Inner Mongolia under five vegetation restoration patterns, i. e., mixed-planting of Agropyron cristatum, Hedysarum fruticosum, Caragana korshinskii, and Elymus nutans(ACHE)and of Agropyron cristatum and Hedysarum fruticosum(AC), and mono-planting of Caragana korshinskii(UC), Agropyron cristatum(UA), and Hedysarum fruticosum(UH)with bare land as the control(CK)using polymerase chain reaction-denaturing gradient gel electrophoresis(PCR-DGGE), cloning and sequencing analysis. The results indicated that the Shannon index of the 16S rRNA gene was the highest under AC, followed by UC, UA, ACHE and UH. The fivevegetation restoration patterns all had a significantly higher Shannon indexes than CK(P<0.05). The phylogenetic analysis showed that the soil ammonia-oxidizing bacteria under CK were mainly the Cluster 2 and Cluster 3 of Nitrosospira. But the composition of soil ammonia-oxidizing bacteria under the five vegetation restoration patterns had undergone significant changes compared to CK, composed of Cluster 3 of Nitrosospira and Cluster 6 of Nitrosomonas. Five vegetation restoration patterns improved soil physical and chemical properties in varying degrees. Canonical correspondence analysis showed that soil ammonia-oxidizing bacterial community structure was significantly(P<0.05) influenced by soil pH, soil moisture, total nitrogen, organic matter and total phosphorus. Significant correlationship(P<0.01)was found between pH, soil moisture, total nitrogen, organic matter and total phosphorus. These findings indicate that soil ammonia-oxidizing bacterial communities was dependent on the combined effects of the various physico-chemical factors.