Table_2_Composition and diversity of soil bacterial communities under identical vegetation along an elevational gradient in Changbai Mountains, China.doc

Soil bacteria play important roles in biogeochemical cycling and biodiversity in mountain ecosystems. Past studies have investigated the bacterial community composition and diversity in elevation gradations covered by different vegetation types, but for a better assessment of elevation effects, here we studied bacterial communities in soil under identical vegetation cover. High-throughput amplicon sequencing of the V3-V4 region of bacterial 16S rDNA was used to investigate the diversity and composition bacterial communities in soil from 700 to 1,000 m above sea level collected on the north slope of Changbai Mountains, Northeast China. Obviously differences (p < 0.05) in soil physicochemical parameters (i.e., total nitrogen, nitrate and ammonium nitrogen, soil moisture content, available potassium, microbial biomass carbon and nitrogen) were observed at different elevations. Soil bacterial abundance indices (Richness, Chao1, ACE) differed significantly along the elevation gradient, whereas the Shannon index remained unchanged. Principal Coordinates Analysis indicated separated soil bacterial communities of the different elevations. The dominant phyla in all soil samples were Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia, and Bacteroidetes, which in combination reached 80%–85%. Soil pH to some extend related to soil bacterial community along altitude gradations. The relative abundance of a multiple phyla was negatively affected by the soil nutrients, such as ammonium and nitrate nitrogen, available potassium, soil moisture content, available phosphorus, microbial biomass nitrogen and soil organic C. The strongest effects were seen for Proteobacteria. The pH either positively or negatively correlated with specific genera. The soil bacterial function differed significantly among four elevations. The chemoheterotrophy, aerobic chemoheterotrophy and nitrification were the most dominant functions of soil bacteria among four elevations. Overall, the changes in soil physicochemical properties with elevation are important in shaping the bacterial diversity, composition and function in soil with the same above-ground vegetation of Changbai Mountains.

土壤细菌在山地生态系统的生物地球化学循环与生物多样性维持中发挥着关键作用。既往研究已针对不同植被类型覆盖的海拔梯度开展了细菌群落组成与多样性相关研究，但为更精准地评估海拔的影响效应，本研究聚焦于相同植被覆盖下的土壤细菌群落展开调查。本研究采集中国东北长白山北坡海拔700~1000 m的土壤样品，采用细菌16S rDNA V3-V4区高通量扩增子测序技术，解析土壤细菌群落的多样性与组成特征。结果显示，不同海拔梯度下的土壤理化参数（即总氮、硝态氮与铵态氮、土壤含水量、速效钾、微生物量碳与微生物量氮）均存在显著差异（p<0.05）。土壤细菌的丰度指数（Richness、Chao1、ACE）随海拔梯度呈现显著差异，而Shannon指数则无明显变化。主坐标分析（Principal Coordinates Analysis, PCoA）结果表明，不同海拔的土壤细菌群落结构存在明显分异。所有土壤样品中的优势菌门为变形菌门（Proteobacteria）、酸杆菌门（Acidobacteria）、放线菌门（Actinobacteria）、疣微菌门（Verrucomicrobia）以及拟杆菌门（Bacteroidetes），这五大菌门的相对总丰度可达80%~85%。土壤pH在一定程度上与海拔梯度上的土壤细菌群落组成相关。多个菌门的相对丰度与土壤养分（如铵态氮、硝态氮、速效钾、土壤含水量、有效磷、微生物量氮以及土壤有机碳）呈显著负相关关系，其中变形菌门受土壤养分的影响最为显著。土壤pH则与部分特定菌属的相对丰度分别呈现正相关或负相关关系。四个海拔梯度的土壤细菌功能存在显著差异，化能异养、好氧化能异养以及硝化作用是四个海拔梯度下土壤细菌最主要的功能类群。综上，在长白山相同地上植被覆盖的土壤中，土壤理化性质随海拔的变化是驱动土壤细菌多样性、群落组成及功能结构发生改变的关键因素。