Abstract:

The altitudinal pattern of soil bacterial community composition and diversity has been a hot topic in the field of ecological environment. In this study, vegetation investigation and soil sampling of shrub communities were conducted along an altitudinal gradient in Luya mountain, and the Illumina MiSeq sequencing technology was used to analyze the characteristics of soil bacterial communities in the Rosa xanthina shrub (low altitude (LA): 1368-1392 m), Hippophae rhamnoides subsp. sinensis shrub (middle altitude (MA): 1835-1855 m) and Caragana jubata shrub (high altitude (HA): 2668-2689 m). The results indicated that Proteobacteria, Actinobacteria, Chloroflexi, Acidobacteria, Bacteroidetes and Gemmatimonadet were the dominant phyla of soil bacterial communities in the shrub. With the increase of altitude, the relative abundance of Proteobacteria increased gradually, while that of Actinobacteria decreased gradually. Soil bacterial diversity showed hump-backed patterns along the altitudinal gradient. The linear discriminant analysis of effect size (LEfSe) showed that the soil bacterial communities were enriched with more biomarkers in the low altitude and high altitude plots (LDA>4, P<0.05), while the middle altitude plots had relatively fewer biomarker species and the relatively higher diversity. The relative abundances of dominant phyla in bacterial communities were significantly correlated with biotic and abiotic factors (P<0.05). The composition of soil bacterial communities in the shrub was significantly different among different altitudes (P<0.05) based on non-metric multidimensional scale analysis (NMDS) and similarity analysis (ANOSIM). Redundancy analysis (RDA) showed that the composition of bacterial communities was mainly affected by the characteristics of plant community in the middle altitude and low altitude plots, while that in the high altitude plots were mainly affected by altitude and soil physicochemical properties (SOC, TN, pH and TP). Finally, the variation partitioning analysis (VPA) showed that the composition of soil bacterial communities was jointly influenced by altitude, soil physicochemical properties and plant community characteristics, and altitude was the main influencing factor, which directly or indirectly affected the composition and diversity of soil bacterial communities by affecting plant community characteristics and soil physicochemical properties. This study preliminarily discussed the composition changes of soil bacterial communities in the shrub under different altitudes and different origins, and our study provided a theoretical basis for the altitudinal pattern and succession changes of soil bacterial communities in Luya mountain.

Key words: soil bacterial community, altitudinal gradient, shrub community, Luya mountain

摘要：

揭示土壤细菌群落组成和多样性海拔格局及其驱动因素一直是生态环境研究的热点问题。以芦芽山灌丛土壤细菌群落为研究对象，沿海拔梯度分别在高海拔（2668-2689 m）、中海拔（1835-1855 m）和低海拔（1368-1392 m）选取鬼箭锦鸡儿灌丛、中国沙棘灌丛和黄刺玫灌丛进行植被调查和土壤取样，利用Illumina MiSeq测序技术对3个不同海拔段土壤细菌群落特征进行分析。研究结果表明，变形菌门（Proteobacteria）、放线菌门（Actinobacteria）、绿弯菌门（Chloroflexi）、酸杆菌门（Acidobacteria）、拟杆菌门（Bacteroidetes）、芽单胞菌门（Gemmatimonadetes）是灌丛样地土壤细菌优势类群。随着海拔的升高，变形菌门的相对丰度逐渐增加，而放线菌门的相对丰度却逐渐减少，土壤细菌群落多样性整体上呈现先上升后下降的趋势。线性判别分析（LEfSe）分析表明低海拔样地和高海拔样地土壤细菌群落具有较多的显著差异物种（P<0.05），在组成上表现出一定的特有性，而中海拔样地的特有性相对较低，但多样性相对较高。相关性结果表明细菌群落优势门的相对丰度与生物和非生物因素间具有显著的关系（P<0.05）。非度量多维尺度分析（NMDS）和相似性分析（ANOSIM）结果发现不同海拔段灌丛土壤细菌群落组成上存在显著差异（P<0.05）；进一步通过冗余分析（RDA）发现植物群落特征主要影响中、低海拔样地细菌群落组成，而高海拔段样地土壤细菌群落组成主要受海拔和土壤理化性质的影响。最后方差分解分析（VPA）结果表明土壤细菌群落组成受到海拔、土壤理化性质和植物群落特征的共同作用，海拔直接或间接地通过植物群落特征和土壤理化性质影响土壤细菌群落的组成和多样性，是影响土壤细菌群落主要的因素。该研究可以为提示芦芽山灌丛土壤细菌群落海拔格局和演替变化提供理论依据。

关键词: 土壤细菌群落, 海拔梯度, 灌丛群落, 芦芽山