祁连山中段退化高寒草地土壤细菌群落分布特征

为探究祁连山中段不同退化高寒草地土壤细菌群落分布特征,采用Illumina HiSeq PE250高通量测序平台对轻度、中度和重度退化草地土壤细菌群落变化特征进行研究,并对土壤细菌群落与土壤酶活性、土壤理化因子间关系进行分析。结果表明:随着退化程度加剧,植被盖度、高度、地上生物量和多样性指数均明显降低(P<0.05);土壤理化性质和酶活性变化各异且差异显著(P<0.05)。高通量测序共得到257971条有效序列,219017条优质序列和2004个OTUs。细菌群落丰富度指数依次为轻度>中度>重度,多样性指数为轻度>重度>中度,Beta多样性分析表明各样地间差异为轻度>重度>中度。其中,放线菌门(Actinobacteria)、厚壁菌门(Firmicutes)、酸杆菌门(Acidobacteria)和变形菌门(Proteobacteria)为3种退化草地土壤的优势菌门,在轻度、中度和重度退化草地土壤中分别占77.25%、84.27%和78.66%;乳球菌属为3种退化草地土壤的优势菌属,在轻度、中度和重度退化草地土壤中分别占14.29%、38.84%和7.39%。冗余分析表明:土壤酶活性和土壤理化性质均对细菌群落的组成具有影响,其中土壤pH是影响土壤细菌群落分布的主要驱动因子。祁连山中段不同退化高寒草地土壤细菌群落的变化主要受土壤理化性质和酶活性的影响。

Soil bacterial community changes across a degradation gradient in alpine meadow grasslands in the central Qilian Mountains

The objective of this research was to explore the distribution characteristics of soil bacterial communities in alpine meadows with different degrees of degradation in the central Qilian mountains. Illumina HiSeq PE250 high-throughput sequencing technology was used to study the bacterial communities in soils of grasslands with light, moderate and severe degradation. The relationships between soil bacterial communities, soil enzyme activities, and soil physiochemical characteristics were also analyzed. It was found that: with increased intensity of degradation, vegetation cover, height, aboveground biomass and diversity index were all significantly decreased (P<0.05), while the soil enzyme activities and soil physiochemical characteristics generally showed significant decline (P<0.05). The high throughput sequencing identified 257971 effective sequences, 219017 high quality sequences and 2004 operational taxonomic units. The three categories of grassland ranked in order: lightly degraded>moderately degraded>severely degraded, for abundance of soil bacterial communities, while the diversity index ranked lightly degraded>severely degraded>moderately degraded grassland. Analysis of Beta diversity showed that the differences among all plots ranked lightly degraded>severely degraded>moderately degraded grassland. The main feature of change in soil bacterial communities across the three categories of grassland degradation was a change in microbial biomass, and the effect on bacterial community structure was not obvious. Actinobacteria, Firmicutes, Acidobacteria, and Proteobacteria were the dominant phyla at all three levels of degradation in the tested grassland soils, with the proportion of the total bacterial population from these phyla being 77.25%, 84.27% and 78.66%, in mildly, moderately and severely degraded soils, respectively. Lactococcus was found to be a dominant genus in all three soil degradation categories, and the corresponding proportion of this genus in the total population was 14.29%, 38.84% and 7.39%, respectively. Redundancy analysis showed that soil enzyme activities and soil physiochemical characteristics differed based on the distribution of bacterial communities, and that the soil pH is the main driving factor affecting the distribution of soil bacterial communities. The degradation-linked changes in soil bacterial communities in alpine meadow grassland in the central Qilian mountains were strongly linked to the soil enzyme activities and the soil physiochemical characteristics.