植被退化对滇西北高寒草地土壤微生物群落的影响

Effect of vegetation degradation on microbial communities in alpine grassland soils in Northwest Yunnan

摘要:

[目的]在同尺度下比较我国滇西北高寒草地土壤（GS）及其退化土壤（DGS）中细菌和真菌群落，研究植被退化对高寒草地土壤微生物群落的影响，并探索其环境驱动因子。[方法]分别以16S rRNA基因和ITS基因作为细菌和真菌分子生态学分析的靶标基因，采用定量PCR法测定基因数量来表征微生物群落丰度，采用Illumina Hiseq测序及生物信息学分析研究土壤微生物群落组成和群落结构。[结果]草地退化后，土壤pH值显著上升0.65个单位，土壤水分、总有机碳、可溶性氮含量和C/N比分别显著下降了18.4%、67.5%、47.2%和71.2%；草地退化显著降低了土壤细菌和真菌群落丰度，降低幅度分别为92.4%和94.9%；草地退化没有影响土壤细菌和真菌群落α-多样性，但显著改变了细菌和真菌群落β-多样性（群落结构）；草地退化改变了土壤细菌和真菌在OTU水平上的物种组成，土壤真菌OTU种类变化更为显著；草地退化没有影响土壤细菌在门水平上的群落组成，但改变了细菌在纲水平上的群落组成（如Acidimicrobiia、Betaproteobacteria、Chloroplast等）；草地退化没有影响土壤真菌在门水平和纲水平上的群落组成。[结论]本研究发现植被退化后滇西北高寒草地土壤质量显著降低，寄居在土壤中的微生物群落丰度也显著降低、微生物群落结构明显改变。

Abstract:

[Objective] By comparing the bacterial and fungal communities in alpine grassland soil and their degraded soil in Northwest Yunnan, we investigated the effect of vegetation degradation on microbial communities in alpine grassland soils.[Methods] Bacterial 16S rRNA genes and fungal ITS genes were chosen as the target genes. Quantitative PCR was performed to measure the gene copies to assess the abundance of microbial communities. Illumina Hiseq sequencing and bioinformatics analysis were carried out to determine microbial community composition and community structure.[Results] After grassland degradation, soil pH value was greatly increased by 0.65 units, and soil moisture, total organic carbon, dissolved nitrogen and C/N ratio were significantly decreased by 18.4%, 67.5%, 47.2% and 1.2%, respectively. Grassland degradation significantly reduced soil bacterial and fungal community abundances by 92.4% and 94.9%, respectively. Grassland degradation significantly altered the β-diversity of soil bacterial and fungal community, but had no effect on that of α-diversity. In addition, grassland degradation changed the species composition of soil bacterial and fungal communities at the OTU level, and the fungal OTUs changed largely. Grassland degradation had no effect on bacterial community composition at the phylum level, but changed the composition at the class level (such as Acidimicrobiia, Betaproteobacteria, Chloroplast etc.). No significant difference was detected in fungal community composition between grassland soils and degraded soils.[Conclusion] These findings suggested that the vegetation degradation in alpine grassland lead to a decline in soil quality and microbial abundance, and changes in microbial community structure.