Effects of Alpine Wetland Degradation on Soil Microbial Structure and Diversity on the Qinghai Tibet Plateau

The characteristics of microbial structure in different soil degradation stages caused by the drought processes from wetland to meadow on the Qinghai Tibet Plateau were analyzed. The composition and diversity of soil bacteria and fungi were also analyzed by using high-throughput sequencing technology. The results showed that Proteobacteria was the highest abundance among bacteria, and Ascomycota was the highest among fungi. The degradation transition from alpine wetland to alpine meadow had insignificantly affected on the dominant bacteria, but had significantly affected on Gracilibacteriae and Ignavibacteriae bacterial phyla (P < 0.05), which characterized low abundance. The relative abundance of the dominant, fungal phyla Mortierellomycota (P < 0.05) significantly increased in soils along the degradation gradient. There was no significant difference between soil bacteria and fungi for Alpha diversity in different soil degradation stages. Beta diversity was found to be significant difference in soil bacterial structure for alpine swamp wetland and alpine meadow. Soil pH, water content, total organic carbon (TOC), total nitrogen (TN) decreased significantly (P < 0.05) with the degradation stages. RDA analysis showed that TN and TOC achieved the highest effect on the bacteria number expressed as operational taxonomic units and their Shannon index, moreover soil water content significantly affected on fungi number and Shannon index. TN and bacterial number had a significant positive correlation (P < 0.05). The relative abundance of Gracilibacteriae, Ignavibacteriae and Elusimicrobiae, which are beneficial to soil C and N contents and that Gemmatimonadetes are beneficial to N fixation, decreased in the drought processes of alpine wetland. This result could increase the relative abundance of the fungi phylum of Mortierellomycota, and might decrease the soil microbial diversity.