Changes in Soil Microbial Community during Permafrost Collapse Process on the Northeast Qinghai-Tibetan Plateau, China

Due to ongoing climate change, permafrost collapse has become widely distributed across the Qinghai-Tibet Plateau (QTP). However, it is not yet understood how soil microbial composition changes after the development of permafrost collapse. In this study, evaluations were conducted on three stages (the collapsed areas, the collapsing area and the control areas) of the permafrost collapse. The composition and biomass of the soil microorganisms were quantified by the phospholipid fatty acid (PLFA) method. The results showed that the permafrost collapse stages affected the soil microbial communities. The PCA suggested that the soil microbial communities were separated into 3 groups, i.e., the control areas, collapsing areas and collapsed areas. The contents of total PLFAs, gram-negative (GN) bacteria, total bacteria and fungi in the collapsed areas and the collapsing areas were significantly lower than those in the control areas. Soils in the collapsing areas had higher abundance of GN bacteria, total bacteria, total PLFAs and gram-positive bacteria to gram-negative (GP/GN) ratio than those in the collapsed areas. The collapsed areas had a higher ratio of GP/GN among the three stages. The soil microbial communities did not change significantly with increasing soil depth. The contents of GN bacteria, actinomycetes and total PLFAs had a significant positive correlation with pH. The contents of GP bacteria and the GP/GN ratio were positively correlated with soil water content (SWC). Soil microbial biomass decreased significantly during the permafrost collapse development. The inherent characteristics of soil physicochemical properties, especially soil pH and SWC, are the main factors affecting changes in microbial communities after the development of permafrost collapse.