The diversity and function of microbial community in the sediment and terrestrial area of thermokarst lakes

Abstract

Thermokarst lakes are widely distributed across the Qinghai-Tibet Plateau (QTP) and have been identified as an important source of greenhouse gases. However, previous studies on soil microbes have mainly focused on the aquatic area of thermokarst lakes, and the changes in microbial communities in the terrestrial area around thermokarst lakes are still unclear. We used high-throughput sequencing to analyse the soil microbial communities in the sediment and terrestrial area around three thermokarst lakes on the QTP. The results showed that the relative abundances of Bacteroidetes and Proteobacteria were high in the sediment areas, while the relative abundances of Actinobacteria and Acidobacteria were high in the terrestrial area around the thermokarst lakes. As the distance from the thermokarst lakes decreases, the α-diversity of the microbial communities increased in the mature thermokarst lake (MTL), whereas the α-diversity of the microbial communities decreased in the developing thermokarst lake (DTL). The β-diversity of the microbial communities also varied significantly as the distance from the thermokarst lakes decreases. As the distance from the thermokarst lakes decreases, the abundances of most genes responsible for C decomposition decreased in the MTL and were high in the middle lakeside areas and sediment of the DTL. Soil organic carbon (SOC), total nitrogen (TN), pH, soil water content (SWC) and the pore equivalent diameter were critical factors that affected the microbial community. The microbial richness increased in relatively arid areas (SWC < 60%) and decreased in relatively humid areas (SWC > 60%) as the distance from the thermokarst lakes decreases. These results suggest that the potential C decomposition was high in the far lakeside areas of the MTL and was high in the middle lakeside areas and sediment of the DTL.