Soil microbial community dynamics and contribution to litter decomposition in two years in a Tibetan alpine forest along an elevational gradient

Soil microbial communities are crucial to drive litter decomposition and regulate carbon cycle for mitigating the effects of climate change. However, in alpine forest ecosystems, the relative importance of dynamic litter degradation and changes in abiotic factors across elevational mountain gradients in affecting soil microbial communities is little understood. In this study, five sites along elevation gradient (3500-4300 m) were set according to the distribution range of Rhododendron simsii Planch to investigate the changes in soil microbial community structure during litter decomposition process. Based on the two-year field litter burial experiment and soil microbial sequencing, our results revealed that the litter mass loss for two years at different elevations ranged from 37 % to 61 %, and lignin contributed the most to litter decomposition. Proteobacteria, Actinobacteria and Acidobacteria were the dominant bacteria, and the dominant fungal communities were Basidiomycota and Ascomycota, which played a major role in promoting lignocellulose decomposition. The similarity in soil microbial community structure and alpha diversity between elevations increased with the decomposition of litter. Correlation analysis showed that microbial Chao1 index, available potassium and pH significantly influenced the decomposition of litter. Soil microbial communities were mainly influenced by soil moisture, soil texture (clay + silt) and the content of carbon and nitrogen. Overall, the changes in the soil microbial community especially in alpine forests can be strongly affected by litter decomposition in turn, further regulating ecosystem functions and processes. More attention should be paid to global climate-sensitive and vulnerable areas, which are essential for soil ecological quality improvement.