Soil development following glacier retreat shapes metagenomic and metabolomic functioning associated with asynchronous C and N accumulation

Glacier retreat caused by global warming may result in the variation of soil organic carbon and nutrient cycling. Yet, the dynamic change of soil microbial functional profiles, especially C metabolism-related, with soil development following glacier retreat are still unclear. In the present study, we investigated the soil microbial communities, metagenomic functioning, and metabolomic profiles along the Hailuogou Glacier forefield representing a 120-year chronosequence. The alpha diversity indices of soil bacteria, protozoa and nifH genes showed an upward trend with increased soil ages, and the beta diversity of soil archaea, bacteria, fungi, protozoa, nifH and nirS genes were significantly correlated with soil ages, in which increasing soil C and P while decreased C/N and pH significantly contributed to the differences of soil microbial communities among the analyzed environmental variables. The metagenomic functional genes related to the metabolisms of Glycogen and Cellulosome, Iron Acquisition and Metabolism were significantly decreased with chronosequence, while the utilization of Xylose and Lactate, Potassium Metabolism, Sulfur Metabolism showing an upward trend with soil ages, in which soil C/N ratios and pH were the most influential factors. In addition, soil C and C/N ratios were also significantly correlated to metabolomic compositions, in which the complexity of the metabolite structure increased with soil ages. Our results indicate that glacier retreat may lead to the asynchronous C and N accumulation along the chronosequence, thereby affecting the metagenomic and metabolomic functioning of soil microbial communities related to C metabolisms during soil development following glacier retreat.