Different Responses of Soil Nutrient Dynamics and Microbial Activities to Soil Moisture Changes in Alpine Wetlands and Meadows on the Tibetan Plateau

Abstract

Alpine wetlands on the Tibetan Plateau are important carbon pools and are undergoing severe degradation, generally with decreasing vegetation and soil water contents. However, the ecological responses of alpine wetlands to hydrological changes vary greatly among habitats. In this study, topsoil from alpine wetlands and meadows (degraded wetlands) was incubated under 50%, 70%, and 100% saturated water content (SWC) and then characterized based on soil nutrients, enzyme activities, the molecular composition of dissolved organic matter (metabolomes), and microbial communities (metagenomes). Compared with meadow soils, wetland soils had greater nutrient contents and hydrolase activities and more complex compositions of metabolomes and metabolomes. After incubation, wetland soils presented the highest activities of all enzymes under 70% SWC, whereas meadow soils presented the highest activities of β-glucosidase and acid phosphatase under 50% SWC, both together with the lowest dissolved organic carbon content and the highest dissolved phosphorus content. Drought increased the number of microbial species in wetland soils but decreased that in meadow soils. The Shannon and Pielou indices were highest under 100% SWC (in wetlands) or 70% SWC (in meadows) and lowest under 50% SWC (in both soils) and were significantly positively correlated with acid phosphatase activity in wetland soils. Distance-based redundancy analysis revealed the important role of peroxidase in alpine wetlands. Procrustes analysis further indicated the different drought-induced ecological responses in two alpine soils. This study deepens our understanding of the soil-type-related ecological responses in alpine ecosystems and provides a valuable reference for the application of emerging multiomics techniques.