Soil microbial communities and carbon and nitrogen forms across snow-driven vegetation types in alpine tundra

Alpine tundra vegetation, also shaped by snow persistence, is expected to undergo shifts in plant community composition under climate change as snow cover duration declines, with potential consequences for soil biogeochemistry and microbial communities. However, the relationships among snow-driven vegetation types, soil carbon (C) and nitrogen (N) forms, and prokaryotic community functional organization remain poorly understood.

In this study, we investigated soil C and N forms and the functional organization of prokaryotic communities across three vegetation types shaped by different snow cover duration: snowbed communities dominated by Salix herbacea (SB, with long snow cover duration), alpine sedge swards dominated by Carex curvula (CC, with short snow cover duration), and intermediate transitional plant assemblages.

C-related forms were mainly associated with vegetation type, with higher C content in CC than in SB. Conversely, mineral N forms varied primarily with timing within the snow free season, with higher concentrations in the early snow free season, indicating different spatial and temporal controls on soil C and N dynamics. Microbial community composition differed among vegetation types, whereas alpha diversity varied little. Despite this, prokaryotic functional groups differed markedly. CC were associated with higher relative abundance of cellulolytic prokaryotes, whereas SB were enriched in N-related functional groups inferred from FAPROTAX assignments, suggesting potential differences in N cycling-related microbial functions among vegetation types.

These results show that soil biogeochemistry and microbial functional organization in alpine tundra soils are shaped by both snow-driven vegetation types and timing across the snow free period. Under climate change, reduced snow cover duration and SB contraction may cause the loss of a microhabitat with specific functional biodiversity, with potential consequences for soil C and N cycling.