Divergent ecosystem responses: Biological activity and soil organic matter vulnerability under increased snow depth in Arctic tundra

Snow cover strongly affects Arctic tundra soils, regulating temperature, moisture, and nutrient availability across seasons. Although warming increases winter snowfall and prolongs snow cover, the biogeochemical impacts remain uncertain in contrasting tundra types. We installed snow fences in moist tundra (Council, Alaska) and dry tundra (Cambridge Bay, Nunavut) for five to six years to assess how deeper snow cover modifies soil conditions, biological activity, and soil organic matter (SOM) fractions, focusing on mineral-associated organic matter (MAOM). Deeper snow cover raised winter soil temperatures at both sites. However, only the moist tundra showed higher summer soil temperature and moisture, leading to higher plant greenness and a slight rise in SOM vulnerability. At this site, free particulate organic matter fraction rose while MAOM declined, indicating that MAOM, less chemically processed (high C/N, low δ¹⁵N), was more susceptible to decomposition. In contrast, the dry tundra’s colder conditions showed no major shifts in soil chemistry, vegetation, microbes, or SOM fractions, likely because temperatures stayed below thresholds for winter biological activity. These site-specific results indicate that soil temperature and moisture drive Arctic tundra responses to deeper snow cover, highlighting the importance of understanding such differences when predicting biogeochemical feedback under rapid climate change.