Vegetation-driven shifts in soil microbial communities and predicted carbon-cycling potential across soil depths in High-Arctic islands

Abstract Background Arctic ecosystems are experiencing unprecedented warming, driving vegetation expansion into previously barren areas. Although Arctic greening is expected to alter biogeochemical cycles, how vegetation cover shapes soil microbial communities and their functional potential remains poorly understood. Here, we investigated how vegetation cover structures bacterial and fungal communities across three soil depths (0–2, 5–10 and 30–50 cm) on remote Russian High-Arctic islands using soil DNA metabarcoding and functional prediction. Results Vegetation cover had a stronger influence on soil microbial communities than soil depth. Vegetated islands had significantly higher soil organic matter content and distinct bacterial and fungal community compositions, with enrichment of plant-associated and symbiotic taxa. Vegetation was also associated with shifts in predicted microbial functional potential, particularly in carbohydrate metabolism and carbon-related pathways, with the strongest differences observed in surface soils. Conclusions Even sparse High-Arctic vegetation can restructure soil microbial communities and their predicted functional potential, while vegetation-associated carbon accumulation extends into deeper soil layers. These findings suggest that ongoing Arctic greening may substantially alter belowground microbial communities and carbon cycling throughout the soil profile.