Plant functional types drive spatial and temporal variation in soil microbial community composition and extracellular enzyme activities in a tundra heath

Abstract

Aims In this study we investigated divergent effects of two dominant plant functional types in tundra heath, dwarf shrubs and mosses, on microbial decomposition processes and soil carbon (C) and nutrient cycling. Methods We analysed samples of organic soil under three dwarf shrub species of distinct mycorrhizal association and life form (Betula nana, Empetrum hermaphroditum and Arctostaphylos alpinus) and under three moss species (Hylocomium splendens, Aulacomnium turgidum and Tomentypnum nitens) in early and late growing season. Results Our results revealed contrasting effects of shrubs and mosses on extracellular enzyme activities and soil C and nutrient pools which were linked with strong differences in soil microbial community structure. Specifically, moss soils were characterized by a bacterial-dominated microbial community associated with high soil nitrogen availability, while shrubs promoted a fungal-dominated microbial community and soil C accrual. The variation in soil microbial community composition under different plant species was explained by mycorrhizal association, root morphology, litter and soil organic matter quality and soil pH-value. Furthermore, we found that the seasonal variation in microbial biomass and enzyme activities, driven by plant belowground C allocation during the growing season, was most pronounced under the tallest shrub B. nana. Conclusion Our study demonstrates a close coupling of plant functional types with soil microbial communities, microbial decomposition processes and soil nutrient availability in tundra heath, which suggests potential strong impacts of global change-induced shifts in plant community composition on carbon and nutrient cycling in high-latitude ecosystems.