Multi-scale spatial patterns of soil microbial communities and biogeochemical processes in three arctic ecosystems
Microbial communities and their functional role in soil biogeochemical processes vary across spatial scales. Although soil and microbial spatial variability has been studied in various tropical and temperate ecosystems, little information is available from arctic ecosystems. Arctic soils represent a significant proportion of global land mass and contain about one fourth of total soil carbon pool. Soil microbial nitrogen (N) transformations such as nitrification and denitrification have significant implications for N availability and N loss in nutrient-limited arctic ecosystems. This study explored the spatial relationships among microbial communities, functional processes and soil properties in three Canadian arctic ecosystems. Despite adverse climatic conditions and frequent cryopedogenic processes, soil attributes and microbial abundance are highly spatially structured and their spatial autocorrelation is consistent within and between the ecohabitats. However, the zone of spatial autocorrelation is substantially smaller than non-arctic ecosystems. Ammonia-oxidizing and denitrifying communities are spatially structured within 5 m whereas potential nitrification and denitrification are spatially autocorrelated within 40 m in arctic soils. Nitrification activities are driven at small scales (<1 m) by moisture and total organic carbon content whereas gene abundance and other edaphic factors drive at medium (1-10 m) and large (10-100 m) scales. Soil moisture, organic carbon and nitrogen content are the predominant driving factors with nirK abundance also correlated to denitrification across spatial scales. Overall, this study unravels the multi-scale determinants of nitrification and denitrification in Arctic ecosystems.