The activity and function of subarctic soil microbial communities vary across vegetation types. Subarctic soil microbial communities

Global warming accelerates activity of soil microbial communities in high-latitudes, resulting in potentially higher greenhouse gas emissions. However, these microbial processes are not thoroughly understood. We analyzed 116 soil metatranscriptomes from 73 tundra sites and investigated how bacterial and archaeal communities and their functions vary horizontally (i.e. vegetation type) and vertically (i.e. topsoil organic and mineral layers) during the summer season, in relation to soil factors, namely pH, moisture, soil organic matter (SOM), carbon and nitrogen content. Active microbial communities were significantly different in organic and mineral soil layers. Interestingly, the communities also differed significantly between the four different vegetation types both in organic and in mineral layer. The results show that vegetation type together with pH and SOM are important drivers of microbial activity in subarctic tundra soils. Various plant polymer degraders were particularly active in soils with high SOM and low pH dominated with shrub vegetation, whereas in lower SOM and higher pH associated with graminoid vegetation, less known mixotrophic groups, such as Chloroflexi, were active. Additionally, we detected transcripts of Alphaproteobacterial methanothrophs which potentially moderate methane release from tundra soils in deeper soil layer. Our results provide insights into the drivers of microbial communities of the high-latitudes under climate change.