The Influence of Vegetation Type on the Dominant Soil Bacteria, Archaea, and Fungi in a Low Arctic Tundra Landscape

Arctic vegetation communities vary greatly over short distances due to landscape heterogeneities in topography and hydrological conditions, but corresponding patterns and controls for soil microbial communities are not well understood. We characterized and compared the most abundant phylotypes within replicate soil microbial communities (n = 4) underlying the four principal vegetation types in Canadian low Arctic tundra (dry heath, birch hummock, tall birch, and wet sedge) using denaturing gradient gel electrophoresis (DGGE) of small subunit rRNA genes. We identified 10 major bacterial phylotypes. Although most were present in all soil samples, their relative abundances differed significantly and consistently according to vegetation type. By contrast, the fungal communities of all vegetation types were dominated by two common phylotypes. The communities of major archaea (11 identified) differed substantially among some of the vegetation types and even among replicate patches of the same vegetation type, indicating large spatial heterogeneities that could not be attributed to the influence of vegetation type. Bacterial and fungal communities in all vegetation types were dominated by Acidobacteria and Zygomycota, respectively. Archaeal communities were dominated by Euryarchaeota in tall birch and wet sedge although both Euryarchaeota and Thaumarchaeota were abundant in the birch hummock and dry heath soils. We conclude that vegetation type exerts a strong influence on soil bacterial community structure, and a relatively small and varying influence on archaeal and fungal communities in low Arctic tundra. Finally, variation in bacterial community structure among the vegetation types was correlated with soil soluble N and N mineralization potential, suggesting a close association between the relative abundances of dominant soil bacteria and N availability across low Arctic tundra.