Microorganisms in small patterned ground features and adjacent vegetated soils in the High Arctic, Canada

We compared 1) microbial biomass C (MBC), 2) number of bacteria (MPN), 3) diversity of fungal isolates (FI), and 4) the composition of the bacterial community in patterned ground features (PGFs) and adjacent vegetated soils (AVS) in study sites from three islands (Ellef Ringnes, Prince Patrick and Banks Islands) located along a bioclimatic gradient in the High Arctic of Canada. Soil samples were collected from PGFs and AVS located along transects in zonal (mesic) sites, and within a range of topographic conditions (drier and wetter areas at each island). FI and MPN inoculates were grown at two temperatures (7 vs. 25°C). MBC at the mesic position was greatest in Green Cabin, intermediate in Mould Bay, and lowest in Isachsen. MBC was higher in AVS than in PGFs in Green Cabin and Mould Bay but when we compared other topographic position within the study sites (islands), we found that microbial biomass C was also higher in AVS than in PGF in the dry position in Isachsen and Green Cabin. MPN were different among study sites and locations but not between incubation temperatures. MPN were higher in AVS than in PGF. FI were greater in AVS than in PGF but not different among sites. We conclude that MBC decreased with increasing latitude in these High Arctic islands. In addition, heterotrophic bacteria, some fungal genera and the number of TRFLP phylophytes vary along the gradient. Further, microbial activities are lower in PGFs as compared to AVS; and this effect could be decoupled by the effect of topographic position and temperature.