Abstract
Abstract. The unique and fragile High Arctic ecosystems are vulnerable to global climate warming. The elucidation of factors driving microbial distribution and activity in arctic soils is essential for a comprehensive understanding of ecosystem functioning and its response to environmental change. The goals of this study were to investigate microbial biomass and activity, microbial community structure (MCS), and their environmental controls in soils along three elevational transects in the coastal mountains of Billefjorden, central Svalbard. Soils from four different altitudes (25, 275, 525 and 765 m above sea level) were analyzed for a suite of characteristics including temperature regimes, organic matter content, base cation availability, moisture, pH, potential respiration, and microbial biomass and community structure using phospholipid fatty acids (PLFAs). We observed significant spatial heterogeneity of edaphic properties among transects, resulting in transect-specific effects of altitude on most soil parameters. We did not observe any clear elevation pattern in microbial biomass, and microbial activity revealed contrasting elevational patterns between transects. We found relatively large horizontal variability in MCS (i.e., between sites of corresponding elevation in different transects), mainly due to differences in the composition of bacterial PLFAs, but also a systematic altitudinal shift in MCS related to different habitat preferences of fungi and bacteria, which resulted in high fungi-to-bacteria ratios at the most elevated sites. The biological soil crusts on these most elevated, unvegetated sites can host microbial assemblages of a size and activity comparable to those of the arctic tundra ecosystem. The key environmental factors determining horizontal and vertical changes in soil microbial properties were soil pH, organic carbon content, soil moisture and Mg2+ availability.
Highlights
Knowledge about the spatial distribution and activity patterns of soil microbial communities is essential to understand ecosystem functioning as soil microbes play a fundamental role in biogeochemical cycling and drive productivity in terrestrial ecosystems (van de Heijden et al, 2008)
The effect of altitude on soil moisture was significant along Tr1 and Tr3 (P < 0.001 and 0.01, F = 22.76 and 7.39, respectively), with soil moisture content decreasing with increasing elevation, but nonsignificant along Tr2
The high microbial biomass and activity at the most elevated sites were almost exclusively associated with biological soil crusts, largely contributed by fungi
Summary
Knowledge about the spatial distribution and activity patterns of soil microbial communities is essential to understand ecosystem functioning as soil microbes play a fundamental role in biogeochemical cycling and drive productivity in terrestrial ecosystems (van de Heijden et al, 2008). Soil microbial diversity in the Arctic is comparable to that in other biomes (Chu et al, 2010), and the spatiotemporal variability in microbial community composition is large (Lipson, 2007; Blaud et al, 2015; Ferrari et al, 2016). It is still uncertain which environmental factors drive the heterogeneity of soil microbial properties in the Arctic. Kotas et al.: Soil microbial biomass, activity and community composition
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