Compositional Stability of the Bacterial Community in a Climate-Sensitive Sub-Arctic Peatland.

James T Weedon,Peter M Van Bodegom,Stef Freriks,Rien Aerts,Wilfred F M Röling,George A Kowalchuk

doi:10.3389/fmicb.2017.00317

Abstract

The climate sensitivity of microbe-mediated soil processes such as carbon and nitrogen cycling offers an interesting case for evaluating the corresponding sensitivity of microbial community composition to environmental change. Better understanding of the degree of linkage between functional and compositional stability would contribute to ongoing efforts to build mechanistic models aiming at predicting rates of microbe-mediated processes. We used an amplicon sequencing approach to test if previously observed large effects of experimental soil warming on C and N cycle fluxes (50–100% increases) in a sub-arctic Sphagnum peatland were reflected in changes in the composition of the soil bacterial community. We found that treatments that previously induced changes to fluxes did not associate with changes in the phylogenetic composition of the soil bacterial community. For both DNA- and RNA-based analyses, variation in bacterial communities could be explained by the hierarchy: spatial variation (12–15% of variance explained) > temporal variation (7–11%) > climate treatment (4–9%). We conclude that the bacterial community in this environment is stable under changing conditions, despite the previously observed sensitivity of process rates—evidence that microbe-mediated soil processes can alter without concomitant changes in bacterial communities. We propose that progress in linking soil microbial communities to ecosystem processes can be advanced by further investigating the relative importance of community composition effects versus physico-chemical factors in controlling biogeochemical process rates in different contexts.

Highlights

Underlying many studies in microbial ecology is the premise that there is a relation between the microbial community composition (“who is there?”) and the functional potential (“what can they do or are doing?”) of a community (Raes and Bork, 2008; Vandenkoornhuyse et al, 2010)
Phyla-level assignments of sequences in the core 618 Operational taxonomic units (OTUs) dataset were broadly similar between the DNA- and RNA-based analyses (Figure 1)
Given that sampling time explained a higher proportion of variance in community composition relative to climate-change treatments, we focused on this temporal effect by determining which OTUs show shifts in relative abundance across the sampling period (Figure 3)

Summary

Introduction

Underlying many studies in microbial ecology is the premise that there is a relation between the microbial community composition (“who is there?”) and the functional potential (“what can they do or are doing?”) of a community (Raes and Bork, 2008; Vandenkoornhuyse et al, 2010). For some transformations, performed by well-defined functional groups, it is possible to make a direct link between community composition and biogeochemical fluxes (e.g., ammonia oxidation, denitrification, methane oxidation; Mertens et al, 2009; Salles et al, 2009; Bodelier et al, 2012; Bier et al, 2015). Evidence for such a link remains elusive for ecosystem processes mediated by a broader range of microorganisms, such as soil heterotrophic respiration, and the turnover of organic nitrogen. Given the importance of these “general community” processes for understanding and predicting ecosystem dynamics, it is imperative to establish if and when such a link exists

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