Spatial heterogeneity of belowground microbial communities linked to peatland microhabitats with different plant dominants

Abstract

Peatland vegetation is composed mostly of mosses, graminoids and ericoid shrubs, and these have a distinct impact on peat biogeochemistry. We studied variation in soil microbial communities related to natural peatland microhabitats dominated by Sphagnum, cotton-grass and blueberry. We hypothesized that such microhabitats will be occupied by structurally and functionally different microbial communities, which will vary further during the vegetation season due to changes in temperature and photosynthetic activity of plant dominants. This was addressed using amplicon-based sequencing of prokaryotic and fungal rDNA and qPCR with respect to methane-cycling communities. Fungal communities were highly microhabitat-specific, while prokaryotic communities were additionally directed by soil pH and total N content. Seasonal alternations in microbial community composition were less important; however, they influenced the abundance of methane-cycling communities. Cotton-grass and blueberry bacterial communities contained relatively more α-Proteobacteria but less Chloroflexi, Fibrobacteres, Firmicutes, NC10, OD1 and Spirochaetes than in Sphagnum. Methanogens, syntrophic and anaerobic bacteria (i.e. Clostridiales, Bacteroidales, Opitutae, Chloroflexi and Syntrophorhabdaceae) were suppressed in blueberry indicating greater aeration that enhanced abundance of fungi (mainly Archaeorhizomycetes) and resulted in the highest fungi-to-bacteria ratio. Thus, microhabitats dominated by different vascular plants are inhabited by unique microbial communities, contributing greatly to spatial functional diversity within peatlands.

Plant functional type indirectly affects peatland carbon fluxes and their sensitivity to environmental change

“…It is possible that changes in microbial communities among PFT treatments were not detected due to use of PLFA analysis, which cannot detect changes in specific functional groups such as methanogens and methanotrophs, unlike DNA analysis. Elsewhere, dominant PFTs have been shown to influence methane‐cycling communities, with consequences for CH 4 fluxes (Chronakova et al, 2019; Robroek et al, 2015). Removal of graminoid and ericoid PFTs from peatland plots reduced bacterial abundance and numbers of methanotrophs (Robroek et al, 2015).…”

“…Living vegetation can directly affect GHG fluxes by moderating the influence of climate on CO 2 uptake through growth, in addition to moderating CO 2 and CH 4 release through differences in plant physiology between PFTs, which affect decomposition and gas transport (Greenup, Bradford, McNamara, Ineson, & Lee, 2000). However, PFT can also indirectly affect C fluxes through differences in the quality and quantity of rhizodeposits and plant litter entering the soil (De Deyn, Cornelissen, & Bardgett, 2008; Dieleman, Branfireun, & Lindo, 2017), which influence the abiotic and biotic properties of peat (Chronakova, Barta, Kastovska, Urbanova, & Picek, 2019; Robroek et al, 2015; Robroek et al, 2016; Ward, Bardgett, McNamara, & Ostle, 2009). Separating the direct and indirect effects of living and decomposing plants on peatland C dynamics is complex and has received little attention (Armstrong et al, 2015; Kuiper, Mooij, Bragazza, & Robroek, 2014; Wiedermann, Kane, Potvin, & Lilleskov, 2017).…”

Rewiring of peatland plant-microbe networks outpaces species turnover

“…Moreover, our study confirms previous suggestions that enviro-climatological conditions are important drivers that underlie the composition of the vegetation, and that changes in these drivers result in alterations of the plant community (Gunnarsson et al 2002, Pinceloup et al 2020) and associated biotic interactions (Wiedermann et al 2007). Indeed, we note that site-specificity of plant communities is paralleled in the prokaryotic community, a pattern that is likely explained by the strong links between plant and microbial communities (Chronakova et al 2019;Ivanova et al 2020). Despite the variation in prokaryotic community composition between sites, the archaea to bacteria ratio remains strikingly stable.…”

“…Indeed, peatland microbial community structure and activity are strongly connected to plant community assemblage (Bragina et al 2014, Chronakova et al 2019, Martí et al 2019b, Ivanova et al 2020.…”

Root exudate input stimulates peatland recalcitrant DOC decomposition by r-strategic taxa of Gammaproteobacteria and Bacteroidetes

“…The composition of microbial community actively utilizing the present substrates, its succession and a potential contribution of particular bacterial and fungal representatives to PE depend not only on the quantity and quality of entering exudates but also on initial composition of microbial community [35]. Because of the prevailing microaerophilic or anaerobic nature of peatlands, bacteria dominate the microbial community [36,37], while fungi are highly suppressed, and their abundance increases only in oxic microsites [38]. It is therefore likely that bacteria will play dominant role in decomposition of exudates, recalcitrant peatland DOC and in the PE, which may be induced by root exudates input.…”