Temporal and spatial influences incur reconfiguration of Arctic heathland soil bacterial community structure

Abstract

Microbial responses to Arctic climate change could radically alter the stability of major stores of soil carbon. However, the sensitivity of plot-scale experiments simulating climate change effects on Arctic heathland soils to potential confounding effects of spatial and temporal changes in soil microbial communities is unknown. Here, the variation in heathland soil bacterial communities at two survey sites in Sweden between spring and summer 2013 and at scales between 0-1 m and, 1-100 m and between sites (> 100 m) were investigated in parallel using 16S rRNA gene T-RFLP and amplicon sequencing. T-RFLP did not reveal spatial structuring of communities at scales < 100 m in any site or season. However, temporal changes were striking. Amplicon sequencing corroborated shifts from r- to K-selected taxon-dominated communities, influencing in silico predictions of functional potential. Network analyses reveal temporal keystone taxa, with a spring betaproteobacterial sub-network centred upon a Burkholderia operational taxonomic unit (OTU) and a reconfiguration to a summer sub-network centred upon an alphaproteobacterial OTU. Although spatial structuring effects may not confound comparison between plot-scale treatments, temporal change is a significant influence. Moreover, the prominence of two temporally exclusive keystone taxa suggests that the stability of Arctic heathland soil bacterial communities could be disproportionally influenced by seasonal perturbations affecting individual taxa.

Microbial diversity and functional capacity in polar soils

“…Interestingly, the application of network analysis suggested that Burkholderia species might be keystone species in Arctic soils [21]. This is consistent with previous observations that Burkholderia taxa may confer cold tolerance to plant species exposed to low temperatures [26].…”

“…In contrast to many other extremophilic biomes, cold environments appear to have a higher level of spatial heterogeneity [20][21][22]. Within cold regions, both soils and permafrost niches appear to be dominated by bacterial (mainly Proteobacterial, Actinobacterial and Acidobacterial), archaeal (mostly Euryarchaeota) and fungal (dominated by Ascomycota) lineages [7,23,24,25 ] (Table 1).…”

“…A recent (and unique) analysis of the temporal and spatial trends in Arctic heartland soils reported a change in microbial community structure in response to simulated climate change, with a general shift from r-to K-selected taxa [21]. Interestingly, the application of network analysis suggested that Burkholderia species might be keystone species in Arctic soils [21].…”

“…Through application of metagenomic approaches (Figure 1), it is now known that most extreme environments harbour lower levels of microbial diversity (species richness and relative 1 abundance), than more 'benign' ecosystems [16,17]. This is thought to be due to the requirement for specific physiological adaptations, which allow organisms to exploit the combination of physical and biochemical stressors, but result in simplified ecosystems dominated by a relatively few taxa [18,19].In contrast to many other extremophilic biomes, cold environments appear to have a higher level of spatial heterogeneity [20][21][22]. Within cold regions, both soils and permafrost niches appear to be dominated by bacterial (mainly Proteobacterial, Actinobacterial and Acidobacterial), archaeal (mostly Euryarchaeota) and fungal (dominated by Ascomycota) lineages [7,23,24,25 ] (Table 1).…”

“…Within cold regions, both soils and permafrost niches appear to be dominated by bacterial (mainly Proteobacterial, Actinobacterial and Acidobacterial), archaeal (mostly Euryarchaeota) and fungal (dominated by Ascomycota) lineages [7,23,24,25 ] (Table 1). While these studies have provided a comprehensive, and reasonably consistent, survey of microbial diversity at the specific sites sampled, few of these studies have any temporal component; that is, they are single time-point analyses which provide, at best, a baseline for future assessments of the effects of environmental change.A recent (and unique) analysis of the temporal and spatial trends in Arctic heartland soils reported a change in microbial community structure in response to simulated climate change, with a general shift from r-to K-selected taxa [21]. Interestingly, the application of network analysis suggested that Burkholderia species might be keystone species in Arctic soils [21].…”