Microbes on the Cliff: Alpine Cushion Plants Structure Bacterial and Fungal Communities

Abstract

Plants affect the spatial distribution of soil microorganisms, but the influence of the local abiotic context is poorly documented. We investigated the effect of a single plant species, the cushion plant Silene acaulis, on habitat conditions, and microbial community. We collected soil from inside (In) and outside (Out) of the cushions on calcareous and siliceous cliffs in the French Alps along an elevation gradient (2,000–3,000 masl). The composition of the microbial communities was assessed by Capillary-Electrophoresis Single Strand Conformation Polymorphism (CE-SSCP). Univariate and multivariate analyses were conducted to characterize the response of the microbial beta-diversity to soil parameters (total C, total N, soil water content, N-NH4+,N-NO3-, and pH). Cushions affected the microbial communities, modifying soil properties. The fungal and bacterial communities did not respond to the same abiotic factors. Outside the cushions, the bacterial communities were strongly influenced by bedrock. Inside the cushions, the bacterial communities from both types of bedrock were highly similar, due to the smaller pH differences than in open areas. By contrast, the fungal communities were equally variable inside and outside of the cushions. Outside the cushions, the fungal communities responded weakly to soil pH. Inside the cushions, the fungal communities varied strongly with bedrock and elevation as well as increases in soil nutrients and water content. Furthermore, the dissimilarities in the microbial communities between the In and Out habitats increased with increasing habitat modification and environmental stress. Our results indicate that cushions act as a selective force that counteracts the influence of the bedrock and the resource limitations on the bacterial and fungal communities by buffering soil pH and enhancing soil nutrients. Cushion plants structure microbial communities, and this effect increases in stressful, acidic and nutrient-limited environments.

Long-lasting modification of soil fungal diversity associated with the introduction of rabbits to a remote sub-Antarctic archipelago

“…The exclusion of the cushion plant A. selago from areas affected by rabbits may be particularly significant in terms of explaining differences between soil fungal communities. Specifically, the cushion growth form has been shown to modify local abiotic conditions and promote soil microhabitat diversity [14]. This hypothesis is also consistent with our results for individual plots on the Isthme Bas where more diverse fungal communities were found under mixed species cover than mono-specific Acaena cover (figure 2b; electronic supplementary material, figures S2 and S7).…”

Nitrogen limitation and microbial diversity at the treeline

“…These results confirm recent findings from a montane elevational gradient in eastern Peru (Fierer et al 2011) according to which the composition of microbial community changes with elevation even though microbial diversity is independent of altitude. Although not in the context of the treeline, the influence of elevation on soil fungal communities has also been recently observed in the case of Silene acaulis cushions (Roy et al 2013). By contrast to fungal communities, bacterial communities did not differ along the elevational gradient (Table 3).…”

Microbial communities and primary succession in high altitude mountain environments

“…In the pioneer stage, the rhizobacterial community was determined by the environmental conditions, whereas in the later stages, plants were selected for a specific microbial community related to soil properties and carbon supply (Tscherko et al 2004). The selective role of pioneer plants, which counteracts resource scarcity of bare soils, was clearly confirmed by some studies about pioneer plants in high elevation alpine environments (Roy et al 2013;Ciccazzo et al 2014a, b).…”

“…), the cushion pioneer plant Silene acaulis affected the microbial communities modifying soil properties on calcareous and siliceous bedrocks in the French Alps (Roy et al 2013). The bedrock type outside the cushions strongly influenced the bacterial communities, whereas inside the cushions, the bacterial communities were highly similar in both types of bedrock.…”