Abstract
Microbial communities in alpine environments are exposed to several environmental factors related to elevation and local site conditions and to extreme seasonal variations. However, little is known on the combined impact of such factors on microbial community structure. We assessed the effects of seasonal variations on soil fungal and bacterial communities along an elevational gradient (from alpine meadows to a glacier forefield, 1930–2519 m a.s.l.) over 14 months. Samples were taken during all four seasons, even under the winter snowpack and at snowmelt. Microbial community structures and abundances were investigated using Terminal Restriction Fragment Length Polymorphism (T-RFLP) and quantitative PCR (qPCR) of the 16S and 18S rRNA genes. Illumina sequencing was performed to identify key bacterial groups in selected samples. We found that the soil properties varied significantly with the seasons and along the elevational gradient. For example, concentrations of soluble nutrients (e.g., , , ) significantly increased in October but decreased drastically under the winter snowpack. At all times, the alpine meadows showed higher soluble nutrient concentrations than the glacier forefield. Microbial community structures at the different sites were strongly affected by seasonal variations. Under winter snowpack, bacterial communities were dominated by ubiquitous groups (i.e., beta-Proteobacteria, which made up to 25.7% of the total reads in the glacier forefield). In the snow-free seasons, other groups (i.e., Cyanobacteria) became more abundant (from 1% under winter snow in the glacier forefield samples to 8.1% in summer). In summary, elevation had a significant effect on soil properties, whereas season influenced soil properties as well as microbial community structure. Vegetation had a minor impact on microbial communities. At every elevation analyzed, bacterial, and fungal community structures exhibited a pronounced annual cycle.
Highlights
The high adaptive capacity and physiological flexibility of microorganisms allows them to colonize a huge variety of ecosystems
dissolved organic carbon (DOC) concentrations were higher at the vegetated sites B, T, and A than at the sparsely vegetated site F
In the samples from F, concentrations were an order of magnitude lower
Summary
The high adaptive capacity and physiological flexibility of microorganisms allows them to colonize a huge variety of ecosystems. Alpine ecosystems experience a striking range of seasonal variations (Ernakovich et al, 2014). In these habitats, elevational gradients, seasonal snow cycles, and varied precipitation regimes affect plant species compositions and soil properties (Cebon et al, 1999), which influence the composition of the resulting microbial communities. Alpine ecosystems are ideal platforms for exploring how microbial communities respond to environmental changes. Such studies provide insights into how future changes in climate, which are expected to strongly influence alpine plant and microbial communities, will affect ecosystem functioning (Djukic et al, 2010)
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