Long-term monitoring of structures of microbial communities along a vegetation gradient from alpine meadows to a glacier forefield. Seasonal dynamics of microbial communities in an alpine meadow

In a 14-months monitoring campaign, we assessed seasonal changes in soil properties and in microbial community structures at 4 locations representing an altitude and vegetation gradient (from alpine meadows at 1980 m a.s.l. to a glacier forefield at 2519 m a.s.l.). Fungal and bacterial community structures and abundances were investigated through T-RFLP profiling and qPCR of the 16S and 18S rRNA genes. In addition, Illumina sequencing was performed to identify key bacterial groups on selected samples. Seasons affected the soils and the soil microbial communities more significantly than sites (plant species, grazing). The physico-chemical properties of the soils changed greatly during the course of the year. Bacterial and fungal community structures changed during the sampling period, but didn’t always complete a full seasonal cycle. Our sequence data indicates that under winter snowpack, bacterial communities were dominated by ubiquitous opportunistic groups (i.e. beta-Proteobacteria), while in the snow-free seasons, other groups (i.e. Cyanobacteria) became more abundant.