Effects of soil warming and season on the bacterial community in a temperate mountain forest soil assessed by 16S rRNA gene pyrosequencing

We investigated the effects of experimental soil warming (+4°C) on the bacterial community composition in a temperate mountain forest soil. A plot experiment had been established in 2004, with subplots that were kept 4 °C above soil temperature in adjacent control plots throughout each snow free season. We pyrosequenced 16S rRNA gene amplicons prepared from soil DNA sampled in July 2008 and March 2009 to survey the effects of artificial warming as well as natural fluctuations in community composition between summer and winter. The aims of the study were i) to assess the seasonal plasticity of the bacterial community, ii) to identify at which level of taxonomic resolution seasonal shifts can be observed best, iii) to determine whether experimental warming introduced additional shifts at the same or at any other taxonomic level, and iv) to differentiate whether possible warming-induced changes were transient and only detectable in summer, or persistent throughout the following winter.