The Microbial Landscape in Soils - Biogeography of Soil Microorganisms in the German Biodiversity Exploratories.

In the framework of an initiative to advance biodiversity research in Germany, three exemplary large-scale and long-term research sites were established to understand the role of land use and management for biodiversity and to understand the role of biodiversity for ecosystem processes across Germany (www.biodiversity-exploratories.de). This platform is used to investigate the effects of land use intensity on single trophic levels, interacting organisms, as well as foodweb structures. We identified general relationships between abiotic soil properties and soil biota across spatial scales, ecosystems (forest and grassland) and different land-use intensities. Whereas abiotic soil properties and climatic conditions mainly explained differences in microbial community structure and function on the regional scale, on the local and plot scale differences were related to the land use intensity level. In 2011, we tested whether microbial biogeography of a grassland plot (10 m x 10 m) changes over the growing season. We sampled the plot (60 samples within a grid of 20 cm x 20 cm) six times within one season to cover the different stages of substrate release and nutrient demands of plant communities. Microbial community spatial structure (based on PLFA data) was positively correlated with the local environment in spring and autumn, while the density and diversity of plants had an additional effect in the summer period. Spatial relationships among plant and microbial communities were detected only in the early summer and autumn periods when aboveground biomass increase was most rapid and its influence on soil microbial communities was greatest due to increased demand by plants for nutrients. Individual properties exhibited varying degrees of spatial structure over the season. Finer phylogenetic resolution of microbial groups using next generation sequencing helped determine the importance of plant species density, composition, and growth stage in shaping microbial community composition and spatial patterns.