G2L_Alb
16S rRNA analysis of bacterial communities of forest and grassland sites located in the German Biodiversity Exploratory Schwäbische Alb
Soil samples were collected from 9 forest and 9 grassland plots of the German Biodiversity Exploratory Schwäbische Alb. The forest sampling sites included 3 spruce age class forests (SAF1-3), 3 beech age class forests (BAF1-3), and 3 near natural beech forests (BF1-3). Grassland sampling sites contained 3 fertilized intensely used grasslands (FUG1-3), 3 fertilized meadows grazed by horse and cow (FMG1-3), and 3 unfertilized pastures grazed by sheep (UPG1-3).
Soil bacteria are important components for nearly all biogeochemical cycles in terrestrial ecosystems and participate in most nutrient transformations in soil. In contrast to the importance of soil bacteria for ecosystem functions, we understand little how different management types affect the soil bacterial community composition. We used pyrosequencing-based analysis of the V2-V3 16S rRNA gene region to identify changes in bacterial diversity and community structure in nine forest and nine grassland soils under six different management types (three replicates each) from the Schwäbische Alb (southwestern Germany). The data set comprised 598,962 sequences that were affiliated to the domain Bacteria. The number of classified sequences per sample ranged from 23,515 to 39,259. The dominant taxonomic groups across all samples (> 1% of all sequences) were Acidobacteria, Alphaproteobacteria, Actinobacteria, Betaproteobacteria, Deltaproteobacteria, Gammaproteobacteria, and Firmicutes. Significant variations in relative abundances of bacterial phyla, including Actinobacteria, Firmicutes, Cyanobacteria, and Alphaproteobacteria, between the land use types forest and grassland were observed. At the genus level, differences were also recorded for the dominant genera Phenylobacter, Polyangium, Bacillus, Kribbella, Agromyces, and Defluviicoccus. The separate analysis of bacterial community composition in forest and grassland soils revealed strong correlations of relative abundances of bacterial groups at different taxonomic levels and soil pH, but little or no relationships to the management type and other soil properties were found. A pH effect was recorded for the Bacteroidetes, Alphaproteobacteria, Betaproteobacteria, Acidobacteria (subgroups 1, 4, 6, 13, 16, 17, and 22), Caulobacterales, and Dyella in forest soils, and for acidobacterial subgroup 3 and Acetobacteraceae in forest as well as in grassland soils. In addition, soil bacterial community structure showed significant differences between beech and spruce forest soils. Thus, soil pH and tree species were the major drivers of bacterial community composition in forest soils.