Disentangling the Effect of Distance Decay on Soil Bacterial Communities

Soil bacterial communities play critical roles in ecosystem functioning. However, the processes that govern bacterial diversity and community assembly are influenced by both dispersal and selection pressures. This study explores the ecological distance decay relationship, where bacterial community similarity declines with geographic distance, across grassland soils in the Hainich-Duen and Schorfheide-Chorin regions of Germany, sampled within the framework of the Biodiversity Exploratories. We assess how dispersal, abiotic factors, and biotic interactions, particularly plant community composition, influence bacterial beta diversity. DNA was extracted from 0.25 g of soil for each sample using the NucleoSpin Soil kit (Macherey Nagel), according to manufacturer instructions, and DNA quality and concentration were confirmed with gel electrophoresis and Qubit. The 16S rRNA gene was amplified using primers targeting the V4 region (515F-806R), using the standard Earth Microbiome Project protocols (Thompson et al. 2017) and primers 16S_Illu_515F and 16S_Illu_806R. Amplicons were sequenced with an Illumina MiSeq sequencer (Illumina Inc., San Diego, CA, United States) with the MiSeq Reagent Kit v3 (600 bp).