All plant species house communities of microorganisms within their tissues, collectively called the endosphere. Root endosphere assembly is a multistage process, influenced by biotic and abiotic filters. Firstly, abiotic conditions limit the soil community and, therefore, the available microbial pool. Secondly, plants act as a biotic filter by cultivating a subset of the microbial pool, creating a distinct endosphere community. It is well established that abiotic conditions drive soil community assembly, including pH and nutrient availability, but whether these factors also directly influence endosphere assembly is unknown. Here we investigate the influence of soil chemistry on root and soil fungal community assembly of a wetland clonal plant, Phragmites australis. Metagenomic sequencing was performed on soil and root samples from 84 1m2 plots dominated by P. australis across eight marshes in southeast Louisiana. Abiotic soil conditions in each plot were quantified and dbRDAs were used to assess whether abiotic factors impact soil and root fungal composition. Two models were used to analyze the effects of abiotic conditions on microbial composition at the landscape and local level. We hypothesize that root and soil community assembly will be driven by the same abiotic variables at both spatial scales.
Results/Conclusions
We find that root and soil fungal community composition are influenced by the same abiotic conditions at the landscape scale, pH, nitrogen, and salinity; however, at local scale, different factors structured soil and root communities. Locally, soil community assembly was largely influenced by pH, which is consistent with other studies that have found pH to be a strong determinant of local variation in soil microbial composition. However, local root community composition was not influenced by changes in soil acidity, and preliminary results suggested that plant species richness is the main driver of root community composition. This indicates that while soil fungi are vulnerable to abiotic variations in their surrounding environment, the stable chemical environment provided by plant hosts buffers root microbes from environmental stressors to some extent. These results suggest that endosphere communities are more strongly influenced by biotic factors, like plant diversity, compared to the abiotic conditions that drive soil communities on a local scale.