Functional diversity of microbial communities in herbaceous vegetation patches in coal mine heaps

Coal mine heaps represent unique novel environments, suitable for studying plant succession and its influence on the activity of microbes inhabiting the rhizosphere. Our aim was to verify if the functional diversity and catabolic activity of soil microorganisms would increase along with the plant succession from non-vegetated and forbs-dominated to grass-dominated communities. The study was conducted on coal mine heaps located in Upper Silesia (Southern Poland), focusing on non-vegetated patches, patches dominated by forbs-Tussilago farfara and Daucus carota (in the early stages of succession), and by grasses-Poa compressa and Calamagrostis epigejos (in later stages of primary succession). The catabolic activity and functional diversity of soil microbial communities were analyzed based on community-level physiological profiles using BIOLOG EcoPlatesTM and the activity of dehydrogenase, alkaline phosphatase, acid phosphatase, and urease. Our results showed that spontaneous vegetation on coal mine heaps strongly affects the physicochemistry of the substrate and the functional diversity of soil microbial communities. Grasses' rhizosphere was hosting more active and functional diversified microbial communities, while non-vegetated and T. farfara-vegetated patches were accompanied by a reduced development of soil microbiota. Furthermore, grasses were mainly associated with a substantial delivery of plant litter to the substrate, providing a source of carbon for microorganisms.