Soil Microbiome After Nine Years Of Fly Ash Dump Spontaneous Revegetation

Fly ash dumps of thermal power stations have been increasing in area worldwide due to the growing demand for power. One of the cost-effective approaches for restoring such sites is spontaneous revegetation in those areas where adjacent indigenous ecosystems can supply seeds and living organisms. We assessed microbiome taxonomic diversity in a Technosol developed during nine years of spontaneous revegetation of the terminated fly ash pond of a thermal power station in Novosibirsk, Russia, in comparison with microbiome diversity in undisturbed Phaeozem under adjacent birch forest by using 16S (V3-V4) and ITS2 (ITS3-ITS4) amplicon sequencing with Illumina MiSeq. We identified 577 fungal and 5542 bacterial operational taxonomic units (OTUs); 95-99% of them were minor or rare species. The dominant OTUs were completely different in the studied soils. At the phylum level, the ultimate dominants were Ascomycota (84%) in the Technosol and Basidiomycota (89%) in the Phaeozem. Three phyla (Proteobacteria, Acidobacteria and Actinobacteria), together comprising more than a half of the bacteriobiome, prevailed in both soils; however, at the OTU level, soil-related differences were found for 31% of the OTUs. The Technosol bacteriobiome was less structured and more diverse compared to the mycobiome, displaying the same phylum-level structure and OTU-based alpha-biodiversity as in the adjacent mature soil. Our finding that few fungal and bacterial OTUs dominated in the soil microbiome, the majority being minor or rare members, implies that key ecosystem processes performed by soil microorganisms rely on a very limited taxonomic diversity, both in young and mature soils.