Wildfires effect on soil properties and bacterial biodiversity of postpyrogenic Histic Podzols (middle taiga, Komi Republic)

Data on the main morphological, physicochemical, chemical and microbiological properties of Histic Podzols in pine forests of semi-hydromorphic landscapes in the middle taiga of the Komi Republic after forest fires are presented. Due to climate change and dry periods, fires in the European part of the Russian Federation have recently spread northward, affecting large areas that are usually less susceptible to pyrogenesis. As a result of fires and the accumulation of pyrogenic carbon, physicochemical soil properties, water-air and hydrothermal regimes change significantly, the amount and stability of organic matter change, and heavy metals accumulate in upper soil horizons, which has a direct impact on their biological properties. The effect of the fire can be traced to a depth of approximately 20-30 cm. The carbon and nitrogen content in the studied soils, as well as their microbial biomass, had a significant impact on the qualitative composition of the microbiomes of pyrogenic and control soil horizons. A significant influence of the pyrogenic factor on the alpha and beta diversity of the soil microbiome was noted. It has been shown that representatives of the dominant bacteria phyla Pseudomonadota, Bacteroidota, Bacillota and Actinobacteriota actively participate in the organic matter decomposition with pyrogenic carbon presence. The microbiome's response to a forest fire can be divided into an increased proportion of spore-forming microorganisms, including those with a complex set of catalytic enzymes (Domibacillus, representatives of penibacillus), and an increased proportion of gram-negative microorganisms with complex metabolism as well (Bacillota - Sphingobacterium alimentarium, Flavobacterium lindanitolerans, Gammoproteobacteria - Acinetobacter).