Insight into the long-term impact of fire in dry pine forests on biological soil crust and underlying soil

Although the impact of wildfires on vegetation and soil properties is well documented, long-term effects on biocrusts and underlying soils in dry temperate pine forests remain unclear. The aim of this study was to determine microbiological parameters of biocrusts and characteristics of two underlying soil layers in a post-fire area 12 years after the wildfire, relative to an unburned forest. The wildfire caused long-lasting effects on biocrusts, leading to altered species composition and reduced species richness of lichens and bryophytes. Biocrusts from the post-fire area had lower chlorophyll a and a + b levels, indicating slow recovery of photosynthetic biomass. Although microbial activity, as reflected by dehydrogenase activity, was lower in soil after the fire than in the control forest, elevated concentrations of exopolysaccharides (EPS) were found. This suggests reduced EPS degradation due to suppressed microbial activity and/or selective enrichment of EPS-producing microorganisms following fire. The increased content of soil organic carbon and total nitrogen in the 1–5 cm soil layer indicates that wildfire can promote a long-lasting accumulation of C and N in the studied ecosystem. Soil pH was significantly higher in the post-fire area, while conductivity showed the opposite trend, but only for soil directly below biocrust. Despite reduced microbial activity and EPS production, post-fire biocrusts showed a stronger influence on underlying soils, as reflected by a significantly higher soil-to-biocrust microbial activity ratio. Finally, local site conditions strongly influenced soil microbiological and chemical parameters, highlighting the importance of accounting for environmental heterogeneity in post-fire management. Consequently, restoration practices should focus on enhancing biocrust functions to accelerate ecosystem recovery, while adapting approaches to site-specific conditions. • Post-fire biocrusts had reduced microbial activity and photosynthetic biomass • Soils in post-fire area had increased content of organic carbon and total nitrogen • Elevated EPS after fire may reflect its reduced decomposition or increased production • Local site conditions had strong effect on microbiological and chemical soil traits • Restoration should enhance biocrust functions and be tailored to site conditions