Erosion barriers act as potential reservoirs for soil fungal species key for restoring areas affected by high-severity wildfire in Sierra de la Culebra (NW Spain)

A short-term consequence of increasingly frequent and severe wildfires in the Mediterranean Basin is runoff-induced soil erosion in areas where vegetation has been removed by high-intensity fires. To mitigate this problem, erosion control barriers are often installed in gullies to reduce runoff velocity. The potential impact of these barriers on soil fungal diversity and community composition has not been commonly studied. To assess this effect, we collected soil samples from plots with barriers and plots without barriers in an area affected by the 2022 megafire in the Sierra de la Culebra, Spain. Fungal operational taxonomic units were identified by sequencing the ITS1 region of fungal DNA in soil samples. Vegetation cover and substrate type were also recorded via transects at each sampling point. Our findings suggest that barriers create a microenvironment that supports greater fungal species richness. This may contribute positively to broader-scale diversity if these localized islands of richness serve as sources of soil fungi for the recolonization of surrounding areas. Fungal communities in plots with barriers were significantly different from those in plots without barriers and were enriched with animal endosymbionts, mycoparasites, and plant pathogens-functional guilds whose role in postfire recovery remains uncertain. However, certain species associated with barrier plots, such as Mortierella elongata and Mortierella alpina, may play a role in promoting vegetation recovery. This research highlights the adequacy of the use of soil erosion barriers as a postfire management tool that can have a positive impact both on direct preservation of soil fungal diversity and subsequent vegetation recovery of burned areas.