Preliminary insights into the potential of fire-prevention treatments to shape fire-resilient soil fungal communities in Mediterranean high-fire-risk shrublands

Abstract

Mediterranean ecosystems are frequently affected by wildfires; however, the increasing occurrence of megafires represents a concerning shift in the region’s fire regime. Soil fungal communities are among the ecosystem components most affected by fire, with potentially severe consequences for ecosystem functioning and for the local mushroom-based economy. This study evaluates the impact of wildfire on soil fungi and assesses the effectiveness of prescribed burning and total mechanical clearing as fire-prevention strategies in areas at high risk of megafires, with a particular focus on their effects on soil fungal communities. We studied plots that had undergone prescribed burning or total mechanical clearing in 2020, some of which were later affected by the 2022 Sierra de la Culebra megafire. Fungal diversity and community composition were assessed using a meta- barcoding approach by amplifying the ITS1 region and identifying operational taxonomic units (OTUs) in soil samples. Soil physicochemical properties, vegetation and substrate surface cover data were also collected. Although no significant differences in species richness were observed between burned and unburned plots, wildfire-affected communities showed greater dominance imbalance. Changes in community composition, significantly correlated with fire occurrence, suggest the emergence of new ecological niches occupied by pyrophilous taxa after the megafire. Several pyrophilous indicator species were identified in wildfire-affected plots; however, some edible taxa had declined in abundance. Although the effects of fire-prevention manage- ment in the wildfire-affected area were not statistically significant, prescribed burning appeared to buffer the post-fire loss of fungal diversity more effectively than total mechanical clearing. We conclude that prescribed burning may foster the development of more fire-resilient fungal communities. Furthermore, we suggest that fire- prevention treatments not only help to reduce fuel loads in fire-prone areas but also do not appear to be detrimental to certain valuable edible fungal species that support the mushroom-harvesting economy in these rural landscapes.