Burn Severity and Recurrence Effects on Soil Fungal Communities in Mediterranean Pine Forests

Wildfires can produce alterations to soil, water, and vegetation. In the case of the soil, wildfires act directly through changes in its chemical composition and physical properties. This work aims to evaluate the presence of fungi in soil affected by wildfires. We collected soil samples to analyse the soil fungal communities and monitor soil respiration, soil infiltration and soil water repellency to assess if frequent and severe wildfires reduce the fungal flora that form mycorrhizal associations in SE Spain (Yeste, Albacete) where there were severe wildfires in 1994 (14.000 ha) and 2017 (3500 ha) with an area burned by both wildfires. In this experimental design, we established four zones to compare different burn severities (unburnt, low, high, and high with recurrence) throughout the study period (2021–2022). Fungal species were identified using PacBio real-time sequencing of the ITS2 region. Sequences were quality filtered, clustered into Operational Taxonomic Units (OTUs) using UNITE, and taxonomically classified using SH matching and manual BLAST analysis. FUNGuild was used to assign trophic habits to identified taxa. The results showed that the fungal community’s richness and uniformity did not differ across burn severity levels or periods; soil respiration rates were reduced in soils affected by high burn severity and high burn severity with recurrence; soil infiltrations rates did not differ, water repellency was reduced as severity rose; changes were observed in pH, K, Ca, K/Mg ratio, and CEC; the soil parameters most affected by the fire were the enzymatic activities (amount of phosphatase and β-glucosidase), basal soil respiration and carbon in microbial biomass. The study provides insights into the resilience of fungal communities in Mediterranean pine ecosystems, highlighting their potential role in post-fire ecosystem recovery. However, long-term research is required to assess the time needed for microbiological parameters to return to pre-fire conditions, and it is essential to study fungal communities and soil properties in Mediterranean pine ecosystems following forest fires in order to comprehend their impact on mushroom production, the local economy, and forest recovery.