Level terraces improve the generation of fungal niches and modify fungal communities under post-megafire conditions: Soil management insights in the context of climate change

Forest plowing to create level terraces was part of Spain's 1950s reforestation strategy, preparing sites for planting. Although this practice has been controversial due to its short-term negative impacts on soil properties, its long-term effects on ecosystems affected by megafires may have important implications for fungal community recovery. This study evaluates the impact of historical terraces on soil fungal communities under post-megafire conditions. The research was conducted in the Sierra de la Culebra (Zamora, Spain), the site of the largest recorded wildfire in the country's history. The objectives were: (a) to compare soil chemical properties and vegetation cover between terraced and non-terraced plots; (b) to assess the diversity and composition of fungal communities; (c) to analyze the composition of fungal trophic guilds; and (d) to examine fungal interactions under post-fire conditions. Terraces significantly modified pH, the C/N ratio, and grass cover, generating microhabitats that act as nutrient islands for fungi. Fungal richness and diversity remained stable, but community composition shifted. Fifty out of 145 fungal indicator genera were exclusive to terraced plots, including the arbuscular mycorrhizal genera Acaulospora and Ambispora, and the saprotrophic genera Pyronema and Holtermanniella. Saprotrophic fungi, the dominant trophic guild, were more abundant in terraced soils. Soil pH, nitrogen, potassium, C/N ratio, and grass cover were significantly correlated with fungal dynamics. These results suggest that historical soil management infrastructures offer a climate change adaptation strategy, meriting their integration into post-fire restoration plans in Mediterranean landscapes.