Trajectories of Collembola community composition, diversity and functional traits following fire in Mediterranean forest soils

Fire significantly shapes Mediterranean forest ecosystems by influencing ecological processes. The mid-term post-fire recovery of soil Collembola is poorly understood in the Mediterranean area. This study aimed to identify the post-fire trajectories of Collembola assemblages in surface soils of burnt sites under trees and shrubs, compared to unburnt control sites, in the Vesuvius National Park (Italy, Campania region), at 38–74 months after fire. Collembola were extracted, taxonomically identified, and assessed through density, species richness, Shannon and soil quality (QBS-c) indices, and taxonomic and functional trait composition to evaluate post-fire recovery trajectories. The results highlighted that after fire Collembola assemblages were primarily structured by time and to a lesser extent by vegetation type. Similar dynamics were observed in soils under burnt trees and shrubs for species richness (1–2.6 taxa), Shannon (0.04–0.82) and QBS-c (18–49) indices. In addition, in soils under burnt trees, several hemi and epi-edaphic and dispersive species (e.g., Brachystomella parvula, Cryptopygus bipunctatus, Neanura muscorum) showed a significant increase within 38–62 months. In soils under burnt shrubs, the surface-active species were almost absent for the first 4–5 years and reappeared only after 62–74 months. The results indicated that in burnt soils Collembola assemblages followed alternative trajectories rather than converging toward pre-fire conditions. These findings highlight the need to integrate soil fauna into post-fire management, emphasizing the protection or restoration of tree cover patches to accelerate soil ecological functioning in Mediterranean forests.