Patterns of post-fire vegetation composition across contrasting Mediterranean climates: Insights from a chronosequence of managed and unmanaged burned forests

The combined influence of post-fire management and recovery time on plant community trajectories in contrasting Mediterranean and Atlantic-Mediterranean forest ecosystems remains poorly understood, particularly when environmental and management contexts differ among sites. We used a space-for-time chronosequence approach to compare vegetation community composition, multivariate dispersion, and α-diversity among unburned reference (UB), burned without post-fire management (B+NA), and burned with post-fire management (B+A) conditions at two post-fire stages (short-term, mid-term) in two contrasting Spanish environmental systems. The study included four independent sites: Liétor and Hellín in the semi-arid Mediterranean region of Castilla-La Mancha, and Pedro Bernardo and Quilamas in the Atlantic-Mediterranean region of Castilla y León. Vegetation cover data from 120 and 99 transects, respectively, were analysed with NMDS, nested PERMANOVA, PERMDISP, and SIMPER, and α-diversity indices. Post-fire management condition, post-fire stage, and their interaction were significantly associated with differences in plant community composition in both environmental systems (p < 0.001). Compositional differences between the sampled short- and mid-term stages were stronger in Castilla y León than in Castilla-La Mancha. In Castilla y León, the mid-term B + A community did not differ significantly from the UB reference (p = 0.078), whereas B + NA remained compositionally distinct. In Castilla-La Mancha, both burned conditions remained significantly different from UB at the mid-term stage, although their similarity to the reference increased relative to the short-term stage. Post-fire management was associated with greater within-group heterogeneity in the short term in both environmental systems. Species-level patterns further identified Cytisus striatus as a dominant component of the short-term unmanaged community in Castilla y León, whereas Macrochloa tenacissima and Helianthemum syriacum were characteristic of burned communities in Castilla-La Mancha. Differences in soil organic carbon, microbial biomass, hydraulic conductivity, and other environmental characteristics provide a plausible context for the contrasting community patterns, but cannot be separated experimentally from differences in climate, vegetation, fire history, and management. Overall, the results indicate that post-fire vegetation responses differ among environmental and management contexts and support the use of site-specific reference conditions and long-term monitoring strategies.