Spatio-temporal patterns and drivers of secondary succession in a Mediterranean landscape

In recent years, many Mediterranean agricultural lands have been abandoned, reforested, rewilded and ecologically restored, creating different templates and trajectories for the development of secondary succession. Our objective was to verify whether past legacies of woody vegetation (remnant forest, shrub patches and reforestations) influenced the current spatial pattern of woody cover in a mid-successional Mediterranean area, identifying spatial cold and hotspots (i.e: low/slow or high/fast cover increase) and looking for footprints of seed-disperser and herbivore-mediated processes at landscape and local scales. The study took place in three 500x200 m plots in a formerly managed and partially reforested pastureland in the Ficuzza Natural Reserve (Palermo, PA), the last large forest remnant in western Sicily. We sampled woodland and shrubland cover over a 24-year interval (from abandonment to the present), by combining current field sampling and a GIS-based interpretation of sequential high resolution satellite images and greyscale aerial photographs. The overall woody vegetation cover almost doubled through the studied period, with a balanced increase of woodland and shrubland patches. Fraxinus angustifolia reforestation contributed marginally to woodland expansion, while the major increase was due to the natural regeneration consisted mainly of five fleshy-fruited and one dry-fruited species, all of them well protected against herbivory. Most of woody cover expansion was correlated with initial cover, although some hotspots presented 100% of cover increase from bare areas even further than 100 m away from any woody patch. Our results reveals that the composition and spatial configuration of past vegetation legacies can influence the secondary succession evolution, as well as the specific contribution of natural regeneration, human-made reforestation, herbivory and animal seed dispersal in creating these patterns, setting a template for further investigations regarding mechanisms and functional traits driving these patterns.