Burning season, grazing intensity and scrub type determine Mediterranean shrubland responses to pyric herbivory

Abstract Background Herbivores grazing and fires have historically shaped Mediterranean shrublands by maintaining open habitats and diverse plant communities. Rural abandonment has reversed this process, resulting in fuel accumulation, increased forest connectivity, and wildfire risk. Pyric herbivory, combining prescribed burning and grazing, can mitigate these threats by reducing fuel loads, controlling woody encroachment, and restoring ecosystem processes. This case study investigated the short-medium term effects of prescribed burning and pyric herbivory with two different burning seasons in Mediterranean shrublands with different scrub types. We conducted a 2-year field experiment applying spring and autumn prescribed burns ranging from moderate to high intensity, with and without low-intensity grazing by sheep, across four vegetation types: low- and medium-cover areas, and dense areas dominated by Macrochloa tenacissima or Genista scorpius . Results The observed patterns suggest that both prescribed burning and pyric herbivory reduced fuel loads while preserving forage quality, but only combined fire, mostly in autumn, and grazing seemed to increase plant diversity, and only in the dense areas. In dense Macrochloa areas, spring burns during active growth, apparently, favored rapid Macrochloa clonal recovery and competitive dominance, limiting diversity, whereas autumn burns during plant dormancy seemed to reduce Macrochloa vigor, enabling more diverse herbaceous establishment under grazing. In Genista areas, irrespective of burning season, its lignotuber resprouting and seed-bank recruitment probably allowed its recovery, albeit slower, favoring a maximized increase in diversity when burns were followed by grazing. Conclusions These findings underscore the need for vegetation- and season-specific fire-grazing regimes that align with plant phenology, growth forms, and life strategies. Pyric herbivory emerges as an adaptable strategy to mitigate wildfire risk, maintain pasture quality, and enhance biodiversity in fire-prone Mediterranean landscapes.