Life in the graveyard: Ancient stone burial mounds as refuges for Mediterranean grassland vegetation

Ancient burial sites are increasingly recognized as important biodiversity hotspots and refuges for grassland vegetation in human-modified landscapes. While the ecological value of earthen burial mounds in Eurasia has been widely documented, the biodiversity potential of globally distributed stone burial mounds remains largely unexplored. Here, we assess the role of stone mounds as biodiversity hotspots and refuges from grassland degradation. We studied 15 stone mounds in the late Bronze Age necropolis of San Magno (southern Italy), a cultural heritage site affected by grazing abandonment and wild boar rooting. Plant species cover was recorded in concentric ring-plots on the mounds and in the surrounding grassland matrix. We compared community composition, species richness and diversity, as well as functional and ecological characteristics (life forms, ecological indicator values, habitat specificity) using non-metric multidimensional scaling, indicator species analyses, and bootstrap paired t-tests. Plant community composition differed significantly between mounds and surrounding grasslands. Mounds supported higher species richness and greater cover of perennial grasses, chamaephytes, and grassland specialists, alongside lower representation of short-lived grasses and weeds. This might be explained by the increased rockiness and decreased wild boar rooting intensity on the mounds. Our results show that ancient stone mounds can function as refuges for grassland biodiversity in the Mediterranean biome. By maintaining plant communities in a favorable conservation status, they may buffer degradation processes. These findings highlight synergies between cultural and natural heritage and suggest that both ancient and artificial stone mounds could support grassland conservation and restoration strategies.