Efeito do pastoreio de asininos na diversidade de artrópodes e na estrutura da vegetação lenhosa e herbácea na Reserva da Biosfera Transfronteiriça da Meseta Ibérica (RBTMI)

Abstract

The Mediterranean biome is a biodiversity hotspot historically sustained by agroforestry systems. However, rural exodus and the abandonment of traditional land management practices have led to a critical accumulation of plant fuel, increasing the frequency and severity of wildfires. In this context, silvopasture emerges as a key strategy for fuel load management and fire mitigation. This study evaluated the impact of donkey (Equus asinus) grazing on arthropod biodiversity and vegetation structure across four plots within the Meseta Ibérica Biosphere Reserve (Portugal and Spain). Field monitoring during the peak biomass accumulation period (May to August) combined line-intercept sampling, destructive biomass harvesting, and remote sensing via an Unmanned Aerial Vehicle (UAV) equipped with a LiDAR sensor to assess vertical structural complexity. Pitfall traps were used to sample the arthropod community prior to and following the grazing period. Grazing significantly altered arthropod taxonomic composition (PERMANOVA, p = 0.001), driven primarily by high species turnover (85–90%). Species richness remained stable in shrublands and increased in wet meadows (lameiros), suggesting ecological niche remodeling without biodiversity loss. Functionally, predator abundance declined in open areas due to reduced shelter, whereas decomposers benefited from dung deposition. Vegetation analysis demonstrated a drastic reduction in total herbaceous biomass (p < 0.001). The biovolume response was asymmetrical: shrubland architecture was disrupted through mechanical impact and browsing, whereas wet meadows showed no statistically significant changes (p = 0.192). Increases in bare ground and litter confirmed the effective removal of fine fuels. LiDAR metrics corroborated the multiscale impact of herbivory, revealing that structural changes occurred predominantly in the lower strata (0–75 cm), alongside partial herbaceous recovery two months post-grazing. Controlled grazing with native donkey breeds represents an important tool for wildfire prevention and sustainable ecosystem management. This practice disrupts vertical and horizontal fuel continuity while promoting biodiversity, and the integration of LiDAR metrics promoves monitoring precision to support public policies centered on resilient silvopastoral management.