STILL ROOTING FOR RECOVERY: LEGACY EFFECTS AND VEGETATION DYNAMICS IN SANTA CRUZ ISLAND GRASSLANDS

Disturbance legacies can shape plant communities long after the initial event. The persistence and scale of these effects remain complicated, however, which in many instances can conflict with restoration efforts. Santa Cruz Island (SCI), California, presents a compelling case study in legacy effects. It was subject to over a century of intensive grazing by non-native cattle and feral sheep and rooting by feral pigs (Sus scrofa), and later to large-scale eradication and fire management interventions. We resurveyed 40 permanent grassland plots in southwestern SCI that were originally sampled in the 1990s—during the height of pig activity—and compared them to surveys conducted in 2023, 17 years after pig eradication. Using redundancy analysis (RDA), we asked: 1) did fine-scale pig rooting influence vegetation composition during the 1990s, 2) did rooting legacies on composition persist into the present, and 3) does current vegetation reflect longer-term legacy effects of non-native plant invasion? We found that rooting intensity and frequency explained significant variation in composition in the 1990s, but that these effects had largely dissipated by 2023. Instead, long-term changes were characterized by shifts among invasive herbaceous species, with no evidence of native shrub expansion or return to pre-disturbance states. Our results suggest that while pig disturbance had acute short-term effects, the most enduring legacy may be the non-native-dominated communities that became established in the late 19th century. These findings demonstrate the context dependence of ecological recovery, the deep ecological memory of intensively altered grasslands, and the need for active, tailored restoration approaches where passive recovery has stalled.