Topographic controls on vegetation recovery in mass-movement scars after an extreme rainfall event in Southern Brazil

Abstract Understanding vegetation recovery in landslide scars is essential for risk assessment and post‑disaster management. This study investigated how geomorphometric attributes influence vegetation regeneration in 85 mass‑movement scars triggered by an extreme precipitation event in January 2017 in southern Brazil. Annual time series (2018–2026) of four Sentinel‑2 spectral indices were integrated with topographic variables derived from the Copernicus GLO‑30 DEM. Principal component analysis (PCA) and k-means clustering classified scars into high, medium, and low regeneration groups, while linear mixed models evaluated topographic effects on recovery trajectories. Results demonstrated that regeneration follows a non-linear temporal trajectory, characterized by rapid initial recovery followed by progressive leveling off, which is partly tied to optical index saturation limits in maturing canopies. Slope negatively affected vegetation moisture levels, and elevation significantly modulated the bare soil trajectory, with higher altitudes showing faster soil recovery rates. Scar shape, measured by the circularity index, did not exert a significant effect on any spectral index. Curvature and aspect did not significantly influence regeneration trajectories. The high-regeneration class represented 42.3% of the scars analyzed, indicating relatively greater spectral recovery in most areas, while steep, low‑elevation sites require targeted restoration to reduce erosion and landslide reactivation risk. These results demonstrate that geomorphometric attributes are associated with different dimensions of the observed spectral recovery trajectories and that the approach integrating multiple spectral indices and non-linear modeling is effective for identifying priority areas for long-term ecological monitoring, thereby supporting landslide risk mitigation in subtropical environments.