Assessing the spatio-temporal cumulative drought effects on two Mediterranean forest types in Central Chile

Abstract

Droughts are long-lasting events that can drive persistent functional changes in ecosystems, particularly in drought-prone areas like Mediterranean forests. We integrated a phenology-based anomaly method, combining kernel density estimation (KDE) with cumulative sums (CUSUMs) to assess long-term drought impacts on two Mediterranean forest types in Central Chile. Using MODIS Enhanced Vegetation Index (EVI), the Moisture Stress Index (MSI), and Evapotranspiration (ET) from 2000 to 2024, we quantified cumulative deviations in canopy productivity, moisture conditions, and energy exchange. Our framework revealed persistent negative functional trajectories preceding the well-documented 2010–present megadrought. Spatially explicit metrics identified coherent degradation hotspots in northern sclerophyllous and southern deciduous forests, where canopy greenness, moisture, and evapotranspiration declined synchronously. Seasonal models indicated a post-2010 strengthening of soil–water controls over forest functioning, with soil moisture and water storage variables becoming influential predictors. The convergence of cumulative negative EVI, MSI, and ET signals highlights widespread and sustained functional weakening under prolonged drought conditions. Our results demonstrate that integrating KDE-derived anomalies with cumulative deviation tracking provides a sensitive and transferable framework to detect early and persistent vegetation stress in water-limited ecosystems.