Subsurface constraints amplify vegetation stress during extreme heat and drought in a Mediterranean forest

Abstract Drought and extreme heat events are becoming more frequent and intense as the global climate warms, threatening forests worldwide. Subsurface conditions such as soil depth and groundwater availability can influence plant drought vulnerability. Yet, how subsurface factors interact with climate stress and shape forest vulnerability and die-off at landscape scales remains poorly understood. The record-breaking hot and dry 2023–2024 summer in southwestern Australia induced widespread stress in the Jarrah Forest ecosystem. Analysis of vegetation greenness anomalies using airborne geophysics data, groundwater depth records, climate data, and remote sensing revealed that vegetation die-off emerged from the interactions of heat, water stress, and subsurface conditions. Shallow soils, rocky substrates, and limited access to subsurface water predisposed vegetation to experience heat and drought stress. Identifying the role and location of subsurface features enables identification of vulnerable, and resilient, areas and will guide adaptive forest management for resilience against future climate extremes.