Drought Response Is Not a Species Trait: Tropical Tree Drought Sensitivity Is Shaped by Drought Characteristics, Species Adaptations and Individual Microenvironments

Increased frequency and severity of droughts threatens forest health worldwide. Tree species-specific adaptations-for example, dry-season deciduousness in tropical seasonal forests-and individual traits-for example, size, crown position-shape drought resistance, but such resistance may be variable across species, microenvironments and drought events. Here, we assess growth responses of 1820 trees across 30 species to three climatically distinct droughts in a seasonally dry tropical forest in Western Thailand. Species and individuals exhibited a wide range of growth responses within each drought, and differences in response intensity and affect among the drought events. Deciduous and evergreen species were more sensitive to wet- and dry-season drought respectively. While individuals with more exposed crowns tended to grow less in all droughts, stem diameter and topographic wetness had variable effects. Heterogeneous drought responses of species and individuals indicate potential biological insurance effects in diverse forests in the face of increased drought.