Drought is an important factor driving tropical forests’ community composition and species distribution. Although tropical trees show strong interspecific differences in drought resistance, the underlying mechanisms are far from being solved, with a significant lack of studies that specifically link functional traits and tree performance.
We aimed at filling this fundamental gap with a functional trait approach, by measuring and compiling an exhaustive dataset of traits related to desiccation avoidance and tolerance. We performed the first compilation of all available traits in Panama tropical forests databases, adding newly proposed traits to commonly measured traits and performance responses in situ.
Material and Methods
We conducted a broad screening of 44 traits in 48 lowland tropical forest species in the field and an intensive trait screening in the greenhouse, including commonly measured traits (e.g. leaf traits) and newly proposed traits related to hydraulic efficiency (e.g. water potential at turgor loss) and carbon starvation avoidance (accumulation of non-structural carbohydrates).
Most of the commonly measured traits were poor predictors for tropical tree performance under drought, whereas some ‘hard’ traits related to hydraulic efficiency were good predictors of drought resistance. Namely, the turgor loss point (i.e. wilting point) emerged as the best predictor of tropical trees performance under drought, with species with lower turgor loss point exhibiting higher drought resistance. Stomatal closure and NSC accumulation were unrelated to any performance variable. Ongoing analyses will further evaluate which suits of traits are the best predictors of drought vulnerability in tropical forest trees.
These findings have important implications to predict tropical forest trees' response to the altered rainfall patterns expected with global change and to understand the broader effects of increasing drought periods in this important ecosystems.