Predicting species' and communities' responses to environmental change is a key goal for ecology. Three major challenges include: 1) establishing empirically strong relationships between traits and the environment; 2) advancing mechanistic theory to better predict trait responses to environmental change, and 3) scaling up trait-based predictions to communities. Ecophysiology can offer solutions in each area through modeling of underlying mechanisms. Developing concepts in plant hydraulics can advance predictive capability at species and community scale. The presentation will specifically examine the role of leaf venation networks in mediating water transport and species interactions (challenge 1) in tropical forests, the role of stomata in determining water use under heat stress (challenge 2) in deserts, and the role of polyploidy-environment interactions in determining mortality risk (challenge 3) in montane forests. Together this work offers approaches for advancing a more predictive ecology across biological scales.