Scaling plant hydraulic traits to predict ecosystem fluxes under drought

Expanding plant hydraulic trait measurements and advances in hydraulic modeling have improved mechanistic predictions of water-carbon fluxes under drought. However, mismatches between individual-scale traits and ecosystem-scale model representations introduce prediction uncertainties and obscure how drought impacts propagate across scales. This synthesis identifies four key sources of scale-induced uncertainty: trait variability, Jensen's inequality, within-community processes, and compensation errors. I review current efforts to bridge these gaps using both forward modeling and inversion approaches and highlight emerging opportunities from improved characterization of trait variability, mechanistic models that represent community diversity and interactions, and multi-scale observational networks. Leveraging these opportunities will elucidate the mechanistic propagation of drought impacts across scales and improve predictions of ecosystem flux responses to future droughts.