Certain Plant Traits Mitigate the Risk of Hydraulic Failure Under Future Climate Change in the Tropical Forests of Panama

Tropical hydraulic trait diversity allows for community-level resilience to a wide range of water availability and temperature. Recent drought-induced mortality in tropical forests suggests that there may be thresholds beyond which communities face the risk of widespread mortality. Many different mechanisms could lead to increased tropical forest mortality. One key mechanism is hydraulic failure, resulting from water stress in the soil and vapor pressure deficit in the air. A diverse set of plant hydraulic traits determine the plant's functional water use strategies to avoid drought (through stomatal closure and investments in greater water access) or tolerate it (through investments in increased water use efficiency). Future projected droughts that may favor certain functional strategies, reorganizing tropical communities. Using 1,000 ensembles of hydraulic traits, we parameterized a plant hydrodynamic model within Functionally Assembled Terrestrial Ecosystem Simulator (FATES) coupled to the land surface model within Energy Exascale Earth System Model (E3SM) for the forests of Barro-Colorado Island, Panama. We calibrated this model against observational data from Barro-Colorado Island to constrain hydraulic risk and growth behavior. We then simulated these ensemble parameterizations under multiple climate scenarios to assess the risk of hydraulic failure and resulting mortality. We found that traits governing a drought avoidance strategy become increasingly important as drought frequency and severity increase. This work is crucial in understanding how demography and carbon capture in the tropics may change under increased future drought.