Implementation and evaluation of the unified stomatal optimization approach in the Functionally Assembled Terrestrial Ecosystem Simulator (FATES)

Abstract. Stomata play a central role in regulating the exchange of carbon dioxide and water vapor between ecosystems atmosphere. Their function is represented land surface models (LSMs) by conductance models. The Functionally Assembled Terrestrial Ecosystem Simulator (FATES) dynamic vegetation demography model that can simulate both detailed plant demographic physiological dynamics. To evaluate effect stomatal formulation on forest fluxes FATES, we implemented an optimality-based – Medlyn (MED) simulates relationship photosynthesis (A) to (gsw) as alternative FATES default Ball–Woodrow–Berry (BWB) model. how behavior affected choice, conducted sensitivity analysis explore response gsw climate forcing, including atmospheric CO2 concentration, air temperature, radiation, pressure deficit (VPDa). We found modeled values varied greatly BWB MED formulations due different slope parameters (g1). After harmonizing g1 holding intercept parameter (g0) constant for formulations, divergence was limited conditions when VPDa exceeded 1.5 kPa. then evaluated simulation results against measurements from wet evergreen Panama. Results showed were able capture magnitude diurnal changes measured A but underestimated about 30 % soil predicted be very dry. Comparison content reanalysis product captured drying well, translation physiology reduced models' ability match observations. Our study suggests parameterization current drought are critical areas improving tropical forests.