Modeling the Hydrologic Balance of Epiphytes: Towards an Improvement of Evapotranspiration Estimates in Rainforests

Abstract

Ecohydrological models are essential to the study of ecological processes, water resources engineering, and climate modeling. Epiphytes make up to a third of the biomass in some rainforests and can impact the regional water budget, but the unique hydrologic characteristics of epiphytes have not yet been included in ecohydrological models. The aim of this work is to develop a water balance model for epiphytes, and use the model to determine how varying climactic conditions affect water use in C3 and CAM epiphytes. In this study, the unique water uptake and utilization behavior of epiphytes is modeled in a numerical water balance model that is coupled to the Photo3 photosynthesis model. The results of the model are in agreement with the general water use behavior of epiphytes, and are validated with G. monostachia. The application of vertical profiles of environmental inputs within the rainforest canopy show increasing transpiration rates with increasing canopy height. The results of this work help to provide a crucial missing piece to current ecohydrological models, and can be integrated into climate models to help improve estimations of transpiration and free-surface evaporation from canopy, which will become increasingly important for future climate change projections.