Title
Development of a tree-level hydrodynamics model for ELM to study competition of water
Authors
Gautam Bisht (PNNL), William Riley (Unlicensed) (LBNL), Gil Bohrer (The Ohio State University), and Ashley Matheny (The University of Texas at Austin)
Abstract
Water availability impacts transpiration which in turn modifies water, energy, carbon, and nutrient cycling in vegetation, and ultimately growth and survival. Plants dynamically regulate their water availability through active controls in their roots, xylem, and leaves. Yet, most current generation global land surface models, including the E3SM Land Model (ELM), do not explicitly resolve water transport through the root and xylem of a plant. Furthermore, ELM allows each plant functional type (PFT) within a grid cell to extract soil water without concurrently accounting for competition from other PFTs in the same grid cell within a given timestep. In this work, we report on our Next Generation Development effort to apply E3SM’s terrestrial Multi-Physics Problem (MPP) library to resolve water transport across the soil-plant continuum and explicitly account for water competition among plants. The plant hydrodynamics model is based on the variably saturated Richards equation and accounts for water storage within plant roots and xylem. We apply our model to the US-UMB Ameriflux site and simulate tree-level hydrodynamics for four PFTs within a grid cell. Our model results agree well with soil moisture observations at multiple depths and observed sapflow. Diurnal profiles of simulated transpiration stress within the plant canopy are also analyzed. Lastly, our results show the importance of model structure (i.e., inclusion or exclusion of water storage within a plant) on simulated plant water stress.