Representing Plant Hydraulics in Noah-MP and Its Responses to Different Representations of Soil Hydraulics

Abstract:

Water transport from the soil to the atmosphere through plant xylem is driven by the hydraulic gradient between the soil and the plant living tissues. Land surface models (LSMs) for use in weather and climate models have started to represent the water movements through the plant roots, stems, leaves, and the leaf stomata driven by water pressure gradient. However the uncertainties in soil water pressure caused by different representations of soil hydraulic models have not received much attention. In this talk, I will present a simple plant hydraulic model we recently developed in the Noah-MP LSM and its responses to two different soil hydraulic models: the Clapp-Hornberger (CH) and the van Genuchten (VG) water retention models. Generally, the VG model produces a greater water pressure (or lower soil matrix suction head) than does the CH model, allowing less water being retained in the soil matrix and facilitating both root water uptake and gravitational drainage. I will show some results on the impacts of the two different models on plant draught resilience and runoff production over the contiguous US river basins.