Representation of Plant Hydraulics in the Noah‐MP Land Surface Model: Model Development and Multiscale Evaluation

Journal of Advances in Modeling Earth Systems

Nate G. McDowell¹  L. Ruby Leung¹  David M. Lawrence²  Sean C. Swenson²  Michael Barlage³  Hui Zheng⁴  Zong‐Liang Yang⁵  Ashley M. Matheny⁵  Binyan Yan⁵  Lingcheng Li⁵ 

[1] Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory Richland WA USA;Climate and Global Dynamics Laboratory, National Center for Atmospheric Research Boulder CO USA;Environmental Modeling Center, NOAA/NWS/NCEP, College Park MD USA;Institute of Atmospheric Physics, Chinese Academy of Sciences Beijing China;Jackson School of Geosciences University of Texas at Austin Austin TX USA;

关键词: land surface model;    plant hydraulics;    water and carbon cycles;   

DOI  :  10.1029/2020MS002214

来源: DOAJ

【 摘 要 】

Abstract Plants are expected to face increasing water stress under future climate change. Most land surface models, including Noah‐MP, employ an idealized “big‐leaf” concept to regulate water and carbon fluxes in response to soil moisture stress through empirical soil hydraulics schemes (SHSs). However, such schemes have been shown to cause significant uncertainties in carbon and water simulations. In this paper, we present a novel plant hydraulics scheme (PHS) for Noah‐MP (hereafter, Noah‐MP‐PHS), which employs a big‐tree rather than big‐leaf concept, wherein the whole‐plant hydraulic strategy is considered, including root‐level soil water acquisition, stem‐level hydraulic conductance and capacitance, and leaf‐level anisohydricity and hydraulic capacitance. Evaluated against plot‐level observations from a mature, mixed hardwood forest at the University of Michigan Biological Station and compared with the default Noah‐MP, Noah‐MP‐PHS better represents plant water stress and improves water and carbon simulations, especially during periods of dry soil conditions. Noah‐MP‐PHS also improves the asymmetrical diel simulation of gross primary production under low soil moisture conditions. Noah‐MP‐PHS is able to reproduce different patterns of transpiration, stem water storage and root water uptake during a 2‐week dry‐down period for two species with contrasting plant hydraulic behaviors, i.e., the “cavitation risk‐averse” red maple and the “cavitation risk‐prone” red oak. Sensitivity experiments with plant hydraulic capacitance show that the stem water storage enables nocturnal plant water recharge, affects plant water use efficiency, and provides an important buffer to relieve xylem hydraulic stress during dry soil conditions.

【 授权许可】

Unknown