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.

中文翻译：

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Noah-MP地表模型中植物水力学的表示：模型开发和多尺度评估

在未来的气候变化下，植物将面临越来越多的水分胁迫。包括Noah-MP在内的大多数陆地表面模型都采用理想化的“大叶”概念，通过经验性土壤水力学方案（SHS）响应土壤水分压力来调节水和碳通量。但是，这种方案已显示出在碳和水模拟中引起很大的不确定性。在本文中，我们提出了一种适用于Noah-MP（以下称为Noah-MP-PHS）的新型工厂液压方案（PHS），该方案采用了大树而非大叶的概念，其中考虑了整个工厂的液压策略包括根级土壤水分获取，茎级水力传导和电容，以及叶面等水度和水力电容。根据来自成熟，与默认的Noah‐MP相比，Noah‐MP‐PHS混合了密歇根大学生物站的硬木森林，可以更好地代表植物的水分胁迫并改善水和碳的模拟，尤其是在干旱土壤条件下。Noah-MP-PHS还改善了低土壤湿度条件下总初级生产的不对称diel模拟。Noah-MP-PHS能够在两个星期的干旱期中为两个物种再现不同的蒸腾模式，茎干水分存储和根系水分吸收，这两种物种具有相反的植物水力行为，即“空化风险规避”红枫。以及“易空化风险”的红橡树。利用植物水力电容进行的敏感性实验表明，茎干蓄水可实现夜间植物补水，影响植物水分利用效率，