Modelling tree stem‐water dynamics over an Amazonian rainforest

Yan, Binyan; Mao, Jiafu; Dickinson, Robert E.; Thornton, P. E.; Shi, Xiaoying; Ricciuto, Daniel M.; Warren, Jeffrey M.; Hoffman, Forrest M.

doi:10.1002/eco.2180

Cited by 11 publications

(15 citation statements)

References 44 publications

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“…Besides the resistor, RCMs also consider plant water storage or capacitance, e.g., the schemes developed by Sperry et al (1998), Steppe et al (2006), Gentine et al (2016), andXu et al (2016). The hydraulic capacitance, especially for large trees, has been demonstrated by field observation to play a critical role in regulating transpiration at both short-term and long-term scales (Matheny et al, 2015;Yan et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, these models can describe in detail the spatiotemporal dynamics of a tree's hydraulic system, but at the cost of substantial computational and parametric demands. The architecture of PMMs ranges from single beam (stem only) models (Chuang et al, 2006;Mirfenderesgi et al, 2016Mirfenderesgi et al, , 2019Yan et al, 2020), to the FETCH model with a three-dimensional stem and branch structure (Bohrer et al, 2005), to the Xylem Water Flow (XWF) model including root, stem, and branches (Bittner et al, 2012;Janott et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

“…This PHS considers plant water storage in the stem and leaves. Biomass hydraulic capacitance regulates water economy and tree function on time scales ranging from diel to seasonal (Yan et al, 2020), by maintaining daily transpiration, buffering drought impacts on xylem embolism and consequent hydraulic failure, and supporting leaf growth in the dry season for seasonally deciduous trees (Goldstein et al, 1998;Huang et al, 2017;Meinzer, 2003).…”

Section: Plant Hydraulics Scheme For Noah-mpmentioning

confidence: 99%

“…Given the advancements in theory development, physics-based models, and data availability (e.g., in situ plant hydraulic traits and vegetation water status-related remote-sensing observations), mechanistic representations of plant hydraulic processes are increasingly being incorporated into LSMs to improve water and carbon simulations (Christoffersen et al, 2016;Eller et al, 2020;Hickler et al, 2006;Kennedy et al, 2019;Luo et al, 2013;Yan et al, 2020). One of the earliest examples for considering plant hydraulics in LSMs dates back to the work of Sellers et al (1986); they employed "leaf water potential" in describing the Simple Biosphere (SiB) model, although SiB did not account for stem hydraulic capacitance.…”

Section: Introductionmentioning

confidence: 99%

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

Yang

Matheny

et al. 2021

J Adv Model Earth Syst

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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 leaflevel 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 riskaverse" 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.Plain Language Summary Plants regulate transpiration dynamically through the stomatal aperture, which, in many cases, is governed by plant water status and hydraulic properties. Plant hydraulics describes the mechanics of water movement through plant vascular systems, which is the culmination of emergent phenotypical hydraulic functional traits at the leaf, stem, and root levels. Such physiological mechanisms are excluded in most land surface models, which typically represent plant water stress through empirical soil hydraulics schemes (SHSs) based on either soil water content or soil water potential. In this study, we present a novel plant hydraulics scheme (PHS) to represent plant water stress and the regulation of stomatal conductance for use in the Noah-MP land surface model. Our results show Noah-MP-PHS performs better in its water and carbon simulations than the default Noah-MP with traditional SHSs, especially under dry soil conditions. Noah-MP-PHS also successfully captures the different plant hydraulic behaviors between the "cavitation risk-averse" red maple and the "cavitation risk-prone" red oak. Sensitivity experiments also highlight the vital role played by plant water storage in water and carbon simulations in terms of buffering xylem hydraulic stress during soil moisture dry-down periods. The ...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Plant Hydraulics Scheme For Noah-mpmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Yang

Matheny

et al. 2021

J Adv Model Earth Syst

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“…(3) LSMs may have difficulties simulating access to soil water at clay soils (e.g., K67) and although some recent model improvements have addressed this issue (e.g., ED2; see Longo, Knox, Levine, et al, 2019), measurements of field capacity and hydraulic conductivity were unavailable at our and other similar study sites. (4) To accurately estimate transpiration may require to include processes related to plant hydraulics, like the addition of stem‐water and other additional storage terms (e.g., CLM5; see Yan et al, 2020). (5) The time of rainfall, precipitation intensity, and number of events (here we report significant differences among forest sites), rather than absolute precipitation values, may significantly influence the H /LE partition.…”

Section: Discussionmentioning

confidence: 99%

Understanding water and energy fluxes in the Amazonia: Lessons from an observation‐model intercomparison

Restrepo‐Coupe

Albert

Longo

et al. 2021

Global Change Biology

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Tropical forests are an important part of global water and energy cycles, but the mechanisms that drive seasonality of their land‐atmosphere exchanges have proven challenging to capture in models. Here, we (1) report the seasonality of fluxes of latent heat (LE), sensible heat (H), and outgoing short and longwave radiation at four diverse tropical forest sites across Amazonia—along the equator from the Caxiuanã and Tapajós National Forests in the eastern Amazon to a forest near Manaus, and from the equatorial zone to the southern forest in Reserva Jaru; (2) investigate how vegetation and climate influence these fluxes; and (3) evaluate land surface model performance by comparing simulations to observations. We found that previously identified failure of models to capture observed dry‐season increases in evapotranspiration (ET) was associated with model overestimations of (1) magnitude and seasonality of Bowen ratios (relative to aseasonal observations in which sensible was only 20%–30% of the latent heat flux) indicating model exaggerated water limitation, (2) canopy emissivity and reflectance (albedo was only 10%–15% of incoming solar radiation, compared to 0.15%–0.22% simulated), and (3) vegetation temperatures (due to underestimation of dry‐season ET and associated cooling). These partially compensating model‐observation discrepancies (e.g., higher temperatures expected from excess Bowen ratios were partially ameliorated by brighter leaves and more interception/evaporation) significantly biased seasonal model estimates of net radiation (Rn), the key driver of water and energy fluxes (LE ~ 0.6 Rn and H ~ 0.15 Rn), though these biases varied among sites and models. A better representation of energy‐related parameters associated with dynamic phenology (e.g., leaf optical properties, canopy interception, and skin temperature) could improve simulations and benchmarking of current vegetation–atmosphere exchange and reduce uncertainty of regional and global biogeochemical models.

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SurEau: a mechanistic model of plant water relations under extreme drought

Cochard

Pimont

Ruffault

et al. 2021

Annals of Forest Science

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Key message A new process-based model,SurEau, is described. It predicts the risk of xylem hydraulic failure under drought. Context The increase in drought intensity due to climate change will accentuate the risk of tree mortality. But very few process-based models are currently able to predict this mortality risk. Aims We describe the operating principle of a new mechanistic model SurEau that computes the water balance, water relations, and hydraulics of a plant under extreme drought. Methods SurEau is based on the formalization of key physiological processes of plant response to water stress. The hydraulic and hydric functioning of the plant is at the core of this model, which focuses on both water flows (i.e., hydraulic) and water pools (i.e., hydric) using variable hydraulic conductances. The model considers the elementary flow of water from the soil to the atmosphere through different plant organs that are described by their symplasmic and apoplasmic compartments. For each organ, the symplasm is described by a pressure-volume curve and the apoplasm by its vulnerability curve to cavitation. The model is evaluated on mature oak trees exposed to water stress. Results On the tested oak trees, the model captures well the observed soil water balance, water relations, and level of embolism. A sensitivity analysis reveals that the level of embolism is strongly determined by air VPD and key physiological traits such as cuticular transpiration, resistance to cavitation, and leaf area. Conclusion The process-based SurEau model offers new opportunities to evaluate how different species or genotypes will respond to future climatic conditions.

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Modelling tree stem‐water dynamics over an Amazonian rainforest

Abstract: This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Cited by 11 publications

References 44 publications

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

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

Understanding water and energy fluxes in the Amazonia: Lessons from an observation‐model intercomparison

SurEau: a mechanistic model of plant water relations under extreme drought

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