Optimal stomatal behaviour under stochastic rainfall

Lu, Yun-Ju; Duursma, Remko A.; Medlyn, Belinda E.

doi:10.1016/j.jtbi.2016.01.003

Cited by 32 publications

(45 citation statements)

References 48 publications

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“…At longer time scales where soil moisture varies substantially, much research has highlighted that λ should change over weekly, seasonal, and interannual scales dependent on drivers such as phenology and soil water potential (11,12,28,32,33,40,43,80). Indeed, empirical studies of changes in λ associated with longtime-scale changes in ψ L have revealed a wide diversity of patterns, including increasing, decreasing, and humped relationships (11,15,24,81).…”

Section: Discussionmentioning

confidence: 99%

“…For this reason, the WUEH is widely used to guard against out-of-sample behavior in the novel climates created in ecosystem models (35)(36)(37)(38)(39). Finally, several notable efforts have been made to extend WUEH to situations including soil moisture stress (11,12,28,33,(40)(41)(42) and competition (43) and to develop a theory of the value of λ over the short time scales during which it should be approximately constant and how λ should change over weeks, months, or seasons (9,11,12,28,32). However, a priori prediction of the value of λ remains challenging and no modeling study has to our knowledge shown whether or not Eq.…”

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confidence: 99%

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Optimal stomatal behavior with competition for water and risk of hydraulic impairment

Wolf

Anderegg

Pacala

2016

Proc. Natl. Acad. Sci. U.S.A.

264

311

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For over 40 y the dominant theory of stomatal behavior has been that plants should open stomates until the carbon gained by an infinitesimal additional opening balances the additional water lost times a water price that is constant at least over short periods. This theory has persisted because of its remarkable success in explaining strongly supported simple empirical models of stomatal conductance, even though we have also known for over 40 y that the theory is not consistent with competition among plants for water. We develop an alternative theory in which plants maximize carbon gain without pricing water loss and also add two features to both this and the classical theory, which are strongly supported by empirical evidence: (i) water flow through xylem that is progressively impaired as xylem water potential drops and (ii) fitness or carbon costs associated with low water potentials caused by a variety of mechanisms, including xylem damage repair. We show that our alternative carbon-maximization optimization is consistent with plant competition because it yields an evolutionary stable strategy (ESS)-species with the ESS stomatal behavior that will outcompete all others. We further show that, like the classical theory, the alternative theory also explains the functional forms of empirical stomatal models. We derive ways to test between the alternative optimization criteria by introducing a metric-the marginal xylem tension efficiency, which quantifies the amount of photosynthesis a plant will forego from opening stomatal an infinitesimal amount more to avoid a drop in water potential.biosphere-atmosphere feedbacks | carbon cycle | embolism | hydraulic vulnerability S tomata are openings in plant leaves that determine the rate of water loss and photosynthetic carbon gain by plants. The importance of stomata and the basic mechanics of what they do have been known for well over a century (1). Stomatal aperture increases with increased humidity and light, decreases with increased CO 2 (2), and decreases with desiccation (3). Most fundamentally, stomatal conductance is correlated with photosynthesis (4). Because mechanistic understanding of stomatal function is incomplete, all current ecosystem and Earth system models use empirical equations to capture the observed relationships between stomatal conductance and environmental drivers (2, 5). As a result, theories of stomatal behavior based on maximizing evolutionary fitness are critical to help avoid the risks of out-of-sample prediction inherent in empirical models (6-8).The preeminent theory of the adaptive value of stomatal behavior is that stomatal aperture should be regulated to keep marginal water use efficiency constant, at least over short periods of time:This stipulates that the benefit of increased photosynthetic rate (A) caused by a small increase in stomatal conductance to water vapor (g s ) should always equal the corresponding cost of increased evaporative water loss (E) times the carbon price of water (λ) [henceforth the water use efficiency hypothesis...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Optimal stomatal behavior with competition for water and risk of hydraulic impairment

Wolf

Anderegg

Pacala

2016

Proc. Natl. Acad. Sci. U.S.A.

264

311

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“…The multiplicity of time scales exists to both explicitly accommodate variable environmental drivers and abiotic (e.g., drainage) as well as biotic (i.e., overlapping rooting zones of adjacent plants) competition for water and optimize plant fitness (here seen as total carbon assimilated). The theoretical framework to be employed is based on the calculus of variations and dynamic optimization principles because they allow for (i) directly accounting for plant-water use strategies (i.e., aggressive vs. conservative water users), (ii) using multiple constraints (hydrologic balance, energy balance, etc...), and (iii) extending the deterministic analysis used here to a stochastic framework (at least for rainfall) using conventional approaches (Cowan, 1986;Mäkelä et al, 1996;Manzoni et al, 2013;Lu et al, 2016). Setting a "carbon value" to the terminal soil moisture content around the rooting zone at the end of the dry-down period allows mathematically assigning a plant water use strategy (Manzoni et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

A Dynamic Optimality Principle for Water Use Strategies Explains Isohydric to Anisohydric Plant Responses to Drought

Mrad

Sevanto

Domec

et al. 2019

Front. For. Glob. Change

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“…For example, Lu et al (2016) explored how m w should vary during multiple successive random droughts and predicted a roughly exponential decline in l over time during drought and a sigmoidal relationship between stomatal conductance and soil moisture, with closure accelerating at low soil water contents. Wolf et al (2016) took a different approach that avoided CF's arbitrary time interval and thereby obviated the Lagrange multiplier.…”

Section: The Co 2 Response Problemmentioning

confidence: 99%

“…More work is needed to translate the results from recent creative efforts like those of Lu et al (2016), Wolf et al (2016) and Sperry et al (2016) into analytical forms that contain no arbitrary abstractions, and whose parameters are experimentally quantifiable. The difficulty in relating CF's Lagrange multiplier to measurable biophysical and environmental parameters was, after all, a critical barrier to adoption of the CF theory, and nearly 30 years passed between Givnish's (1986) initial effort to place m w on a biophysical basis and the more recent surge of interest in this challenge (Manzoni et al, 2013;Zhou et al, 2013;Buckley et al, 2016).…”

Section: Future Directionsmentioning

confidence: 99%

Modeling Stomatal Conductance

2017

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ORCID ID: 0000-0001-7610-7136 (T.N.B.).Robust models of stomatal conductance are greatly needed to predict plant-atmosphere interactions in a changing climate and to integrate new knowledge in physiology and ecological theory. Recent years have brought major advances in the experimental and theoretical understanding underpinning both processbased and optimality-based approaches to modeling stomatal function. I review these advances, highlight areas in need of more research, and argue that these modeling approaches are poised to supersede the long-dominant empirical approach.A reliable and general model for leaf stomatal conductance (g s ) has long been one of the holy grails of plant physiology. By controlling the exchange of water and carbon dioxide between plants and the atmosphere, stomata play a central role in the regulation of leaf and plant water status and transport, photosynthesis, drought sensitivity and tolerance, competition for soil resources, and even landscape and global hydrology (Hetherington and Woodward, 2003). An integrative formal theory-a mathematical model-that links stomatal function to plant traits and environmental variables would thus have incalculable value, both for making forward predictions and for drawing inferences about the physiology and ecology of observed stomatal behavior. My aim in this article is to summarize recent progress toward such models of stomatal conductance.Stomatal conductance has historically been predicted almost exclusively using empirical or phenomenological models, such as the widely used Jarvis and Ball-Berry families of models (Jarvis, 1976;Ball et al., 1987). Such models are perfectly adequate for forward prediction in situations where their parameters can be estimated with confidence, and indeed, these models continue to inform gas exchange projections across the modeling community (e.g. Oleson et al., 2008). However, the phenomenology of stomatal behavior in seed plants is by now very well established, so little further progress is likely in the area of empirical modeling, nor is it likely worth pursuing given that empirical models cannot provide insight about the underlying controls on gas exchange, but can only summarize and project what we already know about stomata. (Some aspects of the phenomenology of stomatal behavior in nonseed plants remain unresolved, such as the responses to CO 2 and abscisic acid [e.g. Brodribb and McAdam, 2011;Chater et al., 2011;Ruszala et al., 2011;Brodribb and McAdam, 2017]; empirical models have yet to be thoroughly validated for these taxa, so progress remains possible on that front.) This article will therefore focus on process-based ("mechanistic") and goaldirected ("optimality") approaches to predicting and interpreting stomatal function.In what follows, I will very briefly review the background to each of these approaches, describe important advances over the last decade or so, and then suggest directions for continuing work. I prefer to avoid reproducing equations and instead refer readers to articles cited here...

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Optimal stomatal behaviour under stochastic rainfall

Cited by 32 publications

References 48 publications

Optimal stomatal behavior with competition for water and risk of hydraulic impairment

Optimal stomatal behavior with competition for water and risk of hydraulic impairment

A Dynamic Optimality Principle for Water Use Strategies Explains Isohydric to Anisohydric Plant Responses to Drought

Modeling Stomatal Conductance

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