Eagleson’s optimality theory of an ecohydrological equilibrium: quo vadis?

Hatton, Tom; Salvucci, Guido D.; Wu, Hsin‐I

doi:10.1046/j.1365-2435.1997.00159.x

Cited by 68 publications

(65 citation statements)

References 106 publications

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“…They thus reflect short-to mid-term acclimation of leaf area to water availability following Eagleson [15] and Hatton et al [25]. For longer time scales, changes in species composition may be observed that are beyond the scope of this study [23,44].…”

Section: Relating Water Availability and Laimentioning

confidence: 65%

An examination of the interaction between climate, soil and leaf area index in a Quercus ilex ecosystem

Hoff

Rambal

2003

Ann. For. Sci.

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-In Mediterranean-type ecosystems, water availability is one of the most significant variables that regulates whole plant leaf area. An equilibrium should exist between climate, soil and leaf area in such water-limited conditions. The aim of this study was to identify the relations between leaf area index (LAI), environment (climate, soil) and fluxes (water, carbon) in Mediterranean evergreen oak (Quercus ilex L.) ecosystems. To achieve this objective, 50-years simulations were performed using the FOREST-BGC model by varying LAI for a reference site and for different climates and soil water holding capacities (SWC). Transpiration, drought stress, net photosynthesis and canopy water use efficiency (WUE) were examined on a yearly basis for the last ten years of the simulation. Similar to other findings, our results show that LAI depends on site water availability, including both climate (precipitation, potential evapotranspiration) and soil factors (e.g. water storage capacity). Low SWC limit the development of the ecosystem. On high SWC soils, development is mainly limited by the climate. When LAI increases under constant SWC and climate conditions, the decrease in annual transpiration per unit of LAI is accompanied by an increase in drought stress. Equilibrium LAI maximizes carbon assimilation. For the reference site, the equilibrium LAI is close to the observed value, 3.25. The corresponding transpiration, assimilation and WUE are 375 mm, 1251 g C m -2 and 3.1 mmol CO 2 mol -1 H 2 O, respectively. For the different sites, there is an hyperbolic decline of WUE with increasing SWC. This implies that production efficiency per unit leaf area is higher in most water-limited environments. Our study shows that a model such as FOREST-BGC allows inter-relations between water balance, carbon balance and drought stress to be taken into account to better understand ecosystem LAI.leaf area index / hydrological equilibrium / water availability / climate / soil factor / Mediterranean-type ecosystem / Quercus ilex L. / evergreen oak Résumé -Interactions entre climat, sol et surface foliaire dans un écosystème à Quercus ilex. Dans les écosystèmes méditerranéens, la disponibilité en eau est une des variables les plus significatives qui régulent la surface foliaire. Un équilibre doit exister entre le climat, le sol et la surface foliaire dans ces conditions de limitation en eau. L'objectif de cette étude est d'identifier les relations entre l'indice foliaire (LAI), l'environnement (climat, sol) et les flux (eau, carbone) pour les écosystèmes à chêne sempervirent méditerranéen Quercus ilex L. Pour cela, des simulations de 50 ans ont été effectuées avec le modèle FOREST-BGC en faisant varier le LAI pour un site de référence et pour différents climats et capacités en eau du sol (SWC). La transpiration, la contrainte hydrique, la photosynthèse nette et l'efficacité d'utilisation de l'eau de la canopée (WUE) ont été examinées au niveau annuel pour les dix dernières années de la simulation. Le LAI dépend de la disponibilité en...

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Section: Relating Water Availability and Laimentioning

confidence: 65%

An examination of the interaction between climate, soil and leaf area index in a Quercus ilex ecosystem

Hoff

Rambal

2003

Ann. For. Sci.

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“…Second, as the timescales get longer, the species whose potential transpiration efficiency make the soil moisture highest will be selected through natural selection. Third, the soil properties will be altered to ensure the species get their maximum canopy cover (Eagleson, 2002;Hatton et al, 1997). These hypotheses mentioned two important canopy state variables, i.e., the canopy cover (M) and canopy conductance (k v ).…”

Section: Methodsmentioning

confidence: 99%

“…The optimality theory provides a new way to explore the quantitative relationship between vegetation and climate factors. Despite the fact that Eagleson's work is regarded as the basis for ecohydrology and is of great importance (Hatton et al, 1997;Kerkhoff et al, 2004), limited studies have been conducted using the theory in practice (Shao et al, 2011;Mo et al, 2015), which is partly due to the limitation of longterm temporal scale, partly due to the difficulty to measure vegetation characteristics. In Eagleson's ecohydrological optimality theory, the optimal canopy cover (M * ) is determined by the trade-off between water supply depending on water balance and water demand depending on canopy transpiration.…”

Section: Introductionmentioning

confidence: 99%

Ecohydrological optimality in the Northeast China Transect

Cong

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. The Northeast China Transect (NECT) is one of the International Geosphere-Biosphere Program (IGBP) terrestrial transects, where there is a significant precipitation gradient from east to west, as well as a vegetation transition of forest-grassland-desert. It is remarkable to understand vegetation distribution and dynamics under climate change in this transect. We take canopy cover (M), derived from Normalized Difference Vegetation Index (NDVI), as an index to describe the properties of vegetation distribution and dynamics in the NECT. In Eagleson's ecohydrological optimality theory, the optimal canopy cover (M * ) is determined by the trade-off between water supply depending on water balance and water demand depending on canopy transpiration. We apply Eagleson's ecohydrological optimality method in the NECT based on data from 2000 to 2013 to get M * , which is compared with M from NDVI to further discuss the sensitivity of M * to vegetation properties and climate factors. The result indicates that the average M * fits the actual M well (for forest, M * = 0.822 while M = 0.826; for grassland, M * = 0.353 while M = 0.352; the correlation coefficient between M and M * is 0.81). Results of water balance also match the field-measured data in the references. The sensitivity analyses show that M * decreases with the increase of leaf area index (LAI), stem fraction and temperature, while it increases with the increase of leaf angle and precipitation amount. Eagleson's ecohydrological optimality method offers a quantitative way to understand the impacts of climate change on canopy cover and provides guidelines for ecorestoration projects.

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“…At longer time scales (i.e. over many generations), species will be selected whose potential transpiration efficiency results in the maximum equilibrium soil moisture and over evolutionary time scales, vegetation will alter soil physical properties towards equilibrium values which maximises canopy density (Eagleson, 1982;Eagleson and Tellers, 1982;Hatton et al, 1997). The framework predicts a close coupling between canopy structure and water availability.…”

Section: Introductionmentioning

confidence: 99%

“…The framework predicts a close coupling between canopy structure and water availability. Although, Kerkhoff et al (2004) criticised the ecological optimality theory as proposed, in particular the assumption that soil water availability would be maximised, it has also been argued that ecological optimality potentially provides a useful underpinning framework for the emerging field of ecohydrology (Hatton et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Can we predict groundwater discharge from terrestrial ecosystems using existing eco-hydrological concepts?

O’Grady

Carter

Bruce

2011

Hydrol. Earth Syst. Sci.

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Abstract. There is increasing recognition of the role that groundwater plays in the maintenance of ecosystem structure and function. As a result, water resources planners need to develop an understanding of the water requirements for these ecosystems. In this study we reviewed estimates of groundwater discharge from terrestrial vegetation communities around Australia and explored this data set for empirical relationships that could be used to predict groundwater discharge in data poor areas. In particular we explored how leaf area index and the water balance of groundwater systems conformed to two existing ecohydrological frameworks; the Budyko framework, which describes the partitioning of rainfall into evapotranspiration and runoff within a simple supply and demand framework, and Eagleson's theory of ecological optimality. We demonstrate strong convergence with the predictions of both frameworks. Terrestrial groundwater systems discharging groundwater lie above the water limit line as defined in the Budyko framework. However, when climate wetness was recalculated to include groundwater discharge there was remarkable convergence of these sites along this water limit line. Thus, we found that there was a strong correlation between estimates of evapotranspiration derived from the Budyko's relationship with observed estimates of evapotranspiration. Similarly, the LAI of ecosystems with access to groundwater have higher LAI than those without access to groundwater, for a given climatic regime. However, again when discharge was included in the calculation of climate Correspondence to: A. P. O'Grady (anthony.ogrady@csiro.au) wetness index there was again strong convergence between the two systems, providing support for ecological optimality frameworks that maximize LAI under given water availability regimes. The simplicity and utility of these simple ecohydrological insights potentially provide a valuable tool for predicting groundwater discharge from terrestrial ecosystems, especially in data poor areas.

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Eagleson’s optimality theory of an ecohydrological equilibrium: quo vadis?

Cited by 68 publications

References 106 publications

An examination of the interaction between climate, soil and leaf area index in a Quercus ilex ecosystem

An examination of the interaction between climate, soil and leaf area index in a Quercus ilex ecosystem

Ecohydrological optimality in the Northeast China Transect

Can we predict groundwater discharge from terrestrial ecosystems using existing eco-hydrological concepts?

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