Examining evapotranspiration in a semi-arid region using stable isotopes of hydrogen and oxygen

Walker, Colin D.; Brunel, Jean-Pierre

doi:10.1016/0022-1694(90)90250-2

Cited by 64 publications

(45 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…2). In several previous studies, the Craig-Gordon evaporative enrichment model was observed to overestimate the degree of isotopic enrichment observed in leaves (1,2,14,19,20,22,24,26). There are at least three possible factors contributing to the discrepancy between the modeled and observed leaf water isotopic composition, as will be discussed below.…”

Section: Discussion Diurnal Change In Leaf Water-stable Isotopic Compmentioning

confidence: 89%

Effects of Mild Water Stress and Diurnal Changes in Temperature and Humidity on the Stable Oxygen and Hydrogen Isotopic Composition of Leaf Water in Cornus stolonifera L.

Flanagan

Ehleringer²

1991

Plant Physiol.

View full text Add to dashboard Cite

In this paper we make comparisons between the observed stable isotopic composition of leaf water and the predictions of the Craig-Gordon model of isotopic enrichment when plants (Cornus stolonifera L.) were exposed to natural, diurnal changes in temperature and humidity in a glasshouse. In addition, we determined the effects of mild water stress on the isotopic composition of leaf water. The model predicted different patterns of diurnal change for the oxygen and hydrogen isotopic composition of leaf water. The observed leaf water isotopic composition followed qualitatively similar patterns of diurnal change to those predicted by the model. At midday, however, the model always predicted a higher degree of heavy isotope enrichment than was actually observed in leaves. There was no effect of mild water stress on the hydrogen isotopic composition of leaf water. For the oxygen isotopic composition of leaf water, there was either no significant difference between control and water-stressed plants or the stressed plants had lower 6180 values, despite the enriched stem water isotopic composition observed for the stressed plants.Measurement of the carbon isotope composition of plant tissue has become an important technique for assessing the A/E3 of plants (9, 10). The relationship between A/E and plant carbon isotopic composition occurs because both are related to the ratio of leaf intercellular CO2 and atmospheric CO2 concentrations (9, 10). A/E, however, is also a function of VPD. Estimates of A/E could potentially be improved if information from carbon isotope analysis was combined with long-term information concerning VPD (9, 10).It is possible that measurements ofthe hydrogen and oxygen isotopic composition of leaf cellulose could be used to infer the long-term integrated value of VPD (10,18,21 procedure may be possible because the isotopic composition of leaf cellulose is influenced by the isotopic composition of leaf water (17,21,22). Leaf water isotopic composition is, in turn, influenced by VPD (10, 12, 13). Cellulose should contain, therefore, long-term integrated information about the short-term changes in leaf water isotopic composition that result because of variation in VPD during leaf development (10, 13). Studies have shown that the isotopic composition of plant cellulose is strongly correlated with average daytime RH during the growing season (6, 7). Although no fractionation of isotopes occurs during water uptake by plants, the stable isotopic composition of plant leaf water is altered during transpiration (13,21,25). Water vapor molecules containing the lighter isotopes of oxygen and hydrogen escape from the leaf more readily than do heavy isotope molecules, so that during transpiration, leaf water becomes enriched in heavy isotope molecules (13,17,21,25). A model of isotopic fractionation, which was originally developed by Craig and Gordon (4) for processes occurring during the evaporation of water from the ocean, has been used to model leaf water isotopic composition (5,12,13,21,22). The Crai...

show abstract

Section: Discussion Diurnal Change In Leaf Water-stable Isotopic Compmentioning

confidence: 89%

Effects of Mild Water Stress and Diurnal Changes in Temperature and Humidity on the Stable Oxygen and Hydrogen Isotopic Composition of Leaf Water in Cornus stolonifera L.

Flanagan

Ehleringer²

1991

Plant Physiol.

View full text Add to dashboard Cite

show abstract

“…Although the Craig-Gordon model basically describes water enrichment at the sites of evaporation compared with locally transpired water, it cannot adequately account for other aspects of leaf water enrichment, particularly the spatial variation of leaf water 18 O and/or D contents (Luo and Sternberg, 1992; Bariac et al, 1994;Wang and Yakir, 1995;Helliker and Ehleringer, 2000). Also, the Craig-Gordon model has often been found to overestimate the isotopic enrichment of bulk leaf water (Allison et al, 1985; Bariac et al, 1989;Walker et al, 1989;Walker and Brunel, 1990;Yakir et al, 1990;Flanagan et al, 1991aFlanagan et al, , 1991bFlanagan et al, , 1994Wang et al, 1998). To explain such observations, several other models have been suggested in conjunction with the Craig-Gordon model, namely the two-pool model (Leaney et al, 1985), the Péclet model , and the string-of-lakes model (Gat and Bowser, 1991).…”

mentioning

confidence: 99%

18O Spatial Patterns of Vein Xylem Water, Leaf Water, and Dry Matter in Cotton Leaves

et al. 2002

View full text Add to dashboard Cite

Three leaf water models (two-pool model, Péclet effect, and string-of-lakes) were assessed for their robustness in predicting leaf water enrichment and its spatial heterogeneity. This was achieved by studying the 18 O spatial patterns of vein xylem water, leaf water, and dry matter in cotton (Gossypium hirsutum) leaves grown at different humidities using new experimental approaches. Vein xylem water was collected from intact transpiring cotton leaves by pressurizing the roots in a pressure chamber, whereas the isotopic content of leaf water was determined without extracting it from fresh leaves with the aid of a purpose-designed leaf punch. Our results indicate that veins have a significant degree of lateral exchange with highly enriched leaf water. Vein xylem water is thus slightly, but progressively enriched in the direction of water flow. Leaf water enrichment is dependent on the relative distances from major veins, with water from the marginal and intercostal regions more enriched and that next to veins and near the leaf base more depleted than the Craig-Gordon modeled enrichment of water at the sites of evaporation. The spatial pattern of leaf water enrichment varies with humidity, as expected from the string-of-lakes model. This pattern is also reflected in leaf dry matter. All three models are realistic, but none could fully account for all of the facets of leaf water enrichment. Our findings acknowledge the presence of capacitance in the ground tissues of vein ribs and highlight the essential need to incorporate Péclet effects into the string-of-lakes model when applying it to leaves.The isotopic composition of leaf water reflects local humidity, and its imprints on plant cellulose and other fossil materials have been widely explored for palaeoclimatic reconstruction. To date, isotopic values of wood cellulose (Epstein et al., 1977;Yapp and Epstein, 1982;Edwards et al., 1985;Edwards and Fritz, 1986;Roden et al., 2000), grassland phytoliths (Webb and Longstaffe, 2000), and deer bone (Cormie et al., 1994) have been shown to be related to leaf water isotopic composition. Leaf water isotopic signature is not only imprinted on plant organic matter but is also recorded in atmospheric CO 2 and O 2 . The CO 2 interacts and undergoes isotopic exchange with leaf water, and O 2 is released by the plant during photosynthesis. Changes in the oxygen isotope ratios of CO 2 and O 2 can thus be used to study variations in the net exchange of CO 2 in terrestrial ecosystems and in the balance of terrestrial and marine productivity (Bender et al., 1985;Bender et al., 1994). Because all of these applications critically depend on estimation of the leaf water oxygen isotopic ratio, a good understanding of the nature of leaf water enrichment is needed.The isotopic composition of leaf water is most commonly estimated from the model of a freely evaporating water surface (Craig and Gordon, 1965) where isotopic fractionation is driven by the lower vapor pressure and diffusivity of the heavier molecules. Although the Craig-Gordon m...

show abstract

“…Allison et al, 1985;Bariac et al, 1989;Walker et al, 1989;Walker and Brunel, 1990;Yakir et al, 1990b;Flanagan et al, 1991aFlanagan et al, , 1991bFlanagan et al, , 1993Flanagan et al, , 1994Wang et al, 1998), and there have been two main approaches taken to explain this discrepancy. The first, proposed by White (1983), suggested that leaf water is divided into at least two pools, only one of which is exposed to evaporation.…”

mentioning

confidence: 99%

Variation in the Oxygen Isotope Ratio of Phloem Sap Sucrose from Castor Bean. Evidence in Support of the Péclet Effect

et al. 2000

View full text Add to dashboard Cite

Theory suggests that the level of enrichment of 18 O above source water in plant organic material (⌬) may provide an integrative indicator of control of water loss. However, there are still gaps in our understanding of the processes affecting ⌬. One such gap is the observed discrepancy between modeled enrichment of water at the sites of evaporation within the leaf and measured enrichment of the leaf water as a whole (⌬ L ). Farquhar and Lloyd (1993) suggested that this may be caused by a Péclet effect. It is also unclear whether organic material formed in the leaf reflects enrichment of water at the sites of evaporation within the leaf or ⌬ L . To investigate this question castor bean (Ricinus communis L.) leaves, still attached to the plant, were sealed into a controlled-environment gas exchange chamber and subjected to a step change in leaf-to-air vapor pressure difference. Sucrose was collected from a cut on the petiole of the leaf in the chamber under equilibrium conditions and every hour for 6 h after the change in leaf-to-air vapor pressure difference. Oxygen isotope composition of sucrose in the phloem sap (⌬ suc ) reflected modeled ⌬ L . A model is presented describing ⌬ suc at isotopic steady state, and accounts for 96% of variation in measured ⌬ suc . The data strongly support the Péclet effect theory.

show abstract

Examining evapotranspiration in a semi-arid region using stable isotopes of hydrogen and oxygen

Cited by 64 publications

References 23 publications

Effects of Mild Water Stress and Diurnal Changes in Temperature and Humidity on the Stable Oxygen and Hydrogen Isotopic Composition of Leaf Water in Cornus stolonifera L.

Effects of Mild Water Stress and Diurnal Changes in Temperature and Humidity on the Stable Oxygen and Hydrogen Isotopic Composition of Leaf Water in Cornus stolonifera L.

18O Spatial Patterns of Vein Xylem Water, Leaf Water, and Dry Matter in Cotton Leaves

Variation in the Oxygen Isotope Ratio of Phloem Sap Sucrose from Castor Bean. Evidence in Support of the Péclet Effect

Contact Info

Product

Resources

About