Transpiration rate relates to within‐ and across‐species variations in effective path length in a leaf water model of oxygen isotope enrichment

Song, Xin; Barbour, Margaret M.; Farquhar, Graham D.; Vann, David R.; Helliker, Brent R.

doi:10.1111/pce.12063

Cited by 96 publications

(163 citation statements)

References 52 publications

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“…On the other hand, an increase in transpiration due to an increase in the energy load absorbed in the mesophyll reduces the peristomatal fraction, as the resulting increase in the temperature gradient shifts the balance of molecular transport toward the vapor phase. As the latter effect is more likely to be important in driving E on diurnal time scales, the resulting shifts in evaporation sites may help explain the inverse relationship in oxygen isotope studies of leaf water between transpiration and the effective pathlength from the veins to the sites of evaporation (Song et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

The Competition between Liquid and Vapor Transport in Transpiring Leaves

2014

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In leaves, the transpirational flux of water exits the veins as liquid and travels toward the stomata in both the vapor and liquid phases before exiting the leaf as vapor. Yet, whether most of the evaporation occurs from the vascular bundles (perivascular), from the photosynthetic mesophyll cells, or within the vicinity of the stomatal pore (peristomatal) remains in dispute. Here, a onedimensional model of the competition between liquid and vapor transport is developed from the perspective of nonisothermal coupled heat and water molecule transport in a composite medium of airspace and cells. An analytical solution to the model is found in terms of the energy and transpirational fluxes from the leaf surfaces and the absorbed solar energy load, leading to mathematical expressions for the proportions of evaporation accounted for by the vascular, mesophyll, and epidermal regions. The distribution of evaporation in a given leaf is predicted to be variable, changing with the local environment, and to range from dominantly perivascular to dominantly peristomatal depending on internal leaf architecture, with mesophyll evaporation a subordinate component. Using mature red oak (Quercus rubra) trees, we show that the model can be solved for a specific instance of a transpiring leaf by combining gas-exchange data, anatomical measurements, and hydraulic experiments. We also investigate the effect of radiation load on the control of transpiration, the potential for condensation on the inside of an epidermis, and the impact of vapor transport on the hydraulic efficiency of leaf tissue outside the xylem.

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Section: Discussionmentioning

confidence: 99%

The Competition between Liquid and Vapor Transport in Transpiring Leaves

2014

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“…As such, the isotopic difference between δ 2 H terr and δ 2 H aq (ε terr-aq ) can be attributed to mean leaf water evaporative 2 H enrichment ( 2 H e ) (Sachse et al, 2004). Based on recent field and greenhouse studies we further assume that ε terr-aq captures a growing season signal, probably biased towards the earlier summer months in temperate climate zones as the majority of leaf waxes are produced during leaf development, with suggested integration periods of somewhere between weeks (Kahmen et al, 2013b;Tipple et al, 2013) and several months (Sachse et al, 2015).…”

Section: Approach and Modelmentioning

confidence: 92%

“…Variations in the Péclet effect are minimal over time, in particular for angiosperm species Song et al, 2013) Concentration of produced nalkanes from monocots and dicots are almost equal Both of our vegetation correction approaches assume that palynological reconstructions are representative of leaf-wax-producing plants and that both monocots and dicots produce similar quantities of n-alkanes.…”

Section: O Rach Et Al: a Dual-biomarker Approach For Quantificationmentioning

confidence: 99%

“…4) (Kahmen et al, 2011b). However, we did not include the Péclet effect in our calculations because we assume that variations in the Péclet effect are minimal over time Song et al, 2013), in particular for angiosperm species.…”

Section: Approach and Modelmentioning

confidence: 99%

“…The Hijkermeer record is interpreted as a record of mean July temperatures for western Europe with a mean error of about 1.59 • C (Heiri et al, 2007). Since leaf wax synthesis most likely occurs during the early part of the growing season (spring and summer) (Kahmen et al, 2011a;Sachse et al, 2015;Tipple et al, 2013), the Hijkermeer record might slightly overestimate spring temperatures. However, when reconstructing RH during the Younger Dryas, it is important that paleotemperature data capture the changes in temperature before and during that period, rather than absolute temperatures.…”

Section: Sensitivity Testsmentioning

confidence: 99%

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A dual-biomarker approach for quantification of changes in relative humidity from sedimentary lipid <i>D</i>∕<i>H</i> ratios

et al. 2017

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Abstract. Past climatic change can be reconstructed from sedimentary archives by a number of proxies. However, few methods exist to directly estimate hydrological changes and even fewer result in quantitative data, impeding our understanding of the timing, magnitude and mechanisms of hydrological changes.Here we present a novel approach based on δ 2 H values of sedimentary lipid biomarkers in combination with plant physiological modeling to extract quantitative information on past changes in relative humidity. Our initial application to an annually laminated lacustrine sediment sequence from western Europe deposited during the Younger Dryas cold period revealed relative humidity changes of up to 15 % over sub-centennial timescales, leading to major ecosystem changes, in agreement with palynological data from the region. We show that by combining organic geochemical methods and mechanistic plant physiological models on well characterized lacustrine archives it is possible to extract quantitative ecohydrological parameters from sedimentary lipid biomarker δ 2 H data.

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Temporal dynamics of oxygen isotope compositions of soil and canopy CO₂ fluxes in a temperate deciduous forest

et al. 2014

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Partitioning of CO 2 exchange into canopy (F A ) and soil (F R ) flux components is essential to improve our understanding of ecosystem processes. The stable isotope C 18 OO can be used for flux partitioning, but this approach depends on the magnitude and consistency of the isotope disequilibrium (D eq ), i.e., the difference between the isotope compositions of F R (δ A ) and F A (δ R ). In this study, high temporal resolution isotopic data were used (1) to test the suitability of existing steady state and nonsteady models to estimate H 2 18 O enrichment in a mixed forest canopy, (2) to investigate the temporal dynamics of δ A using a big-leaf parameterization, and (3) to quantify the magnitude of the C 18OO disequilibrium (D eq ) in a temperate deciduous forest throughout the growing season and to determine the sensitivity of this variable to the CO 2 hydration efficiency (θ eq ). A departure from steady state conditions was observed even at midday in this study, so the nonsteady state formulation provided better estimates of leaf water isotope composition. The dynamics of δ R was mainly driven by changes in soil water isotope composition, caused by precipitation events. Large D eq values (up to 11‰) were predicted; however, the magnitude of the disequilibrium was variable throughout the season. The magnitude of D eq was also very sensitive to the hydration efficiencies in the canopy. For this temperate forest during most of the growing season, the magnitude of D eq was inversely proportional to θ eq , due to the very negative δ R signal, which is contrary to observations for other ecosystems investigated in previous studies.

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Transpiration rate relates to within‐ and across‐species variations in effective path length in a leaf water model of oxygen isotope enrichment

Cited by 96 publications

References 52 publications

The Competition between Liquid and Vapor Transport in Transpiring Leaves

The Competition between Liquid and Vapor Transport in Transpiring Leaves

A dual-biomarker approach for quantification of changes in relative humidity from sedimentary lipid <i>D</i>∕<i>H</i> ratios

Temporal dynamics of oxygen isotope compositions of soil and canopy CO₂ fluxes in a temperate deciduous forest

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Transpiration rate relates to within‐ and across‐species variations in effective path length in a leaf water model of oxygen isotope enrichment

Cited by 96 publications

References 52 publications

The Competition between Liquid and Vapor Transport in Transpiring Leaves

The Competition between Liquid and Vapor Transport in Transpiring Leaves

A dual-biomarker approach for quantification of changes in relative humidity from sedimentary lipid &lt;i&gt;D&lt;/i&gt;∕&lt;i&gt;H&lt;/i&gt; ratios

Temporal dynamics of oxygen isotope compositions of soil and canopy CO2 fluxes in a temperate deciduous forest

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A dual-biomarker approach for quantification of changes in relative humidity from sedimentary lipid <i>D</i>∕<i>H</i> ratios

Temporal dynamics of oxygen isotope compositions of soil and canopy CO₂ fluxes in a temperate deciduous forest