Variation of transpiration within a canopy of silver birch: effect of canopy position and daily versus nightly water loss
Identifieur interne : 001B51 ( Main/Exploration ); précédent : 001B50; suivant : 001B52Variation of transpiration within a canopy of silver birch: effect of canopy position and daily versus nightly water loss
Auteurs : Arne Sellin [Estonie] ; Kristina Lubenets [Estonie]Source :
- Ecohydrology [ 1936-0584 ] ; 2010-12.
English descriptors
- KwdEn :
Abstract
Sap flux density (FLA) in branches of Betula pendula trees was examined with respect to environmental variables and canopy position. FLA of branches sampled within the basal and top thirds of crowns was analysed with respect to stomatal (gs), canopy (gc) and soil‐to‐leaf hydraulic conductance (KT). The canopy positions differed significantly (P < 0·001) by FLA: the day‐time values in the upper canopy were on average 1·8 times greater than in the lower canopy (59·2 vs 33·2 g m−2 h−1), associated with greater gs, gc and KT observed in the upper canopy. The differences in gc among the canopy positions resulted primarily from a ∼10‐fold greater aerodynamic boundary‐layer conductance (gbl) in the upper canopy (mean gbl was 1695 vs 161 mmol m−2 s−1, respectively) in the day time. The asymptotic nature of gs versus gc relationship observed in the lower canopy suggests that stomata limit transpiration from the shade foliage at higher gbl. The linear relationship (R2 = 0·49–0·58, P < 0·001) between KT and FLA alludes to the role of hydraulic capacity in the control of sap fluxes. The dominant environmental factor affecting FLA in the day time was irradiance, and air relative humidity at night. The strong dependence of FLA on atmospheric evaporative demand in the night time proved that nocturnal branch sap flow indeed represents transpiration, but not tissue water recharge. Nocturnal FLA was about 24·7 and 19·5% of the respective mean day‐time rates for the upper and lower canopy. Owing to short northern nights in summer, nocturnal transpiration constituted only 6–8% of the daily total water loss. The variation in branch‐level sap flow is determined not merely by environmental gradients existing within the forest canopy, but depends largely on trees' internal properties, including stomatal conductance and plant hydraulic properties. Copyright © 2010 John Wiley & Sons, Ltd.
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DOI: 10.1002/eco.133
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<record><TEI wicri:istexFullTextTei="biblStruct"><teiHeader><fileDesc><titleStmt><title xml:lang="en">Variation of transpiration within a canopy of silver birch: effect of canopy position and daily versus nightly water loss</title><author><name sortKey="Sellin, Arne" sort="Sellin, Arne" uniqKey="Sellin A" first="Arne" last="Sellin">Arne Sellin</name></author><author><name sortKey="Lubenets, Kristina" sort="Lubenets, Kristina" uniqKey="Lubenets K" first="Kristina" last="Lubenets">Kristina Lubenets</name></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:70061A23C0855BFAACB6AC1E34B1F81C7E19880E</idno><date when="2010" year="2010">2010</date><idno type="doi">10.1002/eco.133</idno><idno type="url">https://api.istex.fr/document/70061A23C0855BFAACB6AC1E34B1F81C7E19880E/fulltext/pdf</idno><idno type="wicri:Area/Istex/Corpus">001747</idno><idno type="wicri:Area/Istex/Curation">001746</idno><idno type="wicri:Area/Istex/Checkpoint">000358</idno><idno type="wicri:doubleKey">1936-0584:2010:Sellin A:variation:of:transpiration</idno><idno type="wicri:Area/Main/Merge">001B89</idno><idno type="wicri:Area/Main/Curation">001B51</idno><idno type="wicri:Area/Main/Exploration">001B51</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a" type="main" xml:lang="en">Variation of transpiration within a canopy of silver birch: effect of canopy position and daily versus nightly water loss</title><author><name sortKey="Sellin, Arne" sort="Sellin, Arne" uniqKey="Sellin A" first="Arne" last="Sellin">Arne Sellin</name><affiliation wicri:level="1"><country xml:lang="fr">Estonie</country><wicri:regionArea>Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, 51005 Tartu</wicri:regionArea><wicri:noRegion>51005 Tartu</wicri:noRegion></affiliation></author><author><name sortKey="Lubenets, Kristina" sort="Lubenets, Kristina" uniqKey="Lubenets K" first="Kristina" last="Lubenets">Kristina Lubenets</name><affiliation wicri:level="1"><country xml:lang="fr">Estonie</country><wicri:regionArea>Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, 51005 Tartu</wicri:regionArea><wicri:noRegion>51005 Tartu</wicri:noRegion></affiliation></author></analytic><monogr></monogr><series><title level="j">Ecohydrology</title><title level="j" type="abbrev">Ecohydrol.</title><idno type="ISSN">1936-0584</idno><idno type="eISSN">1936-0592</idno><imprint><publisher>John Wiley & Sons, Ltd.</publisher><pubPlace>Chichester, UK</pubPlace><date type="published" when="2010-12">2010-12</date><biblScope unit="volume">3</biblScope><biblScope unit="issue">4</biblScope><biblScope unit="page" from="467">467</biblScope><biblScope unit="page" to="477">477</biblScope></imprint><idno type="ISSN">1936-0584</idno></series><idno type="istex">70061A23C0855BFAACB6AC1E34B1F81C7E19880E</idno><idno type="DOI">10.1002/eco.133</idno><idno type="ArticleID">ECO133</idno></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">1936-0584</idno></seriesStmt></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>canopy position</term><term>daily water use</term><term>environmental factors</term><term>nightly water use</term><term>sap flux density</term><term>silver birch</term><term>transpiration</term><term>xylem sap flow</term></keywords></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">Sap flux density (FLA) in branches of Betula pendula trees was examined with respect to environmental variables and canopy position. FLA of branches sampled within the basal and top thirds of crowns was analysed with respect to stomatal (gs), canopy (gc) and soil‐to‐leaf hydraulic conductance (KT). The canopy positions differed significantly (P < 0·001) by FLA: the day‐time values in the upper canopy were on average 1·8 times greater than in the lower canopy (59·2 vs 33·2 g m−2 h−1), associated with greater gs, gc and KT observed in the upper canopy. The differences in gc among the canopy positions resulted primarily from a ∼10‐fold greater aerodynamic boundary‐layer conductance (gbl) in the upper canopy (mean gbl was 1695 vs 161 mmol m−2 s−1, respectively) in the day time. The asymptotic nature of gs versus gc relationship observed in the lower canopy suggests that stomata limit transpiration from the shade foliage at higher gbl. The linear relationship (R2 = 0·49–0·58, P < 0·001) between KT and FLA alludes to the role of hydraulic capacity in the control of sap fluxes. The dominant environmental factor affecting FLA in the day time was irradiance, and air relative humidity at night. The strong dependence of FLA on atmospheric evaporative demand in the night time proved that nocturnal branch sap flow indeed represents transpiration, but not tissue water recharge. Nocturnal FLA was about 24·7 and 19·5% of the respective mean day‐time rates for the upper and lower canopy. Owing to short northern nights in summer, nocturnal transpiration constituted only 6–8% of the daily total water loss. The variation in branch‐level sap flow is determined not merely by environmental gradients existing within the forest canopy, but depends largely on trees' internal properties, including stomatal conductance and plant hydraulic properties. Copyright © 2010 John Wiley & Sons, Ltd.</div></front></TEI><affiliations><list><country><li>Estonie</li></country></list><tree><country name="Estonie"><noRegion><name sortKey="Sellin, Arne" sort="Sellin, Arne" uniqKey="Sellin A" first="Arne" last="Sellin">Arne Sellin</name></noRegion><name sortKey="Lubenets, Kristina" sort="Lubenets, Kristina" uniqKey="Lubenets K" first="Kristina" last="Lubenets">Kristina Lubenets</name></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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