Storage and transpiration have negligible effects on delta13C of stem CO2 efflux in large conifer trees

N UBIERNA, A KUMAR, Lucas Cernusak, R PANGLE, P GAG, J MARSHALL

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    Stem respiration rates are often quantified by measuring the CO2 efflux from stems into chambers. It has been suggested that these measurements underestimate respiration because some of the respired CO2 can be either retained or transported upwards in the transpiration stream. If the stem CO2 efflux does not represent all respired CO2, then the interpretation of its isotopic signal may be compromised as well. The C-isotope composition of the respired CO2 and the measured efflux could differ due to (i) the release of CO2 produced elsewhere into the stem and transported upwards in xylem water (soil CO2 or root respired CO 2); (ii) the retention or release of CO2 storage pools within the tree stem and (iii) the removal of CO2 by the transpiration stream. We investigated the effects of these processes in large conifer trees using two manipulative experiments: a labelling experiment and a crown removal experiment. The labelling experiment used an extreme enrichment of dissolved CO2 in soil water to assess the C uptake by the roots. In this experiment, we found no contamination of the stem CO2 pool despite clear evidence that the water itself had been taken up. The crown removal experiment tested for vertical CO2 flux in xylem water by eliminating transpiration. Here, we found no change in the ?13C of stem CO2 efflux (?EA; P > 0.05). We concluded that for these large conifers, sap-flow influenced neither ?13C of stem efflux nor that of the stem CO2 pool. By parameterizing Henry's Law for conditions inside the stem, we estimated the transport flux to represent 13% of the stem CO 2 efflux to the atmosphere. Finally, assuming a 2� difference between ?13C of root and stem respiration, we estimated that potential contamination of ?EA by root respired CO2 would be < 0.1�. Thus, neither the release of soil or root CO2, nor storage in the stem, nor vertical transport of CO2 in the xylem sap had any detectable influence on ?13C of the CO2 measured in stem efflux.
    Original languageEnglish
    Pages (from-to)1563-1574
    Number of pages12
    JournalTree Physiology
    Volume29
    Issue number12
    Publication statusPublished - 2009

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    Coniferophyta
    Xylem
    conifers
    transpiration
    carbon dioxide
    stems
    Soil
    Water
    Carbon Monoxide
    Crowns
    Respiration
    Respiratory Rate
    Atmosphere
    Isotopes
    xylem
    tree crown
    soil water
    dissolved carbon dioxide

    Cite this

    UBIERNA, N., KUMAR, A., Cernusak, L., PANGLE, R., GAG, P., & MARSHALL, J. (2009). Storage and transpiration have negligible effects on delta13C of stem CO2 efflux in large conifer trees. Tree Physiology, 29(12), 1563-1574.
    UBIERNA, N ; KUMAR, A ; Cernusak, Lucas ; PANGLE, R ; GAG, P ; MARSHALL, J. / Storage and transpiration have negligible effects on delta13C of stem CO2 efflux in large conifer trees. In: Tree Physiology. 2009 ; Vol. 29, No. 12. pp. 1563-1574.
    @article{643c690bf6134ca4a8c3cb1537e9ef2a,
    title = "Storage and transpiration have negligible effects on delta13C of stem CO2 efflux in large conifer trees",
    abstract = "Stem respiration rates are often quantified by measuring the CO2 efflux from stems into chambers. It has been suggested that these measurements underestimate respiration because some of the respired CO2 can be either retained or transported upwards in the transpiration stream. If the stem CO2 efflux does not represent all respired CO2, then the interpretation of its isotopic signal may be compromised as well. The C-isotope composition of the respired CO2 and the measured efflux could differ due to (i) the release of CO2 produced elsewhere into the stem and transported upwards in xylem water (soil CO2 or root respired CO 2); (ii) the retention or release of CO2 storage pools within the tree stem and (iii) the removal of CO2 by the transpiration stream. We investigated the effects of these processes in large conifer trees using two manipulative experiments: a labelling experiment and a crown removal experiment. The labelling experiment used an extreme enrichment of dissolved CO2 in soil water to assess the C uptake by the roots. In this experiment, we found no contamination of the stem CO2 pool despite clear evidence that the water itself had been taken up. The crown removal experiment tested for vertical CO2 flux in xylem water by eliminating transpiration. Here, we found no change in the ?13C of stem CO2 efflux (?EA; P > 0.05). We concluded that for these large conifers, sap-flow influenced neither ?13C of stem efflux nor that of the stem CO2 pool. By parameterizing Henry's Law for conditions inside the stem, we estimated the transport flux to represent 13{\%} of the stem CO 2 efflux to the atmosphere. Finally, assuming a 2� difference between ?13C of root and stem respiration, we estimated that potential contamination of ?EA by root respired CO2 would be < 0.1�. Thus, neither the release of soil or root CO2, nor storage in the stem, nor vertical transport of CO2 in the xylem sap had any detectable influence on ?13C of the CO2 measured in stem efflux.",
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    author = "N UBIERNA and A KUMAR and Lucas Cernusak and R PANGLE and P GAG and J MARSHALL",
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    language = "English",
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    UBIERNA, N, KUMAR, A, Cernusak, L, PANGLE, R, GAG, P & MARSHALL, J 2009, 'Storage and transpiration have negligible effects on delta13C of stem CO2 efflux in large conifer trees', Tree Physiology, vol. 29, no. 12, pp. 1563-1574.

    Storage and transpiration have negligible effects on delta13C of stem CO2 efflux in large conifer trees. / UBIERNA, N; KUMAR, A; Cernusak, Lucas; PANGLE, R; GAG, P; MARSHALL, J.

    In: Tree Physiology, Vol. 29, No. 12, 2009, p. 1563-1574.

    Research output: Contribution to journalArticleResearchpeer-review

    TY - JOUR

    T1 - Storage and transpiration have negligible effects on delta13C of stem CO2 efflux in large conifer trees

    AU - UBIERNA, N

    AU - KUMAR, A

    AU - Cernusak, Lucas

    AU - PANGLE, R

    AU - GAG, P

    AU - MARSHALL, J

    PY - 2009

    Y1 - 2009

    N2 - Stem respiration rates are often quantified by measuring the CO2 efflux from stems into chambers. It has been suggested that these measurements underestimate respiration because some of the respired CO2 can be either retained or transported upwards in the transpiration stream. If the stem CO2 efflux does not represent all respired CO2, then the interpretation of its isotopic signal may be compromised as well. The C-isotope composition of the respired CO2 and the measured efflux could differ due to (i) the release of CO2 produced elsewhere into the stem and transported upwards in xylem water (soil CO2 or root respired CO 2); (ii) the retention or release of CO2 storage pools within the tree stem and (iii) the removal of CO2 by the transpiration stream. We investigated the effects of these processes in large conifer trees using two manipulative experiments: a labelling experiment and a crown removal experiment. The labelling experiment used an extreme enrichment of dissolved CO2 in soil water to assess the C uptake by the roots. In this experiment, we found no contamination of the stem CO2 pool despite clear evidence that the water itself had been taken up. The crown removal experiment tested for vertical CO2 flux in xylem water by eliminating transpiration. Here, we found no change in the ?13C of stem CO2 efflux (?EA; P > 0.05). We concluded that for these large conifers, sap-flow influenced neither ?13C of stem efflux nor that of the stem CO2 pool. By parameterizing Henry's Law for conditions inside the stem, we estimated the transport flux to represent 13% of the stem CO 2 efflux to the atmosphere. Finally, assuming a 2� difference between ?13C of root and stem respiration, we estimated that potential contamination of ?EA by root respired CO2 would be < 0.1�. Thus, neither the release of soil or root CO2, nor storage in the stem, nor vertical transport of CO2 in the xylem sap had any detectable influence on ?13C of the CO2 measured in stem efflux.

    AB - Stem respiration rates are often quantified by measuring the CO2 efflux from stems into chambers. It has been suggested that these measurements underestimate respiration because some of the respired CO2 can be either retained or transported upwards in the transpiration stream. If the stem CO2 efflux does not represent all respired CO2, then the interpretation of its isotopic signal may be compromised as well. The C-isotope composition of the respired CO2 and the measured efflux could differ due to (i) the release of CO2 produced elsewhere into the stem and transported upwards in xylem water (soil CO2 or root respired CO 2); (ii) the retention or release of CO2 storage pools within the tree stem and (iii) the removal of CO2 by the transpiration stream. We investigated the effects of these processes in large conifer trees using two manipulative experiments: a labelling experiment and a crown removal experiment. The labelling experiment used an extreme enrichment of dissolved CO2 in soil water to assess the C uptake by the roots. In this experiment, we found no contamination of the stem CO2 pool despite clear evidence that the water itself had been taken up. The crown removal experiment tested for vertical CO2 flux in xylem water by eliminating transpiration. Here, we found no change in the ?13C of stem CO2 efflux (?EA; P > 0.05). We concluded that for these large conifers, sap-flow influenced neither ?13C of stem efflux nor that of the stem CO2 pool. By parameterizing Henry's Law for conditions inside the stem, we estimated the transport flux to represent 13% of the stem CO 2 efflux to the atmosphere. Finally, assuming a 2� difference between ?13C of root and stem respiration, we estimated that potential contamination of ?EA by root respired CO2 would be < 0.1�. Thus, neither the release of soil or root CO2, nor storage in the stem, nor vertical transport of CO2 in the xylem sap had any detectable influence on ?13C of the CO2 measured in stem efflux.

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    KW - carbon dioxide

    KW - deuterium

    KW - carbon flux

    KW - carbon isotope

    KW - carbon sequestration

    KW - coniferous tree

    KW - isotopic composition

    KW - parameterization

    KW - sap flow

    KW - soil water

    KW - xylem

    KW - article

    KW - conifer

    KW - metabolism

    KW - transport at the cellular level

    KW - Biological Transport

    KW - Carbon

    KW - Carbon Dioxide

    KW - Carbon Isotopes

    KW - Coniferophyta

    KW - Deuterium

    M3 - Article

    VL - 29

    SP - 1563

    EP - 1574

    JO - Tree Physiology

    JF - Tree Physiology

    SN - 0829-318X

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    ER -

    UBIERNA N, KUMAR A, Cernusak L, PANGLE R, GAG P, MARSHALL J. Storage and transpiration have negligible effects on delta13C of stem CO2 efflux in large conifer trees. Tree Physiology. 2009;29(12):1563-1574.