EGU2020-16180, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-16180
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Revealing the bark water uptake of isotopically-enriched water by intact branches in the field and its potential contribution (or consequences) to (or for) transpiration estimates

Teresa Gimeno1,2, Noelia Saavedra3, Adrià Barbeta4, Zsofia R. Stangl3, José-Ignacio García-Plazaola5, Lisa Wingate6, and John D. Marshall3
Teresa Gimeno et al.
  • 1Basque Centre for Climate Change, Leioa, Spain (teresa.gimeno@bc3research.org)
  • 2Ikerbasque, Basque Foundation for Science, 48008, Bilbao, Spain
  • 3Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 907 36 Umeå, Sweden
  • 4BEECA, Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain
  • 5Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Bilbao, Spain
  • 6INRAE, UMR1391 ISPA, 33140 Villenave d’Ornon, France

In plants, the constant demand for water driven by transpiration is supplied by uptake from the soil through the roots. Alternative water-uptake pathways through the leaves and the bark have been demonstrated for some species, mainly conifers. Alternative water-uptake pathways could allow plants to complement their water supply with canopy interception, fog or dew, sources often assumed unavailable as they are lost via evaporation before they can contribute to soil water recharge. Bark water-uptake has been putatively linked to repair of xylem embolism, although this has only been demonstrated in cut branches and/or under artificial conditions. We hypothesized that besides embolism repair, bark water uptake might also contribute to maintaining the transpiration stream in upper canopy branches when the xylem water column is subject to excess negative pressure, either because temperature drops, and water viscosity increases, or under high vapour pressure deficit and low soil water availability. We used a novel labelling methodology combining online measurements of the isotope composition (δ2H and δ18O) of the transpiration stream with analyses of δ2H and δ18O from leaf, bark and xylem water in Pinus sylvestris and Fagus sylvatica. We conducted sampling campaigns in two study sites: a boreal (northern Sweden) and a temperate (northern Spain) forest. We applied semi-permeable bandages injected with 2H-enriched water (0.8% 2H2O), on intact upper canopy branches (7-13 m), and monitored δ2H and δ18O of the transpiration stream with a Cavity Ring-Down Spectrometer (CRDS) in three branches (only P. sylvestris in Sweden) for 24 h and then sampled branch segments 2 cm upstream and downstream of the bandage. We determined δ2H and δ18O of leaf, bark and xylem water from sampled segments with a CRDS after cryogenic extraction. Xylem, bark and leaf water from segments downstream of the bandage were enriched in δ2H with respect to their corresponding upstream segments. The δ2H and δ18O from leaf, bark and xylem water from upstream segments were similar to those of control branches (no bandages). Results were similar for both study species, sites and campaigns, indicating that bark water uptake is not restricted to gymnosperms and may be more ubiquitous than previously considered. Enrichment in δ2H in the transpiration stream was also detected in one out of the three continuously monitored pine branches within the 12 h following the bandage application. Our results demonstrate that water taken up through the bark may be incorporated into the transpiration stream and that transpiration might not solely rely on water absorbed through the roots and transported through the main stem. This could imply, for example, that sapflux measurements would underestimate canopy transpiration. Combining empirical flux measurements with stable isotopes and/or other atmospheric tracers could render more realistic estimates of transpiration and help constrain partitioning of evaporation and transpiration and its coupling to gross primary productivity.

How to cite: Gimeno, T., Saavedra, N., Barbeta, A., Stangl, Z. R., García-Plazaola, J.-I., Wingate, L., and Marshall, J. D.: Revealing the bark water uptake of isotopically-enriched water by intact branches in the field and its potential contribution (or consequences) to (or for) transpiration estimates, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16180, https://doi.org/10.5194/egusphere-egu2020-16180, 2020

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Display material version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-16180, Maurizio Mencuccini, 06 May 2020

    Hola Teresa,

    an excellent presentation. La pregunta mas obvia es como se compara la absorcion de las hojas con la de la corteza. Seguimos hablando. Muy interesante.
    cheers
    Maurizio

    • AC1: Reply to CC1, Teresa Gimeno, 06 May 2020

      Gracias Maurizio!

      Pues la corteza en teoria es más permeable que la cutícula de las hojas, pero en comparación con las raíces estamos en tasas de absorción 10-50 veces más bajas, pero aún lo tengo que mirar con detalle. Fue un experimento muy divertido de llevar a cabo!

      Hablamos!

      Teresa

      • CC2: Reply to AC1, Maurizio Mencuccini, 06 May 2020

        Hola Teresa

        pues la cuticula si', pero hay varias rutas de absorcion an las hojas.

        https://onlinelibrary.wiley.com/doi/abs/10.1111/pce.13663

        Tenemos que hablarlo porque' hay implicaciones de varias naturalezas que se podrian explorar.