Evaporative enrichment and time lags between delta(18)O of leaf water and organic pools in a pine stand

Romain L. Barnard*, Yann Salmon, Naomi Kodama, Karin Soergel, Jutta Holst, Heinz Rennenberg, Arthur Gessler, Nina Buchmann

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Understanding ecosystem water fluxes has gained increasing attention, as climate scenarios predict a drier environment for many parts of the world. Evaporative enrichment of (18)O (Delta(18)O) of leaf water and subsequent enrichment of plant organic matter can be used to characterize environmental and physiological factors that control evaporation, based on a recently established mechanistic model. In a Pinus sylvestris forest, we measured the dynamics of oxygen isotopic composition (delta(18)O) every 6 h for 4 d in atmospheric water vapour, xylem sap, leaf water and water-soluble organic matter in current (N) and previous year (N-1) needles, phloem sap, together with leaf gas exchange for pooled N and N-1 needles, and relevant micrometeorological variables. Leaf water delta(18)O showed strong diel periodicity, while delta(18)O in atmospheric water vapour and in xylem sap showed little variation. The Delta(18)O was consistently lower for N than for N-1 needles, possibly related to phenological stage. Modelled leaf water Delta(18)O showed good agreement with measured values when applying a non-steady state evaporative enrichment model including a Peclet effect. We determined the time lags between delta(18)O signals from leaf water to water-soluble foliar organic matter and to phloem sap at different locations down the trunk, which clearly demonstrated the relevance of considering these time-lag effects for carbon transport, source-sink and carbon flux partitioning studies.

Original languageEnglish
Pages (from-to)539-550
Number of pages12
JournalPlant, Cell and Environment
Volume30
Issue number5
DOIs
Publication statusPublished - May 2007

Keywords

  • Pinus sylvestris
  • oxygen isotopes
  • Peclet effect
  • phloem sap
  • temporal variation
  • STABLE-ISOTOPE COMPOSITION
  • FAGUS-SYLVATICA L.
  • VEIN XYLEM WATER
  • PHLOEM SAP
  • EUCALYPTUS-GLOBULUS
  • NONSTEADY STATE
  • EUROPEAN BEECH
  • DRY-MATTER
  • STOMATAL CONDUCTANCE
  • SPATIAL-PATTERNS

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