Vapour pressure deficit was not a primary limiting factor for gas exchange in an irrigated, mature dryland Aleppo pine forest

Yakir Preisler*, José M. Grünzweig, Ori Ahiman, Madi Amer, Itai Oz, Xue Feng, Jonathan D. Muller, Nadine Ruehr, Eyal Rotenberg, Benjamin Birami, Dan Yakir

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Climate change is often associated with increasing vapour pressure deficit (VPD) and changes in soil moisture (SM). While atmospheric and soil drying often co-occur, their differential effects on plant functioning and productivity remain uncertain. We investigated the divergent effects and underlying mechanisms of soil and atmospheric drought based on continuous, in situ measurements of branch gas exchange with automated chambers in a mature semiarid Aleppo pine forest. We investigated the response of control trees exposed to combined soil‒atmospheric drought (low SM, high VPD) during the rainless Mediterranean summer and that of trees experimentally unconstrained by soil dryness (high SM; using supplementary dry season water supply) but subjected to atmospheric drought (high VPD). During the seasonal dry period, branch conductance (gbr), transpiration rate (E) and net photosynthesis (Anet) decreased in low-SM trees but greatly increased in high-SM trees. The response of E and gbr to the massive rise in VPD (to 7 kPa) was negative in low-SM trees and positive in high-SM trees. These observations were consistent with predictions based on a simple plant hydraulic model showing the importance of plant water potential in the gbr and E response to VPD. These results demonstrate that avoiding drought on the supply side (SM) and relying on plant hydraulic regulation constrains the effects of atmospheric drought (VPD) as a stressor on canopy gas exchange in mature pine trees under field conditions.

Original languageAmerican English
Pages (from-to)3775-3790
Number of pages16
JournalPlant, Cell and Environment
Volume46
Issue number12
DOIs
StatePublished - Dec 2023

Bibliographical note

Publisher Copyright:
© 2023 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.

Keywords

  • VPD
  • automated branch chambers
  • drought
  • irrigation
  • semiarid
  • soil moisture
  • supply and demand
  • transpiration
  • water potential

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