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Vapor pressure deficit was not a primary limiting factor for gas exchange in an irrigated, mature dryland Aleppo pine forest
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  • Yakir Preisler,
  • José Grünzweig,
  • Ori Ahiman,
  • Madi Amer,
  • Itay Oz,
  • Xue Feng,
  • Jonathan D. Muller,
  • Nadine Ruehr,
  • Eyal Rotenberg,
  • Benjamin Birami,
  • Dan Yakir
Yakir Preisler
Weizmann Institute of Science Department of Earth and Planetary Sciences

Corresponding Author:[email protected]

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José Grünzweig
Hebrew University of Jerusalem Robert H Smith Faculty of Agriculture Food and Environment
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Ori Ahiman
Hebrew University of Jerusalem Robert H Smith Faculty of Agriculture Food and Environment
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Madi Amer
Weizmann Institute of Science Department of Earth and Planetary Sciences
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Itay Oz
Weizmann Institute of Science Department of Earth and Planetary Sciences
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Xue Feng
University of Minnesota Twin Cities Department of Civil Environmental and Geo-Engineering
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Jonathan D. Muller
Weizmann Institute of Science Department of Earth and Planetary Sciences
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Nadine Ruehr
Karlsruher Institut fur Technologie Institut fur Meteorologie und Klimaforschung Atmospharische Umweltforschung
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Eyal Rotenberg
Weizmann Institute of Science Department of Earth and Planetary Sciences
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Benjamin Birami
Karlsruher Institut fur Technologie Institut fur Meteorologie und Klimaforschung Atmospharische Umweltforschung
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Dan Yakir
Weizmann Institute of Science Department of Earth and Planetary Sciences
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Abstract

Climate change is often associated with increasing vapor 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 (g br), transpiration rate (E) and net photosynthesis (A net) decreased in low-SM trees but greatly increased in high-SM trees. The response of E and g br 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 g br and E response to VPD. These results demonstrate that avoiding drought on the supply side (soil moisture) 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.
10 Jul 2023Submitted to Plant, Cell & Environment
10 Jul 2023Submission Checks Completed
10 Jul 2023Assigned to Editor
10 Jul 2023Review(s) Completed, Editorial Evaluation Pending
20 Jul 2023Reviewer(s) Assigned
24 Aug 2023Editorial Decision: Accept