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Seeking the ‘point of no return’ in the sequence of events leading to mortality of mature trees
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  • Yakir Preisler,
  • Fedor Tatarinov,
  • José Grünzweig,
  • Dan Yakir
Yakir Preisler
Weizmann Institute of Science
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Fedor Tatarinov
Weizmann Institute of Science
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José Grünzweig
Hebrew University of Jerusalem Robert H Smith Faculty of Agriculture Food and Environment
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Dan Yakir
Weizmann Institute of Science
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Abstract

Drought-related tree mortality is increasing globally, but the sequence of events leading to it remains poorly understood. To identify such sequence, we used a 2016 tree mortality event in the semi-arid pine forest of Yatir were dendrometry and sap flow measurements were carried out in 31 trees, of which seven died. A comparative analysis revealed three stages leading to mortality. First, a decrease in tree diameter in all dying trees, but not in the living ones, eight months ‘prior to the visual signs of mortality’ (PVSM; e.g., brown needles). Second, a decay to near zero in the diurnal stem swelling/shrinkage dynamics, reflecting the loss of stem radial water flow in the dying trees, six months PVSM. Third, cessation of stem sap flow three months PVSM. Eventual mortality could therefore be detected long before visual signs are observed, and the three stages identified here demonstrated the differential effects of drought on stem growth, water storage capabilities, and soil water uptake. The results indicated that breakdown of radial stem water flow and phloem functionality is a critical element in defining the ‘point of no return’ in the sequence of events leading to mortality of mature trees.

Peer review status:UNDER REVIEW

11 Sep 2020Submitted to Plant, Cell & Environment
11 Sep 2020Assigned to Editor
11 Sep 2020Submission Checks Completed
15 Sep 2020Reviewer(s) Assigned