אסיף מאגר המחקר החקלאי

In situ, direct observation of seasonal embolism dynamics in Aleppo pine trees growing on the dry edge of their distribution

Year:

2022

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Co-Authors:

Yael Wagner,
Feng Feng,
Dan Yakir,
Tamir Klein,
Uri Hochberg

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Abstract:

• Xylem embolism impairs hydraulic conductivity in trees and drives drought-induced mortality. While embolism has been monitored in-vivo in potted plants, and research has revealed evidence of embolism in field-grown trees, continuous in-situ monitoring of cavitation in forests is lacking.
• Seasonal patterns of embolism were monitored in branchlets of Aleppo pine (Pinus halepensis) trees growing in a dry Mediterranean forest. Optical visualization sensors (OV) were installed on terminal branches, in addition to monthly sampling for μCT scans.
• We detected 208 cavitation events among four trees, which represented an embolism increase from zero to ~12% along the dry season. Virtually all the cavitation events occurred during the daytime hours, with 77% occurring between 10 and 16. The probability for cavitation in a given hour increased as vapor pressure deficit (VPD) increased, up to 42% chances for cavitation when VPD > 5 kPa.
• The findings uniquely reveal the instantaneous environmental conditions that lead to cavitation. The increased likelihood of cavitation events under high VPD in water-stressed pines is the first empirical support for this long hypothesized relation. Our observations suggest that low levels of embolism are common in Aleppo pine trees at the dry edge of their distribution.

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