Abstract
Abstract Extreme weather events such as megadroughts (long duration and intense droughts) are becoming common in regions with Mediterranean climates and threaten the continuity of fruit production. In this context, this study assesses the effects of a single-season megadrought on the physiological response and mortality of mature apple trees in a high-density orchard. Two treatments were imposed in two weighing lysimeters with four trees in each one, (i) Control: fully irrigated according to the crop evapotranspiration; and (ii) Drought: rainfed from 7 May 2023, until the end of the season. Trees’ evapotranspiration and trunk water potential were continuously monitored during the experiment in combination with periodic measurements of the soil water content, stomatal conductance, midday stem water potential, and apple size. The trunk water potential of apple trees in the drought lysimeter during the 2023 season fell below − 4.5 MPa, with stomatal conductance decreasing from 0.4 mmol m − 2 s − 1 before withholding irrigation to 0 mmol m − 2 s − 1 60 days later. In the following spring 2024, the four apple trees subjected to the megadrought were agronomically dead (did not sprout). Our results showed that, for apple trees, a threshold value of water potential of -3.5 MPa must not be surpassed to ensure the tree survival, while values below − 4.0 MPa for 27 days cause the death of the trees.
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Claims 5
Claim · model-written summary
Apple trunk water potential under drought fell below − 4.5 MPa.
- Taxon
- apple trees
Malus domesticae0 - Treatment
- Drought: rainfed from 7 May 2023, until the end of the seasone1
- Outcome
- trunk water potentiale0
- Direction
- fell belowe0
- Value
- − 4.5 MPae0
- Comparator
- Control: fully irrigated according to the crop evapotranspiratione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The trunk water potential of apple trees in the drought lysimeter during the 2023 season fell below − 4.5 MPa”
e1“Control: fully irrigated according to the crop evapotranspiration; and (ii) Drought: rainfed from 7 May 2023, until the end of the season”
Claim · model-written summary
Apple stomatal conductance dropped from 0.4 to 0 after irrigation was withheld.
- Taxon
- Apple treesMalus domesticat0
- Treatment
- withholding irrigatione0
- Outcome
- stomatal conductancee0
- Direction
- decreasinge0
- Value
- 0 mmol m − 2 s − 1e0
- Qualifier
- 0.4 mmol m − 2 s − 1e0
- Comparator
- before withholding irrigatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stomatal conductance decreasing from 0.4 mmol m − 2 s − 1 before withholding irrigation to 0 mmol m − 2 s − 1 60 days later”
t0“Apple trees”
Claim · model-written summary
All four megadrought-exposed apple trees failed to sprout in spring 2024.
- Taxon
- apple treesMalus domesticae0
- Treatment
- megadroughte0
- Outcome
- agronomically dead (did not sprout)e0
- Value
- foure0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the following spring 2024, the four apple trees subjected to the megadrought were agronomically dead (did not sprout)”
Claim · model-written summary
Authors set a water potential survival threshold of -3.5 MPa for apple trees.
- Taxon
- apple treesMalus domesticae0
- Outcome
- threshold value of water potentiale0
- Value
- -3.5 MPae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“for apple trees, a threshold value of water potential of -3.5 MPa must not be surpassed to ensure the tree survival”
Claim · model-written summary
Water potential below − 4.0 MPa for 27 days caused apple tree death.
- Taxon
- Apple treesMalus domesticat0
- Treatment
- values below − 4.0 MPa for 27 dayse0
- Outcome
- death of the treese0
- Value
- − 4.0 MPae0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“values below − 4.0 MPa for 27 days cause the death of the trees”
t0“Apple trees”
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