Abstract
Global climate change-induced droughts are provoking events of forest mortality worldwide, with loss of tree biomass and consequent ecosystem services. Ameliorating the effects of drought requires understanding the causes of forest mortality, with failure of the hydraulic system being an important contributor. Comparative anatomical data strongly suggest that, all else being equal, wider conduits are more vulnerable to drought-induced embolism than narrow ones. However, physiology experiments do not provide consistent support for such a link. If a vulnerability-diameter link exists, though, it would contribute not only to explaining and predicting forest mortality but also to interventions to render individual trees more drought resistant. Given that xylem conduits scale with plant height, taller plants have wider conduits. If there is a vulnerability-diameter link, then this would help explain why taller plants are often more vulnerable to climate change-induced drought. Links between conduit diameter, plant height, and vulnerability would also provide guidance for standardizing sampling of hydraulic variables across individuals and suggest that selecting for relatively narrow conduits at given height from the tree top could produce more drought resistant varieties. As a result, given current ambiguities, together with the potential importance of a link, it is important to maintain the vulnerability-diameter link as a research priority.
Highlights
A major effort is underway to understand the causes of death of millions of trees worldwide under climate change-induced drought (Breshears et al, 2013, 2018; Allen et al, 2015; Anderegg et al, 2015, 2016; Adams et al, 2017; Choat et al, 2018; Trugman et al, 2018, 2021; Brodribb et al, 2020)
The key point we focus on here is the possible link between vulnerability to drought-induced hydraulic failure and xylem water-transporting conduit diameter
Testing the link between drought-induced embolism vulnerability and conduit diameter remains a priority because of the explanatory reach it would have if such a link existed, and that it is consistent with comparative anatomical evidence often spanning hundreds or thousands of species (Olson, 2020)
Summary
A major effort is underway to understand the causes of death of millions of trees worldwide under climate change-induced drought (Breshears et al, 2013, 2018; Allen et al, 2015; Anderegg et al, 2015, 2016; Adams et al, 2017; Choat et al, 2018; Trugman et al, 2018, 2021; Brodribb et al, 2020). Testing the link between drought-induced embolism vulnerability and conduit diameter remains a priority because of the explanatory reach it would have if such a link existed, and that it is consistent with comparative anatomical evidence often spanning hundreds or thousands of species (Olson, 2020).
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