The xylem of anisohydric Quercus alba L. is more vulnerable to embolism than isohydric co-dominants

Abstract

The coordination of plant leaf water potential (Ψ) regulation and xylem vulnerability to embolism is fundamental for understanding the tradeoffs between carbon uptake and risk of hydraulic damage. There is a general consensus that trees with vulnerable xylem regulate Ψ more conservatively than plants with resistant xylem. We evaluated if this paradigm applied to three important eastern US temperate tree species, Quercus alba L., Acer saccharum Marsh., and Liriodendron tulipifera L., by synthesizing 1600 Ψ observations, 122 xylem embolism curves, and xylem anatomical measurements across ten forests spanning pronounced hydroclimatological gradients and ages. We found that, unexpectedly, the species with the most vulnerable xylem (Q. alba) regulated Ψ less strictly than the other species. This relationship was found across all sites, such that coordination among traits was largely unaffected by climate and stand age. Quercus species are perceived to be among the most drought tolerant temperate US forest species; however, our results suggest their relatively loose Ψ regulation in response to hydrologic stress occurs with a substantial hydraulic cost that may expose them to novel risks in a more drought-prone future. We end by discussing mechanisms that allow these species to tolerate and/or recover from hydraulic damage.

Aridity‐dependent sequence of water potentials for stomatal closure and hydraulic dysfunctions in woody plants

“…However, at a large scale, species in xeric climates need more negative Ψ close for carbon assimilation and more negative P50 for improving hydraulic safety, while a wider safety margin of xeric species also tends to be more isohydric, this stomatal strategy would be more successful under extreme drought conditions (Martin-StPaul et al, 2017;Pivovaroff et al, 2018). In addition, one recent local study also confirmed that anisohydric Quercus alba L. is more vulnerable to embolism than isohydric co-dominants (Benson et al, 2022). Overall, SSM provides a comprehensive isohydric-anisohydric framework to characterize plant response to drought.…”