Skip to Main Content
Forest canopy hydraulicsAuthor(s): David R. Woodruff; Frederick C. Meinzer; Katherine A. McCulloh
Source: Book - Canopy Photosynthesis: From Basics to Applications. Volume 42 of the series Advances in Photosynthesis and Respiration. Springer Netherlands
Publication Series: Book Chapter
Station: Pacific Northwest Research Station
PDF: Download Publication (935.0 KB)
DescriptionWater and carbon cycles are strongly coordinated and water availability is a primary limiting factor in many terrestrial ecosystems. Photosynthesis requires sufficient water supply to leaves and constraints on delivery at any point in the hydraulic continuum can lead to stomatal closure and reduced photosynthesis. Thus, maximizing water transport enhances assimilation and can provide plants with a competitive advantage. Unregulated water transport, however, can lead to excessive gradients in xylem tension that result in the development of air or vapor bubbles (i.e. embolisms) that block xylem water transport, potentially leading to permanent loss of function of the xylem. As such there can be a tradeoff between maximizing water transport and minimizing the risk of xylem embolism. This tradeoff has led to the development of a variety of hydraulic mechanisms to maximize efficiency and reduce vulnerability. Although several of these were first described centuries ago (such as stomatal control of transpiration), research in this field continues to uncover previously unrecognized processes employed by plants for maintaining hydraulic safety and/or efficiency. The hydraulic traits described in this chapter include xylem structural characteristics that enhance resistance to embolism such as pit and cell wall architecture; a continuum of strategies for constraining xylem tension to avoid embolism including isohydric and anisohydric control of leaf water potential; and safety and recovery mechanisms such as the capacitive discharge of stored water, hydraulic “circuit breakers” and the ability to repair xylem embolisms. Each of these will be discussed in terms of the variation in their use by contrasting tree types, their variability across organs and species, and their plasticity across environmental gradients. Beyond providing information about the means by which trees currently compete and survive, understanding the hydraulic mechanisms described in this chapter may provide insight into ways that trees are affected by, and the degree to which they may acclimate to rapidly changing climatic conditions.
- Visit PNW's Publication Request Page to request a hard copy of this publication.
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationWoodruff, David R.; Meinzer, Frederick C.; McCulloh, Katherine A. 2016. Forest canopy hydraulics. In: Hikosaka, Kouki; Niinemets, Ülo; Anten, Niels P. R., eds. Canopy photosynthesis: from basics to applications. Dordrecht, Springer Netherlands: 187-217. Chapter 7.
KeywordsAcademics, students, scientists
- Xylem hydraulic safety margins in woody plants: coordination of stomatal control of xylem tension with hydraulic capacitance
- Hydraulic safety margins and embolism reversal in stems and leaves: Why are conifers and angiosperms so different?
- The blind men and the elephant: the impact of context and scale in evaluating conflicts between plant hydraulic safety and efficiency
XML: View XML