Hydraulic failure and tree size linked with canopy die-back in eucalypt forest during extreme drought

Rachael H. Nolan*, Alice Gauthey, Adriano Losso, Belinda E. Medlyn, Rhiannon Smith, Shubham S. Chhajed, Kathryn Fuller, Magnolia Song, Xine Li, Linda J. Beaumont, Matthias M. Boer, Ian J. Wright, Brendan Choat

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    74 Citations (Scopus)
    20 Downloads (Pure)

    Abstract

    Eastern Australia was subject to its hottest and driest year on record in 2019. This extreme drought resulted in massive canopy die-back in eucalypt forests. The role of hydraulic failure and tree size on canopy die-back in three eucalypt tree species during this drought was examined. 

    We measured pre-dawn and midday leaf water potential (Ψleaf), per cent loss of stem hydraulic conductivity and quantified hydraulic vulnerability to drought-induced xylem embolism. Tree size and tree health was also surveyed. 

    Trees with most, or all, of their foliage dead exhibited high rates of native embolism (78–100%). This is in contrast to trees with partial canopy die-back (30–70% canopy die-back: 72–78% native embolism), or relatively healthy trees (little evidence of canopy die-back: 25–31% native embolism). Midday Ψleaf was significantly more negative in trees exhibiting partial canopy die-back (−2.7 to −6.3 MPa), compared with relatively healthy trees (−2.1 to −4.5 MPa). In two of the species the majority of individuals showing complete canopy die-back were in the small size classes. Our results indicate that hydraulic failure is strongly associated with canopy die-back during drought in eucalypt forests. 

    Our study provides valuable field data to help constrain models predicting mortality risk.

    Original languageEnglish
    Pages (from-to)1354-1365
    Number of pages12
    JournalNew Phytologist
    Volume230
    Issue number4
    DOIs
    Publication statusPublished - May 2021

    Keywords

    • cavitation
    • drought
    • Eucalyptus
    • hydraulic failure
    • mortality
    • tree size
    • water potential
    • xylem embolism

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