Patterns of Tree Dieback in Queensland, Australia: The Importance of Drought Stress and the Role of Resistance to Cavitation

• Published in: Oecologia Vol. 139; no. 2; pp. 190 - 198
• Main Authors: Rice, Kevin J., Matzner, Steven L., Byer, William, Brown, Joel R.
• Format: Journal Article
• Language: English
• Published: Berlin Springer-Verlag 01.04.2004; Springer; Springer Nature B.V
• Subjects: Adaptation, Physiological; Age structure; Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; Cardigans; Cavitation; Cavitation flow; Corymbia erythrophloia; Dieback; Disasters; Drought; Ecophysiology; El Nino; Embolisms; Eucalyptus; Eucalyptus - growth & development; Eucalyptus - physiology; Fundamental and applied biological sciences. Psychology; Mortality; Plants; Plants and fungi; Population Dynamics; Queensland; Rain; Roots; Saplings; Trees; Water potential; Water pressure; Water stress; Water-Electrolyte Balance; Xylem; Queensland; Australia, Queensland; Xylem; Environmental factor; Hydraulic conductivity; Cavitation; Stress; Resistance; Eucalyptus; Sensitivity resistance; Dicotyledones; Angiospermae; Myrtaceae; Tree; Spermatophyta; Drought
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-004-1503-9

During the extreme 1992-1997 El Niño drought event, widespread stem mortality, or tree "dieback", of both mature and juvenile eucalypts occurred within the tropical savannas of northeast Australia. Most of the dieback occurred in individuals of the ironbark species complex (Eucalyptus crebra-E. xanthoclada) while individuals of the bloodwood species Corymbia erythrophloia, exhibited significantly less stem mortality. Indicative of greater water stress, predawn and midday xylem water potentials of ironbark adults and saplings were significantly more negative than predawn values of bloodwoods. The very negative xylem water potentials in ironbarks suggest that stem mortality in both adult and juvenile ironbarks results from drought-induced embolism and that ironbarks perhaps have a shallower and less extensive root system than bloodwoods. Although pre-dawn and midday water potentials for ironbark adults and saplings were similar, a census of mature and juvenile ironbark trees indicated that mortality was higher in adult trees. Cavitation vulnerability curves indicated that ironbark saplings may be better buffered against cavitation than adult trees. If they possess smaller root systems, saplings are more likely than adults to experience low xylem water potentials, even in non-drought years. Xylem conduits produced in adult trees during periods of normal rainfall, although perhaps more efficient in water conduction, may be more vulnerable to cavitation during infrequent severe droughts.