University Of Tasmania

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Responses of transpiration and canopy conductance to partial defoliation of Eucalyptus globulus trees

journal contribution
posted on 2023-05-17, 04:36 authored by Quentin, AG, Anthony O'GradyAnthony O'Grady, Christopher BeadleChristopher Beadle, Worledge, D, Elizabeth Pinkard
Partial defoliation has been shown to affect the water relations and transpiration (gas exchange) of plants. Over one growing season, the water relations in response to partial (45%) defoliation were examined in four-year-old Eucalyptus globulus trees in southern Australia. Daily maximum transpiration rates (Emax), maximum canopy conductance (GCmax), and diurnal patterns of tree water-use were measured over a period of 215 days using the heat-pulse technique in adjacent control (non-defoliated) and defoliated trees. Sap-flux measurements were used to estimate canopy conductance and soil-to-leaf hydraulic conductance (KP); leaf water potential (Ø) and climate data were also collected. Following the removal of the upper canopy layer, defoliated trees exhibited compensatory responses in transpiration rate and canopy conductance of the remaining foliage. Defoliated E. globulus had similar predawn but higher midday Øl, transpiration rates (E), canopy conductance (GC) and KP compared to the non-defoliated controls, possibly in response to increased water supply per unit leaf area demonstrated by higher midday Øl. Higher E in defoliated E. globulus trees was the result of higher GC in the morning and early afternoon. This paper also incorporates the cumulative effect of defoliation, in a phenomenological model of maximum canopy conductance of E. globulus. These results contribute to a mechanistic understanding of plant responses to defoliation, in particular the often observed up-regulation of photosynthesis that also occurs in response to defoliation.


Publication title

Agricultural and Forest Meteorology








Tasmanian Institute of Agriculture (TIA)


Elsevier Science Bv

Place of publication

Po Box 211, Amsterdam, Netherlands, 1000 Ae

Rights statement

The definitive version is available at

Repository Status

  • Restricted

Socio-economic Objectives

Forestry not elsewhere classified