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Constraints on transpiration of Eucalyptus glbulus in southern Tasmania, Australia


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O'Grady, AP and Worlege, D and Battaglia, M (2008) Constraints on transpiration of Eucalyptus glbulus in southern Tasmania, Australia. Agricultural and Forest Meteorology, 148. pp. 453-465.

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The constraints on transpiration were studied in plantation grown Eucalyptus globulus
trees over the summer of 2004/2005 at a research site in southern Tasmania. Diurnal
patterns of leaf water potential and tree water use,measured using heat pulse techniques,
were examined monthly in rain-fed and irrigated trees growing under similar atmospheric
conditions. Soilmatric potential declined during the summer in rain-fed plots but
remained high in irrigated plots. Pre-dawn leaf water potentials decreased in rain-fed
trees and this was associated with increasing soil water deficit. The difference between
pre-dawn and midday leaf water potential declined with decreasing pre-dawn water
potential, suggesting isohydric regulation of plant water potential. Transpiration and
canopy conductance were lower in rain-fed trees than irrigated trees and the decline in
transpiration and canopy conductance was related to pre-dawn leaf water potential.
There was marked hysteresis in the relationship between transpiration and D in both
rain-fed and irrigated trees. Hysteresis was also observed in the relationship between
transpiration and leaf water potential. However, in this case hysteresis was only evident
in rain-fed trees. For the relationship between transpiration and D, hysteresis was larger
at high D’s than at low D’s in both rain-fed and irrigated trees and was not related to
diurnal changes in soil to leaf hydraulic conductance. Diurnal changes in leaf conductance,
however, may play an important role in controlling stomatal sensitivity to D and
may help to explain the hysteresis in the relationship between transpiration and D. Soilto-
leaf hydraulic conductance of rain-fed trees declined in response to decreasing predawn
leaf water potential. We propose that loss of hydraulic conductance is an important

Item Type: Article
Journal or Publication Title: Agricultural and Forest Meteorology
Page Range: pp. 453-465
Identification Number - DOI: 10.1016/j.agrformet.2007.10.006
Date Deposited: 07 May 2008 00:38
Last Modified: 18 Nov 2014 03:39
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