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Seasonal Variation in Water Relations of Trees of Differing Leaf Phenology in a Wet-Dry Tropical Savanna near Darwin, Northern Australia

Myers, BA, Duff, G, Eamus, D, Fordyce, I, O'Grady, AP and Williams, RJ (1997). Seasonal Variation in Water Relations of Trees of Differing Leaf Phenology in a Wet-Dry Tropical Savanna near Darwin, Northern Australia. Australian Journal of Botany,45(2):225-240.

Document type: Journal Article
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Title Seasonal Variation in Water Relations of Trees of Differing Leaf Phenology in a Wet-Dry Tropical Savanna near Darwin, Northern Australia
Author Myers, BA
Duff, G
Eamus, D
Fordyce, I
O'Grady, AP
Williams, RJ
Journal Name Australian Journal of Botany
Publication Date 1997
Volume Number 45
Issue Number 2
ISSN 0067-1924   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-0031009850
Start Page 225
End Page 240
Total Pages 16
Place of Publication Melbourne
Publisher CSIRO Publishing
HERDC Category C1 - Journal Article (DEST)
Abstract The seasonal variation in leaf xylem pressure potential at dawn (cdawn), leaf tissue water characteristics and daily maximum leaf conductance was measured in eight woody species in a wet–dry tropical savanna near Darwin, northern Australia, between October 1992 and October 1993. The species were Eucalyptus miniata, E. tetrodonta, E. clavigera, Xanthostemon paradoxus, Erythrophleum chlorostachys, Planchonia careya, Terminalia ferdinandiana and Cochlospermum fraseri. The species represented the major leaf phenological types, evergreen, semi-deciduous and fully deciduous. The climate of the region is characterised by annual drought during the winter months, when virtually no rain falls and vapour pressure deficit (VPD) in the afternoon reaches 3 kPa for 5 consecutive months each year. Despite this drought, cdawn remained high (–1.3 to –1.5 MPa in evergreen species and –0.5 to –1.5 MPa in deciduous species) relative to those trees that experience summer drought in temperate and arid Australia. There was a tendency for evergreen and semi-deciduous species to maintain positive turgor to lower xylem pressure potentials (mean osmotic potential at incipient plasmolysis, p0 = –2.15 MPa) than the fully deciduous species (p0 = –2.03 MPa). For all species, the daily maximum leaf conductance (gmax) was maximal in the wet and decreased during the dry season. Diurnally, gmax occurred near midday in the wet season, but at about 0800–1000 hours during the dry season and the ‘buildup’, the transitional period between the dry and wet seasons. There was substantial decrease in gmax (from 650–1000 mmol m–2 s–1 in March to 200 mmol m–2 s–1 in May) early in the dry season in two of the three fully deciduous species (Planchonia careya and Cochlospermum fraseri). The dominant evergreen species Eucalyptus miniata, by contrast, had high gmax (> 400 mmol m–2 s–1) throughout the dry season, suggesting it had access to groundwater. For each species, gmax declined with decreasing dawn water potential in a log-linear manner; the slope of this relationship tended to increase with increasing degree of deciduousness.
DOI http://dx.doi.org/10.1071/BT96015   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)
 
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