Groom: Water relations of Myrtaceae shrubs during drought 
all the sites with summer soil moisture content < 0.5% 
down to 2 m depth (Fig 5). Substantial increases in 
gravimetric soil moisture contents at depth for the 
embankment and midslope sites indicate the presence of 
the capillary fringe, a zone of saturated soil just above 
the water table. 
Deuterium analysis 
Groundwater 5 2 H was generally less negative than 
5 2 H in the soil profile (see Fig 6 for exceptions) and 
became less negative as the seasons progressed, with 
summer and winter data displaying minimal variation 
between sites (Fig 7). Dampland spring groundwater 5 2 H 
varied from -16.25 to -21.78 %o compared with -16.52 to - 
19.20 %o at the embankment/midslope sites. 
For spring and winter data, species with lowest WP d 
had the lowest xylem 8 2 H (A. fascicular is in spring and fi. 
angustifolium in winter were the exceptions) (Fig 7). This 
was not the case in summer, where xylem 5 2 H became 
less negative as WP decreased, with the three shallow 
rooted species (A. fascicularis, P . ellipticum , H. 
angustifolium; all < 1 m rooting depth; Dodd et al. 1984) 
having more negative 5 2 H values than £. pauciflora (> 2 m 
rooting depth). 
Comparing xylem water 5 2 H with soil water and 
groundwater 5 3 H data (Fig 6) it appears that P. ellipticum 
was utilising surface soil moisture (<0.2 m) in spring and 
soil moisture at relative depth (0.8-1.0 m) in winter. 
Spring xylem water 5 2 H for A. fascicularis (-25.29 ± 0.90 
% 0 ; mean ± SD) was less than that of groundwater (-16.25 
to -21.78 %o) and soil moisture (-4.50 to -21.82 %o). 
Summer data suggest that both A. fascicularis and P. 
ellipticum were accessing soil moisture throughout the 
profile, although soil water 5 2 H at 0.8 m was more 
negative than the xylem water. Summer xylem water 5 2 H 
of P. ellipticum (-29.15 ± 4.62 %o) was more negative than 
Spring 2000 
Summer 2001 
Winter 2001 
5 2 H (%o) 
Figure 6. Seasonal profiles of soil 8 2 H at the three topographical locations including groundwater (GW) values. Bars represent the range 
of xylem water 8 2 H for the study species at each site. Shaded and unshaded bars are displayed to distinguish between different species 
at the same site. Summer and winter midslope profiles did not extend below 2 and 3 m respectively. Species abbreviations are provided 
in Fig 1. The values represent a single analysis from one sample per soil depth. 
37 
