Id. Jolly et Gr. Walker, IS THE FIELD WATER-USE OF EUCALYPTUS LARGIFLORENS MUELL,F. AFFECTED BY SHORT-TERM FLOODING, Australian journal of ecology, 21(2), 1996, pp. 173-183
Transpiration of and water sources for Eucalyptus largiflorens F. Muel
l trees at three sites on a semi-arid floodplain of the lower River Mu
rray in southern Australia were investigated during the course of a fl
ood. Two of the sites were flooded for 32 days while the third was not
flooded. At both flooded sites transpiration was not suppressed durin
g the period when the sites were flooded, indicating that anoxia did n
ot occur. Available literature suggests that E. largiflorens has very
low O-2 consumption, and that lateral roots can absorb O-2 from soil w
ater at very low partial pressures. The oxygen stored in the unsaturat
ed region of the soil appeared sufficient, in this case, to meet the r
equirements of the trees. Transpiration at the flooded sites did not i
ncrease in comparison with that at the non-flooded site in the period
following flooding. We suggest that this was possibly due to the above
-average rainfall experienced in the months preceding the flood and/or
physiological adaptations to the highly saline conditions that preven
ted the trees taking full advantage of the additional water. The sourc
es of water used by the trees were investigated using the naturally oc
curring stable isotopes of water and measurements of soil water suctio
n. These showed that prior to the flood shallow cain-derived soil wate
r was being used at all three sites. Ten days after flooding ceased tr
ees at both flooded sites were using shallow flood-derived soil water
while at the non-flooded sites they were using groundwater. Results fr
om the flooded sites 7 and 22 weeks after flooding ceased showed that
as the flood- and rain-derived water became limited the trees suppleme
nted their supplies with groundwater from the capillary fringe. The no
n-flooded trees used various combinations of rain-derived soil water a
nd groundwater during this period.