Water relations of feral olive trees (Olea europaea) resprouting after severe pruning

Water relations of feral olives (Olea europaea L.) were studied on a location in the Mt Lofty Ranges, South Australia. In spring (October-November), 6 months before the study commenced, an area of trees had been cut back to stumps as part of an eradication project. The stumps resprouted vigorously over summer, similarly to regrowth seen following wildfire. The following autumn and winter, plant water potentials and soil matric potentials were measured on the cut trees and adjacent control trees, to determine whether the cut trees were better hydrated due to the pruning treatment. In autumn, before the winter rains began, the resprouting trees were more hydrated than the control trees, with a difference in predawn water potentials of between 2 and 4 MPa, and 1.5 MPa or greater throughout the day. The soil matric potential was much less negative on the cleared site, both at the surface and at 50-cm depth, indicating that soil water had been less depleted by the cut trees than by the intact trees. This improved hydration was similar to that reported for sclerophyll vegetation after defoliation by fire. Results have some significance for feral olive eradication projects.