Water Relations of Rural Eucalypt Dieback.

Abstract

The water relations of healthy and dieback-affected individuals of three Eucalyptus species typical of the northern tablelands of New South Wales were compared. Dawn water potentials of healthy and dieback-affected trees were all very similar. Midday water potentials of trees with the most severe dieback symptoms were often lower than those of nearby healthy trees by up to 0.6 MPa. Leaf con- ductances of the most severely dieback-affected trees were usually greater than those of healthy trees. Differences decreased with time and when more trees with less severe symptoms were measured late in the study no significant differences in water relations were found. It seems therefore that the effects of dieback on the water relations of trees are too small for measurements of leaf water potentials or leaf conductances to be useful indicators of disease severity in individual trees.