Canopy Dynamics of Eucalyptus maculata Hook .IV. Contrasting Responses to Two Severe Droughts

Abstract

Contrasting responses of a Eucalyptus maculata forest at Kioloa on the south coast of New South Wales, Australia, to two serious droughts of similar duration and overall rainfall deficiency in 1980 and 1982 are described. Annual rainfall in 1982 was the lowest and that in 1980 the second lowest in a century. Pronounced shrinkage of tree boles in winter, wilting of foliage and massive leaf-shedding in the forest when soil moisture was exhausted during spring 1980 were not repeated in 1982-83, although measured soil water deficits reached extreme values on three occasions. Annual rainfall in 1982 was of more favourable distribution in relation to the occurrences of critical soil moisture deficits than in 1980. This, together with relatively low evaporative demand, enabled eucalypts to maintain an adequate internal water status, and explains the small response of forest canopies to one of the worst droughts ever in terms of rainfall deficiency.