Growth and Differential Frost-Resistance of Topoclinal Forms of Eucalyptus fastigata D.&M. Planted in South Africa

Abstract

SUMMARY Three provenances of topoclinal forms of cut-tail (E. fastigata D.&M.) from 2,400 ft, 3,500 ft and 3,800 ft were tested in plantations in Natal and the Transvaal. Several trends in behaviour in South Africa in relation to Australian origin were disclosed. The higher-altitude provenances showed a relatively higher mortality in establishment than that from the lowest altitude. There was a disinctly slower rate of growth with increasing altitude of origin, and the highest altitude provenance showed generally more capacity to resist frost and cold winds. This last conclusion was based on results from the first winter, and was not repeated in the second. Presumably, this was because growth in the faster-growing provenances had taken the tender, frost-susceptible tips to a level above ground beyond which radiation frost in the second winter could damage them. The analysis of results was considerably complicated by position effects in the plots due to minor differences in topography and also to the nature of the surrounds, particularly as to whether there were stands of other species adjoining the test plots which could cause pools of cold air. In the trial, major volume differences were disclosed at a very early age among the different provenances, the largest, that from the lowest altitude, being 75 per cent higher than the smallest. While extensive testing from many more Australian sources, including different latitudinal provenances, would be necessary to evaluate the position thoroughly, the possible gains in growth in South Africa by the use of particular provenances for specific localities seem considerable.