Genetic variation in Eucalyptus delegatensis.  2. Altitudinal variation in growth (two years), seed dormancy and cold hardiness.  I. D. Abbott and L. A. Pederick.  November 1984.  33 pp. (unpubl.)

SUMMARY

No relationship was found between height growth (to two years) of Eucalyptus delegatensis R. T. Baker (alpine ash) trees and the altitudes of their seed sources at sample points along four altitudinal transects on the slopes of Mt Stirling, east of Mansfield in North-eastern Victoria. The young trees were grown in large field trials planted at two sites (Bindaree and Toombullup) near Mansfield in 1981, undertaken to supplement earlier studies of natural variation within the species. The trials are at an early stage and the results presented should be regarded as tentative at this stage.

There were significant differences in the mean heights of some families in the trials, indicating the presence of genetic variation in early growth rate, though there seemed no obvious association between the locations in the forest of the trees providing the faster growing genotypes and any factor of the site. Mean height of families derived from one of the transects was significantly greater than that from one of the other transects. Within transects, the trees providing faster growing families appeared to be distributed at random. At this stage, the results should be interpreted simply as due to the random variation that occurs in natural populations on a tree-to-tree or group-to-group basis.

Families derived from pairs of near-adjacent trees at collection points along the transects exhibited the smallest level of variation, indicative of genetic similarity due to relatedness that normally occurs in groups of trees in natural stands of many forest species.

Germination percentage and dormancy of seeds sampled on two of the altitudinal transects did not vary in response to altitude of the seed source. Therefore it is concluded that the length of stratification treatment should not be reduced for seedlots collected at low altitudes.

Seedlings from the higher altitude collections suffered less leaf damage when exposed to -10°C in the laboratory. Seedlings from high altitude seed sources are therefore likely to be more frost-resistant and exhibit greater survival in the field at high altitude sites than those from low altitude sources.

The two trials also included seventeen families derived from phenotypic selection of vigorous, high quality trees in three Forest Districts, to gain evidence on the prospects for genetic improvement of the species in response to selection. After two years the families derived from Alexandra District were tallest, Mansfield the shortest, with Swifts Creek intermediate. The faster growth of the Alexandra provenance over Mansfield confirmed results presented in an earlier report.

Also published:

Pederick, L.A. (1985)  Dormancy of Eucalyptus delegatensis seeds unaffected by altitude of seed source.  Dep. Conserv., For. and Lands, State For. and Lands Serv., For. Tech. Pap. 30: 35-9.