Bulletin No. 4

A study of some factors associated with the natural regeneration of alpine ash, Eucalyptus delegatensis R.T. Baker, syn. E. gigantea Hook. f.  R.J. Grose.  1957.  Forests Commission, Victoria.  22 pp.


Quadrat samplings in clear-felled areas of alpine ash forest in Delatite forest district in north-eastern Victoria indicated that seed supply was poorly distributed and probably inadequate, and that seed beds were only partially receptive, seedlings appearing to be largely restricted to parts of the area cultivated during logging operations.

Production, time and mode of cast, and distance of dissemination of seeds have been studied. Dominant and co-dominant trees produce the bulk of the seed crop. Heavier seed crops are produced by trees on north and west aspects than by those on south and east aspects. More seeds are usually cast from capsules than are cast in capsules. Peak cast of seeds from capsules occurs in late summer and early autumn while full capsule cast is heavy in late autumn and winter. The effective distance of dissemination from group, strip and single tree seed sources appears to lie between 2 and 2½ chains. Retention of 3-4 single seed trees per acre selected from the dominant crown class should provide an effective seed source.

Time of germination and factors affecting total germination have been studied. Most alpine ash seeds are dormant but will germinate if after-ripened by stratification, hence only a few seeds germinate in autumn. The majority are capable of rapid germination in spring and early summer after dormancy has been removed by cold moist conditions in late autumn, winter, and early spring. High percentage germination is obtained if the post-thaw period is moist and cool, but warm and dry conditions in spring induce a secondary dormancy in seeds not covered with soil or mulch and low percentage germination results. Best germination is obtained on ash bed or cultivated seed beds. Germination on grassed seed beds is lower and affected more by weather conditions in spring. Seed-harvesting insects, including Dieuches notatus Stal. and Iridomyrmex foctans Clarke, have a significant effect on total germination.

The first twelve months is the most critical period for survival of seedlings. Exposure of roots by water wash, soil desiccation and damage by snow are the most devastating agencies in this period. Sown plots indicated that few or no seedlings survive on grass or scrub-covered seed beds. Best percentage survival resulted on ash bed, mainly due to the resistance to snow damage by seedlings so placed. Survival was moderate on cultivated seed beds.