Towards an explanation of the altitudinal distributions of three species of Eucalyptus in central Tasmania.

Abstract

Eucalyptus gunnii, E. rodwayi and E. ovara are parapatrically distributed in grassy woodlands at high, medium and low altitude, respectively, in central Tasmania. Seedlings from provenances from the middle of the altitudinal ranges of all species were capable of survival for 18 months on sites dominated by the other two species. However, 9 years after planting E. ovala had died out in open vegetation on all sites. In contrast, E. rodsoayi had survived in open vegetation on all sites and was the sole or major survivor in the two lower altitude areas. E. gunnii had performed marginally better than E. rodsoayi in the open vegetation at the highest altitude site, had survived in the E. roduiayi site and had died out in the E. ouaia site. The results of field trials, and experiments in the glasshouse and laboratory, suggested that E. ouata is absent from open vegetation at the higher altitudes because of its susceptibility to frost, that E. rodwayi dominates the middle altitudes because of its superior frost resistance, that E. guunii dominates the highest altitudes because of superior growth rates to E. rodsoayi in misty and cool conditions, and that E. ouata is dominant at low altitudes because of its superior growth rates in warm conditions. Recent climatic changes arc posited to have had some effect on the results of the field experiment. Key words: climate, distribution, drought, Eucalyptus, frost, germination, growth rate, heat re