by
J.W. Turnbull
Forest Research Institute
Forestry and Timber Bureau
Banks St.
Yarralumla, A.C.T., Australia
Eucalyptus globulus Labill.
Tasmanian blue gum, southern blue gum, blue gum.
MYRTACEAE: (SUB-FAMILY: LEPTOSPERMOIDEAE).
Description: A medium to large tree, up to 60 m high and 2.25 m in diameter. Bark rough and fissured to 3 m at the base of the trunk, decorticating in long strips from the remainder of the trunk and branches leaving a smooth bluish grey surface.
Foliage heterophyllous, the juvenile leaves opposite, sessile, the base cordate to amplexicaul; outline ovate or broadly lanceolate; margins entire; apex blunt of apiculate. Leaf surface covered by grey waxy bloom. Leaf size 8cm – 15cm × 5cm – 10cm. Adult leaves alternate, petiolate, lanceolate or falcate lanceolate; apex acuminate, margins entire. Surface dark, glossy green. Size: 12cm – 30cm × 2cm – 4cm.
Flowers axilliary, usually solitary, on very short or rudimentary peduncles. Buds topishaped, 4-ribbed, warty, the surface glaucous; 1.5cm – 3.0cm × 1cm – 2cm. Anthers very numerous, spreading, creamy-white in colour. Fruit a woody “capsule”, 2.5cm diameter, broadly top shaped or globose, sessile with a broad, flat or convex thickened disc extending over the valves. The capsule is warty, glaucous, 4-ribbed. The seeds are small, there are approximately 70 seeds per gram.
Illustrations: See Maiden (1914), Kelly (1969), Hall, Johnston and Chippendale (1970).
Habitat and Ecology: The Tasmanian blue gum is a dominant or sub-dominant species in moist temperate sclerophyll forest. It is seldom found in extensive pure stands, usually being associated with at least one other species of eucalypt. Within a particular area it is closely tied to a restricted range of habitats and as a result a mosaic pattern is formed with local stands of E. globulus being separated by stands of species occupying different habitats (Kirkpatrick, 1973).
This species occurs in undulating country near the coast in the cooler parts of its distribution but in the warmer parts it is usually in the moister valleys of hilly country. It grows best on moderately deep soils with good drainage but it will tolerate poorer soils. The annual rainfall is from 550 mm to 950 mm.
Present Distribution: The main occurrence is in eastern Tasmania from 0 m – 500 m above sea level. It is less common on Flinders Island, King Island and Rodondo Island in Bass Strait. Isolated, very small relict stands occur on the west coast of Tasmania. In Victoria there are small occurrences in the Otway Ranges and South Gippsland. The distribution of populations in Victoria is somewhat fragmented, the situation is complicated by the intermediate populations of E. globulus grading into E. pseudoglobulus in South Gippsland and into E. bicostata (st. johnii) in the Otway Ranges (Kirkpatrick, 1971, 1973).
In early published references to the species in the more northern part of Victoria and southern New South Wales, there was confusion with the closely related species E. bicostata.
Status: This is not an endangered species. However, some of the small populations cannot be considered safe. The relatively large area of E. globulus on the east coast of Tasmania, is well represented in State Forest Reserves and appears to be in little danger at present although wood chip operations may ultimately reduce the population size. The populations at the highest altitudes in Tasmania (450m – 500m) are on private land and cannot be considered safe. The very small relict stands on the west coast of Tasmania may also need some conservation measures.
Before settlement, the forests of King Island were dominated by E. globulus. This forest has since been burnt and cleared out of existence but a small number of individuals of E. globulus still exist. The population on Flinders Island is partially included in a National Park. The small population on the uninhabited Rodondo Island is intact although its ability to regenerate itself appears to be related to the frequency of chance fires caused by lightning.
The greatest threat to E. globulus is in Victoria. The Otway Range populations are relatively safe as some are included in Forest Commission Parks but there is some clearing for pines on the inland slopes. In South Gippsland, apart from in Wilson's Promontory National Park, the populations are not safe. Distinct populations intermediate between E. globulus and E. pseudoglobulus around Yarram and Neerim South are on private land with the possible exception of riverine corridors. There are populations in the Crown Forest in the hills to the north of the Latrobe Valley. On the northern slopes of the South Gippsland hills there is a threat to the populations as a result of forest clearing and replacement with conifers, E. regnans, or E. globulus of Tasmanian origin. In the Crown Forests, clearing and progressive alienation pose a future threat. Within the South Gippsland area one population is conserved in the Morwell National Park.
Protective measures already taken; measures recommended
There are many populations of E. globulus included in National Parks and Forest Parks and these will ensure the survival of the species and much of its genetic variation.
There are some distinct populations in South Gippsland and Tasmania which are in a precarious state. Where these populations occur on Crown Land the local authority could create one or more reserves to ensure their survival. Where the trees are on private land their preservation in situ may not be possible and the collection of seed from a large number of individuals and the establishment of a plantation in a reserved area may be a more practical measure to conserve the gene resource.
Cultivation: E. globulus is easily raised from seed and this is the only practical method. Germination usually takes from 5–8 days and the seedlings may be potted after about 6 weeks. Planting out may be done as soon as the seedlings have become established.
Value: The timber is used in both heavy and light construction and is highly regarded for purposes in which bending is necessary. It is used for poles, piles, sleepers and in the manufacture of pulp and paper. Outside Australia it is one of the most widely planted of all eucalypts and forms the basis of forest industries in some countries.
References:
Blakely, W.F. (1965) A Key to the Eucalypts. 3rd Ed. Forestry and Timber Bureau, Canberra.
Curtis, Winifred M. (1956) The Students Flora of Tasmania. Vol. I. Govt. Printer, Hobart.
Hall, N., Johnston, R.D. and Chippendale, G.M. (1970) The natural occurrence of the eucalypts. Leaft. No. 65. 2nd Ed. For. Timb. Bur. Canberra.
Kelly, S. (1969) Eucalypts. Thomas Nelson. Melbourne.
Kirkpatrick, J.B. (1971) A probable Hybrid Swarm in Eucalyptus. Silvae Genet. 20: 157–159.
Kirkpatrick, J.B. (1973) Geographic variation in Eucalyptus globulus Labill. Vols. I and II, PhD. Thesis. Univ. Melbourne (unpublished).
Maiden, J.H. (1914) A critical revision of the genus Eucalyptus. Vol. II. Govt. Printer, Sydney.
