3.13 eucalyptus hallii brooker
Eucalyptus hallii is endemic to south east Queensland where it is known between Bundaberg and Howard. It has a distributional range of approximately 45 km and encompasses an area of occurrence of approximately 1300 km2. Presently the main area for this species is on freehold, vacant crown and State Forest lands (SF 840 Fty 1633). The species is present in Burrum Coast National Park. There is no quantitative data on population sizes. Current or perceived threats to the continued survival of E. hallii are habitat loss and changes in soil hydrology.
3.13.2 Species description and identification
The genus Eucalyptus is placed in the family Myrtaceae and has approximately 700 species mostly which are endemic to Australia but several species extending to parts of Malesia and the Philippines (Chippendale 1988).
Eucalyptus hallii Brooker was formally described in 1975 from material collected near Goodwood, approximately 30 km south of Bundaberg (Brooker 1975). The botanical description of Eucalyptus hallii is as follows:
A tree to 28 m high with smooth bark on the trunk and branches. The bark is orange to pinkish-grey when fresh, then turns to a mottled grey or dark grey with age. The juvenile leaves are lanced-shaped to ovate, measure up to 15 cm long by 8 cm wide and are arranged in pairs along the branches. The slightly glossy green or grey-green, adult leaves are lance-shaped or sometimes sickle-shaped. They measure up to 15 cm long by 2.5 cm wide. The white flowers are grouped into axillary clusters of up to seven on laterally flattened stalks that reach 1 cm in length. Mature flower buds are egg or club shaped, measure up to 9 mm long and have a rounded or cone-shaped cap. The seed capsules are obconical, 5-8 mm long by 5-7 mm in diameter, with 3 chambers. For a more detailed description refer to Brooker (1975) and Chippendale (1988). The species is illustrated in Brooker and Kleinig(1994).
Eucalyptus hallii is a distinctive species and difficult to confuse with other species within its narrow range. E. bancroftii is another smooth bark species in the area. E. hallii can be distinguished from this species by its ovoid buds with hemispherical or conical operculums, and it grows in drier and slightly more elevated sites than E. bancroftii.
3.13.3 Current conservation status
Eucalyptus hallii is presently listed on the schedule of the Queensland Nature Conservation Act 1992 as “vulnerable wildlife”. The species has been assigned a national conservation status of V (vulnerable) by ANZECC (1993). It is also listed on Schedule 1 Part 2 (vulnerable) of the Commonwealth Endangered Species Protection Act 1992.
3.13.4 Distribution and abundance
E. hallii was not surveyed during the present study. Details from Queensland Herbarium specimens of E. hallii are listed in Appendix 1.12. Altogether 22 specimens of E. hallii have been collected. Three CORVEG sites have also been recorded but are presently not vouchered. E. hallii has a distribution from the Bundaberg of south to Howard and from Childers east to the coast. There is a single record from Fraser Island. However, investigations have not confirmed this locality and it is considered highly unlikely to be present on the island (Mr A.R. Bean pers. comm.). The species is conserved in Burrum Coast National Park (Kinkuna, Woodgate and Burrum River sections). Presently the main extent of this species is on freehold, vacant crown and State Forest lands (SF 840 Fty 1633). The distribution of E. hallii has a range of approximately 45 km and encompasses an area of occurrence of approximately 1300 km2. Extensive surveys have been undertaken by Erskine (1992). However, there is no quantitative data available on the number of individuals in the wild.
Eucalyptus hallii is most commonly found in open eucalypt forest or woodland at altitudes of 5 to 70 m. It occurs in coastal areas on low flat to undulating terrain on gentle slopes and broad rises. The surface soils are generally grey sandy to silty in texture with a acidic reaction and derived from Tertiary sedimentary rocks. Eucalyptus hallii is usually dominant or co-dominant in the canopy of the community in which it grows. The more frequent tree species recorded with this species are Eucalyptus umbra, Corymbia intermedia, C. trachyphloia, Angophora leiocarpa, Melaleuca quinquenervia and Syncarpia glomulifera.
3.13.6 Life history and ecology
Eucalyptus hallii is one of the few threatened Queensland species that has been studied in some detail. Erskine (1992) examined the life cycle and environment of this species and most of the information presented here comes from his report.
E. hallii is a medium size tree reaching 28 m high. The longevity of individual plants is unknown. However, it is suspected to be at least 100 years. The main method of reproduction is by sexually produced seeds. E. hallii appears to become reproductive when its girth exceeds 30 cm (Erskine 1992). Cultivated material of this species has been observed to flower within three years of germination. However, trees growing under natural field conditions have been observed for approximately 17 years and have never flowered.
Flowering has been reported in January and February by Brooker and Kleinig (1994) and from December to April (Erskine 1992). Plants have been recorded with buds throughout the year. The most common pollinators of Australian Myrtaceae are insects (Beardsell et al. 1993). Erskine (1992) reports anecdotal evidence that native bees may be effective in the pollination of E. hallii. Fruits have been recorded on the branches throughout the year. It is unknown how long the seed is retained in the woody fruits on the tree. Pryor and Johnson (1981) reported that many tropical eucalypt species shed their seeds and drop their fruit a few months after flowering, whereas southern species may retain their fruits for more than a year. The seed once released from the fruit falls to the ground. The seed has no adaptation for secondary dispersal by animals. Cremer (1977) observed that wind is probably the only important agent of seed dispersal in the eucalypts. The seeds readily germinate given reasonable moisture and temperature conditions. Erskine (1992) found high levels of vigour and viability of fresh seed. It is unlikely that a soil seed bank would develop for this species.
Fire is a major environmental factor in Australia, in particular in dry sclerophyll forest. Eucalypts are among the most resistant of trees to intense fire. E. hallii has the capacity to sprout from proventitious buds on the trunk, producing epicormic shoots. As with most eucalypt species E. hallii forms a lignotuber in the early stages of its life cycle. If for some reason the seedling which has developed from the tuber is destroyed growth is vigorously renewed by the development of new shoots from the lignotuber. The time required before the seedlings can tolerate fire is estimated to be 1 or 2 years (Erskine 1992). Once the plant develops to a particularly girth it appears that the tuber is no longer detectable. It has been observed that mature plants which have been cut off above ground level can coppice from the stump.
There can be no doubt that habitat alienation (for agriculture and exotic pine plantations) in the species’ narrow geographical range has lead to a decline in populations in the past. A large proportion of the presently known populations is estimated to be on freehold land, State Forest lands of low commercial timber values and Vacant Crown Land. These areas are still under the potential threat of conversion to agricultural land for sugarcane, subdivision and clearing for semi rural blocks, forestry production or other uses that could be detrimental for the populations.
Erskine (1992) observed a correlation between the level and extent of soil waterlogging and the distribution of E. hallii within its restricted range. It could be speculated that the soil hydrology may be significant in the establishment and survival of the species in the region. Changes in soil hydrology through irrigation or the drainage of areas may affect the ability of this species to survive.
Populations mapped by Erskine need to be vouchered and the landholders should be contacted and made aware of the significance of the species.
Only a small portion of known population is protected within land set aside for conservation purposes. The protection of the remaining natural vegetation in the state forest lands should be pursued through either declaration of a State Forest Scientific Area under the Forestry Act 1959 or by converting the land to a conservation reserve.
There is little detailed information available on the role of fire in the ecology and biology of E. hallii. This needs to be understood if successful management techniques are to be developed for the conservation of the species in the wild. Research into the effect of fire on reproductive ecology and population dynamics is required.
It is speculated that levels and extent of waterlogging may be significant in the survival of the species. The relationship between soil hydrology and the local distribution of E. hallii should be established.