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eucalyptus subcrenulata

Image of E. subcrenulata trunk and seeds

Yellowish trunk on left with leaves and immature seed capsules of recently discovered E. subcrenulata (Alpine Yellow Gum) at Coupe GC134F on the lower slopes of Blue Tier.

- f. duncan and p. rosevear

..... Laurie Gregson (FT Bass District) found an unfamiliar eucalypt near the southern boundary of the coupe (GC134F), where the bench grades into slopes with occasional outcropping granite Samples were dispatched to the FPB's botany section. A few characteristics sparked interest - ridges on fruits and buds and a yellowish tinge to the bark and leaves indicated a relationship with the yellow gum group - a series of eucalypt species that had not been collected previously in the Northeast Highlands. There was further excitement (botanists are easily excited!) when this conjecture was supported by Professor Jim Reid and Associate Professor Brad Potts - eucalypt aficionados from the School of Plant Science at the University of Tasmania

In November 2003, the site was visited by staff of the Forest Practices Board, Forestry Tasmania (Bass District and the Conservation Planning Section), Brad Potts (Uni. of Tasmania) and Beris Hansberry of the Friends of the Blue Tier community group. Samples of leaves and reproductive material were collected from several trees, ranging in height from 5 m on exposed rocky sites, to 25 m on the more sheltered and humid slopes to the south of the coupe. The field diagnosis suggested that the species had close affinities with Eucalyptus subcrenulata (alpine yellow gum) and this was subsequently confirmed by analysis of chloroplasts. An inspection of the slope showed that E. subcrenulata occupied an area of at least 80 ha, in some places co-occurring with E. obliqua and in others dominating a wet sclerophyll understorey. Some of the trees, particularly towards the upper slopes, had a handsome open-growing form, their yellowish leaves and trunk seeming to glow in the afternoon light. A few seedlings and saplings were found, and there were also signs of some regeneration from coppice.

The presence of S. subcrenulata in this area is of great biogeographic interest. The nearest population is about 100 km away, on the northeastern rim of the Central Plateau. The species typically occurs at altitudes above 800 m, as its common name indicates. This would suggest that its occurrence near Blue Tier is a relict of the colder glacial climate, in the same way that occurrences of E. coccifera on isolated peaks in the Eastern Tiers can be considered as survivors from this period. However, the relatively low altitude of this population (500-600 m) and its presence on sheltered slopes not subject to the temperature extremes of Blue Tier itself, does not sit comfortably with this explanation. In other parts of Tasmania E. subcrenulata grades into E. johnstonii at lower altitudes, and the Blue Tier trees may also be intermediate between these two nodes on the yellow gum continuum. It is possible that E. subcrenulata occurs elsewhere in the Northeast Highlands, with other populations being mistaken for other gum-barked species (E. viminalis, E. darympleana, E. brookeriana or E. regnans).

The slope that supports most of the E. subcrenulata has not been logged in the past, though it seems to have been burnt by wildfire (possibly also associated with mining activities). The original coupe boundary excluded most of the E. subcrenulata population, but an additional buffer was subsequently added to provide further protection. A few E. subcrenulata trees are scattered in the coupe. The Forest Practices Plan has been modified so that such occurrences are preferentially retained (e.g. in wildlife habitat clumps). It is inevitable that some individuals will be affected by logging, but the prescriptions outlined above, plus the ability of the species to regenerate after disturbance, will ensure that there is negligible effect on the population

The location of the E. subcrenulata population will be designated by Forestry Tasmania as a Special Management Zone (SMZ) for Flora. This means that maintenance of this value is paramount in any land management decision affecting this area. The SMZ abuts the north-facing slopes off Lehners Ridge, which will also be managed to protect the big trees in old-growth E. obliqua forest, mentioned previously.

Fred Duncan, Senior Botanist, Forest Practices Board
Paul Rosevear, Planing co-ordinator, Bass District, Forestry Tasmania

[Extracted from Forest Practices News, Vol 6 #1, ISSN 1441-1288]

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