Refine
Document Type
- Article (3)
Language
- English (3)
Has Fulltext
- yes (3)
Is part of the Bibliography
- no (3)
Hunter Valley Weeping Myall Woodland is listed as a Critically Endangered Ecological Community (CEEC) under both the New South Wales Threatened Species Conservation (TSC) Act 1995 and the Commonwealth Environment Protection and Biodiversity Conservation (EPBC) Act 1999. Uncertainty regarding the provenance of Weeping Myall (Acacia pendula) in the Hunter has led to questioning of the place of Hunter Valley Weeping Myall Woodland CEEC in State and Commonwealth legislation. A recent publication has endorsed its legislative listing, largely based on the co-association of Weeping Myall with a range of other semi-arid species in some parts of the Hunter Valley. We counter this argument and show that the semi-arid species present in low rainfall areas on Permian sediments of the Hunter Valley floor are in fact more widespread than previously documented. Through examination of distributional records, we demonstrate that these species display no fidelity to purported Hunter Valley Weeping Myall Woodland, but instead occur in a range of other vegetation communities across much of the central and upper Hunter Valley. Habitat suitability modelling undertaken for Acacia pendula shows there to be nearly 900 times the 200 ha of pre-European extent, or 20 times the area of occupancy previously estimated for this community. We also revisit an earlier ordination analysis which showed a divergence in sample data potentially representative of Hunter Valley Weeping Myall Woodland. We add new samples and provide a revised classification of the purported community, which shows that sample plots from two forms of Hunter Valley Weeping Myall Woodland are floristically indistinguishable from comparative data in 20-25 year old mining rehabilitation forests of Eucalyptus cladocalyx, and native grasslands derived predominantly from landscapes of Eucalyptus crebra and Eucalyptus moluccana. Relevant legislation requires any threatened community to be identifiable based on a particular species assemblage and its area of occupancy. We question whether Hunter Valley Weeping Myall Woodland is recognisable with and without the presence of Acacia pendula. We argue that the identification of Hunter Valley Weeping Myall Woodland is unachievable without the visual cue of Acacia pendula, and note that for some time regional botanists have used this species’ presence as a de facto diagnostic tool to identify this community; in fact, there are no examples of the community having been identified as such in the absence of Acacia pendula. Finally, following from our ordination results, and the presence of key diagnostic species within more widespread grassy woodlands and derived native grasslands, we suggest that 200 years of anthropogenic disturbance across the Hunter Valley has sufficiently masked any distributional pattern of western semi-arid species that might have once occurred. We contend that there is little value in conserving a purported community that cannot be confidently delineated in numerical classifications, lacks a consistent and diagnostic suite of characteristic species, and for which there is uncertainty over the origins of its dominant, flagship species, Acacia pendula.
Tetratheca juncea Smith (family Tremandraceae) is a terrestrial herbaceous plant now mainly found in the Lake Macquarie area of coastal NSW and listed as Vulnerable under Schedule 2 of the NSW Threatened Species Conservation Act 1995. This study carried out from July 2001 to June 2002 records the observation and identification of two species of native bee buzz-pollinating its flowers and describes a direct relationship between the first appearance of a pollinator and the commencement of seed set. Findings from this study with respect to the pollination ecology of Tetratheca juncea are:
• There is a strong flowering period from September to January, though a number of flowers can be found on some plants across the geographic range of the plant in all months of the year;
• Two species of native bee Lasioglossum convexum and Exoneura sp, were confirmed collecting pollen from the flowers by way of buzz pollination;
• Fruiting only occurred in coincidence with flower pollination by these bees;
• Flowering, seed set and seed release was a concurrent process while ever the bees were active;
• The bees are polylectic and the sexual reproductive process in Tetratheca juncea appears to be pollinator-limited.
Acacia pendula, Weeping Myall, (family Fabaceae) is the most legislatively protected plant species in the New South Wales Hunter Valley. Under the NSW Threatened Species Conservation Act 1995 it is listed as an Endangered Population (in the Hunter Valley) and as a component of two Endangered Ecological Communities (one in the Hunter, one elsewhere in NSW); it is also listed as a Critically Endangered Ecological Community (in the Hunter Valley) on the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 and listed as threatened in three other eastern Australian States.
To ascertain the likely original distribution of stands of Acacia pendula in the Hunter Valley, this paper examines the writings of early Australian explorers, herbarium and database records, and the species habitat attributes across NSW. None of the journals examined, including those of botanist/explorer Allan Cunningham (who originally collected Acacia pendula from the Lachlan River in 1817), Thomas Mitchell or Ludwig Leichhardt, make note of the species for the Hunter Valley. Several explorers do, however, record Acacia pendula regularly (>100 times) across other parts of NSW, Queensland, and South Australia.
Historical herbarium and database records show a paucity of records from the Hunter prior to the year 2000, after which a 37-fold increase in observations since 1951 is apparent. For the first 128 years of botanical exploration (1823 to 1951), there are no validated collections or records of Acacia pendula from the Hunter Valley. The single exception is a specimen collected by Cunningham from 1825 (lodged at Kew, UK), purported to be from ‘Hunters River’, but which is morphologically different to other collections of Acacia pendula from that time. There is some uncertainty over the origins of this specimen.
Analysis of habitats supporting Acacia pendula in NSW outside of the Hunter show them to differ significantly in geological age, soil type, rainfall and elevation from those in the Hunter.
Collectively, these findings provide a strong circumstantial case that Acacia pendula was absent from the Hunter at the time of European settlement; this has important implications for the conservation and management of Hunter stands. Rather than being a threatened species in the Hunter Valley, it is postulated that Acacia pendula has been intentionally and/or accidentally introduced to the region, and may now be imposing a new and emerging threat to the endangered grassy woodlands and forests there. There is now an urgent need for genetic studies to clarify the origins of the current Hunter Valley stands, and to define the taxonomic limits of Acacia pendula and its close relatives.