Cunninghamia : A Journal of Plant Ecology for Eastern Australia, Volume 20 (2020)
Refine
Year of publication
- 2020 (15)
Document Type
- Article (15)
Language
- English (15)
Has Fulltext
- yes (15)
Is part of the Bibliography
- no (15)
Keywords
- 'bottom–up' and 'top–down' processes (1)
- Aboriginal burning (1)
- Apis mellifera (1)
- Avian seed dispersal (1)
- Avicennia marina (1)
- Frugivory (1)
- Grey mangrove (1)
- Mullions Range State Forest (1)
- Murrumbidgee River (1)
- Prasophyllinae (1)
Many aspects of the biology of Genoplesium baueri R.Br. (Orchidaceae) an endangered terrestrial orchid endemic to New South Wales, Australia, remain unknown. In this study observations were made on (1) plant morphology; (2) the biology of the fruit and seeds; (3) the biology of the plant tuber and the spatial patterning of emergent plants ; (4) the morphology of the pollen and the identity of pollen vectors and (5) to develop a preliminary description of the lifecycle of the orchid, by carrying out annual surveys of two key Genoplesium baueri populations in northern Sydney, for a 12-year period and collecting data on fruits, tubers and pollinators opportunistically. Individual plants cannot be tracked from year to year. We observed that each emergent plant produces a tubular leaf and an inflorescence of 1-15 non-resupinate flowers. Fruit capsules contained numerous tiny seeds, which were slightly larger than seeds of a closely related species, Corunastylis filiformis. The papillose surface of mature tubers of Genoplesium baueri differed greatly from the smooth, spherical tubers of Corunastylis fimbriata and is likely to be the site of orchid mycorrhizae. The occurrence of clumps of closely-packed, variously-sized tubers, each subtending single Genoplesium baueri plants, warrants investigation as development by vegetative increase at the tuber level provides one of several possible explanations. The morphology of the pollinarium and evidence of Chloropid fly-mediated pollination was observed. Our better understanding of the natural history and biology of Genoplesium baueri will contribute to orchid systematics and help inform management decisions regarding this species to ensure its persistence into the future.
Historical sources and the field description of extant remnants were used to reconstruct the distribution and characteristics of the pre-European vegetation of Wolgan Valley resort, in the western Blue Mountains on the western edge of the Sydney Basin. Like many of the agricultural landscapes of Australia the vegetation of this valley has changed dramatically since European settlement, however an understanding of the original state may facilitate effective management and potentially facilitate restoration. Investigation of remnants suggests that the pre-disturbance vegetation of the now cleared valley floor can be described with four plant communities. Grassy Woodland is likely to have occupied most of the valley floor and was part of the Grassy White Box – Yellow Box – Blakely's Red Gum Woodland listed as an Endangered Ecological Community under the NSW Biodiversity Conservation Act 2016 and as Critically Endangered under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. Grassy woodland would have graded into a shrubby woodland extending up the drier footslopes, eventually merging with the existing Talus Slope Woodland. Riparian Forest is likely to have occupied the major drainage lines of the valley and where the water-table was consistently higher, Closed Herbfield and Shrub swamp in swampy meadows/fens was likely in a chains of ponds landscape. The characterisation of the pre-disturbance vegetation allows the identification of a suite of species appropriate for planting in relevant landforms. Significantly, the luxury resort has the space to experiment with the various techniques needed to restore some of this Endangered Ecological Community, and in so doing make a significant contribution to its broader regional survival.
The functional relationships between woody vegetation, climate, soils and disturbances like fire are complex and vary greatly between continents due to historical and environmental differences. In the temperate grasslands of lowland south–eastern Australia, it is hypothesised that the extent of treelessness was influenced by Aboriginal burning practices, although this remains highly contested. This study reconstructed a multi–bioregional–scale grass/ tree boundary map across a large portion of central and northern Victoria from hundreds of historic plans, overlayed with the georeferenced observations of the earliest European accounts to test whether these grasslands were (a) more extensive than previously assumed, and (b) if there is evidence of the targeted, purposeful and frequent use of fire by Aborigines. The archival coverage was well–corroborated and identified extensive treeless 'plains' in unexpected areas compared with reconstructions based on climate–edaphic relationships alone. The historic accounts also served to shed light on the original nature of these treeless 'plains' as diverse and dynamic, and frequently dominated by Kangaroo Grass (Themeda triandra), implying a distinct influence of both frequent fire and people. However, while there is evidence of broad–acre Aboriginal fires in the collective historic accounts (including resistance to European intrusion), there remains a need for more in–depth and reliable historic case studies to clearly describe the use of fire by Aborigines that is inferred in the historic accounts studied here and commonly assumed by historians. The results lend support to treelessness driven by the dynamic interaction of 'bottom–up' and 'top–down' processes and that lowland temperate grassland distribution reconstructions across this region should be extensively corroborated or even derived exclusively from historic sources.
The Australian paintings of Marianne North, 1880–1881: landscapes 'doomed shortly to disappear'
(2020)
The 80 paintings of Australian flora, fauna and landscapes by English artist Marianne North (1830-1890), completed during her travels in 1880–1881, provide a record of the Australian environment rarely presented by artists at that time. In the words of her mentor Sir Joseph Dalton Hooker, director of Kew Gardens, North's objective was to capture landscapes that were 'doomed shortly to disappear before the axe and the forest fires, the plough and the flock, or the ever advancing settler or colonist'. In addition to her paintings, North wrote books recollecting her travels, in which she presented her observations and explained the relevance of her paintings, within the principles of a 'Darwinian vision,' and inevitable and rapid environmental change. By examining her paintings and writings together, North's works provide a documented narrative of the state of the Australian environment in the late nineteenthcentury, filtered through the themes of personal botanical discovery, colonial expansion and British imperialism.
Systematic targeted surveys for the vulnerable and poorly conserved Pterostylis chaetophora (family Orchidaceae) were undertaken during peak flowering over ten days in 2018 and 2019 across 720 ha of Columbey National Park (Columbey). The assumed population size of this species in Columbey prior to this study (c. 20 individuals) was found to be unrepresentative of the number of sub-populations (175) and individuals (544) subsequently located along 141 km of search transects. Extrapolation of this result across the full Columbey study area suggests an upper population size of nearly 3000 plants, increasing the total documented New South Wales population 15-fold. The most commonly occupied communities for Pterostylis chaetophora were found to be Floodplain Redgum-Box Forest (57% of individuals and 54% of sub-populations), Lower Hunter Spotted Gum-Ironbark Forest (28% of individuals, 25% of sub-populations), and Seaham Spotted Gum-Ironbark Forest (14% of individuals, 18% of subpopulations). The largest sub-populations (>10 individuals) were in Floodplain Redgum-Box Forest where Eucalyptus moluccana dominated the canopy, followed by Lower Hunter Spotted Gum-Ironbark Forest and Seaham Spotted Gum-Ironbark Forest. All three occupied communities are relatively widespread in the lower Hunter Valley and lower North Coast regions, suggesting that such habitat elsewhere may harbour undetected populations of Pterostylis chaetophora. These results suggest that systematic targeted surveys for other threatened orchids are necessary to fully understand both the magnitude of a species' population and its occupied habitat. Such surveys may ultimately lead to re-assessment of the conservation status of some of these species where, like Pterostylis chaetophora, considerably more populations and individuals are uncovered within secure land tenure.