Cunninghamia : A Journal of Plant Ecology for Eastern Australia, Volume 12, Issue 3 (2012)
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The pre-colonial distribution of grasslands, woodlands and forests on the Werribee plains, Victoria
(2012)
We use historic plans and recent field observations to reconstruct and describe the former (pre-1750) character and distribution of vegetation on the Werribee Plains, near Melbourne. The primary outcome of this research is a detailed vegetation map. The ecological factors controlling the distribution of trees and open-plains are also discussed. The results show that most of the area was treeless grassland at the time of European settlement (1835). This grassland was broken up by clearly-defined areas of Eucalypt forest, some of which remain. There is, in contrast, little remaining trace of the woodlands of Allocasuarina and Banksia, which we show were once widespread on the plains and stony rises beyond the Eucalypt forest. This work is timely, given the proposal for the creation of two large new reserves in the area, which contain many areas that may be subject to restoration.
Little is known about groundwater-dependent ecosystems in south-eastern Australia and few studies have examined the impact of landclearing upslope of such ecosystems. The eastern edge of Porters Creek wetland, near Warnervale on the Central Coast of New South Wales, supports a Eucalyptus parramattensis subsp. Parramattensis (Parramatta Red Gum) population. The population has been listed as an Endangered Population (EP) and was showing signs of dieback during the 2002 to mid-2007 drought. Water table depth, soil moisture tension, soil temperature and groundwater salinity beneath this woodland were measured to investigate whether the woodland is associated with a shallow aquifer and/or high soil moisture conditions, and whether an upslope construction development would impact on the ecosystem. The composition, structure and health of the Eucalyptus parramattensis Woodland was also examined. Monitoring over 5 years demonstrated that Eucalyptus parramattensis is associated with a shallow, slightly saline to saline (8–12 ppt) water table, 1.4–3.1 m beneath the surface of a drainage depression wetland. During the drought water table drawdown rates were quite rapid, and rainfall events took up to a month to replenish water table levels. Landclearing for an upslope development significantly decreased the average water table level by 0.3–0.5 m during the construction phase, while peaks that occurred at the base of the slope after large rainfall events reversed the normal direction of the water table gradient. The water table re-stabilised to pre-construction levels after construction was completed and the area was landscaped and revegetated with grass. The short-term alteration of groundwater conditions did not appear to impact on tree health; the poor tree health observed prior to construction was most likely due to the lowering of the water table (and/or an increase in groundwater/soil salinity) during the drought years. Our results suggest that developments that revegetate slopes above wetlands as quickly as possible after clearing, orundertake clearing in stages, will minimise effects on water table levels. Pervious detention basins designed to capture runoff and allow infiltration into the soil help replenish aquifers, but also require weed maintenance. This study highlights the significance of maintaining shallow aquifer and catchment processes for the conservation and rehabilitation of coastal wetlands, many of which are listed as Endangered Populations or Endangered Ecological Communities.
Using Australian Virtual Herbarium data to find all the woody rain forest plants in Australia
(2012)
Data bases that provide continental and global scale information about species distributions provide a valuable resource for environmental, ecological and evolutionary research. However to bring a large dataset to a standard that is suitable for quantitative analysis, data quality needed to be checked. Here we provide a worked example using a large dataset (c. 320,000 records) from Australia’s Virtual Herbarium (AVH) database, based on an initial data request for full distribution data for c. 2600 woody rain forest species known to occur in Australia. To reconcile inconsistencies around taxonomic identity prior to merging with our trait data-base, and resolve issues around spatial resolution and accuracy, we implemented extensive data filtering using a ‘cloud-based’ solution (Google Refine). This systematic process resulted in 1) the removal of close to 45% of the records originally downloaded, and 2) a clean and powerful data set based on herbarium backed distribution records for Australia’s woody rain forest species. Such resources can contribute significantly to improving research outcomes related to understanding Australia’s vegetation.
The floristic composition and vegetation partitioning of the ephemeral wetlands of the Pilliga Outwash within the Pilliga National Park and Pilliga State Conservation Area (30˚30’S, 149˚22’E) on the North Western Plains of New South Wales are described. SPOT5 imagery was used to map 340 wetlands across the Pilliga Outwash. A total of 240 plots within 31 wetlands explored composition and species richness in relation to water depth and wetland size. The predominant community described is the species-rich herbfield of shallow basin wetlands, along with the structurally distinct but the less common sedgeland/herbfield of the deeper ‘tank’ wetlands and a single wetland with a floristically depauperate Diplachne fusca wet grassland. A total of 131 taxa were recorded including three species listed under the NSW Threatened Species Conservation Act (1995): Eriocaulon australasicum, Lepidium monoplocoides and Myriophyllum implicatum. New records for an additional six taxa were recorded for the North Western Plains. 11% of taxa were exotic in origin.
Particular botanical sites have always been attractive to botanists, and the recording of such sites even in an ad hoc way, adds to our long-term documentation of ecological change. Here we look at records from an unusual dry rainforest site in western Sydney, first recognised in 1910, and re-recorded on several occasions more recently. Though the site has little formal conservation protection, the records indicate that many of the original species still survive at the site, while the periodic recording draws attention to the scientific value of the site, particularly at a local level, and has increased its value as an ecological reference site. Much of the vegetation of the Cumberland Plain has been subject to major clearing and disturbance over the past 200 years, and almost all vegetation is recovering in some way. Repeated visits are valuable for getting a complete picture of the flora; repeated visits by the same botanist over the shorter term (e.g. within a few years) may also be valuable, especially as the revisiting botanist may be more likely to notice changes. By documenting sites now, and continuing this over future years; we can enhance the value of many existing sites.