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Hurstville Grove, Australia

Gibbons P.,Australian National University | Briggs S.V.,Khan Research Laboratories | Murphy D.Y.,Climate Change and Water NSW | Lindenmayer D.B.,Australian National University | And 2 more authors.
Forest Ecology and Management

Estimates of forest and woodland structure prior to major periods of modification (e.g. prior to European settlement) are routinely used to inform decisions relating to biodiversity conservation, silviculture and carbon sequestration potential in natural forests and woodlands. The techniques used to derive these estimates often demand that data be collected from specific geographic locations (e.g. locations for which historic survey records exist, where pollen accumulates, or where there is little modification by humans since European settlement) and therefore are often inherently biased. In this study we predicted numbers of trees by diameter class for several widespread forest and woodland types in south-eastern Australia under conditions of relatively little modification by humans since European settlement. To do this we fitted Generalised Additive Models (GAMs) separately to counts of stems in eight diameter classes from 495 plots using explanatory variables representing human modification, environmental variation and natural disturbances. We predicted stem densities under conditions of relatively little modification by humans since European settlement from these models by holding the significant explanatory variables representing modification by humans at minimum observed values. We compared these predictions with published estimates of pre-European stem densities and estimates that we derived for stands at theoretical equilibrium using the quotient of diminution (q). Our mean predictions were broadly comparable with estimates derived from both of these sources; however, we appeared to over-estimate numbers of stems in the smaller diameter classes for some vegetation alliances. A key outcome of this research - and rarely reflected in other techniques used to predict pre-European forest structure - was the amount of variation in stem numbers even within a single diameter class and vegetation alliance. For example, in the white box vegetation alliance, flat parts of the landscape supported 5 times the number of large trees (>80cm DBH) found on upper slopes under conditions of relatively little modification by humans since European settlement. Our results therefore suggest that these forests and woodlands are more structurally heterogeneous than typically reflected in pre-European estimates and vegetation alliance should not be the unit for managing these stands. The methodology we present is applicable in many forests where the objective is to predict forest structure under conditions of relatively little modification by humans. © 2010 Elsevier B.V. Source

Daly G.,PO Box 3109 | Craven P.,Climate Change and Water NSW
Australian Zoologist

We monitored a population of Stuttering Frog Mixophyes balbus tadpoles in Macquarie Pass National Park near Albion Park on the south coast of New South Wales. The species was initially detected by the presence of tadpoles at one site in 2000. Surveys thereafter were conducted at this site and the broader catchment of Macquarie Rivulet in an attempt to detect adults and or other tadpoles. Fifteen 250 m transects located along perennial creeks were surveyed at night for 30 min each and diurnal searches for tadpoles were conducted along approximately five km of creekline. About 200-300 tadpoles were recorded at this same site in January 2005; this cohort declined to about 15 tadpoles by September 2005. A total of 20 small tadpoles were taken into captivity in January 2005 in an attempt to maintain a captive population. Swab samples taken from free-living tadpoles indicated the presence of the frog chytrid fungus, Bactrachochytrium dendrobatidis. Mixophyes balbus may no longer persist at this site and managers now have to decide if the last cohort should be allowed to breed in captivity or an attempt made to outbreed this contracted genetic base. The captive population raises the dilemma, what should we do with captive populations that represents the last genetic vestige of an isolated population that may not persist in the wild?. Source

Bradstock R.A.,University of Wollongong | Ooi M.K.J.,Climate Change and Water NSW | Ooi M.K.J.,University of Sheffield | Denham A.J.,Climate Change and Water NSW | And 2 more authors.
Australian Journal of Botany

In addition to direct fire cues such as heat, smoke and charred wood, the passage of fire leads indirectly to changes in environmental conditions which may be able to break physical dormancy in hard-coated seeds. After a fire, the open canopy and the burnt material lying on the surface alter the thermal properties of the soil, resulting in elevated soil temperatures for long periods of time. We simulated daily temperature regimes experienced at different depths of soil profile after a summer fire. Our aim was to determine whether these temperature regimes and the duration of exposure (5, 15 and 30 days) play an important role breaking physical seed dormancy in six legumes from south-eastern Australia. Our results showed that simulated temperature regimes break seed dormancy. This effect is specially pronounced at temperatures that are expected to occur near the soil surface (0-2 cm depth). The duration of exposure interacts with temperature to break dormancy, with the highest germination rates reached after the longest duration and highest temperatures. However, the germination response varied among species. Therefore, this indirect post-fire cue could play a role in the regeneration of plant communities, and could stimulate seedling emergence independent of direct fire cues as well as in interaction with direct cues. © 2010 CSIRO. Source

Parnaby H.,Climate Change and Water NSW | Lunney D.,Climate Change and Water NSW | Lunney D.,Murdoch University | Silannon I.A.N.,Climate Change and Water NSW | Fleming M.,Climate Change and Water NSW
Pacific Conservation Biology

Hollows in trees are recognized as a critical and threatened resource for a wide range of fauna in Australian forests and woodlands, yet little data are available on the impact of fire on hollow-bearing trees. We report an opportunistic, post-fire assessment of the proportion of burnt, hollow-bearing trees that collapsed in stands near roads following low intensity prescription burns in three areas of mixed eucalypt forest in the Pilliga forests. Mean collapse rates on 29 plots (40 by 50m), separated by bum Area, ranged from 14-26% for a total of 329 burnt hollow-bearing trees. Collapse rates on individual plots ranged from 0-50%. Collapsed, hollow-bearing trees were predominantly older, with 40% of senescent trees and 44% of live stags collapsing. The best predictor in models of tree collapse was the presence of a basal fire entry point. We cannot determine the extent to which collapse rates on our plots are representative of burnt areas away from containment roads due to sampling limitations, but they appear to be higher than those reported from wildfire and more intense prescription burns in southern Australia. Our results point to an urgent need for comprehensively designed studies to address the impacts of prescribed burns on hollow-bearing trees. Source

Spikmans V.,Climate Change and Water NSW | Vaughan G.,Climate Change and Water NSW | Guo C.,Climate Change and Water NSW | Fuller S.,Climate Change and Water NSW
Environmental Forensics

An increase in the production of biodiesel has been accompanied by a rise in the occurrence of biodiesel spills. To determine the source of a spill, fatty acid methyl ester fingerprinting is generally used. However, in the experience of these authors, this approach was of limited use for matching biodiesel residues back to the source material. The present work demonstrates sterol profiling for matching spill samples to a source. Sterol profiling was found to be a better approach for this than fatty acid methyl ester profiling, with the added benefit that sterol analysis could determine the feedstock used in the production of biodiesels. © Taylor & Francis Group, LLC. Source

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