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Melbourne, Australia

Garrard G.E.,University of Melbourne | McCarthy M.A.,University of Melbourne | Vesk P.A.,University of Melbourne | Radford J.Q.,Bush Heritage Australia | And 2 more authors.
Journal of Animal Ecology | Year: 2012

1. Informative Bayesian priors can improve the precision of estimates in ecological studies or estimate parameters for which little or no information is available. While Bayesian analyses are becoming more popular in ecology, the use of strongly informative priors remains rare, perhaps because examples of informative priors are not readily available in the published literature. 2. Dispersal distance is an important ecological parameter, but is difficult to measure and estimates are scarce. General models that provide informative prior estimates of dispersal distances will therefore be valuable. 3. Using a world-wide data set on birds, we develop a predictive model of median natal dispersal distance that includes body mass, wingspan, sex and feeding guild. This model predicts median dispersal distance well when using the fitted data and an independent test data set, explaining up to 53% of the variation. 4. Using this model, we predict a priori estimates of median dispersal distance for 57 woodland-dependent bird species in northern Victoria, Australia. These estimates are then used to investigate the relationship between dispersal ability and vulnerability to landscape-scale changes in habitat cover and fragmentation. 5. We find evidence that woodland bird species with poor predicted dispersal ability are more vulnerable to habitat fragmentation than those species with longer predicted dispersal distances, thus improving the understanding of this important phenomenon. 6. The value of constructing informative priors from existing information is also demonstrated. When used as informative priors for four example species, predicted dispersal distances reduced the 95% credible intervals of posterior estimates of dispersal distance by 8-19%. Further, should we have wished to collect information on avian dispersal distances and relate it to species' responses to habitat loss and fragmentation, data from 221 individuals across 57 species would have been required to obtain estimates with the same precision as those provided by the general model. © 2011 The Authors. Journal of Animal Ecology © 2011 British Ecological Society.

Polyakov M.,University of Western Australia | Rowles A.D.,Australian Department of Primary Industries and Fisheries | Rowles A.D.,La Trobe University | Radford J.Q.,Bush Heritage Australia | And 4 more authors.
Landscape Ecology | Year: 2013

The removal, alteration and fragmentation of habitat are key causes of biodiversity decline worldwide. In Australia, temperate woodlands have been disproportionately cleared following European settlement. Biodiversity decline in such systems may be reversed by restoration of native vegetation on agricultural land. However, rebuilding functioning habitat will require understanding the determinants of species distributions in existing habitat. We used logistic regression of bird occurrence data from 240 sites across northern Victoria, to determine the probability of occurrence of 29 woodland-dependent bird species. We modelled occurrence as a function of habitat variables that characterise both the extent (amount) and composition of native vegetation surrounding sites. Our specific goal was to determine whether the predictive performance of models is improved by accounting for both extent and composition of native vegetation compared with models that characterise native vegetation by extent alone. For nearly all species, accounting for vegetation composition in addition to extent and weighting habitat variables by distance improved the explanatory power of models, explaining on average 5. 4 % (range 0-27. 6 %) of the residual uncertainty in models that accounted for extent alone. Models that incorporate variation in vegetation composition can not only provide more accurate predictions of species occurrence, but also guide more appropriate restoration. They highlight the need for restoration to incorporate sites with fertile soils that support productive vegetation types. These models of woodland birds will be used to inform a spatially-explicit optimisation model for restoring native vegetation cover on agricultural land in this region, with the goal of achieving biodiversity gains while minimizing loss to production. © 2013 Springer Science+Business Media Dordrecht.

Bennett J.M.,Monash University | Nimmo D.G.,Deakin University | Clarke R.H.,Monash University | Thomson J.R.,University of Canberra | And 6 more authors.
Diversity and Distributions | Year: 2014

Aim: Climate change is expected to increase the frequency and intensity of extreme climatic events, such as severe droughts and intense rainfall periods. We explored how the avifauna of a highly modified region responded to a 13-year drought (the 'Big Dry'), followed by a two-year period of substantially higher than average rainfall (the 'Big Wet'). Location: Temperate woodlands in north central Victoria, Australia. Methods: We used two spatially extensive, long-term survey programmes, each of which was repeated three times: early and late in the Big Dry, and in the Big Wet. We compared species-specific changes in reporting rates between periods in both programmes to explore the resistance (the ability to persist during drought) and resilience (extent of recovery post-drought) of species to climate extremes. Results: There was a substantial decline in the reporting rates of 42-62% (depending on programme) of species between surveys conducted early and late in the Big Dry. In the Big Wet, there was some recovery, with 21-29% of species increasing substantially. However, more than half of species did not recover and 14-27% of species continued to decline in reporting rate compared with early on in the Big Dry. Species' responses were not strongly related to ecological traits. Species resistance to the drought was inversely related to resilience in the Big Wet for 20-35% of the species, while 76-78% of species with low resistance showed an overall decline across the study period. Conclusions: As declines occurred largely irrespective of ecological traits, this suggests a widespread mechanism is responsible. Species that declined the most during the Big Dry did not necessarily show the greatest recoveries. In already much modified regions, climate extremes such as extended drought will induce on-going changes in the biota. © 2014 John Wiley & Sons Ltd.

Burgess E.E.,University of Queensland | Moss P.,University of Queensland | Haseler M.,Bush Heritage Australia | Maron M.,University of Queensland
International Journal of Wildland Fire | Year: 2015

The post-fire response of vegetation reflects not only a single fire event but is the result of cumulative effects of previous fires in the landscape. For effective ecological fire management there is a need to better understand the relationship between different fire regimes and vegetation structure. The study investigated how different fire regimes affect stand structure and composition in subtropical eucalypt woodlands of central Queensland. We found that fire history category (i.e. specific combinations of time since fire, fire frequency and season of last burn) strongly influenced richness and abundance of species categorised as mid-storey trees and those individuals currently in the mid-level strata. Time since fire and fire frequency appeared to have the strongest influence. A longer time since fire (>4 years since last burn), combined with infrequent fires (<2 fires in 12 year period) appeared to promote a dense mid-storey with the opposite conditions (<4 years since last burn; >2 fires in 12 year period) promoting more-open woodlands. Consideration of these combined fire regime attributes will allow fire managers to plan for a particular range of fire-mediated patches to maintain the desired diversity of vegetation structures. © 2015 IAWF.

Silcock J.L.,University of Queensland | Tischler M.,Bush Heritage Australia | Smith M.A.,Center for Historical Research
Ethnobotany Research and Applications | Year: 2012

Pituri (Duboisia hopwoodii (F. Muell.) F. Muell.) (Solanaceae) is a narcotic shrub which grows in the parallel dune fields of the Simpson Desert of far south-western Queensland, Australia. The ethnographic literature points to an impressive scale of trade of pituri between Aboriginal groups across inland eastern Australia, and suggests total annual production of 2500-3000 kg of dried plant material. However, there has been no attempt to assess the feasibility of these figures, or investigate the number of pituri plants required to sustain such a scale of trade. We mapped the distribution and density of D. hopwoodii along four one km wide transects, totally 130 km in length. Our results suggest that the population of pituri west of the Mulligan River could number around 36,000 mature plants. Ninety randomly selected plants were measured, and the foliage of six of these was harvested and dried. Plants yielded between 0.15 and 6.68 kg of dry matter. Our 90 measured plants would have yielded around 155 kg of dried pituri. Therefore, between 1450 and 1740 plants would be required to sustain the purported level of trade and use. With knowledge of the location of dense pituri groves and highly efficient expeditions, harvesting this number of plants is feasible. However, numerous questions remain surrounding the ecological and ethnographic aspects of the pituri trade.

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