Suchergebnisse

Abstract. Extreme fires have substantial adverse effects on society and
natural ecosystems. Such events can be associated with the intense coupling of
fire behaviour with the atmosphere, resulting in extreme fire
characteristics such as pyrocumulonimbus cloud (pyroCb) development. Concern
that anthropogenic climate change is increasing the occurrence of pyroCbs
globally is driving more focused research into these meteorological
phenomena. Using 6 min scans from a nearby weather radar, we describe the
development of a pyroCb during the afternoon of 4 January 2013 above the
Forcett–Dunalley fire in south-eastern Tasmania. We relate storm development
to (1) near-surface weather using the McArthur forest fire danger index
(FFDI) and the C-Haines index, the latter of which is a measure of the vertical atmospheric
stability and dryness, both derived from gridded weather reanalysis for
Tasmania (BARRA-TA); and (2) a chronosequence of fire severity derived from
remote sensing. We show that the pyroCb rapidly developed over a 24 min
period on the afternoon of 4 January, with the cloud top reaching a height
of 15 km. The pyroCb was associated with a highly unstable lower atmosphere
(C-Haines value of 10–11) and severe–marginally extreme (FFDI 60–75) near-surface
fire weather, and it formed over an area of forest that was severely burned
(total crown defoliation). We use spatial patterns of elevated fire weather
in Tasmania and fire weather during major runs of large wildfires in
Tasmania for the period from 2007 to 2016 to geographically and historically
contextualise this pyroCb event. Although the Forcett–Dunalley fire is the
only known record of a pyroCb in Tasmania, our results show that eastern and
south-eastern Tasmania are prone to the conjunction of high FFDI and
C-Haines values that have been associated with pyroCb development. Our
findings have implications for fire weather forecasting and wildfire
management, and they highlight the vulnerability of south-east Tasmania to extreme
fire events.

Context Some large herbivores introduced to Australia have achieved population densities so high as to cause considerable ecological damage. Intriguingly, others have been relatively less successful and have correspondingly perturbed their new environments less. An excellent example is two similar-sized bovine species that established feral populations in the Northern Territory of Australia in the mid-19th century. Asian swamp buffalo (Bubalus bubalis) rapidly colonised the tropical savannas, causing ecological degradation, especially on freshwater swamps. In contrast, banteng (Bos javanicus) are restricted to their point of introduction and have caused relatively negligible ecological damage. Understanding the reasons of this differential success is of theoretical and applied interest and contributes to managing large herbivore populations for ex situ conservation and feral-animal control. Aims To compare the population structure of buffalo and banteng on the basis of shot samples, so as to construct life tables for four contemporary (low-density) buffalo populations, and collated data from previous work from three historical (high-density) buffalo populations and one banteng population (the only extant ex situ population in existence). Further, to provide a validation of age estimation with and without informed priors in a Bayesian model comparing horn length and ages estimated from tooth cementum annuli. Finally, to interpret our results in the context of relative invasion potential of the two bovid species. Key Results For both species, survival of juveniles was the most important demographic component influencing deterministic population growth. However, buffalo have the demographic capacity to recover swiftly after control because of high survival and fertility rates across a range of population densities. Fertility of buffalo was historically greater than that of banteng, and buffalo fertility increased as their populations were reduced. Conclusions These findings highlight how subtle differences in demographic rates and feeding ecology can influence the success (high population growth and range expansion) of large herbivores, knowledge which is increasingly important for managing invasive species effectively. Implications We show that that individual life-history traits and demographic performance, especially fertility, play an important role in determining the spread of invasive bovids in a novel environment.

Context. Understanding how the individual movement patterns and dispersion of a population change following wildlife management interventions is crucial for effective population management.
Aims. We quantified the impacts of two wildlife management strategies, a lethal intervention and a subsequent barrier intervention, on localised populations of the two most common macropod species in Tasmania, the Tasmanian pademelon (Thylogale billardierii) and the red-necked wallaby (Macropus rufogriseus rufogriseus). This manipulation allowed us to examine two competing hypotheses concerning the distribution of individuals in animal populations – the Ideal Free Distribution (IFD) hypothesis and the Rose Petal (RP) hypothesis. We predicted that the RP would be supported if individuals maintained their previous home ranges following intervention, whereas the IFD would be supported if individuals redistributed following the management interventions.
Methods. The movement patterns of T. billardierii and M. r. rufogriseus were tracked using GPS technology before and after the two management interventions.
Key results. Following lethal intervention, pademelons and wallabies (1) maintained their home-range area, (2) increased their utilisation of agricultural habitat and (3) shifted their mean centroid locations compared with the pre-intervention period. Following barrier intervention, pademelons and wallabies (1) maintained their home-range area, (2) decreased their utilisation of agricultural habitat and (3) shifted their mean centroid locations compared with the pre-intervention period.
Conclusions. On the basis of the individual responses of macropods to the management strategies (1) lethal intervention appeared to induce small shifts in home-range distributions of those remaining individuals in the population with home ranges overlapping the areas of lethal intervention and (2) barrier intervention is likely to induce whole-scale population movements of the animals that survive the lethal intervention in their search of an alternative food source. Both species displayed spatial and temporal shifts in their home-range distributions in response to lethal and barrier interventions that appear to conform broadly to predictions of IFD, at least in the timeframe of the present experiment.
Implications. Wildlife management strategies, which are increasingly constrained by ethical, socio-political and financial considerations, should be based on ecological and behavioural data regarding the likely responses of the target population.

This paper reviews information about field observations of vegetation productivity in Australia's rangeland systems and identifies the need to establish a national initiative to collect net primary productivity (NPP) and biomass data for rangeland pastures. Productivity data are needed for vegetation and carbon model parameterisation, calibration and validation. Several methods can be used to estimate pasture productivity at various spatial and temporal scales, ranging from in situ measurements to satellite-based approaches and biogeochemical modelling. However, there is a barrier to implementing national vegetation and carbon modelling schemes because of the lack of digitised and readily available data derived from field observations, not because of the lack of modelling expertise. Our main goal in this paper is to explore the potential for consolida-tion of existing NPP and biomass databases for Australian rangelands. A protocol structure was proposed to establish a productivity database for Australia. The TERN (Terrestrial Ecosystems Research Network) national field data network for rangeland pasture productivity monitoring and modelling team could potentially coordinate the database. Government agencies and national and international research institutions could use the outputs from productivity models to inform greenhouse gas emissions and in measuring mitigation activities relevant for reporting against the United Nations' Sustainable Development Goals and other international obligations. Other applications include monitoring fire danger, tracking ecological restoration and protec-tion, and estimating fodder availability. Australian researchers have the tools needed to succeed in creating such a national database and a robust community of practice to curate it, enhance it and benefit from its availability.