Myrtle rust surveys of Eastern Australia

Records of Rhodomyrtus psidioides and their level of myrtle rust damage from Eastern Australia from field survey and personal communication with experts

Rainfall-Linked Megafires as Innate Fire Regime Elements in Arid Australian Spinifex (Triodia spp.) Grasslands

Large, high-severity wildfires, or “megafires,” occur periodically in arid Australian spinifex (Triodia spp.) grasslands after high rainfall periods that trigger fuel accumulation. Proponents of the patch-burn mosaic (PBM) hypothesis suggest that these fires are unprecedented in the modern era and were formerly constrained by Aboriginal patch burning that kept landscape fuel levels low. This assumption deserves scrutiny, as evidence from fire-prone systems globally indicates that weather factors are the primary determinant behind megafire incidence, and that fuel management does not mitigate such fires during periods of climatic extreme. We reviewed explorer’s diaries, anthropologist’s reports, and remotely sensed data from the Australian Western Desert for evidence of large rainfall-linked fires during the pre-contact period when traditional Aboriginal patch burning was still being practiced. We used only observations that contained empiric estimates of fire sizes. Concurrently, we employed remote rainfall data and the Oceanic Niño Index to relate fire size to likely seasonal conditions at the time the observations were made. Numerous records were found of small fires during periods of average and below-average rainfall conditions, but no evidence of large-scale fires during these times. By contrast, there was strong evidence of large-scale wildfires during a high-rainfall period in the early 1870s, some of which are estimated to have burnt areas up to 700,000 ha. Our literature review also identified several Western Desert Aboriginal mythologies that refer to large-scale conflagrations. As oral traditions sometimes corroborate historic events, these myths may add further evidence that large fires are an inherent feature of spinifex grassland fire regimes. Overall, the results suggest that, contrary to predictions of the PBM hypothesis, traditional Aboriginal burning did not modulate spinifex fire size during periods of extreme-high arid zone rainfall. The mechanism behind this is that plant assemblages in seral spinifex vegetation comprise highly flammable non-spinifex tussock grasses that rapidly accumulate high fuel loads under favorable precipitation conditions. Our finding that fuel management does not prevent megafires under extreme conditions in arid Australia has parallels with the primacy of climatic factors as drivers of megafires in the forests of temperate AustraliaS

Rainfall-Linked Megafires as Innate Fire Regime Elements in Arid Australian Spinifex (Triodia spp.) Grasslands

Large, high-severity wildfires, or "megafires," occur periodically in arid Australian spinifex (Triodia spp.) grasslands after high rainfall periods that trigger fuel accumulation. Proponents of the patch-burn mosaic (PBM) hypothesis suggest that these fires are unprecedented in the modern era and were formerly constrained by Aboriginal patch burning that kept landscape fuel levels low. This assumption deserves scrutiny, as evidence from fire-prone systems globally indicates that weather factors are the primary determinant behind megafire incidence, and that fuel management does not mitigate such fires during periods of climatic extreme. We reviewed explorer's diaries, anthropologist's reports, and remotely sensed data from the Australian Western Desert for evidence of large rainfall-linked fires during the pre-contact period when traditional Aboriginal patch burning was still being practiced. We used only observations that contained empiric estimates of fire sizes. Concurrently, we employed remote rainfall data and the Oceanic Niño Index to relate fire size to likely seasonal conditions at the time the observations were made. Numerous records were found of small fires during periods of average and below-average rainfall conditions, but no evidence of large-scale fires during these times. By contrast, there was strong evidence of large-scale wildfires during a high-rainfall period in the early 1870s, some of which are estimated to have burnt areas up to 700,000 ha. Our literature review also identified several Western Desert Aboriginal mythologies that refer to large-scale conflagrations. As oral traditions sometimes corroborate historic events, these myths may add further evidence that large fires are an inherent feature of spinifex grassland fire regimes. Overall, the results suggest that, contrary to predictions of the PBM hypothesis, traditional Aboriginal burning did not modulate spinifex fire size during periods of extreme-high arid zone rainfall. The mechanism behind this is that plant assemblages in seral spinifex vegetation comprise highly flammable non-spinifex tussock grasses that rapidly accumulate high fuel loads under favorable precipitation conditions. Our finding that fuel management does not prevent megafires under extreme conditions in arid Australia has parallels with the primacy of climatic factors as drivers of megafires in the forests of temperate Australia

Survey data for remote habitat plants and water points

The plant survey data used in the study and including the distance from permanent and non-permanent water

Obscure oases: natural, cultural and historical geography of western Queensland's Tertiary sandstone springs

The distribution of surface water dictates human and animal activity in arid zones. Although typically small, hidden, and inaccessible, springs and wells fed by local aquifers were the only sources of reliable water across vast areas of inland Australia until the last century. Compared to larger, more accessible water sources such as riverine waterholes and Great Artesian Basin discharge springs, their history is sketchy and poorly documented, although rich in intrigue and mythology. Since the expansion of artificial waters and motorised transport, many of these small oases have become forgotten, and their location and permanence are now less well-known than for thousands of years. We examine the distribution, hydrogeology, cultural history, and biological values of Tertiary sandstone springs in western Queensland based on a review of historical literature, interviews with long-term residents, and extensive field surveys. One hundred and sixty springs were documented, and nearly 40% of these have declined in flow or become inactive since pastoral settlement for reasons that are not well understood. While their decline in some areas seems related to shallow bores sunk into their local aquifers, it is possible that some smaller springs owed their existence to regular human maintenance. Others are probably naturally dynamic over decadal time scales. This study documents an almost-forgotten aspect of Queensland's natural and cultural history

Threatened species in a threatened ecosystem: the conservation status of four Solanum species in the face of ongoing habitat loss

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Chloris circumfontinalis (Poaceae): A recently discovered species from the saline scalds surrounding artesian springs in north-eastern Australia

The artesian springs of inland Australia are a unique habitat in what is otherwise an arid environment. They support a rich collection of endemic flora and fauna. Here, morphological and molecular data are employed to describe a new species, Chloris circumfontinalis Fahey & Fensham, endemic to artesian spring systems in central Queensland. A morphological ordination failed to distinguish this species from other Australian native flora, but the shape of the florets distinguishes it from the species with which it co-occurs. Phylogenies estimated from molecular data showed that the species represents a distinct lineage that may be sister to species of Chloris from outside Australia. Chloris circumfontinalis occurs only in the saline scalds that form around the springs, and population surveys at the two sites where it occurs indicated a threat status of Endangered under the IUCN Red List criteria

Threatened species in a threatened ecosystem: the conservation status of four Solanum species in the face of ongoing habitat loss

Plant biodiversity is threatened by habitat loss, fragmentation and invasion by exotic species, but the effects of these disturbances on individual plant species are rarely quantified. Since the 1950s, brigalow Acacia harpophylla forests in Australia have been extensively cleared and converted to pastures dominated by exotic grasses. Here we assess the habitat requirements, population numbers and threats for four poorly known bush tomato species, Solanum adenophorum, Solanum dissectum, Solanum elachophyllum and Solanum johnsonianum. Herbarium records and surveys demonstrated a strong association of all four species with brigalow habitat, although S. elachophyllum also occurred in other habitat. We derived historical and current population estimates from plant densities at current sites and the area of mapped brigalow habitat. Density estimates are imprecise because the survey data vary greatly, but the assessment indicates the populations of all four species have declined > 93%. Solanum dissectum and S. johnsonianum did not persist in cleared brigalow habitat, whereas S. adenophorum and S. elachophyllum had some capacity to persist in clearings. None of the species occur where the exotic grass cover is > 40%. Between 27% and 57% of the records of the four species are in brigalow remnants with a high edge-to-area ratio or open canopy (< 50% cover), making them highly vulnerable to invasive grasses. We recommend the categorization of S. dissectum and S. johnsonianum as Critically Endangered, S. adenophorum as Vulnerable and S. elachophyllum as Near Threatened

Variable rainfall has a greater effect than fire on the demography of the dominant tree in a semi-arid Eucalyptus savanna

Rainfall, fire and competition are emphasized as determinants of the density and basal area of woody vegetation in savanna. The semi-arid savannas of Australia have substantial multi-year rainfall deficits and insufficient grass fuel to carry annual fire in contrast to the mesic savannas in more northern regions. This study investigates the influence of rainfall deficit and excess, fire and woody competition on the population dynamics of a dominant tree in a semi-arid savanna. All individuals of Eucalyptus melanophloia were mapped and monitored in three, 1-ha plots over an 8.5 year period encompassing wet and dry periods. The plots were unburnt, burnt once and burnt twice. A competition index incorporating the size and distance of neighbours to target individuals was determined. Supplementary studies examined seedling recruitment and the transition of juvenile trees into the sapling layer. Mortality of burnt seedlings was related to lignotuber area but the majority of seedlings are fire resistant within 12 months of germination. Most of the juveniles (≤1 cm dbh) of E. melanophloia either died in the dry period or persisted as juveniles throughout 8.5 years of monitoring. Mortality of juveniles was positively related to woody competition and was higher in the dry period than the wet period. The transition of juveniles to a larger size class occurred at extremely low rates, and a subsidiary study along a clearing boundary suggests release from woody competition allows transition into the sapling layer. From three fires the highest proportion of saplings (1-10 cm dbh) reduced to juveniles was only 5.6% suggesting rates of 'top-kill' of E. melanophloia as a result of fire are relatively low. Girth growth was enhanced in wet years, particularly for larger trees (>10 cm dbh), but all trees regardless of size or woody competition levels are vulnerable to drought-induced mortality. Overall the results suggest that variations in rainfall, especially drought-induced mortality, have a much stronger influence on the tree demographics of E. melanophloia in a semi-arid savanna of north-eastern Australia than fire

Variable rainfall has a greater effect than fire on the demography of the dominant tree in a semi-arid Eucalyptus savanna

Rainfall, fire and competition are emphasized as determinants of the density and basal area of woody vegetation in savanna. The semi-arid savannas of Australia have substantial multi-year rainfall deficits and insufficient grass fuel to carry annual fire in contrast to the mesic savannas in more northern regions. This study investigates the influence of rainfall deficit and excess, fire and woody competition on the population dynamics of a dominant tree in a semi-arid savanna. All individuals of Eucalyptus melanophloia were mapped and monitored in three, 1-ha plots over an 8.5year period encompassing wet and dry periods. The plots were unburnt, burnt once and burnt twice. A competition index incorporating the size and distance of neighbours to target individuals was determined. Supplementary studies examined seedling recruitment and the transition of juvenile trees into the sapling layer. Mortality of burnt seedlings was related to lignotuber area but the majority of seedlings are fire resistant within 12months of germination. Most of the juveniles (1cm dbh) of E.melanophloia either died in the dry period or persisted as juveniles throughout 8.5years of monitoring. Mortality of juveniles was positively related to woody competition and was higher in the dry period than the wet period. The transition of juveniles to a larger size class occurred at extremely low rates, and a subsidiary study along a clearing boundary suggests release from woody competition allows transition into the sapling layer. From three fires the highest proportion of saplings (1-10cm dbh) reduced to juveniles was only 5.6% suggesting rates of top-kill' of E.melanophloia as a result of fire are relatively low. Girth growth was enhanced in wet years, particularly for larger trees (>10cm dbh), but all trees regardless of size or woody competition levels are vulnerable to drought-induced mortality. Overall the results suggest that variations in rainfall, especially drought-induced mortality, have a much stronger influence on the tree demographics of E.melanophloia in a semi-arid savanna of north-eastern Australia than fire