Jon Luly

Pit Membrane Porosity and Water Stress-Induced Cavitation in Four Co-Existing Dry Rainforest Tree Species

Aspects of xylem anatomy and vulnerability to water stress-induced embolism were examined in stems of two drought-deciduous species, Brachychiton australis (Schott and Endl.) A. Terracc. and Cochlospermum gillivraei Benth., and two evergreen species, Alphitonia excelsa (Fenzal) Benth. and Austromyrtus bidwillii (Benth.) Burret., growing in a seasonally dry rainforest. The deciduous species were more vulnerable to water stress-induced xylem embolism. B. australis andC. gillivraei reached a 50% loss of hydraulic conductivity at −3.17 MPa and −1.44 MPa, respectively; a 50% loss of hydraulic conductivity occurred at −5.56 MPa in A. excelsa and −5.12 MPa in A. bidwillii. To determine whether pit membrane porosity was responsible for greater vulnerability to embolism (air seeding hypothesis), pit membrane structure was examined. Expected pore sizes were calculated from vulnerability curves; however, the predicted inter-specific variation in pore sizes was not detected using scanning electron microscopy (pores were not visible to a resolution of 20 nm). Suspensions of colloidal gold particles were then perfused through branch sections. These experiments indicated that pit membrane pores were between 5 and 20 nm in diameter in all four species. The results may be explained by three possibilities: (a) the pores of the expected size range were not present, (b) larger pores, within the size range to cause air seeding, were present but were rare enough to avoid detection, or (c) pore sizes in the expected range only develop while the membrane is under mechanical stress (during air seeding) due to stretching/flexing.

Hydraulic architecture of deciduous and evergreen dry rainforest tree species from north-eastern Australia

Hydraulic conductivity and xylem anatomy were examined in stems of two evergreen species, Alphitonia excelsa (Fenzal) Benth. and Austromyrtus bidwillii (Benth.) Burret., and two drought-deciduous species, Brachychiton australis (Schott and Endl.) A. Terracc. and Cochlospermum gillivraei Benth., from a seasonally dry rainforest in north Queensland, Australia. The deciduous species possessed hydraulic architecture typical of drought-sensitive plants, i.e. low wood density, wider xylem vessels, higher maximal rates of sapwood specific hydraulic conductivity (Ks) and high vulnerability to drought-induced embolism. In contrast, the evergreen species had lower rates of Kh and leaf specific conductivity (KL) but were less susceptible to embolism. The evergreen species experienced leaf water potentials <−4.0 MPa during the dry season, while the deciduous species shed their leaves before leaf water potentials declined below −2.0 MPa. Thus, the hydraulic architecture of the evergreens allows them to withstand the greater xylem pressure gradients required to maintain water transport to the canopy during the dry season. Our results are consistent with observations made in neotropical dry forests and demonstrate that drought-deciduous species with low wood density and high water storage capacity are likely to be more hydraulically efficient, but more vulnerable to embolism, than coexisting evergreens.

On the equivocal fate of Late Pleistocene Callitris Vent. (Cupressaceae) woodlands in arid South Australia

Fossil pollen assemblages suggest Callitris (Cupressaceae)-dominated woodlands were prominent elements in landscapes near Lake Frome and Lake Eyre during latest Pleistocene times. Callitris woodlands were present at Lake Eyre before 30,000 BP but became fragmented and disappeared in the lead up to the last glacial maximum. Callitris was again prominent from approximately 10,000 BP until about 5000 BP after which time it vanishes from the pollen record and, presumably, the region. At Lake Frome, Callitris was abundant between 16,000 BP and 13,000 BP before declining to low modern levels from 11,000 BP. At both sites, the latest Pleistocene or Holocene decline in Callitris occurrence, and its eventual extinction in the vicinity of Lake Eyre, broadly corresponds with archaeological indications of increasing human presence in the landscape. In the absence of evidence of significant climatic changes at the times in question, these observations lend tentative support to arguments that the composition and structure of modern zone vegetation has been significantly modified by Aboriginal land management practices. Although the charcoal record is ambiguous, fire is argued to be the principle agent of the changes wrought during human re-colonisation of lands around Lake Frome and Lake Eyre.

Holocene palaeoenvironments and change at Three-Quarter Mile Lake, Silver Plains Station, Cape York Peninsula, Australia

Pollen and diatom analyses of organic sediments from Three-Quarter Mile Lake, a perched lake on Cape York Peninsula, north Queensland, indicate that significant changes in vegetation and hydrology occurred during the Holocene. Early Holocene grass-dominated landscapes were replaced in mid-Holocene times by increasingly woody vegetation comprising tropical heathlands, savanna and rainforest. Early-Holocene lake levels fluctuated widely. From mid-Holocene times, lake levels stabilized and water became increasingly acidic as a mature swamp forest developed adjacent to the lake and contributed tannins to the lake water. The timing and character of changes are consistent with those described from the Atherton Tableland in wet tropical Queensland. Holocene dry phases described from the Northern Territory and the western shores of Cape York cannot be identified from Three-Quarter Mile Lake. Rainforest is currently close to its greatest Holocene extent, suggesting that the rainforest-dependent endemic fauna of northern Cape York have been isolated from rainforest blocks to the south throughout the last 10 000 years and, by inference, throughout at least the 120 000 years beyond that.

Demographic indications of decline in the spectacled flying fox (Pteropus conspicillatus) on the Atherton Tablelands of northern Queensland

A lack of information about the spectacled flying fox (Pteropus conspicillatus) makes management and conservation of this vulnerable species difficult. The analysis of population dynamics using life-history traits and life tables is widely used in planning for the conservation and management of wildlife. In the present study, the first life table for any species of bat is provided and age estimates derived from counts of annual increments in tooth cementum rings are used to assess population trends and life-history traits in the spectacled flying fox on the Atherton Tablelands in north Queensland. As a result of high mortality, longevity was much shorter than expected from a theoretical basis. Life-table analyses suggest that the population experienced a 16% decrease during the 2 years of study. Absence of extended longevity to compensate for low reproductive output and delayed sexual maturity in ‘slow end’ mammal species such as P. conspicillatus reduces the window of opportunity for females to reproduce and adapt to changes in mortality rates. This study suggests that spectacled flying fox populations are sensitive to increased mortality and that reducing mortality rates should be the primary goal in conservation planning for P. conspicillatus.

Bat Strikes in the Australian Aviation Industry

Abstract Bat collisions are a threat to commercial and military aircraft in Australia. We examined bat strike records from Australia during 1996–2006 and found that risk of impact from bats is increasing, is greatest in tropical versus temperate regions, and is more likely during early evening and while an aircraft is landing rather than departing. Temporal patterns of bat strikes differ from those of birds, highlighting the need to employ taxon-specific management strategies to minimize animal impacts on the aviation industry. The use of genetics for identification of strike remains and the implementation of nocturnal survey techniques by wildlife managers at airports will contribute to the mitigation of bat strikes.

Flying-fox (Megachiroptera: Pteropodidae) flight altitudes determined via an unusual sampling method: aircraft strikes in Australia

The nocturnal behaviour of bats makes it difficult to determine their foraging habits at night, especially in regards to the height or altitude at which they fly. This is particularly true for the larger flying foxes that can travel up to 40 km in a single night(Spen cer et al., 1991; Parsons et al., 2006). Despite the value of such information for many aspects of the foraging ecology and ecophysiology of bats, gathering information on the flight altitudes used by bats remains a challenge that has led to the use of inventive sampling techniques. Active radar systems monitoring aircraft movements have detected the Mexican free-tailed bat (Tadarida brasiliensis) flying at altitudes of over 3,000 m (10,000 feet) (Williams et al., 1973), while helium filled kite balloons in combination with bat echolocation detection devices have identified molossid and emballonurid bats foraging at heights of almost 600 m (1968.5 feet) (Fenton and Griffin, 1997). The diurnal Sa moan flying fox, Pteropus samoensis, has been observed soaring on thermal updrafts (Rich mond et al., 1998; Lindhe Norberg et al., 2000; Thomson et al., 2002), but unfortunately knowledge on the actual flying altitude of this or any other pteropodid species remains unknown.

The origin of grassy balds in the Bunya Mountains, southeastern Queensland, Australia

Montane grasslands, or grassy balds, are enigmatic features of mountains worldwide. Their origins are often obscure. Pollen, phytolith and charcoal analysis of Dandabah Swamp in the Bunya Mountains in southeastern Queensland, Australia suggest that there, grassy balds comprise a relict vegetation maintained in the face of postglacial tree invasion by fire. The balds are not the product of edaphic phenomena or natural or anthropogenic cataclysms and will require intensive management efforts to be conserved in a world of increased woodiness, rising atmospheric CO2 and changing climate.

Antibodies to Australian bat lyssavirus in an asymptomatic bat carer

[Extract] The recent fatal case of Australian bat lyssavirus (ABLV) in an 8-year-old boy in February 2013[1] as well as infections in horses in May 2013[2] has prompted us to write about an earlier non-fatal exposure. In August 1996, soon after the discovery of ABLV,[3] a serological survey of 14 bat carers in Townsville, North Queensland, detected antibodies (rapid fluorescent focus inhibition test (RFFIT) 0.48 international units (IU)/mL) in a 40-year-old male. As a volunteer bat carer for 10 years, mainly of black flying foxes (Pteropus alecto) and little red flying foxes (Pteropus scapulatus), he had received multiple bites and scratches. He had never received rabies vaccine or rabies immunoglobulin. He did not care for other Australian wildlife and had not visited rabies endemic countries.