Dry Tropics (dry + tropic)

Distribution by Scientific Domains


Selected Abstracts


Head lice on pillows, and strategies to make a small risk even less

INTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 8 2003
Rick Speare
Background Due to a lack of evidence, controversy exists about the role of bedding in the transmission of head lice. Aims To determine the proportion of the head lice population found on pillowcases of people with head lice, and to test strategies available to householders to kill head lice on pillowcases. Methods To assess the incidence of head lice on pillowcases, people with active pediculosis had their head lice collected and counted and the pillowcase they had used the night before examined for head lice. To test strategies to kill head lice on pillowcases, live head lice were experimentally placed in miniature pillowcases, and the cases were subjected to a hot wash, a cold wash, hot dryer, and hanging out to dry on an outdoor clothes line. Results Forty-eight people and their pillowcases were recruited from Townsville, Qld, Australia (dry tropics). One thousand, eight hundred and forty-five lice were collected from their heads to give an average and median intensity of infection of 38.4 and 21 lice, respectively. Two of the 48 pillowcases contained live lice, one nymph on each, 2 h and 9 h after the pillowcases had been removed from the bed. Another pillowcase contained a dehydrated nymph. The incidence of live lice on pillowcases was 4.2% per night and the proportion of the head louse population on the pillowcases was 0.11%. Heat (hot wash and hot clothes dryer) killed head lice experimentally placed in pillowcases. Cold wash and hanging pillowcases out to dry did not kill head lice. Conclusions Head lice transfer to pillowcases at night, but the incidence is low. Pillowcases pose a risk for re-infection with head lice, but the risk is low, and changing the pillowcase is a reasonably cost-efficient strategy to minimize this risk. Lice on pillowcases can be killed by heating the pillowcase by immersion in water at > 60 °C, by a hot wash, or by 15 min in a hot clothes dryer. [source]


Species-specific communication systems in an introduced toad compared with native frogs in Australia

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2009
Mattias Hagman
Abstract 1.Lineage-specific communication systems may offer innovative ways of targeting control measures at invasive species. 2.Recent work has identified such a scenario in invasive cane toads (Bufo marinus) in Australia: toad tadpoles flee from chemical cues derived from crushed conspecifics, and this ,alarm pheromone' reduces tadpole survival rates and reduces body size at metamorphosis. 3.Before this method can be applied in the field, however, the signal's specificity needs to be tested against a wide range of Australian frog taxa, especially tropical species sympatric with cane toads. A signal that affected native frogs as well as toads clearly would be of little use for toad control. 4.Laboratory studies on cane toads and nine native frog taxa from the wet,dry tropics of the Northern Territory (Cyclorana australis, C. longipes, Limnodynastes convexiusculus, Litoria caerulea, L. dahlii, L. nasuta, L. rothii, L. rubella, Opisthodon ornatus) show that toad tadpoles rarely react to chemical cues from crushed frog tadpoles, and that frog tadpoles rarely react to chemical cues from crushed toad tadpoles. Crushed toad tadpoles occasionally elicited low-level attraction (to a potential food source) by frog tadpoles. 5.Overall, frog tadpoles were less responsive to chemical cues (either from crushed conspecifics or crushed toads) than were toad tadpoles. The low level of cross-lineage reactivity is encouraging for the feasibility of using cane toad alarm pheromones to control this invasive species in Australia; the risk of collateral damage to sympatric native frogs appears to be minimal. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Phenological patterns in monsoon rainforests in the Northern Territory, Australia

AUSTRAL ECOLOGY, Issue 5 2002
Christine Susanne Bach
Abstract Monsoon rainforests occur as scattered patches within a landscape dominated by eucalypt savannas across the wet,dry tropics of northern Australia. This study formed part of a larger project that investigated the interactions between frugivores and monsoon rainforest patches in the Top End of the Northern Territory. Phenological patterns in a set of 12 wet monsoon forests (WMF) and four dry monsoon forests (DMF) were examined by monitoring individuals of more than 100 species over 30 months. Phenological patterns of both WMF and DMF were closely related to the strongly seasonal climate. Leaf flush occurred before the onset of the wet season in WMF, and coincided with the onset of the wet in DMF. Major flowering peaks coincided with leaf flush in both forest types. Fruiting was concentrated in the wet season in both forest types, but fruiting peaks of WMF and DMF were separated by 3,4 months. Variations in fruiting patterns among forest types, patches, seasons and groupings of plant species (based on life form and ecological positioning) provide a mosaic of food resources for frugivores. This has important implications for the conservation and maintenance of the frugivore,rainforest system in northern Australia. [source]


Dormancy and germination characteristics of herbaceous species in the seasonally dry tropics of northern Australia

AUSTRAL ECOLOGY, Issue 3 2000
JohN. G. McIvor
Abstract This study investigated changes in dormancy and germination over 8 months for 23 common species (annual and perennial grasses, legumes and other dicotyledons) from herbaceous communities in northern Australia. Seeds were exposed to three storage treatments: relatively constant laboratory conditions, an oven with fluctuating temperatures similar to those found on the soil surface (25/60°C), or exposed on the soil surface at Townsville. There were wide ranges of initial levels of dormancy (9,100%), rates of change of dormancy and response to the different storage conditions showing that species with several types of dormancy characteristics are able to coexist in these communities. The general trend in dormancy levels was a decline with time with the rate of decline greatest for seeds exposed on the soil surface and least for those stored in the laboratory. The species were divided into groups based on dormancy levels in seeds on the soil surface during the late dry and mid wet seasons. The dormancy characteristics of the groups were related to the ecology of the species in the groups. There was an approximately linear increase in germination rate (i.e. a decrease in the number of days to 50% of final germination) over time for all storage treatments; rates for seeds on the soil surface increased more rapidly than those of seeds in laboratory and oven samples. [source]


Dormancy and germination characteristics of herbaceous species in the seasonally dry tropics of northern Australia

AUSTRAL ECOLOGY, Issue 3 2000
JOHN. G. MCIVOR
Abstract This study investigated changes in dormancy and germination over 8 months for 23 common species (annual and perennial grasses, legumes and other dicotyledons) from herbaceous communities in northern Australia. Seeds were exposed to three storage treatments: relatively constant laboratory conditions, an oven with fluctuating temperatures similar to those found on the soil surface (25/60°C), or exposed on the soil surface at Townsville. There were wide ranges of initial levels of dormancy (9,100%), rates of change of dormancy and response to the different storage conditions showing that species with several types of dormancy characteristics are able to coexist in these communities. The general trend in dormancy levels was a decline with time with the rate of decline greatest for seeds exposed on the soil surface and least for those stored in the laboratory. The species were divided into groups based on dormancy levels in seeds on the soil surface during the late dry and mid wet seasons. The dormancy characteristics of the groups were related to the ecology of the species in the groups. There was an approximately linear increase in germination rate (i.e. a decrease in the number of days to 50% of final germination) over time for all storage treatments; rates for seeds on the soil surface increased more rapidly than those of seeds in laboratory and oven samples. [source]


A fish kill event, hypoxia and other limnological impacts associated with early wet season flow into a lake on the Mary River floodplain, tropical northern Australia

LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 3-4 2003
Simon A. Townsend
Abstract The Mary River, in the Australian wet/dry tropics, flows seasonally to inundate a coastal floodplain. In the dry season, the river reduces to a series of disconnected lakes located along the main river channel. This paper examines the impact of riverine inflow, at the beginning of the wet season, on the limnology of Shady Camp Lake, and addresses broader water quality management issues. The first wet season flow of Mary River carried a high biological oxygen demand that reduced the lake's oxygen concentration. The resulting hypoxic conditions prompted fish avoidance behaviour and caused the death of at least 200 fish. There is no evidence of any direct anthropogenic pollution causing the event. After reaching near anoxic conditions, dissolved oxygen concentrations recovered several weeks later, although they remained low. The water quality of the Mary River was characterized by an initial pulse of water with high concentrations of organic carbon, suspended particulate material, colour, total nitrogen and total phosphorus. Phytoplankton biomass, measured as chlorophyll a, did not increase because of nitrogen limitation attributed to low nitrate and ammonia concentrations in the inflow waters. The low concentrations of available nitrogen were probably a result of denitrification, which would have been enhanced by the warm temperatures and low oxygen concentrations. The oxygen sag in Shady Camp Lake caused by the inflow of the Mary River exemplifies the vulnerability of floodplain channel lakes to riverine waters and underscores the need to manage catchment practices to minimize the concentration of labile organic material in the river and its associated oxygen demand. [source]


GIS-based rapid assessment of erosion risk in a small catchment in the wet/dry tropics of Australia

LAND DEGRADATION AND DEVELOPMENT, Issue 5 2001
G. Boggs
Abstract Assessing the impact of various land uses on catchment erosion processes commonly requires in-depth research, monitoring and field data collection, as well as the implementation of sophisticated modelling techniques. This paper describes the evaluation of a geographic information system (GIS)-based rapid erosion assessment method, which allows the user to quickly acquire and evaluate existing data to assist in the planning of more detailed monitoring and modelling programmes. The rapid erosion assessment method is based on a simplified version of the revised universal soil loss equation (RUSLE), and allows the rapid parameterization of the model from widely available land unit and elevation datasets. The rapid erosion assessment method is evaluated through the investigation of the effects of elevation data resolution on erosion predictions and field data validation. The use of raster digital elevation model (DEM)-derived data, as opposed to vector land unit relief data, was found to greatly improve the validity of the rapid erosion assessment method. Field validation of the approach, involving the comparison of predicted soil loss ratios with adjusted in-stream sediment yields on a subcatchment basis, indicated that with decreasing data resolution, the results are increasingly overestimated for larger catchments and underestimated for smaller catchments. However, the rapid erosion assessment method proved to be a valuable tool that is highly useful as an initial step in the planning of more detailed erosion assessments. Copyright © 2001 Commonwealth of Australia. [source]