Habitat choice and vigilance behaviour of brush-tailed rock-wallabies (Petrogale penicillata) within their nocturnal foraging ranges

Habitat choice by brush-tailed rock-wallabies (Petrogale penicillata) in south-east Queensland was investigated by comparing the attributes of the nocturnal foraging locations that they selected with those of random locations within a radius of 50 m. Brush-tailed rock-wallabies were shown to select foraging locations on the basis of forage quality and/or their ability to see predators, rather than protection from predators amongst vegetation that could conceal them. Habitat choice may have been affected by limited food availability, as this study was conducted in the winter dry season. The attributes of foraging locations that brush- tailed rock-wallabies perceived as increasing their predation risk were assessed by recording the proportion of time that brush- tailed rock-wallabies spent vigilant while foraging. To measure vigilance, focal animals were observed with a night- vision scope for two minutes and the proportions of time spent vigilant and feeding were recorded. No measured feature of foraging locations was related to higher vigilance levels, suggesting that brush- tailed rock-wallabies did not alter their vigilance whether sheltered amongst grass tussocks or in open habitat, or whether feeding on good quality or poorer quality vegetation. Vigilance levels significantly declined as overnight temperatures decreased, which may have resulted from higher energy requirements of brush- tailed rock-wallabies during winter. The only factors that were found to significantly increase vigilance levels were high winds and moonlit nights. On bright nights, brush- tailed rock-wallabies were very unsettled and during high winds they often did not emerge to feed. More information is needed about how macropods detect predators at night before the effects of wind and light intensity upon vigilance can be fully understood.

Embryonic mortality in buffaloes synchronized and mated by AI during the seasonal decline in reproductive function

The aim was to determine the factors that contribute to embryonic mortality in buffaloes mated by AI during a period of increasing day length which corresponds to a natural decline in reproductive activity. Italian Mediterranean buffalo cows (n = 243) showing regular estrous cycles were synchronized using the Ovsynch-TAI program and mated by AI at 16 and 40 h after the second injection of GnRH. Blood samples were collected on Days 10 and 20 after the first AI and assayed for progesterone (P-4). Pregnancy diagnosis was undertaken on Days 26 and 40 after the first AI using rectal ultrasonography. Buffaloes with a conceptus on Day 26 but not on Day 40 were judged to have undergone embryonic mortality and for these animals uterine fluid was recovered by flushing and analysed for common infectious agents. Estrus synchronization was achieved in 86% of buffaloes and the pregnancy rate on Day 40 was 34%. Embryonic mortality between Days 26 and 40 occurred in 45% of buffaloes and was associated with the presence of significant infectious agents in only 10 buffaloes (8%). Concentrations of P-4 on Day 10 after AI were higher (P < 0.05) in buffaloes that established a pregnancy than in buffaloes that showed embryonic mortality that was not associated with infectious agents. Similarly, on Day 20 after AI P-4 concentrations were higher (P < 0.01) in pregnant buffaloes compared with non-pregnant buffaloes and buffaloes that had embryonic mortality. It is concluded that a reduced capacity for P-4 secretion can explain around 50% of embryonic mortalities in buffaloes synchronised and mated by AI during a period of low reproductive activity and that other as yet unidentified factors also have a significant effect on embryonic survival. (c) 2004 Elsevier Inc. All rights reserved.

Australia-wide predictions of soil properties using decision trees

This paper describes the construction of Australia-wide soil property predictions from a compiled national soils point database. Those properties considered include pH, organic carbon, total phosphorus, total nitrogen, thickness. texture, and clay content. Many of these soil properties are used directly in environmental process modelling including global climate change models. Models are constructed at the 250-m resolution using decision trees. These relate the soil property to the environment through a suite of environmental predictors at the locations where measurements are observed. These models are then used to extend predictions to the continental extent by applying the rules derived to the exhaustively available environmental predictors. The methodology and performance is described in detail for pH and summarized for other properties. Environmental variables are found to be important predictors, even at the 250-m resolution at which they are available here as they can describe the broad changes in soil property.

Nitrogen cycling in degraded Leucaena leucocephala-Brachiaria decumbens pastures on an acid infertile soil in south-east Queensland, Australia

A grazing trial was conducted to quantify N cycling in degraded Leucaena leucocephala (leucaena)-Brachiaria decumbens (signal grass) pastures grown on an acid, infertile, podzolic soil in south-east Queensland. Nitrogen accumulation and cycling in leucaena-signal grass pastures were evaluated for 9 weeks until all of the leucaena on offer (mean 600 kg edible dry matter (EDM)/ha, 28% of total pasture EDM) was consumed. Nitrogen pools in the grass, leucaena, soil, cattle liveweight, faeces and urine were estimated. The podzolic soil (pH 4.8-5.9) was found to be deficient in P, Ca and K. Leucaena leaf tissues contained deficient levels of N, P and Ca. Grass tissues were deficient in N and P. Grazing was found to cycle 65% of N on offer in pasture herbage. However, due to the effect of the plant nutrient imbalances described above, biological N fixation by leucaena contributed only 15 kg/ha N to the pasture system over the 9-month regrowth period, of which 13 kg/ha N was cycled. Cattle retained 1.8 kg/ha N (8% of total N consumed) in body tissue and the remainder was excreted in dung and urine in approximately equal proportions. Mineral soil N concentrations did not change significantly (-3.5 kg/ha N) over the trial period. The ramifications of grazing and fertiliser management strategies, and implications for pasture rundown and sustainability are discussed.

Disseminated Scedosporium prolificans infection and survival of a child with acute lymphoblastic leukemia

Scedosporium prolificans is a saprophytic fungus responsible for an increasing number of infections among immumocompromised hosts. Historically, disseminated infection with this organism has resulted in death. We report on a pediatric patient who developed overwhelming S. prolificans sepsis after induction chemotherapy for acute lymphoblastic leukemia. She is well 18 months after the diagnosis of fungal sepsis and continues to receive chemotherapy for leukemia, which remains in remission.

Rhizodeposition and the enhanced mineralization of 2,4-dichlorophenoxyacetic acid in soil from the Trifolium pratense rhizosphere

Enhanced biodegradation of organic xenobiotic compounds in the rhizosphere is frequently recorded although the specific mechanisms are poorly understood. We have shown that the mineralization of 2,4-dichlorophenoxyacetic acid (2,4-D) is enhanced in soil collected from the rhizosphere of Trifolium pratense[e.g. maximum mineralization rate = 7.9 days(-1) and time at maximum rate (t(1)) = 16.7 days for 12-day-old T. pratense soil in comparison with 4.7 days(-1) and 25.4 days, respectively, for non-planted controls). The purpose of this study was to gain a better understanding of the plant-microbe interactions involved in rhizosphere-enhanced biodegradation by narrowing down the identity of the T. pratense rhizodeposit responsible for stimulating the microbial mineralization of 2,4-D. Specifically, we investigated the distribution of the stimulatory component(s) among rhizodeposit fractions (exudates or root debris) and the influence of soil properties and plant species on its production. Production of the stimulatory rhizodeposit was dependent on soil pH (e.g. t(1) for roots grown at pH 6.5 was significantly lower than for those grown at pH 4.4) but independent of soil inorganic N concentration. Most strikingly, the stimulatory rhizodeposit was only produced by T. pratense grown in non-sterile soil and was present in both exudates and root debris. Comparison of the effect of root debris from plant species (three each) from the classes monocotyledon, dicotyledon (non-legume) and dicotyledon (legume) revealed that legumes had by far the greatest positive impact on 2,4-D mineralization kinetics. We discuss the significance of these findings with respect to legume-rhizobia interactions in the rhizosphere.

The N-15 natural abundance (delta N-15) of ecosystem samples reflects measures of water availability

We assembled a globally-derived data set for site-averaged foliar delta(15)N, the delta(15)N of whole surface mineral soil and corresponding site factors (mean annual rainfall and temperature, latitude, altitude and soil pH). The delta(15)N of whole soil was related to all of the site variables (including foliar delta(15)N) except altitude and, when regressed on latitude and rainfall, provided the best model of these data, accounting for 49% of the variation in whole soil delta(15)N. As single linear regressions, site-averaged foliar delta(15)N was more strongly related to rainfall than was whole soil delta(15)N. A smaller data set showed similar, negative correlations between whole soil delta(15)N, site-averaged foliar delta(15)N and soil moisture variations during a single growing season. The negative correlation between water availability (measured here by rainfall and temperature) and soil or plant delta(15)N fails at the landscape scale, where wet spots are delta(15)N-enriched relative to their drier surroundings. Here we present global and seasonal data, postulate a proximate mechanism for the overall relationship between water availability and ecosystem delta(15)N and, newly, a mechanism accounting for the highly delta(15)N-depleted values found in the foliage and soils of many wet/cold ecosystems. These hypotheses are complemented by documentation of the present gaps in knowledge, suggesting lines of research which will provide new insights into terrestrial N-cycling. Our conclusions are consistent with those of Austin and Vitousek (1998) that foliar (and soil) delta(15)N appear to be related to the residence time of whole ecosystem N.

Chemical characterization of soils of a tropical humid forest zone: A methodology

A methodology, based on a combination of routinely performed analyses and investigation of fundamental charge and anion sorption properties, was used to characterize the soils of the humid forest zone of Cameroon, In general, the soils have about 2 cmol kg(-1) permanent negative charge, with about 1 cmol kg(-1) from variable-charge sources at current soil pH values, Furthermore, they are impoverished with respect to Ca, Mg, and K, while Al frequently dominates the exchange complex. Thus, the ability of these soils to retain base cations is more limited than is suggested by the cation-exchange capacity (CEC), Therefore we propose the concept of a degradation index (DI) defined as: DI = 100(CEC5.5 - sum of basic cations)/CEC5.5, where CEC5.5 is the CEC measured at pH 5.5, This index encompasses degradation a soil may have experienced from natural or man-made causes, Extractable PO4 concentrations are considered very low and the soils have a moderate to high capacity to fix added PO4. Surface soil SO4 concentrations are considered marginal to deficient for plant growth, though adequate reserves of SO4 are held in the subsoil by SO4 sorption, The approach used demonstrated that the five morphologically different soil profile classes identified in the zone have similar chemical characteristics. Thus, the results of experimentation conducted on one of the soil profile classes will be applicable throughout the zone, Furthermore, the approach has provided a means of identifying comparable soil types in other parts of the world and will guide technology transfer, The analytical methods used in this study are relatively simple and require no specialized equipment, and are therefore within the capabilities of many laboratories in the developing world.

A test of the hypothesis of ecological equivalence in an Australian subtropical rain forest

We tested the hypothesis that tree species in a subtropical rain forest in south-east Queensland are ecologically equivalent and therefore have identical environmental requirements for their regeneration. We assessed the evidence that juveniles of species differed in their distributions in treefall gap microsites and along gradients of light availability, soil pH, soil PO4-P availability and soil NO3-N availability. Pairwise comparisons were made on a subset of the common species selected on the basis that they showed a relatively high level of positive association, and would therefore, a priori, be expected to have similar regeneration requirements. Detailed comparisons between the species failed to demonstrate evidence for species differentiation with respect to their tolerance of the disturbance associated with gap microsites or to the gradient of NO3-N availability. However, species differed markedly in their distributions along the soil pH gradient and along the gradients of light availability and soil PO4-P availability. The overall level of ecological differentiation between the species is high: seven out of the 10 possible species pairings showed evidence for ecological differentiation. Such niche differentiation amongst the juveniles of tree species may play an important role in maintaining the species richness of rain-forest communities.

An overview of APSIM, a model designed for farming systems simulation

The Agricultural Production Systems Simulator (APSIM) is a modular modelling framework that has been developed by the Agricultural Production Systems Research Unit in Australia. APSIM was developed to simulate biophysical process in farming systems, in particular where there is interest in the economic and ecological outcomes of management practice in the face of climatic risk. The paper outlines APSIM's structure and provides details of the concepts behind the different plant, soil and management modules. These modules include a diverse range of crops, pastures and trees, soil processes including water balance, N and P transformations, soil pH, erosion and a full range of management controls. Reports of APSIM testing in a diverse range of systems and environments are summarised. An example of model performance in a long-term cropping systems trial is provided. APSIM has been used in a broad range of applications, including support for on-farm decision making, farming systems design for production or resource management objectives, assessment of the value of seasonal climate forecasting, analysis of supply chain issues in agribusiness activities, development of waste management guidelines, risk assessment for government policy making and as a guide to research and education activity. An extensive citation list for these model testing and application studies is provided. Crown Copyright (C) 2002 Published by Elsevier Science B.V. All rights reserved.

Cleaner fish drives local fish diversity on coral reefs

Coral reefs are one of the most diverse habitats in the world [1], yet our understanding of the processes affecting their biodiversity is limited [1-3]. At the local scale, cleaner fish are thought to have a disproportionate effect, in relation to their abundance and size, on the activity of many other fish species, but confirmation of this species' effect on local fish diversity has proved elusive. The cleaner fish Labroides dimidiatus has major effects on fish activity patterns [4] and may indirectly affect fish demography through the removal of large numbers of parasites [5, 6]. Here we show that small reefs where L. dimidiatus had been experimentally excluded for 18 months had half the species diversity of fish and one-fourth the abundance of individuals. Only fish that move among reefs, however, were affected. These fish include large species that themselves can affect other reef organisms [2, 7]. In contrast, the distribution of resident fish was not affected by cleaner fish. Thus, many fish appear to choose reefs based on the presence of cleaner fish. Our findings indicate that a single small [8] and not very abundant [9] fish has a strong influence on the movement patterns, habitat choice, activity, and local diversity and abundance of a wide variety of reef fish species.

Subsoil nitrogen mineralisation and its potential to contribute to NH4 accumulation in a Vertosol

High concentrations of NH4+ (up to 270 kg N/ha) have been observed in a Vertosol below 1 m depth in south-east Queensland. This study examined the possibility that mineralisation associated with the removal of native vegetation (Acacia harpophylla) for cropping was responsible for the production of NH4+. Particularly, the potential contribution of decomposing root material and/or dissolved organic nitrogen (DON) leached into the subsoil after clearing was investigated. The amount of N that was contained within native vegetation root material was determined from an area of native vegetation adjacent to the cleared site containing elevated NH4+ concentrations. In addition, the amount of NH4+ that could be mineralised in the native vegetation soil was determined by monitoring NH4+ concentrations over 360 days in intact cores, and by conducting waterlogged incubations. To determine the rate at which a source of DON leached into the subsoil would mineralise, soil was amended with glutamic acid at a rate of 250 mg N/kg and placed under waterlogged incubation. The possibility that the acidic pH of the subsoil, or the lack of a significant subsoil microbial population, was inhibiting mineralisation was also examined by increasing soil pH from 4.4 to 7.0, and inoculating the subsoil with surface soil microorganisms during waterlogged incubations. Low concentrations of N, approximately 90 kg N/ha between 1.2 and 3 m, were found in the native vegetation root material. In addition, no net N mineralisation was observed in either the extended incubation of intact cores or in the control samples of the waterlogged incubations. Net N mineralisation was also not detected when the subsoil was amended with a source of organic N. Results indicate that this lack of mineralisation is largely due to pH inhibition of the microbial population. It is concluded that the mineralisation of either in situ organic material, or DON transported to the subsoil during leaching events, is unlikely to have significantly contributed to the subsoil NH4 accumulation at the study site.

Kinetic model for selective cultivation of microfungi in a microscreen process for food processing wastewater treatment and biomass production

The research was aimed at developing a technology to combine the production of useful microfungi with the treatment of wastewater from food processing. A recycle bioreactor equipped with a micro-screen was developed as a wastewater treatment system on a laboratory scale to contain a Rhizopus culture and maintain its dominance under non-aseptic conditions. Competitive growth of bacteria was observed, but this was minimised by manipulation of the solids retention time and the hydraulic retention time. Removal of about 90% of the waste organic material (as BOD) from the wastewater was achieved simultaneously. Since essentially all fungi are retained behind the 100 mum aperture screen, the solids retention time could be controlled by the rate of harvesting. The hydraulic retention time was employed to control the bacterial growth as the bacteria were washed through the screen at a short HRT. A steady state model was developed to determine these two parameters. This model predicts the effluent quality. Experimental work is still needed to determine the growth characteristics of the selected fungal species under optimum conditions (pH and temperature).

Histoplasmosis in Australia: A report of a case with a review of the literature

Histoplasmosis is a rare but serious fungal infection commonly presenting as mucosal ulceration of the oral cavity. It is increasingly recognized in Australia but the source of infection remains obscure and it is likely to be under-diagnosed. We report a case of chronic mucosal ulceration which failed to fully respond to periodontal therapy. Histology and culture of a gingival biopsy was consistent with histoplasmosis, and the patient responded favourably to treatment with oral itraconazole. Histoplasmosis may present to general dental practitioners as chronic mucosal ulceration and should be considered in the differential diagnosis of such lesions. Diagnosis is best made by culture and histology of biopsy specimens.