South-western Queensland Research Articles

Is 'vegetation thickening' occurring in Queensland's mulga lands? A 50-year aerial photographic analysis

Changes in the density of woody vegetation in arid and semiarid rangelands have the potential to dramatically reduce productivity as well as adversely affect ‘natural’ ecosystem processes. Many parts of Australia are believed to have experienced thickening of woody vegetation since European occupation and the associated changes to fire and grazing regimes that followed. Unfortunately there is little empirical evidence to support a widely held perception of thickening. This study analyses the available historical aerial photographic coverage for the mulga lands bioregion of south-western Queensland, Australia; a record spanning the second half of the twentieth century. Changes in woody vegetation canopy cover were assessed for 190 sites. More than half of the sites had no evidence of mechanical disturbance and thus reflected general, or background trends in woody vegetation cover. The region-wide average extent of change on these undisturbed sites was estimated to be approximately a 3.6% increase in canopy cover over the study period. Thus, a trend toward vegetation thickening was detected. However, large variation was observed depending on the land systems and rainfall zone where sites were located. The results are discussed in the context of century scale climate variability and perceptions of vegetation change and a tentative explanatory model is presented to account for the observed data.

METAPOPULATION PERSISTENCE IN A DYNAMIC LANDSCAPE: MORE HABITAT OR BETTER STEWARDSHIP

Habitat loss and fragmentation has created metapopulations where there were once continuous populations. Ecologists and conservation biologists have become interested in the optimal way to manage and conserve such metapopulations. Several authors have considered the effect of patch disturbance and recovery on metapopulation persistence, but almost all such studies assume that every patch is equally susceptible to disturbance. We investigated the influence of protecting patches from disturbance on metapopulation persistence, and used a stochastic metapopulation model to answer the question: How can we optimally trade off returns from protection of patches vs. creation of patches? We considered the problem of finding, under budgetary constraints, the optimal combination of increasing the number of patches in the metapopulation network vs. increasing the number of protected patches in the network. We discovered that the optimal trade-off is dependent upon all of the properties of the system: the species dynamics, the dynamics of the landscape, and the relative costs of each action. A stochastic model and accompanying methodology are provided allowing a manager to determine the optimal policy for small metapopulations. We also provide two approximations, including a rule of thumb, for determining the optimal policy for larger metapopulations. The method is illustrated with an example inspired by information for the greater bilby, Macrotis lagotis, inhabiting southwestern Queensland, Australia. We found that given realistic costs for each action, protection of patches should be prioritized over patch creation for improving the persistence of the greater bilby during the next 20 years.

Melaleuca densispicata in Currawinya National Park, South‐West Queensland: Ecology and preliminary implications for management of a rare plant species

Melaleuca densispicata Byrnes is an uncommon species with a limited distribution, comprising disjunct populations in inland southern Queensland and northern New South Wales, Australia. It is a dense, woody shrub, 2–4 m in height, which exhibits a marked 'clumping' growth habit. It has thick, papery bark and displays many white flowers during spring or early summer. Although it has long been known to exist, M. densispicata was only formally described in 1984, and very little is currently known about its ecology or specific management requirements. There are only seven known subpopulations of the species across its range. A major population at the western limit of its distribution occurs on Currawinya National Park (28°52'S, 144°30'E). Here, it is locally abundant and listed as a noteworthy plant species under the Management Plan (Queensland Parks & Wildlife Service 2001). This study aimed to identify patterns in the distribution of M. densispicata in Currawinya National Park, describe its ecological niche and role, and provide management recommendations for the species within the study area. Recent anecdotal observations of recruitment failure in south-western Queensland (Peter McRae, QPWS, October 2004, pers. comm.; Dick O'Connell, local grazier, July 2005 pers. comm.) caused additional emphasis to be placed on the examination of recruitment and recruitment factors.

Hosts of the exotic ornate kangaroo tick, Amblyomma triguttatum triguttatum Koch, on southern Yorke Peninsula, South Australia

Amblyomma triguttatum triguttatum is assumed to be endemic to south-western Western Australia (including Barrow Island), Queensland (excluding Cape York Peninsula), and New South Wales, south to Dubbo and Barham. The species has been recorded on a range of mammalian hosts including macropods and domestic animals. In Queensland, A. triguttatum triguttatum is implicated in the epidemiology of Q fever. In 2000, the species was detected on southern Yorke Peninsula in South Australia. We aimed to identify A. triguttatum triguttatum's hosts through trapping, sampling of carcasses, and opportunistic capture of vertebrates on Yorke Peninsula. A. triguttatum triguttatum was removed from black rats (Rattus rattus), wild rabbits (Oryctolagus cuniculus), western grey kangaroos (Macropus fuliginosus), Tammar wallabies (M. eugenii eugenii), domesticated cats and dogs, and humans. Before this study, A. triguttatum triguttatum had not been found on black rats or rabbits in the wild. This research has implications for the management of wildlife, livestock, and visitors on Yorke Peninsula. The potential for A. triguttatum triguttatum to spread to other areas of Yorke Peninsula and South Australia is considerable, as visitors (tourists) to southern Yorke Peninsula report the presence of ticks both on themselves and among camping equipment on arriving home.

Simulating the effects of saline and sodic subsoils on wheat crops growing on Vertosols

Soils with high levels of chloride and/or sodium in their subsurface layers are often referred to as having subsoil constraints (SSCs). There is growing evidence that SSCs affect wheat yields by increasing the lower limit of a crop’s available soil water (CLL) and thus reducing the soil’s plant-available water capacity (PAWC). This proposal was tested by simulation of 33 farmers’ paddocks in south-western Queensland and north-western New South Wales. The simulated results accounted for 79% of observed variation in grain yield, with a root mean squared deviation (RMSD) of 0.50 t/ha. This result was as close as any achieved from sites without SSCs, thus providing strong support for the proposed mechanism that SSCs affect wheat yields by increasing the CLL and thus reducing the soil’s PAWC. In order to reduce the need to measure CLL of every paddock or management zone, two additional approaches to simulating the effects of SSCs were tested. In the first approach the CLL of soils was predicted from the 0.3–0.5 m soil layer, which was taken as the reference CLL of a soil regardless of its level of SSCs, while the CLL values of soil layers below 0.5 m depth were calculated as a function of these soils’ 0.3–0.5 m CLL values as well as of soil depth plus one of the SSC indices EC, Cl, ESP, or Na. The best estimates of subsoil CLL values were obtained when the effects of SSCs were described by an ESP-dependent function. In the second approach, depth-dependent CLL values were also derived from the CLL values of the 0.3–0.5 m soil layer. However, instead of using SSC indices to further modify CLL, the default values of the water-extraction coefficient (kl) of each depth layer were modified as a function of the SSC indices. The strength of this approach was evaluated on the basis of correlation of observed and simulated grain yields. In this approach the best estimates were obtained when the default kl values were multiplied by a Cl-determined function. The kl approach was also evaluated with respect to simulated soil moisture at anthesis and at grain maturity. Results using this approach were highly correlated with soil moisture results obtained from simulations based on the measured CLL values. This research provides strong evidence that the effects of SSCs on wheat yields are accounted for by the effects of these constraints on wheat CLL values. The study also produced two satisfactory methods for simulating the effects of SSCs on CLL and on grain yield. While Cl and ESP proved to be effective indices of SSCs, EC was not effective due to the confounding effect of the presence of gypsum in some of these soils. This study provides the tools necessary for investigating the effects of SSCs on wheat crop yields and natural resource management (NRM) issues such as runoff, recharge, and nutrient loss through simulation studies. It also facilitates investigation of suggested agronomic adaptations to SSCs.

Aeolian–fluvial interaction and climate change: source-bordering dune development over the past ∼100 ka on Cooper Creek, central Australia

This study provides an interpretation of interrelated Quaternary fluvial and aeolian activity related to climate change on Cooper Creek in the Lake Eyre Basin in southwestern Queensland, central Australia. The extensive muddy floodplain is characterised by buried sandy palaeochannels now almost entirely invisible but stratigraphically connected to source-bordering dunes that emerge as distinctive sandy islands through the floodplain surface. Luminescence dating has identified pronounced periods of fluvial activity represented by abundant sandy alluvium from Marine Isotope Stages (MIS) 8–3. While all these sandy fluvial episodes on Cooper Creek were much more powerful than anything subsequent, they appear to be ranked in order of declining activity. MIS 8–6 saw reworking of almost the entire floodplain whereas subsequent phases of reworking were far less extensive. Source-bordering dunes were derived from active sandy channels in late MIS 5 (∼85–80ka) and mid MIS 3 (50–40ka). After ∼40ka sand-channel activity largely ceased and the floodplains and channels were inundated with mud, isolating the dunes as emergent features. Although aeolian reworking of the upper parts of some dunes has continued to the present, they show remarkable resilience, having survived without appreciable migration for at least 40ka. Whilst the channels once determined the location of source-bordering dunes, in an interesting role reversal the remnant dunes now determine the position of many contemporary flood-channels and waterholes by deflection and confinement of overbank flows.

Detecting induced in situ erodibility of a dust-producing playa in Australia using a bi-directional soil spectral reflectance model

Two sites on a playa (claypan) in south western Queensland, Australia were chosen to represent the variability in soil surface conditions known to control wind erosion and dust production in the region. The material was very fine and comprised of large amounts and different types of salts, high electrical conductivity, a propensity for slaking and the presence of cyanobacteria. The surfaces of 4 plots at each site were modified using in situ rainfall simulation and wind tunnel abrasion. The changes in the surface conditions were recorded using digital images and multi-angular spectral measurements of reflectance and inverted against a soil bi-directional spectral reflectance model. Optimised values of the model parameters produced the single scattering albedo (SSA) and a description of the scattering behaviour of the soil surfaces that included an estimate of microscopic roughness. The model parameters removed the effect of the measurement conditions (illumination and viewing geometry) on the spectral reflectance. Abrasion of the untreated surfaces demonstrated that the variability in the antecedent surface conditions played an important role in their response. Rainfall, drying and subsequent abrasion appeared to reset the soil surface conditions and controlled the spatial and temporal variation in the soil surface conditions. Redundancy analyses, conducted separately for SSA of selected wavebands, model parameter values and treatments elucidated the subtle and interactive effects of the treatments and surface responses. The results showed that high intensity rainfall and abrasion was associated with wavebands in the visible region and reduced roughness. Low intensity rainfall was associated with wavebands in the near-infrared and short-wave infrared regions and increased roughness. The analysis was interpreted as the result of eluviation due to rainsplash impact which caused size segregation and the preferential translocation of iron oxides to the surface and the creation of a thick surface seal and caused a thin crust which enabled the movement of salts and/or mineral clays to the surface because of the strong evaporation gradient. A poor relationship between aerodynamic resistance and microscopic roughness suggested that features of soil surface erodibility created by natural environmental processes such as rainsplash and wind erosion required a correction for macroscopic roughness. The values of the model parameters appeared to be insensitive to the directional nature of the abrasion process. The findings are significant for the development of this work towards an airborne or satellite-based assessment of soil surface erodibility and erosion.

Taxonomic Resolution and Quantification of Freshwater Macroinvertebrate Samples from an Australian Dryland River: The Benefits and Costs of Using Species Abundance Data

In studies using macroinvertebrates as indicators for monitoring rivers and streams, species level identifications in comparison with lower resolution identifications can have greater information content and result in more reliable site classifications and better capacity to discriminate between sites, yet many such programmes identify specimens to the resolution of family rather than species. This is often because it is cheaper to obtain family level data than species level data. Choice of appropriate taxonomic resolution is a compromise between the cost of obtaining data at high taxonomic resolutions and the loss of information at lower resolutions. Optimum taxonomic resolution should be determined by the information required to address programme objectives. Costs saved in identifying macroinvertebrates to family level may not be justified if family level data can not give the answers required and expending the extra cost to obtain species level data may not be warranted if cheaper family level data retains sufficient information to meet objectives. We investigated the influence of taxonomic resolution and sample quantification (abundance vs. presence/absence) on the representation of aquatic macroinvertebrate species assemblage patterns and species richness estimates. The study was conducted in a physically harsh dryland river system (Condamine-Balonne River system, located in south-western Queensland, Australia), characterised by low macroinvertebrate diversity. Our 29 study sites covered a wide geographic range and a diversity of lotic conditions and this was reflected by differences between sites in macroinvertebrate assemblage composition and richness. The usefulness of expending the extra cost necessary to identify macroinvertebrates to species was quantified via the benefits this higher resolution data offered in its capacity to discriminate between sites and give accurate estimates of site species richness. We found that very little information (<6%) was lost by identifying taxa to family (or genus), as opposed to species, and that quantifying the abundance of taxa provided greater resolution for pattern interpretation than simply noting their presence/absence. Species richness was very well represented by genus, family and order richness, so that each of these could be used as surrogates of species richness if, for example, surveying to identify diversity hot-spots. It is suggested that sharing of common ecological responses among species within higher taxonomic units is the most plausible mechanism for the results. Based on a cost/benefit analysis, family level abundance data is recommended as the best resolution for resolving patterns in macroinvertebrate assemblages in this system. The relevance of these findings are discussed in the context of other low diversity, harsh, dryland river systems.

Queensland's burrowing bettongs… where old news is gut news

The Burrowing Bettong Bettongia lesueur (Quoy and Gaimard 1824) has not previously been recorded from Queensland, although its past presence in all other mainland Australian states (excluding Victoria) is well documented. New evidence linking 11 old unregistered Queensland Museum study skins to 13 incorrectly identified skulls, and archival correspondence relating to an 1885 collection trip, made by museum collector Kendall Broadbent to Charleville, confirms that Burrowing Bettongs were once a part of Queensland's marsupial fauna. While old burrows attributable to B. lesueur are not uncommon in south-western Queensland, unconfirmed reports from the mid 1990s of “football-sized wallabies bouncing off the dingo fence” by kangaroo shooters operating there, throw the 1885 records into a modern context worthy of investigation.

The role of geophysics in understanding salinisation in Southwestern Queensland

This study, combining geophysical and environmental approaches, was undertaken to investigate the causes of secondary salinity in the Goondoola basin, in southwestern Queensland.Airborne radiometric, electromagnetic and ground electromagnetic datasets were acquired, along with data on soils and subsurface materials and groundwater. Relationships established between radiometric, elevation data, and measured material properties allowed us to generate predictive maps of surface materials and recharge potential. Greatest recharge to the groundwater is predicted to occur on the weathered bedrock rises surrounding the basin. Electromagnetic data (airborne, ground, and downhole), used in conjunction with soil and drillhole measurements, were used to quantify regolith salt store and to define the subsurface architecture. Conductivity measurements reflect soil salt distribution. However, deeper in the regolith, where the salt content is relatively constant, the AEM signal is influenced by changes in porosity or material type. This allowed the lateral distribution of bedrock weathering zones to be mapped.Salinisation in this area occurs because of local- and intermediatescale processes, controlled strongly by regolith architecture. The present surface outbreak is the result of evaporative concentration above shallow saline groundwater, discharging at break of slope. The integration of surficial and subsurface datasets allowed the identification of similar landscape settings that are most at risk of developing salinity with groundwater rise.This information is now being used by local land managers to refine management choices that prevent excess recharge and further salt mobilisation.

Microhabitat use and foraging behaviour of Sminthopsis youngsoni (Marsupialia:Dasyuridae) in arid central Australia

In this study, fluorescent pigment tracking was used to determine the microhabitat use and foraging behaviour of a small insectivorous marsupial, Sminthopsis youngsoni (the lesser hairy-footed dunnart), in the dunefields of the Simpson Desert, south-western Queensland. In total, 25 successful trails were traced over the duration of this study, between March 1996 and April 1998. Nocturnal foraging trails were identified, then the distance travelled by the dunnart through each microhabitat type (nine in all) was measured and accumulated for each trail and compared with surrounding available microhabitats along control trails. This provided an index of selectivity of microhabitat use. Terrestrial invertebrates were collected from both actual and control trails to measure food availability. Dunnarts strongly selected open microhabitats when foraging, with the periphery of spinifex hummocks (up to 20 cm from the edge of a spinifex hummock) being favoured. Spinifex itself was avoided unless shelter was sought (i.e. immediately after release). Potential invertebrate prey captured along the actual trails travelled by dunnarts tended to occur in greater numbers and were larger than those captured along the control trails, indicating that dunnarts can accurately locate resource-rich areas in which to forage. Clearly, the foraging strategies used by this species enable it to successfully exploit patchy and unpredictable food resources, thereby ensuring its continued persistence and relative abundance in an unstable environment.

The role of geophysics in understanding salinisation in Southwestern Queensland

This study, combining geophysical and environmental approaches, was undertaken to investigate the causes of secondary salinity in the Goondoola basin, in southwestern Queensland.Airborne radiometric, electromagnetic and ground electromagnetic datasets were acquired, along with data on soils and subsurface materials and groundwater. Relationships established between radiometric, elevation data, and measured material properties allowed us to generate predictive maps of surface materials and recharge potential. Greatest recharge to the groundwater is predicted to occur on the weathered bedrock rises surrounding the basin. Electromagnetic data (airborne, ground, and downhole), used in conjunction with soil and drillhole measurements, were used to quantify regolith salt store and to define the subsurface architecture. Conductivity measurements reflect soil salt distribution. However, deeper in the regolith, where the salt content is relatively constant, the AEM signal is influenced by changes in porosity or material type. This allowed the lateral distribution of bedrock weathering zones to be mapped.Salinisation in this area occurs because of local- and intermediate-scale processes, controlled strongly by regolith architecture. The present surface outbreak is the result of evaporative concentration above shallow saline groundwater, discharging at break of slope. The integration of surficial and subsurface datasets allowed the identification of similar landscape settings that are most at risk of developing salinity with groundwater rise.This information is now being used by local land managers to refine management choices that prevent excess recharge and further salt mobilisation.

Investigation into salinisation in southwestern Queensland

This study, combining geophysical and environmental approaches, was undertaken to investigate the causes of secondary salinity in the Goondoola Basin, in southwestern Queensland. A range of airborne and ground geophysical datasets were acquired, along with information on surface and subsurface materials and groundwater. Relationships established between various spatial and point datasets allowed us to generate predictive maps of surface materials, surficial salt stores and recharge potential. Investigation of groundwater and subsurface architecture identified subsurface salt stores and potential discharge areas. Salinisation in this area occurs as a result of local- and intermediate-scale processes, controlled strongly by regolith architecture. Management strategies can now be tailored specifically to prevent excess recharge and further salt mobilisation.

The ecology of insectivorous bats in the Simpson Desert central Australia: habitat use.

Seven species of insectivorous bats were positively identified within a regional study area in the Simpson Desert in south-western Queensland. This paper describes habitat use by this bat assemblage and the degree to which presence of water, food availability and roosting potential impact on bat activity. Bats predominantly utilised water sources, rock outcrops, dune/swale areas near woodland, dry creek lines and coolibah woodland habitats. However, they rarely used open habitats (open plain and dune/swale), acacia scrub and gidgee woodland. The bats foraged most often over water and on calmer nights, when insects were more active. Although highly active over water in some areas, bats may survive in the Simpson Desert without access to permanent water. Food availability in terms of flying insect abundance and biomass did not appear to significantly determine the use of different habitats. However, activity over the entire study area was concentrated in areas with a higher roosting potential. Consequently both tree and cave roost sites may be a limiting resource, resulting in bat activity being restricted predominantly to oases in the Simpson Desert study area.

Cattle grazing in a hummock grassland regenerating after fire: the short-term effects of cattle exclusion on vegetation in south-western Queensland

In the Simpson Desert of western Queensland fire is being used increasingly by pastoralists to manipulate hard spinifex (Triodia basedowii) pastures. In this study I investigated the short-term (20 month) effects of cattle grazing on hummock grasslands regenerating after fire in the Simpson Desert. Dung counts were used to determine if cattle grazed preferentially in areas regenerating after fire. Cattle exclosures and vegetation surveys were used to determine if grazing by cattle affected the structure and species composition of vegetation regenerating after fire. Cattle grazed preferentially in areas regenerating after fire. Cattle grazing reduced the cover, height, vertical density and species richness of regrowth vegetation. Grazing reduced the cover of Ptilotus polystachyus and reduced the proportion of Eragrostis eriopodia individuals bearing flowers and seed. Grazing visibly disrupted microbiotic soil crusts. It is recommended, as a precaution until additional data is available, that areas regenerating after fire be rested from grazing during the first post-fire wet season. Resting during this period will assist the establishment of vegetation cover and provide opportunities for grasses to set seed.

Lamprothamnium heraldii sp. nov. (Charales, Charophyta) from Australia: the first dioecious representative of the genus

Lamprothamnium heraldii A. García & Casanova sp. nov. (Charales, Charophyta) is a dioecious species collected in Australia. Its dioecious nature and the characteristics of its reproductive organs separate it from other species of the genus. The habit of the male and female plants is similar, and their vegetative morphology is similar in many respects to that of the monoecious species. However, the new species has larger antheridia and oogonia, larger coronula cells on the oogonium, a smaller number of striae and circumvolutions in the oospores and gyrogonites, and different gyrogonite morphology. The new species has been found in ephemeral lakes from the Paroo region in north-western New South Wales (NSW) and south-western Queensland, at the eastern margin of central Australia. Lake Gidgee, NSW, was chosen as the type locality. Lamprothamnium heraldii was also collected from Palaeo Lake, NSW, and Mid-Blue Lake and Lower Bell Lake, Queensland. These habitats are characterized by fluctuating salinity, and can be dry for several years at a time during periods of drought. Healthy populations of L. heraldii were found in salinities ranging from 2 to 25 g l−1 (as total dissolved solids) and pH 7.8–8.4. Scanning electron microscope images of the oospore, oospore ornamentation and gyrogonites are presented, together with photographs of whole plants. The significance of the discovery of a dioecious Lamprothamnium is discussed in relation to the biogeography of charophytes.

Simulations to optimize sampling of aeolian sediment transport in space and time for mapping

AbstractThe sampling frequency in space and time is often inadequate to estimate the accuracy and precision of aeolian sediment transport. The problem stems from a lack of knowledge about the spatial and temporal scale of variation in aeolian transport and is compounded by a shortage of resources (aeolian sediment traps and labour). This study developed a geostatistical methodology for estimating sediment transport at unsampled locations and tested the extent to which it was dependent on sampling networks (nested, grid and random) and frameworks (mobile or static sampling framework between wind erosion events). Aeolian transport data were collected in an area of Australia influenced by wind erosion (Diamantina Lakes National Park, southwestern Queensland) to evaluate the combination of events used for mapping transport. Insufficient wind erosion events occurred to test sediment sampling strategies and hence simulated sampling was conducted using maps of sediment transport produced with existing models of aeolian sediment transport in the same study area. Independent validation data were used to test the estimation performance.The results suggested that sampling networks that did not include information on the spatial scale of variation (i.e. grid and random sampling) did not represent adequately the sediment transport population. In contrast, a bespoke nested sampling network performed consistently better than the other networks. Overall the static framework with a nested network was recommended for estimation and mapping of sediment transport with few resources and was likely to be especially important for use over large areas. This approach has the advantage of requiring only a single pooled within‐event variogram for sediment transport to be used to derive the model parameters for kriging or stochastic simulation for each event. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Modelling the flow regime of an arid zone floodplain river, Diamantina River, Australia

Arid zone, ephemeral rivers are characterised by discharge decreasing downstream in the lower reaches due to transmission losses. Modelling the flow regime of these rivers requires data on the spatial and temporal distribution of transmission losses in these reaches. In this study, a hydrological model is developed for a 330 km reach of the Diamantina River in southwestern Queensland, where the floodplain width varies from 5 to 60 km. Analysis of gauging station data at each end of the reach indicates that transmission losses are between 70 and 98% for floods with total discharge <2300 GL. The flow routing and transmission losses are modelled using a grid-based, daily time-step conceptual model incorporating flow routing algorithms. Satellite images are used to identify the flow-paths used by the range of flood sizes and to identify threshold flow volumes for initiation of flow into new flow-paths. The grid-based approach allows for representative routing of flow through the reach and representation of spatial variability in transmission loss processes, including losses resulting from evaporation, channel/floodplain infiltration and terminal flow storage. A combination of gauging station data and satellite images is used in the calibration of the model parameters.

Feral goats in south-western Queensland: a permanent component of the grazing lands

Feral goats were harvested in south-western Queensland at four sites under two regimes (opportunistic harvesting and sustained control). We assessed how this impacted on their contribution to total grazing pressure, on soil and pasture conditions and on the economics of goat management. The population impact was not consistent across sites with the same treatment, with 62% and 84% reductions in numbers in the two northern sites (one opportunistic harvesting site and one sustained control site) while numbers in the southern sites essentially remained the same. The contribution of goats to grazing pressure ranged from 3 to 30%; kangaroos contributed 16–36%; and livestock contributed 37–72%. Harvest rates of feral goats calculated for each of the sites ranged from 17 to 41%. There was no consistent relationship between population changes and the harvest rates. Seasonal conditions had greater influence on pasture and soil conditions than did changes in feral goat populations. The average cost of mustering goats (based on 34 operations) was $1.93 per head. Mustering costs increased markedly when goat density was lower than 10/km2. Average trapping costs (based on 7 trapping programs) were $2.08 per head. This compared with on-farm prices of $16–$25 per head in 1997. Personal circumstances and preferences of individual landholders were the key determinant of the level of control undertaken. Variability in price contributed to landholders being apprehensive about the viability of the goat industry. There are few simple tools available for landholders to estimate feral goat numbers and this makes effective management of total grazing pressure difficult.

A preliminary analysis of the conchostracans (Crustacea: Spinicaudata and Laevicaudata) of the middle Paroo catchment of the Australian arid-zone

Twelve species in the genera Caenestheria, Caenestheriella, Eocyzicus, Eulimnadia, Limnadia, Limnadopsis, and Lynceus have been collected from intermittent wetlands in the Paroo of northwestern New South Wales and southwestern Queensland. This is the first record of Eocyzicus from Australia. Identifications are partly tentative as the Australian fauna is poorly documented; some species seem to be new. There are many co-occurrences, especially in wetlands connected to others, but generally species are adapted for different ranges of turbidity, salinity and length of the wet phase. The high biodiversity is explained by the presence of many distinct types of wetland, each with its own characteristic species.