Semi-arid Western Australia Research Articles

A new spider species of the genus Proshermacha (Mygalomorphae: Anamidae) from the Coolgardie and Murchison bioregions of Western Australia, collected on a Bush Blitz expedition

The open-holed trapdoor spider genus Proshermacha Simon, 1908 (Anamidae) currently contains ten species. The genus is known to occur from south-western Western Australia, through southern South Australia and into western Victoria. Here, we describe the first species from semi-arid Western Australia, from Credo Station Reserve and surroundings. Several specimens of this species, including the holotype, were collected on a Bush Blitz expedition to Credo Station Reserve, in 2011.

P is for persistence: Soil phosphorus remains elevated for more than a decade after old field restoration.

Understanding constraints to ecological restoration on former agricultural land has become increasingly important due to agricultural land degradation in the developed world, and growing evidence for enduring agricultural legacies that limit native species recovery. In particular, the removal of native plant biomass and subsequent disturbance of soil properties through farming activities can alter soil ecosystem processes. Planting of native plant species is a common approach to restoring native vegetation on agricultural land and is assumed to benefit soil ecosystem processes, but the degree to which altered soil chemical processes recover is poorly documented. We investigated recovery of soil chemical properties after restoration in semiarid Western Australia, hypothesizing that elevated nutrient concentrations would gradually decline post planting, but available phosphorus (P) concentrations would remain higher than reference conditions. We used a space-for-time substitution approach, comparing 10 planted old field plots with matched fallow cropland and reference woodlands. Sampling on planted old fields and reference woodland plots was stratified into open patches and under tree canopy to account for consistent differences between these areas. The most prominent legacy of cropping was significantly and substantially higher concentrations of soil available P in fallow croplands and restored old fields compared with reference woodlands. Soil mineral nitrogen (N) concentrations were elevated in fallow croplands compared to open patches in reference woodlands (ammonium and nitrate) and under the tree canopy (ammonium). However, in restored old fields, mineral N concentrations were similar to woodland sites, providing evidence for amelioration over time. No significant differences in nutrient concentrations under tree canopies compared with open patches had developed in the planted old fields, despite a distinction between open patches and he under ttree canopy in reference woodlands for total N. We conclude that soil P legacies in old fields may inhibit the recolonization of native species that are sensitive to, or uncompetitive at, elevated P concentrations. To achieve full recovery, further research is required to test restoration practices aimed at reducing soil P concentrations to facilitate native plant establishment and persistence.

Incorporating rock in surface covers improves the establishment of native pioneer vegetation on alkaline mine tailings

Background and aimsRates of tailings production and deposition around the world have increased markedly in recent decades, and have grown asynchronously with safe and environmentally suitable solutions for their storage. Tailings are often produced in regions harbouring biodiverse native plant communities adapted to old, highly-weathered soils. The highly-altered edaphic conditions of tailings compared with natural soils in these areas will likely select against many locally endemic plant species, making phytostabilisation, rehabilitation or ecological restoration of these landforms challenging. MethodsWe established four substrate cover composition treatments on a dry-stacked magnetite tailings storage facility in semi-arid Western Australia, representative of standard industry practices for rehabilitating or restoring post-mining landforms in the region. Plots were seeded with a selection of locally native plant species and monitored for five years to determine whether different substrate cover treatments yielded different edaphic conditions (soil moisture, substrate surface temperature and substrate chemistry) and influenced soil development and the success of native vegetation establishment. ResultsNo vegetation established from seeds on unamended tailings with no surface cover, and substrate chemistry changed minimally over five years. In contrast, rock-containing surface covers allowed establishment of up to 11 native plant species from broadcast seeds at densities of ca. 1.5 seedlings m−2, and up to 3.5 seedlings m−2 of five native pioneer chenopods from capture of wind-dispersed seeds from surrounding undisturbed native vegetation. Greater vegetation establishment in rock-containing surface covers resulted from increased heterogeneity (e.g., lower maximum soil temperature, greater water capture and retention, surface microtopography facilitating seed capture and retention, more niches for seed germination). Soil development and bio-weathering occurred most rapidly under the canopy of native pioneer plants on rock-containing surface covers, particularly increases in organic carbon, total nitrogen, and organo-bound aluminium and iron. ConclusionsSeed germination and seedling survival on tailings were limited by extreme thermal and hydrological conditions and a highly-altered biogeochemical environment. The design of surface cover layers appears crucial to achieving closure outcomes on tailings landforms, and designs should prioritise increasing surface heterogeneity through the incorporation of rock or other structure-improving amendments to assist the establishment of pioneer vegetation.

Space use and habitat selection of an invasive mesopredator and sympatric, native apex predator

BackgroundWhere mesopredators co-exist with dominant apex predators, an understanding of the factors that influence their habitat and space use can provide insights that help guide wildlife conservation and pest management actions. A predator’s habitat use is defined by its home range, which is influenced by its selection or avoidance of habitat features and intra- and inter-specific interactions within the landscape. These are driven by both innate and learned behaviour, operating at different spatial scales. We examined the seasonal home ranges and habitat selection of actively-managed populations of a native apex predator (dingo Canis dingo) and invasive mesopredator (feral cat Felis catus) in semi-arid Western Australia to better understanding their sympatric landscape use, potential interactions, and to help guide their management.MethodsWe used kernel density estimates to characterise the seasonal space use of dingoes and feral cats, investigate inter- and intra-species variation in their home range extent and composition, and examine second-order habitat selection for each predator. Further, we used discrete choice modelling and step selection functions to examine the difference in third-order habitat selection across several habitat features.ResultsThe seasonal home ranges of dingoes were on average 19.5 times larger than feral cats. Feral cat seasonal home ranges typically included a larger proportion of grasslands than expected relative to availability in the study site, indicating second-order habitat selection for grasslands. In their fine-scale movements (third-order habitat selection), both predators selected for roads, hydrological features (seasonal intermittent streams, seasonal lakes and wetlands), and high vegetation cover. Dingoes also selected strongly for open woodlands, whereas feral cats used open woodlands and grasslands in proportion to availability.Management recommendationsBased on these results, and in order to avoid unintended negative ecological consequences (e.g. mesopredator release) that may stem from non-selective predator management, we recommend that feral cat control focuses on techniques such as trapping and shooting that are specific to feral cats in areas where they overlap with apex predators (dingoes), and more general techniques such as poison baiting where they are segregated.

Persistence of rare species depends on rare events: demography, fire response and phenology of two plant species endemic to a semiarid Banded Iron Formation range

The association of rare plant species and Banded Iron Formation (BIF) ranges in semiarid Western Australia is a noted phenomenon. These ranges are also a focus of iron ore exploration and mining. Decisions and planning required for development, conservation and management resulting from this interest, often consider translocation of these threatened species. Nonetheless, little is known about the ecology of BIF-endemic species to support any such decisions. We assessed population structure, patterns of growth, mortality, recruitment, reproduction and in situ seedbank persistence for two declared rare flora species. The shrub Darwinia masonii, and sedge Lepidosperma gibsonii are endemic to an area <40 km2 on the south-western boundary of the Australian arid zone. Both species were found to be long lived and slow growing, with evidence for reliance on rare events such as fire, and high rainfall years, including, for some processes, consecutive high rainfall years for growth, reproduction and recruitment. Retrieval and germination of seed batches shows that both species’ seedbanks are long-lived, with seasonal dormancy cycling. This, together with the ability of mature plants to survive through years not supporting growth, and, for L. gibsonii, to resprout after fire, are key mechanism for persistence in this unpredictable and low rainfall environment.

Genetic drift drives evolution in the bird-pollinated, terrestrial island endemicGrevillea georgeana(Proteaceae)

Plant species distributed across terrestrial islands can show significant genetic divergence among populations if seed and pollen dispersal are restricted. We assessed the genetic connectivity between populations of Grevillea georgeana, restricted to seven disjunct inselbergs in semi-arid Western Australia. The phylogeographical pattern and population genetics of populations were determined using sequence data from two plastid DNA intergenic spacers and ten nuclear microsatellite loci. The plastid DNA markers indicated high genetic differentiation among the majority of populations. Haplotypes were restricted to individual inselbergs, with the exception of two that were shared among three isolated populations that formed part of an elongated greenstone belt and that may be connected via inaccessible populations of G. georgeana. There was also strong differentiation within some of the populations, suggesting long-term isolation and persistence of G. georgeana on these terrestrial islands. Overall, the genetic patterns suggest limited seed dispersal, with differentiation in the plastid DNA genome being driven by genetic drift. In contrast, pollen movement, although generally restricted, may occur between neighbouring populations, resulting in a pattern of isolation by distance in the nuclear markers. This potential for limited or no seed dispersal, but connectivity via pollen flow, should be considered, given that many of the inselbergs are under consideration for resource development. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178, 155–168.

The benefits of seed enrichment on sandalwood (Santalum spicatum) populations, after 17 years, in semi-arid Western Australia

Initially, the size-class structure of 1067 natural sandalwood (Santalum spicatum) trees and seedlings, growing in populations at three semi-arid sites (Burnerbinmah, Ninghan and Goongarrie) in Western Australia, was measured during 1996–97. These same populations, and any new sandalwood seedlings and small trees that had established after 1996–97, were measured again after 17 years (2013). Size-class structure was assessed by measuring over-bark stem diameter at 150 mm above the ground. Populations of sandalwood trees at the Burnerbinmah and Ninghan sites failed to regenerate and, after 17 years, they contained only 0–3% small trees and 0–2% seedlings. Their overall population size declined by 21–24% and, combined with recruitment failure, these natural stands of sandalwood may largely disappear within 50–60 years. At the Goongarrie site, the proportion of large trees within the natural population increased from 58% to 82%. The proportion of small trees was constant at 13–16%, while seedlings declined from 29% to 2%. The population reduced by 35%, mainly due to high seedling mortality. Although the population was in decline, there appeared to be enough small trees and seedlings to maintain the population longer than at both the Burnerbinmah and Ninghan sites. In a second study, 16 640 sandalwood seeds were sown at the same three sites during 1996–97, and then assessed for germination, survival, growth and fruit production over 17 years. Sandalwood germination and growth were compared between locations, fencing treatments and land systems. Seed enrichment was successful at each site with 27–45% germination and 6–20% survival (from germinated seeds) after 17 years. The overall seedling survival rates (from total seeds sown) ranged from 2.1% to 5.2%. Mean stem diameter of seedlings was significantly larger at Goongarrie (37 mm) than at both Burnerbinmah and Ninghan (20–22 mm) sites. Grazing significantly affected the performance of sandalwood seedlings at an age of 17 years at the Ninghan site. At this site, seedling survival (from germinated seeds) was 16% in the fenced plots compared with only 6% in the unfenced plots. Mean stem diameter in the fenced plots (24 mm) was also significantly greater than in the unfenced plots (11 mm). Land systems did not affect survival of sandalwood seedlings at the Burnerbinmah site but had a significant impact at the Goongarrie site after 17 years. Seedling survival was significantly greater on the hills and ridges than those growing on the plains with granite and red sand plains. Seed-enrichment programs are recommended to improve long-term regeneration and sustainability of sandalwood trees.

Potential economic pests of solanaceous crops: a new species of Solanum-feeding psyllid from Australia and first record from New Zealand of Acizzia solanicola (Hemiptera: Psyllidae)

Acizzia credoensis sp. n. is described from a single population on the native plant, Solanum lasiophyllum, from semi-arid Western Australia. The host range of Acizzia solanicola Kent & Taylor, initially recorded as damaging eggplant, S. melongena, in commercial crops and gardens and on wild tobacco bush, S. mauritianum in eastern Australia, is expanded to include the following Solanaceae: rock nightshade, S. petrophilum, cape gooseberry, Physalis peruviana, and an undetermined species of angel's trumpet Brugmansia and Datura. New Zealand specimens of A. solanicola collected in early 2012 from S. mauritianum are the first record for this species from outside Australia, and possibly represent a very recent incursion. The potential for the solanaceous-inhabiting Psyllidae to vector Candidatus Liberibacter solanacearum, an economically important plant pathogen, on native Australian Solanaceae is discussed. The occurrence of A. credoensis and A. solanicola on native Australian Solanum supports the Australian origin for the solanaceous-inhabiting Acizzia psyllids.

Slow recruitment in a red-fox population following poison baiting: a non-invasive mark–recapture analysis

Context Optimal management of invasive species should determine the interval between lethal-control operations that will sustain a desired population suppression at minimum cost. This requires an understanding of the species’ rate of recruitment following control. These data are difficult to acquire for vertebrate carnivores such as the red fox (Vulpes vulpes), which are not readily trapped or observed. Aims To provide a long-term evaluation of the effects of 1080 poison baiting on the abundance and extent of movement of red foxes in a semiarid environment. Methods We used non‐invasive DNA sampling of fox hairs in semi-arid Western Australia where the population was subject to two episodes of aerially delivered sodium fluoroacetate (1080) poison baits within 12 months. Sampling took place at ~45-day intervals and individual foxes were identified by genotyping eight microsatellite DNA markers and a gender-specific marker. Open-population and spatially explicit mark–recapture models were used to estimate the density, apparent survival and movements of foxes before and following baiting. Key results Following a severe reduction in density after baiting, fox density during the ensuing 12 months increased slowly (0.01 foxes km–2 month–1), such that density had only reached 22% of pre-baiting levels ~10 months after the initial baiting. Moreover, recovery was non‐linear as population growth was negligible for 6 months, then exhibited a nine-fold increase 7–9 months after control, coincident with the dispersal of juveniles in autumn. Fox movements between recaptures were on average 470% greater after baiting than before, in line with expectations for low-density populations, suggesting that the probability of encountering baits during this period would be higher than before baiting. Conclusions Baiting with 1080 poison significantly reduced the density of foxes, and the low density was sustained for more than 6 months. Foxes moved significantly further between recaptures after baiting when at low densities. Implications Control programs in this region may be carried out at low frequency to suppress fox density to a fraction of unbaited levels. The intensity of follow-up baiting may also be adjusted downwards, to take account of an increased probability of bait encounter in more mobile foxes.

Studies on the soil seed bank of the environmental weed Rumex vesicarius (Fam.: Polygonaceae) at a rehabilitated mine site in semi-arid Western Australia

Long-term control of the weed Rumex vesicarius (Fam.: Polygonaceae) (common name: Ruby Dock) in rehabilitated mine sites in semi-arid areas of Western Australia requires knowledge of the total size of the seed bank and its properties (longevity and germination of the seeds). Ruby Dock seeds are polymorphic (light and dark of various colour shades) and of high potential viability. At the Plutonic mine site near Meekatharra (Western Australia) areas heavily infested with Ruby Dock were characterised by large numbers of fruits, which contained numerous viable, dark seeds. Intact, light seeds were found in only a small percentage of the recovered fruits. Experiments in the greenhouse demonstrate that a large number of potentially viable Ruby Dock seeds remained in the soil after three germination seasons. A high proportion of the seeds, which germinated produced seedlings during the first germination season, soon after watering commenced. The application of herbicides at seedling stage, removal of fruit mats (which consist of large numbers of fruits intermingled with decaying plant material from previous seasons) and increase in competition through native plants currently appear to be the most efficient measures to control the size of the seed bank in rehabilitated mine sites.

Molecular and morphological systematics of hypogean schizomids (Schizomida:Hubbardiidae) in semiarid Australia

We used molecular and morphological techniques to study troglobitic schizomids inhabiting a variety of subterranean landforms in semiarid Western Australia. The study was designed to explore the taxonomic and phylogenetic status of newly discovered populations of subterranean schizomids. Molecular sequences of the mitochondrial DNA (mtDNA) cytochrome oxidase subunit 1 (COI) and small subunit rRNA (12S) were obtained from a total of 73 schizomid specimens. Populations sampled from boreholes within mesa landforms in the Robe Valley were highly genetically distinct from species of Draculoides Harvey, 1992 found elsewhere in the Pilbara (Cape Range and Barrow Island). Pronounced genetic structuring was also evident at a fine spatial scale within the Robe Valley, with populations from each of the mesas examined exhibiting unique and highly divergent mtDNA lineages. These molecular data were generally supported by small but significant morphological features, usually in the secondary male structures, but some species were represented only by female specimens that possessed more conservative morphologies. The molecular data defined two major in-group clades, which were supported by morphological differences. One clade was widespread and included the type species of Draculoides, D. vinei (Harvey), along with D. bramstokeri Harvey & Humphreys, D. brooksi Harvey, D. julianneae Harvey, D. mesozeirus, sp. nov. and D. neoanthropus, sp. nov. The second clade was restricted to the Robe Valley and deemed to represent a new genus, Paradraculoides, which included four new species P. anachoretus, sp. nov., P. bythius, sp. nov., P. gnophicola, sp. nov. and P. kryptus, sp. nov. (type species).

Vegetation communities on the shores of a salt lake in semi-arid Western Australia

The vegetation communities of the eastern and southern shores of Lake Lefroy, a large salt lake near Kambalda, Western Australia, were studied. The aim of the studies was to explore the relationship between the distribution of vegetation along salt lake shores in relation to soil conditions and the depth to ground-water. Four distinct lake shore types were investigated and two-way indicator species analysis (TWINSPAN) was used to classify the vegetation communities occurring on the lake shores. Seven vegetation communities, with a total of 50 vascular plant species, were identified. More than half of the species recorded were herbs. Those communities occurring on highly saline soils close to the shallow hypersaline ground-water-table included the halophytic genera Halosarcia and Frankenia. Communities on less saline soils and at greater elevations were more diverse. It was concluded that depth to ground-water and soil texture were likely to be key factors in determining the distribution of vegetation communities along the shores. The findings of the study have implications for the design of rehabilitation programmes for shores disturbed by mining activity.

A Numerical and Field Investigation of Surface Heat Fluxes from Small Wind-Sheltered Waterbodies in Semi-Arid Western Australia

Shelterbelts are used for a variety of purposes in agricultural environments, primarily because of their ability to improve the downwind microclimate. Excessive evaporative losses from small, agricultural water supply reservoirs in semi-arid Western Australia motivated a combined numerical modelling and field investigation into the potential for using shelterbelts to reduce evaporation from these open waterbodies. A numerical model of the disturbed momentum and turbulence fields in the region modified by the wind-shelter was employed and accounted for the presence of a waterbody downwind. The model was coupled with conservation equations for heat and moisture and sensible and latent heat fluxes were estimated from the simulated momentum, temperature and humidity fields. The numerical simulations were tested against four days of field data from two experiments conducted in the agricultural districts of southwest Western Australia that measured boundary-layer evolution over a variety of small waterbodies protected by artifical and natural wind-shelters. The model provided good predictions of windspeed during neutral conditions, but inadequate specification of the upwind boundary during non-neutral stabilities resulted in the model failing to capture any sensitivity to atmospheric stability as seen in the field data. Despite this limitation, the temperature and humidity fields were adequately captured by the model, and evaporative mass flux predictions also agreed well with estimates taken from water-balance measurements. It is concluded that well-designed wind-shelters can reduce evaporation from open waterbodies by 20–30% as a result of reductions in the velocity scales responsible for removing moisture from the water surface. The model can be used to estimate the values of various shelterbelt design parameters (e.g., porosity, height) that could be applied in the field to provide optimum evaporation reductions.

Growth response of highly tolerant Eucalyptus species to alkaline pH, bicarbonate and low iron supply

The tolerance of 5 Eucalyptus species (E. gracilis F. Muell., E. halophila D. Carr & S. Carr, E. kondininensis Maiden & Blakely, E. loxophleba Benth. and E. platypus Hook var. heterophylla Blakely) to alkaline conditions, bicarbonate, and low iron availability was assessed in solution culture. All 5 species occur naturally in alkaline or saline soils in semi-arid Western Australia. A treatment solution of pH 9 and containing 10 mmol/L bicarbonate (HCO3–) reduced the rate of height increase and leaf and branch production of most species compared with a control of pH 6 with no bicarbonate. Iron concentration within the youngest fully expanded leaves was reduced for seedlings in the bicarbonate-pH 9 solution. Eucalyptus halophila was an exception, responding positively to the alkaline treatment in having taller seedlings, a greater leaf production, and maintaining a high leaf iron concentration. Eucalyptus gracilis, E. loxophleba and E. platypus had the highest growth rates within the alkaline treatment, but the slow growth and sequestering of iron by E. halophila provided this species with the greatest potential for tolerance. The relative growth and tolerance rankings of the species in solution culture were similar to those obtained in previous field trials on alkaline mine processing wastes. Field selection of species from calcareous or sodic sites, and laboratory screening under high bicarbonate conditions can identify species with the greatest potential for the rehabilitation of alkaline mine wastes and other damaged lands with soils of high pH.

Exploration disturbances in semi arid Western Australia: A proactive approach to rehabilitation

ABSTRACT The paper addresses remediation of areas disturbed by exploration activities; drill line disturbance and drill sump holes. Drill line rehabilitation was at US$860 per ha, individual sump holes were US$120. The drill lines had displayed a degree of vehicle compaction and related disturbance. Application of seed over scarified drill lines led to the presence of a variety of plant taxa. Control and scarified drill line treatments (neither seeded) were characterised by the establishment of one or two species only. This is contrasted with higher species richness (16) and a greater range of life forms over the seeded treatment, coupled with significantly greater plant density and cover. The three sump hole treatments where deep ripping occurred are now covered by a variety of chenopods, with many acacias and eucalypts also prevalent. Application of good quality seed at 15 kg/ha with fertiliser, in late autumn, on newly prepared surfaces, has seen successful plant establishment over disturbed highly saline sumps which contained hydrocarbon derivatives. Revegetation was one and a half years old and a quantitative approach to reporting is provided. Cost benefit analysis of early rehabiliation is given.

Ecology of Sandalwood (Santalum Spicatum) Near Paynes Find and Menzies, Western Australia: Size Structure and Dry-Sided Stems.

Population size structure of sandalwood (Santalum spicatum) was studied on four pastoral leases near Paynes Find and Menzies, in semi-arid Western Australia. Stem diameter, height, height to crown and the orientation of dry-sided stems were recorded for 1017 individual sandalwood. Populations of S. spicatum at Paynes Find contained only mature trees, indicating no successful recruitment for at least 30 years. In contrast, populations of S, spicatum at Menzies had a high proportion of seedlings and saplings. Crown measurements of mature S. spicatum trees indicated high grazing intensity at Paynes Find: mean height to crown at Paynes Find (147-148 cm) was significantly higher than Menzies (92-94 cm). Dry-side percentage differed significantly between directional faces, consistent with sun damage. Highest mean dry-side percentages were on stem sides facing the sun between midday and late afternoon: west, north-west, south-west and north. This directional pattern was the same between pastoral leases, and there was no interaction between pastoral lease and dry-side direction. Mean percentage of mature trees with a dry-sided stem was also significantly higher at Paynes Find (76-82%) than at Menzies (42-46%). Significantly less foliage low to the ground on mature trees at Paynes Find may have exposed the stems to more sun damage. Land systems did not significantly influence dry-side direction on Burnerbinmah or Goongarrie. No S. spicatum seedlings or saplings had a dry-sided stem. Key words: Santalum spicatum, size structure, dry-sided stems

The Recognition of Amorphous Silica in Indurated Soil Profiles

AbstractSilica-indurated subsurface horizons of an in situ lateritic profile in semi-arid western Australia were investigated using a range of electron-optical and X-ray diffraction (XRD) techniques. These indurated materials were compared with underlying non-indurated pallid zone material. The secondary silica content of the indurated horizons, as determined by electron microprobe analysis, varied from 8 to 33%. Quantitative digital images for secondary silica, generated by mathematical manipulation of digital Si and AI-Kα: images, showed that kaolinite pseudomorphs after mica contained the lowest amounts of secondary silica, with the highest amounts being present in the inter-pseudomorph clay matrix. Variations in the amount of silica in the matrix are considered to reflect variations in the initial porosity of the clay matrix. Such variations may arise from differences in the Al/Si ratio of parent minerals. Transmission electron microscopy (TEM) showed that amorphous silica adhered to the (001) face of kaolinite crystals. The secondary silica could not be detected by either standard or differential XRD procedures.

Genesis principles for the precipitation of carnotite in calcrete drainages in Western Australia

Carnotite, K 2 (UO 2 ) 2 V 2 O 8 3H 2 O, is a commonly occurring mineral in the calcreted drainage systems of arid and semiarid Western Australia. Weathering of granitoid rock comprising the Archean Yilgarn Block is the likely source of uranium, and ground-water analyses from a representative catchment near Wiluna confirm high (10 to 442 ppb) uranium concentrations in present-day ground waters. Two types of carnotite deposit within the representative catchment can be identified. The first occurs within the margins of the chemical delta formed as the drainage system enters Lake Way and owes its existence primarily to remobilization of carnotite and to decomplexing of uranyl carbonates in waters of higher salinity. Vanadium analyses and solubility indices suggest that the carnotite upstream is at present redissolving and that a different mechanism was primarily responsible for its original precipitation. A redox process, the oxidation of vanadium (IV) to vanadium (V) is suggested as an important genesis feature, first by the observed color range in natural carnotites and by the fact that color changes can be induced in both natural and synthetic carnotite by the application of oxidizing or reducing agents. Second, field measurements also suggest that present-day ground waters of the Yilgarn Block display a natural Eh range which spans the experimentally observed vanadium (IV)-vanadium (V) redox curve. The decomplexing and redox mechanisms are seen to play important parts in carnotite genesis irrespective of the postulated source for vanadium.

A note on the macrofauna of a temporary rainpool in semi-arid Western Australia

The chemistry and macrofauna of a temporary rainpool on soft substrata near Kalgoorlie, Western Australia, are described. The ionic composition of the water was dominated by sodium and chloride and salinity was relatively high (5324 ppm). The fauna was depauperate and many faunal groups typical of fresh water were not recorded. Several groups often found in temporary localities were also not recorded, including chironomids. Insects (Hemiptera, Coleoptera, Diptera) dominated the fauna. Also present was a species of frog (larvae) and various crustaceans.

Development and distribution of soils in the Merredin area, Western Australia

The soil pattern in the Merredin district of Western Australia is closely related to a number of readily recognizable landscape features. An understanding of these relationships is proving useful in broad-scale mapping in semi-arid Western Australia and the units so obtained can be readily subdivided for more detailed mapping. Soil and topographic relationships of the five surfaces recognized are described in detail. These are an expression of erosional modifications of a mature Tertiary landscape resulting from changes in landscape stability. Deep lateritic weathering has influenced the chemistry and morphology of large areas of soils. Smaller areas of soils are developed from less weathered material exposed by complete removal of the lateritic profile, and from lake parna resulting from wind deflation of salinized alluvial sediments. The physical and chemical properties of samples from representative soils are summarized and discussed with reference to profiles which are arranged in groups on the basis of origin of parent material.