The effects of Woylie (Bettongia penicillata) foraging on soil water repellency and water infiltration in heavy textured soils in southwestern Australia

Abstract In the wheatbelt region of Western Australia, brush-tailed bettongs or woylies, Bettongia penicillata, occur in remnant woodlands that have highly water repellent soils. As these marsupials dig for the fruiting bodies of hypogeous fungi they disturb the soil surface. The effect of these diggings was evaluated by laboratory and in situ assessments of soil water repellency. The undisturbed woodland soil surface showed severe water repellence whereas diggings had low water repellence, and appear to act as preferential water infiltration paths after autumn rainfall events. This indicates that Bettongia penicillata has an impact on the non-wetting property of soils in this region.     

Short–rotation woody crops: A prospective method for phytoremediation of agricultural land at risk of salinisation in southern Australia?

Growing short–rotation woody crops (SRWC) in rotation with conventional agriculture (phase farming with trees) is a prospective method for ameliorating degraded soils, particularly those at risk from salinisation. This work details changes in soil water storage and crop and pasture growth in the first 2 years after harvesting SRWCs at two sites in Western Australia between 2002 and 2004.This trial has demonstrated that where the roots of SRWCs can penetrate deeply into the subsoil, it is possible to develop soil water deficits large enough to subsequently allow several decades of conventional agriculture before groundwater recharge is resumed. At one site, Eucalyptus polybractea dried the soil to 10 m, creating a soil water deficit of 1350 mm within 6 years of planting. It is estimated that annual crops and pasture could be grown at this site for 68 years before the soil again reaches field capacity. Further work is required to determine where in the landscape SRWCs can develop these large soil water deficits.Reduced soil fertility limited crop and pasture growth in the first year after the SRWC at one site, while reduced plant–available water limited crop and pasture growth for 2 years after the SRWC at the other. Monitoring is continuing to determine longer-term changes in soil water content and crop and pasture productivity.     

The influence ofPythium on the growth of barley seedlings as affected by soil water and inoculum density

Summary Pythium spp. were more abundant in the southerly and more temperature regions of the barley growing region of South Australia than in the drier and hotter north. Populations were more abundant in the top 10 cm than in the 10 to 20 cm soil zone. Eleven species ofPythium were identified from barley crops.P. irregulare appeared to be the most abundant and was one of the most pathogenic species on barley.P. volutum was also highly pathogenic; it had not been recorded in South Australia before. A factorial experiment using ninePythium spp. and four levels of soil water indicated that unlike other species,P. irregulare, P. volutum andP. graminicolum were most pathogenic in soils with a water content close to field capacity. A factorial experiment usingP. irregulare at four levels of soil water and six inoculum levels showed that inhibition of growth in barley seedlings byP. irregulare increased as the level of water in the soil increased. The experiments support the hypothesis that inhibition of growth of barley seedlings byPythium spp. is most severe in the southerly parts of the barley growing area of South Australia particularly where there is a combination of high soil water and high population densities.     

Variation in Life History of Land-Locked Lacustrine and Riverine Populations of Galaxias maculatus (Jenyns 1842) in Western Australia

Galaxias maculatus is one of the most naturally widely distributed species in the world yet there is no published literature on the biology of Western Australian populations. Galaxias maculatus in the rivers of the south coast of Western Australia inhabit an environment that is variable and at times unpredictable. By examining trends in gonadal development, lengths at first maturity, growth and appearance and persistence of larvae of G. maculatus in two saline rivers (Jerdacuttup River and Oldfield River) and one freshwater lake (Moates Lake), the life histories of populations in contrasting environments were determined. The stable conditions that prevail in the low salinity, cool waters of Moates Lake have fostered an extremely protracted breeding and larval recruitment period (year round) in comparison to limited recruitment in the riverine environments which experience less predictable flow events and water quality (salinity). An upstream migration for breeding in the Jerdacuttup and Oldfield rivers is similar to land-locked G. maculatus in south-eastern Australia and is a reversal of the downstream migration in Moates Lake or populations with marine larval dispersal, i.e. diadromous populations. Differences in population demographics existed between these habitats, with smaller maximum sizes and significantly smaller sizes at maturation occurring in the rivers compared to the lake. In Moates Lake approximately 93, 6 and 1% were 0+, 1+ and 2+, respectively; while cohort progression in the rivers suggests that most fish do not live beyond their first year. As an adaptable opportunist, G. maculatus can modify its life history strategy at a local level to persist in varied and sometimes unpredictable environments.     

Bauxite Mining Restoration by Alcoa World Alumina Australia in Western Australia: Social,Political, Historical,and Environmental Contexts

Alcoa World Alumina Australia mines bauxite under lease agreements with the Government of Western Australia. The leases lie in the Darling Range to the east of Perth, the capital and major population center. In addition to bauxite and other mineral ores, the Darling Range is a major potable water source and harbors a species-rich forest dominated by Jarrah (Eucalyptus marginata), a significant commercial timber. Conservation and recreation are important land uses in the region. Social and political pressures have led to stringent governmental requirements for restoration. In addition, a summer drought period, a soil deficient in most nutrients, water management challenges, an introduced disease, caused by Phytophthora cinnamomi Rands, and a post-mining ecosystem that must be conducive to the prescribed burning management of the region pose significant challenges to successful restoration. Alcoa presently mines and restores approximately 550 ha per annum. Although the “footprint” at the end of the life of the mining operations represents only about 4% of the total forest estate, Alcoa is committed to restoring the forest values of the region of all lands impacted by mining. The major objective of restoration is to enhance or maintain forest values by restoring habitat and structural characteristics of the native forest environment. Completion criteria for Alcoa’s mine restoration have been developed. The original Alcoa mine at Jarrahdale has been rehabilitated, and in 2005, a 975-ha area received a “certificate of completion” and was returned to the management control of the State of Western Australia.     

Establishment and early growth of species in farm plantations near salt seeps

Clearing of native forest has caused a rise in soil watertables and increased the salinity of land and streams in south-western Australia. Reforestation is a possible method of increasing the use of water on cleared catchments, lowering watertables and reducing the output of salt from hillside seeps. One of the first needs is evidence of suitable species for such a project. This paper describes the comparative success of twenty-eight species (mainly Eucalyptus spp.) in establishment and early growth when grown on and near saline seeps during 1976–77. Plantations were located in 850, 500 and 420 mm annual rainfall zones of the Hotham River valley about 150 km south-east of Perth, Western Australia. The sites had saline confined aquifers and seasonal perched watertables which were typical of many landscapes in the region. Though rainfall was below average and only one watering was given, nineteen species had greater than 80% establishment in upslope, midslope and downslope positions. In late winter 1977, 15 months after planting, the leading species were 1–2 metres tall and carried leaf area up to 5.5 m² per tree where current rainfall was highest. The results indicate a high potential for plant establishment and early growth within the rainfall zones. Eucalyptus spp. from many regions of southern Australia were successful at the wettest location. Success at the two driest locations was limited to species from dry climates of southern South Australia and Western Australia. Planting on seep areas decreased the establishment of three species. Eucalyptus wandoo, E. globulus and E. camaldulensis, which performed well on non-seep areas at one or more locations. Implications for a source of further test species and for planting strategy near seeps are discussed.     

Intermittent wetting of soils at high temperature reduces survival of the take-all fungus

Two pot experiments using naturally infested soil and a range of watering regimes were conducted to study the possible effect of level and frequency of wetting of hot soil (to simulate the period between growing seasons in Western Australia) on inoculum of the take-all fungus (Gaeumannomyces graminis var.tritici). In combination with the high soil temperatures, all watering regimes reduced infectivity and propagule number of the take-all fungus, this reduction being absent in dry soils.     

Data on the adult marine and migratory phases in the life cycle of the southern hemisphere lamprey,Geotria australis Gray

Synopsis Large numbers of the Southern Hemisphere lamprey, Geotria australis, have been found in the regurgitated food of albatrosses breeding on South Georgia. This finding suggests that this lamprey is found in large groups at sea, presumably associated with its host, and can travel very large distances from its natal streams. The length and morphology of the individuals from South Georgia, which almost certainly represent a South American stock, were compared with those of representatives of the immediately pre- and post-marine trophic stages of G. australis caught in Western Australia. No significant differences could be detected either in the number of trunk myomeres or in the number and arrangement of the teeth. The mean length of the animals (± 95% confidence limits) from South Georgia was 45.9 ± 0.90 cm compared with 10.0 ± 0.23 cm and 62.5 ± 0.85 cm in G. australis collected from Western Australia just before they had entered and returned from the sea respectively.     

In vitro soil receptivity assays to egg-parasitic nematophagous fungi

Soil application of nematophagous fungi for the biological control of plant-parasitic nematodes often fails, and in many cases it has been difficult to reisolate the agent delivered to the soil. A reason for these results could be the inability of the fungi to proliferate in soil. We used a soil–membrane technique to study the capacity of several isolates of the nematophagous fungi Pochonia chlamydosporia and Paecilomyces lilacinus to grow and establish in sterilized and nonsterilized sandy soils from SE Spain and Western Australia. Growth of all fungi tested was inhibited in nonsterilized soil, although there was intraspecific variability in sensitivity among isolates of the same species. With respect to hyphal density, P. chlamydosporia isolate 5 (from Italy) was the least inhibited in nonsterilized soil from both sites. Relative growth analyses confirmed this result for soil from SE Spain, while with this method, P. chlamydosporia isolate 4624 (from Australia) appeared to be least inhibited in the Australian soil. The results indicate that a soil can be more receptive to its indigenous isolates than to nonindigenous isolates. Apparently, soil microbiota can determine the ability of nematophagous fungi to proliferate in soil.     

Biodegradation of 1080: Testing soils in south‐eastern Australia for sodium fluoroacetate‐degrading micro‐organisms

Sodium fluoroacetate (1080) is a vertebrate poison commonly used for the control of vertebrate pests in Australia. Long‐term environmental persistence of 1080 from baiting operations has likely nontarget species and environmental impacts and is a matter of public concern. Defluorinating micro‐organisms have been detected in soils of Western and central Australia, and Queensland, but not in south‐eastern Australia. The presence or absence of defluorinating micro‐organisms in soils from south‐eastern Australia will assist in determining whether long‐term environmental persistence of 1080 is or is not occurring. Soils from the Central West Slopes and Plains and Central Tablelands of New South Wales were sampled to investigate the presence and capability of 1080 defluorinating soil micro‐organisms. Thirty‐one species of micro‐organisms were isolated from soils from each site after 10 days incubation in a 20 mM 1080 solution. Of these, 13 isolates showed measurable defluorinating ability when grown in a 1080 and sterile soil suspension. Two species, the bacteria Micromonospora, and the actinomycete Streptosporangium, have not been previously reported for their defluorinating ability. These results indicate that defluorinating micro‐organisms are present in soils in south‐eastern Australia, which adds weight to other studies that found that 1080 is subject to microbiological degradative processes following removal from the bait substrate. Soil micro‐organism defluorination, in combination with physical breakdown and uptake by plants, indicates that fluoroacetate in soils and natural water ways is unlikely to persist. This has implications for the better informed use of 1080 in pest animal management programmes in south‐eastern Australia.     

Use of a root assessment tray for the detection of take-all on lateral roots of wheat seedlings

A root assessment tray was designed for the meticulous assessment of take-all on wheat seedling roots from soil bioassays. Subsequently, the detection of lateral root infections (in addition to the more obvious infections on main axes of seminal roots) resulted in increased estimates of propagule numbers of the take-all fungus (Gaeumannomyces graminis var.tritici) for 196 of the 368 soil samples bioassayed in a field study conducted in Western Australia between 1984 and 1986.     

Siderophore production by actinomycetes isolates from two soil sites in Western Australia

The actinomycetes are metabolically flexible soil micro-organisms capable of producing a range of compounds of interest, including siderophores. Siderophore production by actinomycetes sampled from two distinct and separate geographical sites in Western Australia were investigated and found to be generally similar in the total percentage of siderophore producers found. The only notable difference was the proportion of isolates producing catechol siderophores with only 3% found in site 1 (from the north-west of Western Australia and reportedly containing 40% magnetite) and 17% in site 2 (a commercial stone fruit orchard in the hills east of Perth with a soil base ranging from sandy loam to laterite). Further detailed characterization of isolates of interest identified a Streptomyces that produced extracellularly excreted enterobactin, the characteristic Enterobacteriaceae siderophore, and also revealed some of the conditions required for enterobactin production. Carriage of the entF gene, which codes for the synthetase responsible for the final assembly of the tri-cyclic structure of enterobactin, was confirmed by PCR in this isolate. Another separate Streptomyces produced a compound that matched the UV/VIS spectra of heterobactin, a siderophore previously only described in Rhodococcus and Nocardia.     

Gene flow of the canker pathogen Botryosphaeria australis between Eucalyptus globulus plantations and native eucalypt forests in Western Australia

Abstract The eucalypt plantation industry in Western Australia provides a unique opportunity to study the movement of pathogens between closely related host taxa. Eucalyptus globulus, a native to Tasmania and south‐eastern Australia, is the predominant species in Western Australian plantations, often being planted adjacent to native forest containing Eucalyptus marginata and Eucalyptus diversicolor. Since the commencement of the plantation industry 20 years ago, several fungal species, previously known only to eastern Australia or overseas, have been reported on E. globulus in Western Australia. Botryosphaeria australis is a newly described species, recently found causing cankers on Acacia spp. in eastern Australia. However, during a routine survey, B. australis was found to be the predominant species associated with E. globulus plantations and native Eucalyptus spp. in Western Australia. In this study, six short simple repeat markers were used to evaluate genetic diversity and gene flow between collections of B. australis from native eucalypt forest and E. globulus plantations at two locations in south‐western Australia. In both cases, there was no restriction to gene flow between the plantations and the adjacent native forest. Botryosphaeria australis has now been isolated from a wide range of hosts across south‐western Australia and was not isolated from E. globulus in Tasmania or South Australia. This extensive distribution and host range suggests B. australis is native to Western Australia. This study demonstrates the ability of a pathogen to move between plantation and forests.     

Tracing water uptake by jarrah (Eucalyptus marginata) trees using natural abundances of deuterium

 Seasonal change in the δ²H content of water from twig sap, soil, rainfall and groundwater were measured to determine the water sources accessed by jarrah (Eucalyptus marginata) trees at three sites in Western Australia with differing soils and depths to water table. During winter and spring the main contributor to the water uptake of the trees was stored water in the surface layers of the soil replenished by predominantly winter rainfall. With the onset of summer drought jarrah became more reliant on water from deeper down the profile. There was no clear evidence that jarrah could tap water from groundwater more than 14 m deep in deep sands. Defining the source of water for trees in deep lateritic soils using stable isotopes is hampered by the uniform deuterium profiles down most of the unsaturated zone and into the groundwater. There was a limited response in the δ²H values of sapwater in twigs to changes in the δ²H of the upper layers of the deep sand following input of rainfall in autumn. The damped response was related to the small variation in the δ²H composition of rainfall in most events during the year and the mixing in the tree of water extracted from different locations in the soil profile. Received: 21 August 1995 / Accepted: 3 December 1995     

Enhancing tree belt productivity through capture of short‐slope runoff water

A selection of multi‐stemmed, drought‐tolerant mallee eucalypts, planted in belt form and integrated with crops in dryland agricultural areas of Australia, may be able to produce biomass as a commercially attractive feedstock for biofuel production. This study aimed to determine if small (40–50 cm high) bunds along mallee belts could trap otherwise underutilized surface water runoff within paddocks, thereby increasing water available to the mallee trees and their growth rates. An experiment was established in 5 year‐old Eucalyptus polybractea (RT Baker) mallee belts near the town of Narrogin in the central wheatbelt area of Western Australia. Bunds led to significant (12%) increases in biomass accumulation after about 2 years and 35% increases at around 3 years. Bunds also led to significant increases in predawn leaf water potential and significant decreases in soil water deficit within 12 months, which persisted for the remainder of the 39 month trial. We suggest that the increase in biomass accumulation was largely due to increased water availability, but that increased nutrient supply from run‐on and trapping of organic residues may have also had some effect on bunded plots, despite our attempts to mitigate this effect by experimentally adding nutrients to all treatments. Results show that installing bunds along mallee belts would be a cost‐effective investment at sites where within‐paddock runoff is likely (i.e. gently sloping and with a loamy sand or heavier soil texture). Installation costs should be offset by improved biomass production within a few years and ongoing improvements in growth over the long term.     

Water‐use efficiency in a semi‐arid woodland with high rainfall variability

As the ratio of carbon uptake to water use by vegetation, water‐use efficiency (WUE) is a key ecosystem property linking global carbon and water cycles. It can be estimated in several ways, but it is currently unclear how different measures of WUE relate, and how well they each capture variation in WUE with soil moisture availability. We evaluated WUE in an Acacia‐dominated woodland ecosystem of central Australia at various spatial and temporal scales using stable carbon isotope analysis, leaf gas exchange and eddy covariance (EC) fluxes. Semi‐arid Australia has a highly variable rainfall pattern, making it an ideal system to study how WUE varies with water availability. We normalized our measures of WUE across a range of vapour pressure deficits using g₁, which is a parameter derived from an optimal stomatal conductance model and which is inversely related to WUE. Continuous measures of whole‐ecosystem g₁ obtained from EC data were elevated in the 3 days following rain, indicating a strong effect of soil evaporation. Once these values were removed, a close relationship of g₁ with soil moisture content was observed. Leaf‐scale values of g₁ derived from gas exchange were in close agreement with ecosystem‐scale values. In contrast, values of g₁ obtained from stable isotopes did not vary with soil moisture availability, potentially indicating remobilization of stored carbon during dry periods. Our comprehensive comparison of alternative measures of WUE shows the importance of stomatal control of fluxes in this highly variable rainfall climate and demonstrates the ability of these different measures to quantify this effect. Our study provides the empirical evidence required to better predict the dynamic carbon–water relations in semi‐arid Australian ecosystems.     

The influence of local elevation on soil properties and tree health in remnant eucalypt woodlands affected by secondary salinity

More than 2 M ha of remnant vegetation in Australia is predicted to be at risk from shallow water tables by 2050. Currently, vegetation is considered to be at risk where the water table is predicted to be less than 2 m below the soil surface, yet casual observation of areas affected by secondary salinity in the Western Australian wheatbelt has suggested that small differences in elevation (< 0.5 m) are important in determining plant health. In this study, we investigated how small changes in elevation (and hence depth to the water table) affected soil Cl concentrations and water contents, and whether small changes in elevation were associated with major changes in tree health in two remnants of Eucalyptus wandoo Blakely woodland with secondary salinity. At one site there were strong dissimilarities between soil samples collected above or below relative elevations of 0.5 m in areas with a shallow (0.3 m deep in September 2001) and saline water table. This was reflected in almost complete tree mortality at relative elevations below 0.5 m. However, low rainfall in 2001 meant that it was unlikely that current soil conditions had caused tree death. When water table data for 1999 was overlaid over plots of tree health and transect topography, high levels of tree mortality corresponded with areas where the water table was at or above the ground surface. At the other site, there was no clear relationship between elevation, soil characteristics and tree health. Localised variation in abiotic conditions and ecosystem processes at a fine-scale may buffer, to some extent, the spatial impact of soil salinity and waterlogging in remnant vegetation. Collapses in tree health at some sites are likely to be related to extreme and episodic events, which we may have limited ability to predict.     

Smoke Enhanced Seed Germination for Mine Rehabilitation in the Southwest of Western Australia

Cool smoke treatments were applied to unmined Eucalyptus marginata (jarrah) forest soils, rehabilitated bauxite mine soils, and broadcast seed to determine if enhancement in germination could be effected with a view toward maximizng the establishment of species in bauxite mines in Western Australia. Forest sites showed a 48-fold increase in total germinants from the soil seed bank when treated with aerosol smoke. Newly returned bauxite mine soils showed a greater than threefold increase in total germinants after the same treatment. There were also significant increases in the number of species germinating in response to the aerosol smoke treatment in both the forest and the mined soils. Similarly, application of smoked water to the soil seed bank in previously mined sites elicited a significant positive germination response, increasing total germinants and species numbers by 56 and 33%, respectively. Treatment of mixed seed lots with aerosol smoke before broadcast resulted in highly significant improvement in germination when compared to untreated seed. Both total number of germinants, and number of species emerging from mined sites were positively influenced (85% and 34% increases, respectively). Ten target species were used to determine the relative effectiveness of different methods of smoke treatment on the germination of broadcast seed. Nine of the species involved displayed a promotive effect with at least two of the treatments. Generally, however, aerosol smoking of seed before broadcast proved to be the more effective approach. As a result of these findings, all broadcast seed for use in Alcoa's bauxite mined areas in the southwest of Western Australia is now routinely smoke treated before application.     

Electrophoretic analysis of populations of the southern hemisphere lampreys Geotria australis and Mordacia mordax

Electrophoretic data for 15 enzymes encoded by 18 loci were analysed in samples of larval lampreys from two southern hemisphere species (Geotria australis and Mordacia mordax). Low values for Nei genetic distance coefficients for all loci in populations of G. australis from Western Australia, Tasmania and New Zealand (0.0013 to 0.0058) suggest that adults may intermix over distances greater than 4000 km. The average heterozygosity for four populations of G. australis (0.086) was much greater than for two populations of the far less widely distributed M. mordax (0.021).     

Genotype by environment interaction for growth of Eucalyptus globulus in Australia

This study assessed the genotype by environment (G × E) interaction for diameter growth in 15 Eucalyptus globulus progeny trials in Australia. Single-site analyses revealed significant subrace and family-within-subrace variance in all trials. Across-site subrace () and family () correlations were estimated by linear mixed model analyses of pairs of trials. Using a factor analytic structure for subrace and family random terms in a multi-environment mixed model analysis, best linear unbiased predictions of subrace effects were obtained for each trial. These were then averaged for each of four states (Victoria, Tasmania, South Australia and Western Australia) and across all sites. Statistically significant G × E interaction was detected, and weighted means across states for and were 0.73 and 0.76, respectively. Nevertheless, the three subraces from the Otway Ranges were both fast growing and relatively stable in their ranks over all sites. We evaluated the sensitivity of subraces to changing environmental conditions, on the basis of random coefficient models regressing subrace performance on selected trial climatic variables. The results suggested differential susceptibility of subraces to water, light and (to a less extent) temperature stresses during summer. Moreover, using multivariate techniques to visualize and interpret the across-site correlation structure for subrace effects, we could identify site clusters of reduced G × E interaction related to soil water availability and evaporative demand during summer. A revised site-type classification using these factors should allow a better capture of genetic gains from breeding and deployment.