Western Australian Wheatbelt Research Articles

Microsatellite DNA markers for Australian geckos

Nine highly polymorphic microsatellite markers were developed for Gehyra variegata from an enriched library screened for tetranucleotide repeats. An average of 19.44 alleles per locus and an average observed heterozygosity of 0.86 were found in 81 samples from fragmented populations in the Western Australian wheatbelt. Different gecko species exhibit varying rates of extinction in fragmented landscapes and the genetic markers were developed to test whether these difference are due to different rates of dispersal. The loci were tested for their ability to cross amplify in 12 species of Australian Gekkonidae and Pygopodidae, in an attempt to identify species which might be amenable to population genetic analysis using these microsatellite markers.

Comparative water use by Dorycnium hirsutum-, lucerne-, and annual-based pastures in the Western Australian wheatbelt

Dryland salinity in southern Australia has been caused by inadequate water use by annual crops and pastures. The purpose of this study was to compare the water use of annual pastures and Medicago sativa L. (lucerne) with Dorycnium hirsutum (L.) Ser., a potential new perennial forage species. The soil water dynamics under bare ground, annual legume-, lucerne-, and D. hirsutum-based pastures were compared at 2 sites in the low- (Merredin) and medium- (New Norcia) rainfall wheatbelt of Western Australia between September 2002 and February 2005. Soil under D. hirsutum was drier than under annual pastures by 8–23 mm in Year 1, 43–57 mm in Year 2, and 81 mm in Year 3. Lucerne used little additional water (<19 mm, n.s.) compared with D. hirsutum and profile soil water content was similar under both species throughout the experiment. At Merredin, annual pastures used water to a depth of 1.0 m, whereas under both D. hirsutum and lucerne in the first 3 years after establishment the successive maximum depth of water use was 1.0, 1.8, and 2.2 m. At New Norcia, additional soil water was extracted by lucerne and D. hirsutum at depths <1.0 m and no difference between treatments was detected below 1.0 m. Biomass of D. hirsutum pasture harvested in autumn contained minimal annual components and was 15–50% of that produced by lucerne- or annual legume-based pastures. D. hirsutum and lucerne plant density declined each summer (25–80%), but D. hirsutum density was lower than lucerne due to poorer establishment. Nonetheless, the comparable water use of lucerne and D. hirsutum suggests that D. hirsutum could make reductions in recharge similar to those of lucerne in the Western Australian wheatbelt.

Is all salinity the same? I. The effect of ionic compositions on the salinity tolerance of five species of freshwater invertebrates

Salts of marine origin, predominantly consisting of Na+ and Cl− ions, are dominant in most Australian inland saline waters. The proportions of other ions, Ca2+, Mg2+, SO42–, HCO3− and CO32–, in the water may influence salinity tolerance of freshwater organisms and thus the effect of increasing salinity may vary with difference in ionic proportions. We exposed freshwater invertebrates to different concentrations of four ionic compositions and compared them with commercial sea salt (Ocean Nature). They were: synthetic Ocean Nature (ONS) and three saline water types (ONS but without: SO42–, HCO3− and CO32– (S1); Ca2+, HCO3− and CO32– (S2); and Ca2+ and Mg2+ (S3)), which are considered to be the predominant saline water types in south-eastern Australia and the Western Australian wheatbelt. The 96-h LC50 values for the five media were determined for six invertebrate species and sub-lethal responses were observed for two species. There were no differences between responses of invertebrates to various ionic compositions in acute toxicity tests. However, in prolonged sub-lethal tests, animals reacted differently to the various ionic compositions. The greatest effect was observed in water types lacking Ca, for which plausible physiological mechanisms exist. Variation in ionic proportions should be taken into account when considering sub-lethal effects of salinity on freshwater invertebrates.

Predicting the impact of perennial phases on average leakage from farming systems in south-western Australia

Rising watertables and dryland salinity in southern Australia are due to excess groundwater recharge after the replacement of native vegetation by annual crops and pastures. The inclusion of perennial plants into agricultural systems has been proposed as a possible method of recharge reduction, through the creation of a buffer (extra water storage capacity generated by the perennial in comparison with an annual crop or pasture). However, the role of perennial phases under conditions of highly episodic leakage is not well understood. In this paper, a simple Leakage/Buffer Model (LeBuM) was developed to determine the effect of perennial phases on long-term average annual leakage, incorporating episodic events. Mechanistic modelling studies on contrasting soil types were used to demonstrate that leakage for any given May–December period was directly related to soil water storage at 1 May. From this finding, it follows that leakage from a phase rotation can be calculated if the size of the buffer, and the leakage quantity in the absence of a buffer, are known for each stage of the rotation. LeBuM uses a long-term sequence of leakage values in the absence of a buffer as input, and the maximum buffer size, its rate of development, and the length of perennial and annual phases are specified as parameters. LeBuM was applied to leakage data modelled for 5 contrasting soil types over 100 years at 24 sites in the Western Australian wheatbelt. Phase rotations on duplex, waterlogging duplex, or loamy sand soils reduced leakage by >90% for regions with <380 mm annual rainfall, but were less effective in wetter regions and on deep sands or acid loamy sands. Nevertheless, phase rotations if adopted widely could delay the onset of salinity by as much as several decades.

Small grain screenings in wheat—using the grain size distribution for predicting cultivar responses

Small grain is a concern for wheat growers in water-limited environments worldwide. Following from our preliminary results that cultivars can differ for small grain screenings despite similarity of average grain weight in wheat, grain size distribution was investigated with the aim of identifying alternative parameters that could more reliably discriminate cultivars for their tendency to screenings without actually subjecting breeding material to harsh environments. Pre-cleaned harvest samples (using screen with 1.5-mm-wide holes) of 5 cultivars from 2 field cultivar × time of sowing experiments were divided into 5 grain-width fractions using 4 sieves with holes from 2.5 to 3.4-mm wide. The experiments conducted in the Western Australian wheatbelt experienced a dry finish in 2000 and a relatively wetter year in 2003. The grain that was separated into each width fraction was weighed and the average weight of grains for each fraction (called the size-specific weight) was derived from a subsample. The weight of grain (expressed as a percentage of the whole) collected between the 2.8 and 3.1-mm screens (fraction F3) was highly and negatively correlated with small grain screenings (r = –0.85; P < 0.001), thus strengthening the perception that screenings percentages may follow a certain form of grain size distribution. Among various grain size distributions, the skew-Laplace distribution fitted on grain weight was found to be the most suitable to characterise the cultivars. This provides a general approach in the examination of a grain size distribution, which is invariant to combinations of sieve sizes that different individuals may choose. We conclude that: (i) parameters µ and 1/α of the skew-Laplace distribution based on grain weight separated into each fraction can be used as a selection tool in predicting propensity for small grain screenings in wheat without having to subject breeding material to harsh conditions; (ii) higher values for both µ and 1/α are desirable but if the cultivar has small µ, a high 1/α is required to reduce screenings; (iii) breeders could consider the grain size distribution in addition to grain weight as a breeding objective; and (iv) millers should be looking for higher average grain weight and higher weight per unit grain length especially at small width fractions, to maximise flour yield. Hence, we anticipate that future research into aspects of starch packaging such as grain shape and endosperm density will optimise grain size distribution, grain weight per unit grain length, and eventually the flour yield per unit land area.

The performance of lucerne - wheat rotations on Western Australian duplex soils

In field experiments on duplex soils in the south-eastern and central Western Australian wheatbelt, lucerne (Medicago sativa L.) was compared with subterranean clover (Trifolium subterraneum L.) in pasture–crop rotations. Comparative pasture plant densities and biomass, soil water content, available soil nitrogen, wheat grain yield, and protein content were measured during 2 and 3 years of pasture followed by 2 and 1 year of wheat, respectively. Lucerne densities declined by 60–90% over the 3-year pasture phase but produced up to 3 times more total annual biomass than weed-dominant annual pastures and similar total annual biomass when annual pastures were legume dominant. Lower soil water contents were measured under lucerne than under annual pastures from 6 months after establishment, with deficits up to 60 mm in the 0–1.6 m soil profile. However, significant rain events and volunteer perennial weeds periodically negated comparative deficits. Wheat yields were lower following lucerne (1.3 t/ha) than following an annual pasture (1.8 t/ha) in a low-rainfall season, higher (3.7 v. 2.9 t/ha) in a high-rainfall season, and much higher when the previous annual pastures were grass dominant (3.4 v. 1.5 t/ha). Grain protein contents were 1–2% higher in response to the lucerne pasture phase. Overcropping wheat into a lucerne pasture of 19 plants/m2 reduced wheat grain yields, but a lucerne density of 4 plants/m2 reduced yields only where rainfall was low. The study has shown that lucerne–wheat rotations provide a productive farming system option on duplex, sodic soils in both the south-eastern and central cropping regions of Western Australia. This was most evident in seasons of above-average summer and growing-season rainfall and when compared with grass-dominant annual pastures.

Incorporating Research Results into Wetland Management: Lessons from Recovery Catchments in Saline Landscapes

Use of science in wetland management has increased considerably over the last 50 years but there is still scope for improving the transfer of research results into management. Issues that lead to less than optimal transfer include: (1) managers not accessing existing technical information adequately, (2) researchers addressing issues of peripheral importance to management rather than key information needs, (3) managers failing to identify significant information gaps and to resource appropriate research in a timely way, (4) scale of research and certainty of results being inappropriate for application to broad-scale situations by managers responsible for outcomes, and (5) funding bodies not fully recognizing that transfer of research results to management requires a development phase. Establishment of recovery catchments in the Western Australian wheatbelt, with the aim of maintaining regional biodiversity in the face of increasing dryland salinisation, is a program that relies on transferring research results into management. However, the multidisciplinary nature of managing salinisation is a challenge for many catchment managers and formal management systems are probably an important adjunct to close knowledge of the catchment when making management decisions. An examination of management planning and actions in the Lake Warden Natural Diversity Recovery Catchment, south-west Western Australia, highlights the continuum between research and management, the importance of understanding the physical environment when managing biodiversity, and the fact that much wetland conservation relies on management action in terrestrial landscapes.

Tetranucleotide microsatellites in the gecko Oedura reticulata isolated from an enriched library

AbstractTen tetranucleotide microsatellite loci were isolated from an enriched library for the gecko Oedura reticulata. The species is endemic to the southwest of Western Australia, known to be a habitat specialist, and exposed to severe habitat fragmentation in the Western Australian wheatbelt. These highly polymorphic markers (two to 25 alleles) will facilitate the population genetic analyses of this species. In particular, they will enable estimates of gene flow between remnant populations — a critical element in assessing extinction dynamics in fragmented populations.

Constructing Sustainable Rural Landscapes: Oil Mallees and the Western Australian Wheatbelt

AbstractThis paper considers the landscapes of the Western Australian wheatbelt and the possibilities for sustainability signified by the Oil Mallee Project. The Oil Mallee Project aims to develop commercially viable tree crops for the low rainfall wheatbelt region as a means of profitably managing dryland salinity. Interviews with farmers and other stakeholders in the Oil Mallee Project and agriculture are analysed to reveal important elements of landscape construction in the wheatbelt and stages in the emergence of the Project. These elements include historical land clearing, international chemical and machinery companies and the technologies they supply, land of marginal economic productivity, global food markets and alley farming systems. The paper uses material semiotics and actor‐network theory in describing the networks of relationships that shape wheatbelt landscapes. Breakdowns in the dominant networks of industrial agriculture provide spaces for the Oil Mallee Project to build relationships that reconnect industrial systems to the specific ecology of the wheatbelt landscape. However, the networks of industrial agriculture remain powerful and the Project has worked strategically to become integrated with existing agricultural systems, rather than aiming to directly resist or entirely displace dominant patterns of production in the wheatbelt.

The Avon River Basin in 2050: scenario planning in the Western Australian Wheatbelt

Scenario planning was used to identify issues and drivers of change that are relevant to community efforts to improve regional prospects in the Western Australian Wheatbelt. The region, some 20 million hectares in area, is under pressure to respond to a variety of environmental (salinity, erosion, acidification, biodiversity decline), economic (declining agricultural terms of trade), and social forces (rural decline, isolation). Regional strategic plans have been increasingly seen as the means of achieving sustainability in the face of these challenges, but until recently typically had single-activity outlook and timeframes of up to a decade into the future. Systematic futures-based research has been used in various regions to avoid reliance on business-as-usual as the default strategy, and to identify opportunities and challenges not presently apparent. The Avon River Basin, the central region of the Wheatbelt, was selected as the geographic focus of the project, and the time horizon was set at 2050. The project was developed by a group of 50 stakeholders from the basin, with expertise and strategic interests across a wide range of economic, social, and environmental themes. Through a series of workshops the stakeholders identified critical issues and their attendant drivers, then documented relevant past trends. Four regional scenarios, Saline Growth, Grain and Drain, Landcare Bounty, and Harmony with Prosperity, were developed based on positive and negative combinations of 2 clusters of uncertain and important drivers: environmental change and access to new markets. Common opportunities, threats, and critical success factors for the Avon River Basin region out to 2050 were also identified. We also found that the stakeholders have a tendency to strive for positive outcomes despite negative initial conditions. This resulted in 4 scenarios that were superficially similar due to the regional scale of analysis and the continuation of agricultural industries as significant shapers of economy, society, and environment. However, each scenario represents profoundly different outcomes for the residents and communities of the Avon River Basin in 2050. The triple-bottom line outcomes for the Avon River Basin in 2050 were estimated to be in the range 4.9–9.7 Mt of wheat (currently 4.0), 46 000–66 000 people (currently 43 000), and 10–30% of farmland salinised (currently 6). The application of these results to other regions in Australia is discussed.

Protecting stranded biodiversity using groundwater pumps and surface water engineering at Lake Toolibin, Western Australia

Dryland salinity has claimed 8% of the Toolibin Lake catchment and approximately 24% is at risk. As a result, the native fauna and flora of the ephemeral lake, a 300 ha Ramsar Wetland of International Importance, face salinisation. This is a fate that has already befallen over one million hectares of farmland, wetlands and lakes (e.g nearby 830 ha Lake Taarblin) in the Western Australian Wheatbelt. Surface water management and groundwater pumping have been undertaken on the western edge of the lakebed at Toolibin since 1997 to manage the spread of salinity, which first developed in the mid 1970s. In 2001, the pumping system was upgraded when a second series of higher yielding groundwater pumps was commissioned on the eastern half of the lake. Results to date indicate the surface water management has been successful in diverting approximately 5000 tonnes of salt from the lake. The combined effects of low rainfall and pumping (660 kL/d) have lowered groundwater levels ∼3–4 m beneath the lake. Quantifying their individual effects has been difficult. Root zone soil salinities (measured with ground EM) remain high across the majority of the lake, except around older western pumps that are reducing in soil salinity, and the vegetation is recovering. The efficiency of pumping in this terrain is impacted by the low permeability of the eastern floor sediments, iron biofouling and the high operating costs. The eventual fate of the lake and its vegetation are dependent on the sustained effectiveness of the pumps, managed flooding and subsequent leaching By reviewing the effectiveness of the pumping system and surface water management structures, the forecasts for salinisation in the catchment can also be reviewed, which may impact the Toolibin Lake Recovery Plan

Capture of agricultural surplus water determines the productivity and scale of new low-rainfall woody crop industries

This paper presents a conceptual model for estimating the maximum scale of biomass processing industry that may be supported by woody crops grown in the medium and low rainfall agricultural regions of southern Australia. The model integrates paddock scale economics, water capture by woody crops, conversion of water to woody biomass, and estimation of suitable area. It enables estimates to be made of the maximum scale of implementation of commercial woody crops in various climatic regions, and the maximum amount of woody biomass that could be produced commercially within an economic transport distance of a processing facility. To demonstrate the utility of the model, potential biomass supply is estimated for 2 Western Australian wheatbelt towns, Merredin and Narrogin. These estimates are compared with the feedstock requirements of a range of different processing industries. This paper demonstrates that the rate of converting water to biomass and water capture biomass price are key determinants of the potential scale of biomass crops and processing industries in the southern Australian wheat and wool belts and hence the potential contribution of woody crops to dryland salinity management.

Futures for the Wheatbelt—Is 2030 already here?

The Western Australian Wheatbelt has experienced significant social, economic, and environmental changes over the last 25 years, which have affected the viability of the broadacre farm businesses that dominate the Wheatbelt economy as well as the efficacy of the communities that have supported the agricultural industry. This paper considers the consequences of these changes and how the agricultural industry and the people living in the Wheatbelt region have responded to the challenges. As well, the future of the region is considered, based on potential market and capacity building alternatives. It is contended that many of the social, economic, and environmental indicators of the future have been in place for some time and that industry diversification and social options are already being trialled. It would appear that industry and individual resilience and creativity are keys for the Wheatbelt’s survival in the future.

Field-Scale Experiments for Site-Specific Crop Management. Part II: A Geostatistical Analysis

Part II analyses approach C experiments. Field-scale experiments were applied to four wheat fields in the Western Australian wheat belt. Different experimental designs were used two two-dimensional sine-waves, a chequerboard, and a two-factor strip arrangement. In each experiment, the yield associated with a particular treatment was predicted by kriging to where the other treatments were located. Different forms of kriging were investigated. Co-located cokriging, using the previous-season yield map as a covariate, was the most promising. The kriged data were then modelled with polynomial yield response functions. The outcome was a map for each field that described the optimum application of experimental input. The requirements varied continuously across the field, and could justify future site-specific crop management. The two-factor strip experiment was the most successful of those presented; the field on which it was used showed relatively strong responses to the applied inputs. The other sites were affected by lack of rain and/or design flaws. The underlying philosophy is sound, but the method proposed is time-consuming and inefficient. We hope that this paper can stimulate further research on the subject.

Oribatid mite species richness and soil organic matter fractions in agricultural and native vegetation soils in Western Australia

We contrasted oribatid species richness and the distribution of carbon (C) and nitrogen (N) in organic matter (OM) density and size fractions in agricultural fields with the closest area of native vegetation at three locations in the Western Australian wheat belt. Few studies have quantified oribatid richness in WA soils and none has investigated the impact of agriculture on these animals. A total of 22 oribatid species was identified from the samples, of which 8 were found in agricultural fields. A maximum of 5 species was found in individual agricultural fields, and a minimum of 11 species was found in the individual native vegetation areas. There were few differences in the mass of C and N in OM fractions between native and agricultural areas, and no correlation between mite abundance and mass of C in the density and size fractions of soil OM assessed. Therefore, soil disturbance, and not soil OM levels per se, is the likely cause of the low species richness at the agricultural sites.

Diatom and micro-invertebrate communities and environmental determinants in the western Australian wheatbelt: a response to salinization

Diatom and micro-invertebrate communities were analyzed in 56 lentic wetlands from the wheatbelt of Western Australia. Sixteen water quality parameters were measured at each habitat and were tested as determinants of diatom and micro-invertebrate distribution. Nearly all waters were dominated by Na1+ and Cl1− and over half had low buffering capacity ( 240 mS/cm; some hypersaline habitats had pH values as low as 2.1, but most sites were alkaline.

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.

The influence of local elevation on the effects of secondary salinity in remnant eucalypt woodlands: Changes in understorey communities

Increasing land salinization in Australia is predicted to lead to severe declines in species diversity in affected areas, and perhaps significant numbers of species extinctions. Much of the diversity that will be lost consists of understorey and mid-storey species, yet the overwhelming majority of research has focussed on salinity tolerance in tree species. We investigated how the presence of a shallow, saline water table affected the understorey species composition, species richness and species diversity in two remnant Eucalyptus wandoo Blakely woodlands in the Western Australian wheatbelt. Species richness and species diversity were significantly lower in areas with a shallow water table at elevations < 0.5 m above the lowest local elevation, compared with both higher elevations and with areas of low elevation without a shallow water table. Species composition (Bray-Curtis similarities) was also significantly different in low elevation, saline areas. At one site, saline areas were colonized by native and alien species that were not present in the surrounding vegetation, yet the community that has developed does not contain either the species or structural diversity of the surrounding system. At the other site, no colonisation of saline areas by new species occurred. Even though small differences in elevation (< 0.5 m) at our study sites were important in moderating the impacts of salinity in areas with a shallow water table, the loss of species diversity, species richness and structural complexity in low-lying elevations indicated that the ecological risk from secondary salinity to species associated only with drainage lines, seasonally wet flats and other low-lying areas is severe. The priority is to identify those vegetation communities that are restricted to only low relative elevations within the landscape and that only occur in remnants predicted to be at a high risk of developing a shallow and saline water table.

Breeding system, pollination and demography in the rare granite endemic shrub Verticordia staminosa ssp. staminosa in south‐west Western Australia

Abstract Verticordia staminosa C. Gardner &amp; A. S. George staminosa (Myrtaceae) is a rare granite endemic shrub that grows in discrete subpopulations on one isolated rock outcrop in a remnant of native vegetation in the Western Australian wheat belt. Key considerations in assessing the risk of extinction for rare plant species in fragmented landscapes are the reproductive dependence on a pollinator, breeding system, importance of seeds in demography, and regeneration niche. The present study determined the extent to which these factors constrain population growth in V. staminosa ssp. staminosa. Measurements across nine subpopulations on the breeding system, pollinator activity, rates of flowering, pollination and seed production, seedling demography, mature plant mortality and size‐class structure were undertaken over three consecutive years. The study species has a mixed mating system with similar rates of pollen tube development and fertilization observed in self‐, cross‐ and open‐pollinated flowers. Floral morphology, orientation and the concentration and volume of nectar produced suggest some degree of specialization associated with pollination by birds, which were occasionally seen visiting flowers. However, feral honey bees were the most commonly observed flower visitor and they seem to have replaced honeyeaters as the primary pollinator. Honey‐bee abundance increased with subpopulation size. However, rates of pollination and the subsequent proportion of flowers that produced viable seeds were independent of subpopulation size. Germination and seedling emergence occurred each winter but were greatest in the wettest winter. Recruitment was heavily biased towards individuals growing in or over cracks/fissures in the rock. Over the 3‐year study, recruitment exceeded mortality. A relatively unspecialized flower and mixed mating system have buffered the taxon against the effects of pollinator disruption. Seed production does not constrain population growth. The environmental variables of climate and suitable establishment crevices appear to be the major constraints to population growth.

Multiple-herbicide resistance across four modes of action in wild radish (Raphanus raphanistrum)

Populations of wild radish were collected from two fields in the northern Western Australian wheatbelt, where typical herbicide-use patterns had been practiced for the previous 17 seasons within an intensive crop production program. The herbicide resistance status of these populations clearly established that there was multiple-herbicide resistance across many herbicides from at least four modes of action. One population exhibited multiple-herbicide resistance to the phytoene desaturase (PDS)–inhibiting herbicide diflufenican (3.0-fold), the auxin analog herbicide 2,4-D (2.2-fold), and the photosystem II–inhibiting herbicides metribuzin and atrazine. Another population was found to be multiply resistant to the acetolactate synthase–inhibiting herbicides, the PDS-inhibiting herbicide diflufenican (2.5-fold), and the auxin analog herbicide 2,4-D amine (2.4-fold). Therefore, each population has developed multiple-herbicide resistance across several modes of action. The multiple resistance status of these wild radish populations developed from conventional herbicide usage in intensive cropping rotations, indicating a dramatic challenge for the future control of wild radish.