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1
Mcfarlane, DJ, e RJ George. "Factors affecting dryland salinity in two wheat belt catchments in Western Australia". Soil Research 30, n. 1 (1992): 85. http://dx.doi.org/10.1071/sr9920085.
Testo completoAbstract (sommario):
We investigated why the Wallatin Creek Catchment in the Western Australian wheatbelt had an appreciable area of secondary salinity whereas the adjoining North Baandee Catchment had almost none. The Wallatin Creek Catchment, which is long and narrow, had a shallow regolith over granite bedrock. Although this catchment had less salt stored in the regolith than the wider North Baandee Catchment, the groundwaters came close to the ground surface because the regolith was thin and the valley cross-section narrow. Management practices which increase recharge (e.g. using level banks to control runoff), are likely to result in increased salinity in the short term in the Wallatin Creek Catchment. We also investigated whether retaining areas of remnant vegetation had reduced the amount of secondary salinity in a sub-catchment of the Wallatin Creek Catchment. At comparable positions in the landscape, groundwater levels were up to 7 m lower under the remnant vegetation. The vegetation appears to have delayed, if not prevented, the development of salinity in nearby and downslope areas.
2
Gomboso, J., e F. Ghassemi. "Groundwater modelling and optimal salinity control in the North Stirling Land Conservation District, Western Australia". Mathematics and Computers in Simulation 33, n. 5-6 (aprile 1992): 609–14. http://dx.doi.org/10.1016/0378-4754(92)90159-e.
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3
Schofield, NJ, e MA Bari. "Valley reforestation to lower saline groundwater tables - Results from Stene Farm, Western-Australia". Soil Research 29, n. 5 (1991): 635. http://dx.doi.org/10.1071/sr9910635.
Testo completoAbstract (sommario):
Dense planting of selected trees in salt-affected valley floors and non-saline adjacent slopes has been evaluated as one strategy for controlling rising saline groundwater under agriculture. Of the 127 ha experimental catchment, 44% had been cleared of native forest in the 1950s. Valley reforestation covering 35% of the cleared area took place in 1979, by which time a groundwater of 5300 mg L-1 TSS had risen to within 0.5 m of the soil surface. The eucalypt reforestation was successful in lowering the groundwater table by 1.5 m by 1989, whilst groundwater levels under nearby pasture had risen by 1.8 m. The groundwater salinity beneath reforestation decreased by 30% over the study period, allaying fears of a detrimental groundwater salinity increase brought about by transpirative concentration. Measures such as replanting failed areas, implementing agricultural recharge control or selecting higher water using tree species would improve the performance of the valley reforestation strategy.
4
Ferdowsian, Ruhi, Arjen Ryder, Richard George, Geoff Bee e Rob Smart. "Groundwater level reductions under lucerne depend on the landform and groundwater flow systems (local or intermediate)". Soil Research 40, n. 3 (2002): 381. http://dx.doi.org/10.1071/sr01014.
Testo completoAbstract (sommario):
By 1994, an estimated 1.8 million hectares of cleared land in Western Australia was affected by secondary dryland salinity to some extent. The area affected is likely to double in the next 20 years. The cause of this salinity is excessive recharge under traditional agriculture, leading to rising groundwater levels. To effectively reduce land and water salinity a deep-rooted perennial is needed to mimic the temporal and spatial distribution of leaf area that existed prior to clearing. Previous studies have shown lucerne lowers groundwater levels in areas with favourable conditions. We present data showing that lucerne lowered groundwater levels in 4 different landforms and under unfavourable conditions. All sites had very saline groundwater, high sodium chloride chemistry and high groundwater levels. This paper shows that the effectiveness of lucerne in salinity control measures depends on the attributes of the groundwater flow system. salinity, salinity management, monitoring, sustainability.
5
Byrne, M., e L. Broadhurst. "Genetic diversity and the utilisation of Acacia species complexes in agroforestry in Western Australia". Australian Systematic Botany 16, n. 1 (2003): 49. http://dx.doi.org/10.1071/sb01037.
Testo completoAbstract (sommario):
Dryland salinity is a major problem in the agricultural areas of Western Australia, having significant detrimental impacts in both agricultural and non-agricultural arenas. Development of new woody perennial tree crops is an option for recharge control in the management of salinity and there is a focus on development of native species that are adapted to low-rainfall areas, with potential for commercial production. Acacia is an important genus for utilisation of woody perennials as there is a large number of species occurring in a wide variety of habitats, and many Acacia species are utilised throughout the world for a range of purposes. In Western Australia, the following three species are of interest for development for commercial utilisation in agroforestry plantings: A.�microbotrya, A. acuminata and A. saligna. All three species show a high degree of morphological variation and are likely to consist of several taxa. Lack of understanding of taxonomic entities and their genetic relationships will hinder the utilisation and development of these species. A combined genetic and taxonomic study has defined the morphological and genetic variation within the A. acuminata complex and identified several taxa. Similar studies will also be expected to define taxa within the A. microbotrya and A. saligna complexes.
6
De Silva, Jayath, e Robin Smith. "The role of landscape evolution & hydrostratigraphy in dryland salinity development and control in south-west Western Australia". ASEG Extended Abstracts 2007, n. 1 (1 dicembre 2007): 1–4. http://dx.doi.org/10.1071/aseg2007ab032.
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7
Stolte, W. J., D. J. McFarlane e R. J. George. "Flow systems, tree plantations, and salinisation in a Western Australian catchment". Soil Research 35, n. 5 (1997): 1213. http://dx.doi.org/10.1071/s96066.
Testo completoAbstract (sommario):
A lower hillslope in the Western Australian wheatbelt had become waterlogged and saline by 1981, when close-spaced rows of eucalypts were planted in blocks both in and adjacent to the discharge area and piezometers were established on the site. We analysed the trends in the piezometric heads and salinity concentrations over the period of record. We also modelled the hillslope profile using finite element analysis to determine the water flow mechanisms and to see how a change in vegetation in the upland area would affect the waterlogging and salinity. Piezometric levels under the trees decreased for the first 5 years after planting and then stabilised until 1991 when they started gradually decreasing again. The non-treed area between the plantation blocks remained unaffected until about 1991, when the levels there also started to decrease quite significantly, probably because of the trees. The trees therefore appear to have been effective and beneficial in the short to medium term. However, the salinity of the groundwater under the trees has increased significantly in the last 5 years, particularly where the tree density is highest. The continued flow of saline groundwater to the trees is believed to be increasing the salinity. It could not be expected that plantations of this type will maintain health and be able to control the excess water in such an hydrologic setting in the long term. Tree plantations on discharge areas are a short to medium term management strategy, not a solution, and the only way to control salinity in the long term is to plant vegetation species in the recharge areas that use all of the water that falls there. Modelling showed that only a small surplus of water over winter, in the order of 50 mm/year, caused the increased recharge and consequent salinisation. The modelling results also show that the surplus could be managed with an effective vegetation species (e.g. lucerne) with a rooting depth of about 1·5 m that would be able to transpire at least until early to mid summer.
8
Vincent, Wilma J. "Nutrient partitioning in the upper Canning River, Western Australia, and implications for the control of cyanobacterial blooms using salinity". Ecological Engineering 16, n. 3 (gennaio 2001): 359–71. http://dx.doi.org/10.1016/s0925-8574(00)00121-x.
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9
Chan, Terence U., e David P. Hamilton. "Effect of freshwater flow on the succession and biomass of phytoplankton in a seasonal estuary". Marine and Freshwater Research 52, n. 6 (2001): 869. http://dx.doi.org/10.1071/mf00088.
Testo completoAbstract (sommario):
Physico-chemical factors affecting phytoplankton succession and dynamics are examined in the upper Swan River estuary, Western Australia. Freshwater discharge affects the residence time available for different phytoplankton taxa to grow. It also influences succession between marine, estuarine and freshwater phytoplankton taxa according to the extent that it hinders intrusion of marine water into the estuary. The three major phytoplankton groups, Bacillariophyta, Dinophyta and Chlorophyta, are strongly separated temporally by season, and spatially along the estuary according to flow and salinity. Bacillariophyta exhibit the widest range of maximum potential growth rates and occur under a wide range of discharges. Dinophyta, dominated by relatively few brackish water species, have the lowest growth rates, and occur only at very low discharges. Chlorophyta, dominated by Chlamydomonas globulosa, are intermediate in their potential growth rates, and are restricted to freshwater conditions. In the Swan River estuary, nutrients appear to be less important than flow and salinity in regulating phytoplankton succession and biomass. It is highly likely that anthropogenic effects on freshwater discharge to Australian estuaries have had a significant impact on composition and biomass of phytoplankton communities. Control of freshwater discharge thus has the potential to control species assemblages, phytoplankton bloom potential, and eutrophication.
10
Craig, GF, DT Bell e CA Atkins. "Response to Salt and Waterlogging Stress of Ten Taxa of Acacia Selected From Naturally Saline Areas of Western Australia". Australian Journal of Botany 38, n. 6 (1990): 619. http://dx.doi.org/10.1071/bt9900619.
Testo completoAbstract (sommario):
Ten taxa of Acacia were selected from areas of moderate to high soil salinity (electrical conductivities of saturated soil paste extracts (ECe) between 1000 mS m--1 and 4800 mS m-1 at 50-600 mm depth) and sodicity to test the tolerance of young, symbiotic plants to increasing levels of salinity both with and without waterlogging. Nodulated plants, 3 months old, were grown in glasshouse experiments which consisted of four treatments: non-saline drained control (12 weeks); saline drained (12 weeks); non-saline waterlogged (5 weeks); and saline waterlogged (5 weeks). Acacia cyclops, A. brumalis, A. redolens (Ravensthorpe) and A. aff. lineolata had 100% survival after 12 weeks irrigation with saline solution (final ECw = 9500 mS m-1). Generally, the species tested were sensitive to waterlogging with A. patagiata, A. cyclops and A. brumalis being the most sensitive, having 19-44% mortality with no salt in the solution. The combined treatment of salt and waterlogging greatly increased the mortality of plants, with four species having > 70% dead after 5 weeks treatment (ECw = 3900 mS m-1). A. aff. lineolata and A. mutabilis subsp. ,stipulifera were highly tolerant of salt plus waterlogging, with 100% and 96% survival respectively. In salt plus waterlogged treatments, Na+ concentration in phyllodes of all taxa exceeded (0.37-2.13 mmol g-1 dry wt) that taken up by plants in freely drained salt treatments (0.03-0.42 mmol g-1 dry wt). Taxa with the slowest rates of growth tended to accumulate the highest concentrations of Na+ in the uppermost phyllodes. Provenances of A. redolens and A. patagiata collected from sites of high soil salinity (ECe > 2200 mS m-1) had less than half the Na+ concentration in uppermost phyllodes (0.22 mmol -1 dry wt) at the termination of the salt treatment, compared with provenances of the same species collected from moderately saline areas (ECe = 1100 mS m-1). This indicates that Acacia provenances collected from the most saline sites had greater potential to survive high levels of external salinity in the longer term than those from less saline sites.
11
Cocks, P. S. "Ecology of herbaceous perennial legumes: a review of characteristics that may provide management options for the control of salinity and waterlogging in dryland cropping systems". Australian Journal of Agricultural Research 52, n. 2 (2001): 137. http://dx.doi.org/10.1071/ar99170.
Testo completoAbstract (sommario):
Salinity is a widespread problem caused by an imbalance between rainfall and transpiration in the dryland cropping systems of southern Australia. The need to use more perennials has been identified and this paper examines the possibility of replacing annual with perennial pasture legumes and the germplasm available to do so. While lucerne is already used widely in eastern Australia it has only recently been adopted in the wheat belt of Western Australia. There are doubts about its adaptation to acid soils and to climates where summer rainfall is low and ambient temperatures are high. There is also a need to diversify the species available to reduce the likelihood of invasion by exotic diseases and insects. Several genera are likely to be of value in this respect, although few will be as widely adapted as lucerne. Perennial legumes are found in environments ranging from alpine to desert. Targeted collections of genera from the dry areas, especially where soils are acid, are likely to yield species of value. These may include perennial species of Astragalus, Hedysarum, Lotus, Onobrychis, Psoralea, and Trifolium. Some Australian genera, for example Swainsona, Glycine, and Cullen may also be of value. Most of these genera are from alkaline soils, and the need to cope with acid soils that are often high in free aluminium is seen to limit their use in southern Australia. However, since virtually nothing is known of the ecology and ecophysiology of species from the dry areas, it is possible that through selection and the use of adapted rhizobia, some at least may be of value in Australian conditions. Cropping in rotation with perennial legumes is likely to involve several changes in farming systems. It is impossible to predict their nature but it is essential that we understand what these changes are before the species are widely introduced. Account must also be taken of their ability to use water. It is entirely possible that perennials from dry areas are dormant in summer despite the fact that there is no evidence in the literature to this effect. It was concluded that although lucerne is suitable for phase farming, alternatives to lucerne are needed. They will have to match the water-using and nitrogen-fixing capacities of lucerne, and farming systems will be required that make full use of the new germplasm. Collaboration with institutions in the Mediterranean basin and elsewhere is needed and a beginning has been made in this direction.
12
Asseng, S., F. X. Dunin, I. R. P. Fillery, D. Tennant e B. A. Keating. "Potential deep drainage under wheat crops in a Mediterranean climate. II. Management opportunities to control drainage". Australian Journal of Agricultural Research 52, n. 1 (2001): 57. http://dx.doi.org/10.1071/ar99187.
Testo completoAbstract (sommario):
High rates of deep drainage in Western Australia are contributing to groundwater recharge and secondary salinity. Strategies are being sought to increase water use in cropping systems and to reduce deep drainage. Quantifying potential drainage through measurements is hampered by the high degree of complexity of these systems as a result of diverse soil types, a range of crops, and in particular the inherent seasonal variability. Simulation models can provide the appropriate means to extrapolate across time and space. The Agricultural Production Systems Simulator (APSIM) was used to explore the effect of alternative agronomic practices on wheat production and deep drainage for representative soils and rainfall regions of the central wheatbelt of Western Australia. Soil water profiles were reset each year to the lower limit of plant-available water, assuming maximum water use in the previous crop. The long-term simulation studies showed that management practices with N fertiliser directed at yield increase were most effective in achieving these aims in the medium to high rainfall regions. The corresponding effect for drainage reduction was marginal. The small effect on drainage control associated with production increase can be traced to the effect of rainfall distribution with major occurrences of both rainfall and drainage during winter (June–August) coinciding with the lowest potential atmospheric demand for evapotranspiration, in combination with low water-holding capacity soils. Nitrogen-induced increases in crop transpiration were in conjunction with reduced soil evaporation, which increased water use efficiency and occurred mostly after the main drainage period, but had little effect on deep drainage within the season. Similar outcomes of enhanced productivity with minor impact on deep drainage were noted with crops sown at different times and with a hypothetical wheat crop having a deeper rooting system. Simulations without resetting soil water each year enabled the quantification of potential carryover effects on long-term average deep drainage. The carry-over of soil water left behind at crop harvest reduced the water storage capacity of the soil in a subsequent year and could increase long-term deep drainage substantially, depending on soil type. Improved management increased late water use in the high rainfall region, in particular on better water-holding soils, and could largely reduce this carry-over effect. The current wheat-based cropping systems, even with alternative management practices, continue to be a major threat to sustainability on the low water-holding soils in the wheatbelt of Western Australia, as a main cause of secondary salinity.
13
Eastham, J., P. R. Scott e R. Steckis. "Components of the water balance for tree species under evaluation for agroforestry to control salinity in the wheatbelt of Western Australia". Agroforestry Systems 26, n. 3 (giugno 1994): 157–69. http://dx.doi.org/10.1007/bf00711208.
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Salama, R. B., D. Laslett e P. Farrington. "Predictive modelling of management options for the control of dryland salinity in a first-order catchment in the wheatbelt of Western Australia". Journal of Hydrology 145, n. 1-2 (maggio 1993): 19–40. http://dx.doi.org/10.1016/0022-1694(93)90218-x.
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Biggs, Andrew J. W., e Peter Binns. "Soil morphological and chemical profiles adjacent to a bore drain in south-western Queensland, Australia". Soil Research 53, n. 3 (2015): 325. http://dx.doi.org/10.1071/sr14195.
Testo completoAbstract (sommario):
A recently abandoned artesian bore drain in south-western Queensland was sampled to investigate soil morphology and chemistry under, and adjacent to, the drain. Such drains are supplied with alkaline, sodium-rich artesian groundwater and they provide a long-term example of the impacts of these waters on soils. A Red Kandosol and a Grey Vertosol were sampled, in the drain and at 2, 4 and 25 m perpendicular to the drain. Morphological attributes indicative of long-term saturation, such as mottling, were evident around the drains, but were absent at the control sites (25 m away). At the Kandosol location, pH and exchangeable sodium were elevated within 4 m of the drain, and salinity data suggested a horizontally displaced wetting front at ~4 m from the drain. In the Grey Vertosol, which was naturally saline and sodic below 0.5 m, substantial leaching of salts had occurred around the drain, but a horizontal wetting front was also evident and exchangeable sodium was increased within 4 m of the drain. A thin, weak pan was detected in the subsoil of the Red Kandosol under the drain bank, but pans were otherwise absent under the drains. The results indicate that deep drainage is a feature not only of the Red Kandosol, but also the Grey Vertosol, despite it being sodic and despite the application of sodic, alkaline water. The findings reiterate the importance of investigating soil and water chemistry interactions when designing channels, storages and irrigation systems, in particular those using sodic–saline waters.
16
Hamilton, LJ. "Temperature inversions at intermediate depths in the Antarctic Intermediate waters of the South-western Pacific". Marine and Freshwater Research 41, n. 3 (1990): 325. http://dx.doi.org/10.1071/mf9900325.
Testo completoAbstract (sommario):
Deep (about 1000 m) marked temperature inversions and/or salinity reversals found in conductivity- temperature-depth profiles in the south-western Pacific for 1985 to 1987 are shown to arise from confluences of different branches of the Antarctic Intermediate Water (AAIW). Salinity reversals lead to the presence of several intermediate-depth salinity minima instead of the simple broad minimum in the vertical usually described as characterizing the presence of AAIW in this area. The anomalies are found at particular locations, often near ridges and rises. Significantly differing thermohaline properties acquired by the branches from mixing over separate travel paths apparently allows the formation of temperature inversions by isentropic penetrations. Some perturbations are dynamically caused in that at least one branch of AAIW is transported in association with strong surface currents with deep influence. Other confluences are caused by topographic control on AAIW flows moving independently of surface currents. Perturbations south of the Subtropical Convergence are related to the initial formation of the AAIW, but these are not of major interest in this analysis, being well known and simply explained. Locations of perturbations correspond in some areas to flow patterns of intermediate waters inferred by researchers using historical data, and they indicate other areas where the flow patterns need more investigation. Some comments are made on East Australian Current outflows from the Tasman and Coral Seas that have considerable influence on the flow of branches of the AAIW. Other remarks are made concerning the peculiarities of the temperature-salinity regime of the Tasman Front, which inhibits the formation of temperature inversions at depth. In general, the medium- and fine-scale structure in the central Tasman is that of the stepped type, with intrusive type in other areas.
17
Harper, R. J., K. R. J. Smettem e R. J. Tomlinson. "Using soil and climatic data to estimate the performance of trees, carbon sequestration and recharge potential at the catchment scale". Australian Journal of Experimental Agriculture 45, n. 11 (2005): 1389. http://dx.doi.org/10.1071/ea04186.
Testo completoAbstract (sommario):
There is considerable interest in integrating deep-rooted perennial plants into the dryland farming systems of southern Australia as soil, water supplies and biodiversity are continually threatened by salinity. In addition to wood products, trees could provide new products, such as bioenergy, environmental services, such as the sequestration of carbon, reductions in recharge to groundwater and biodiversity protection. Before marketing these services, it is necessary to determine the optimal distribution of trees across the landscape, in terms of land suitability, their productivity, and proximity to existing processing and transport infrastructure. Similarly, understanding how recharge varies across landscapes will allow the targeting of trees to areas where they are most needed for salinity control. Catchment scale (1:100 000) soil and landform datasets are now available across much of the agricultural area of Australia. While these data are at a scale inappropriate for management at the enterprise (farm) scale, they will allow broad planning for new plant-based industries, such as whether there is sufficient suitable land available before embarking on a new enterprise and the likely productivity of that land. In this paper, we outline an approach that combines existing soil and landform data with estimates of climate to produce estimates of likely wood yield, carbon sequestration and potential for recharge to groundwater. Using the 283 686 ha Collie catchment of south-western Australia as an example, this analysis indicated broad areas where land is suitable for forestry, where forestry is unlikely to succeed, or where it was not required because leakage to groundwater is negligible. It also provides broad estimates of wood production and carbon sequestration. The approach is applicable to the integration of deep-rooted perennial plants into farming systems in other regions confronted with multiple natural resource management issues.
18
Farrell, RCC, DT Bell, K. Akilan e JK Marshall. "Morphological and Physiological Comparisons of Clonal Lines of Eucalyptus camaldulensis. II. Responses to Waterlogging/Salinity and Alkalinity". Functional Plant Biology 23, n. 4 (1996): 509. http://dx.doi.org/10.1071/pp9960509.
Testo completoAbstract (sommario):
Eucalyptus camaldulensis Dehnh. has previously been shown to survive and grow in waterlogged, highly saline and highly alkaline soils. The ability of six clones from five provenances of E. camaldulensis to produce biomass and utilise water, and the processes of stomatal conductance and gas exchange under stress conditions was examined under controlled conditions in a glasshouse. A clone originally from Wooramel, Western Australia (M80) produced the largest total plant biomass, the greatest total leaf area and greatest total root dry weight under conditions of waterlogging and gradually increasing salinity. A second clone from Wooramel (M16), however, tended to be among the least productive of the clones under this stress, indicating the wide potential variation in stress tolerance of trees from a single provenance. The response of clones to alkalinity stress was comparable to that measured under waterlogging/salinity stress. Water use was closely related to biomass production. Leaves produced while under salinity and alkalinity stress were comparable in ion content to those produced prior to the test conditions. An ability to control uptake by roots or limit ion transport to leaf tissues were hypothesised as controlling physiological functions resulting in tolerance to severe soil ion imbalances in this species. The impact of solution conductivity on stomatal conductance and water use, secondarily affected photosynthetic rates in these clones of E. camaldulensis. Tolerance of extreme conditions provides the opportunity to use these genotypes to reclaim damaged agricultural landscapes and mine spoils of high soil solution ion concentrations.
19
Eastham, J., P. R. Scott, R. A. Steckis, A. F. M. Barton, L. J. Hunter e R. J. Sudmeyer. "Survival, growth and productivity of tree species under evaluation for agroforestry to control salinity in the Western Australian wheatbelt". Agroforestry Systems 21, n. 3 (marzo 1993): 223–37. http://dx.doi.org/10.1007/bf00705242.
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20
Barrett-Lennard, Edward G., Rushna Munir, Dana Mulvany, Laine Williamson, Glen Riethmuller, Callum Wesley e David Hall. "Micro-Water Harvesting and Soil Amendment Increase Grain Yields of Barley on a Heavy-Textured Alkaline Sodic Soil in a Rainfed Mediterranean Environment". Agronomy 11, n. 4 (8 aprile 2021): 713. http://dx.doi.org/10.3390/agronomy11040713.
Testo completoAbstract (sommario):
This paper focuses on the adverse effects of soil sodicity and alkalinity on the growth of barley (Hordeum vulgare L.) in a rainfed environment in south-western Australia. These conditions cause the accumulation of salt (called ‘transient salinity’) in the root zone, which decreases the solute potential of the soil solution, particularly at the end of the growing season as the soil dries. We hypothesized that two approaches could help overcome this stress: (a) improved micro-water harvesting at the soil surface, which would help maintain soil hydration, decreasing the salinity of the soil solution, and (b) soil amelioration using small amounts of gypsum, elemental sulfur or gypsum plus elemental sulfur, which would ensure greater salt leaching. In our experiments, improved micro-water harvesting was achieved using a tillage technique consisting of exaggerated mounds between furrows and the covering of these mounds with plastic sheeting. The combination of the mounds and the application of a low rate of gypsum in the furrow (50 kg ha−1) increased yields of barley grain by 70% in 2019 and by 57% in 2020, relative to a control treatment with conventional tillage, no plastic sheeting and no amendment. These increases in yield were related to changes in ion concentrations in the soil and to changes in apparent electrical conductivity measured with the EM38.
21
Bolger, T. P., e N. C. Turner. "Water use efficiency and water use of Mediterranean annual pastures in southern Australia". Australian Journal of Agricultural Research 50, n. 6 (1999): 1035. http://dx.doi.org/10.1071/ar98109.
Testo completoAbstract (sommario):
There is a perception in the farming and research communities that annual pastures have low produc- tivity and water use, and contribute disproportionately to problems of rising watertables and dryland salinity. Our aim was to determine potential pasture production in relation to water use and the influence of management factors on this relationship. Experiments were initiated at 4 locations along a gradient of 300–1100 mm annual rainfall across the Western Australian agricultural zone. At each site a high input treatment was compared with a low input control. There was a strong linear relationship between water use and pasture production up to 440 mm of growing- season water use. After 30 mm of water use the potential pasture production was 30 kg/ha.mm. An upper limit to pasture production may be reached at about 12 000 kg/ha in this environment due to rainfall distribution patterns and soil water holding capacity in the root-zone. Although pasture production was increased by as much as 3500 kg/ha, water use was generally similar or only slightly more for high input compared with control plots. The marginally higher water use by the high input pastures resulted in an extra 18 mm of water extracted from the subsoil at one location by the end of the third season. A drier subsoil may provide a buffer for storing excess rainfall and reduce deep drainage. Estimated drainage was small at low rainfall sites so even marginal increases in water use by highly productive annual pastures could play a significant role in reducing water loss to deep drainage and mitigating water-table rise and secondary salinisation in low rainfall regions. Management practices aimed at promoting early growth and adequate leaf area should maximise water use, water use efficiency, and yield. The linear relationship defining potential pasture production provides a useful benchmark to farmers.
22
Burgess, Ray, Sarah L. Goldsmith, Hirochika Sumino, Jamie D. Gilmour, Bernard Marty, Magali Pujol e Kurt O. Konhauser. "Archean to Paleoproterozoic seawater halogen ratios recorded by fluid inclusions in chert and hydrothermal quartz". American Mineralogist 105, n. 9 (1 settembre 2020): 1317–25. http://dx.doi.org/10.2138/am-2020-7238.
Testo completoAbstract (sommario):
Abstract Past changes in the halogen composition of seawater are anticipated based on the differing behavior of chlorine and bromine that are strongly partitioned into seawater, relative to iodine, which is extremely depleted in modern seawater and enriched in marine sediments due to biological uptake. Here we assess the use of chert, a chemical sediment that precipitated throughout the Precambrian, as a proxy for halide ratios in ancient seawater. We determine a set of criteria that can be used to assess the primary nature of halogens and show that ancient seawater Br/Cl and I/Cl ratios can be resolved in chert samples from the 2.5 Ga Dales Gorge Member of the Brockman Banded Iron Formation, Hamersley Group, Western Australia. The values determined of Br/Cl ~2 × 10-3 M and I/Cl ~30 × 10-6 M are comparable to fluid inclusions in hydrothermal quartz from the 3.5 Ga North Pole area, Pilbara Craton, Western Australia, that were the subject of previous reconstructions of ancient ocean salinity and atmospheric isotopic composition. While the similar Br/Cl and I/Cl values indicate no substantial change in the ocean halide system over the interval 2.5–3.5Ga, compared to modern seawater, the ancient ocean was enriched in Br and I relative to Cl. The I/Cl value is intermediate between bulk Earth (assumed chondritic) and the modern seawater ratio, which can be explained by a smaller organic reservoir because this is the major control on marine iodine at the present day. Br/Cl ratios are about 30% higher than both modern seawater and contemporary seafloor hydrothermal systems, perhaps indicating a stronger mantle buffering of seawater halogens during the Archean.
23
Oliver, Y. M., E. C. Lefroy, R. Stirzaker e C. L. Davies. "Deep-drainage control and yield: the trade-off between trees and crops in agroforestry systems in the medium to low rainfall areas of Australia". Australian Journal of Agricultural Research 56, n. 10 (2005): 1011. http://dx.doi.org/10.1071/ar04213.
Testo completoAbstract (sommario):
In the dryland cropping areas of southern Australia, at risk from dryland salinity, tree belts can improve water management by taking up water unused by crops, with the risk that crop yield will be reduced through competition. As there are few direct markets for tree products grown in the medium to low rainfall areas, the design of agroforestry systems becomes important in reducing the trade-off in crop yield. This study examined some factors that influence the trade-off between crop yield and deep-drainage control in order to develop design guidelines for medium to low rainfall agroforestry. Twenty-one sites in the grain-growing region of Western Australia and southern New South Wales were surveyed over 2 years for crop yields, tree leaf area index, and estimated recharge, providing data from 32 tree–crop interfaces on the relative influence of environmental factors and farming system characteristics on the trade-off between water management and crop yield. The factors most strongly correlated with higher yields were water-gaining sites, orientation that provided shelter from southerly to north-westerly (S, SW, W, NW) winds, and tree age (<10 years). The factors most strongly correlated with the area of cropped land protected against deep drainage were tree age (>10 years), lighter soil types, and low rainfall (<400 mm). Economic analysis of the trade-off required to produce a particular deep-drainage reduction target produced 3 groups of sites: (1) those where trees resulted in a gross margin increase of $15/ha and an estimated deep-drainage reduction of 52% (n = 3), (2) those with a gross margin loss of $49/ha and estimated deep-drainage reduction of 47% (n = 11), and (3) those with a gross margin loss of $163/ha and a deep-drainage reduction of 37% (n = 18). None of the 3 sites in the first group were in the most favourable class in both years, highlighting the vulnerability of a relatively fixed farming system to climate variability.
24
Evans, P. M., e G. A. Kearney. "Melilotus albus (Medik.) is productive and regenerates well on saline soils of neutral to alkaline reaction in the high rainfall zone of south-western Victoria". Australian Journal of Experimental Agriculture 43, n. 4 (2003): 349. http://dx.doi.org/10.1071/ea02079.
Testo completoAbstract (sommario):
Dryland salinity is a serious problem in Australia. While some introduced perennial grasses such as tall wheat grass (TWG) Thinopyrum ponticum (Podp. Z.W. Liu & R.R.C. Wang) are adapted to saline soils, there are few pasture legumes that are productive and persistent under saline conditions. Melilotus albus (Medik.) has the potential to be 1 such legume in southern Australia. To test the potential of this species, we conducted 2 experiments over a 3-year period on saline soils at Woorndoo and Glenthompson in south-western Victoria. The soil electrical conductivities (1 : 5 water) of the sites, in autumn before sowing, were 1–3 dS/m at Woorndoo and 3–5 dS/m at Glenthompson (0–10 cm depth).At both sites the herbage yields of 2 Melilotus lines were greater than 10 t/ha of dry matter for the whole season between autumn and late summer. The best commercial control species at Woorndoo, white clover cv. Haifa, produced less than 1/6 of the yield of the best Melilotus line during the summer months. At Glenthompson, during the whole second season the herbage yield of the best Melilotus was 40% greater than that of the best commercial control, Persian clover cv. Nitro plus. In the second season, regeneration of Melilotus at both sites was excellent, averaging 3500 seedlings/m2 at Woorndoo, and 1100 and 3400 seedlings/m2 in mixtures with TWG and in monoculture, respectively at Glenthompson. In the third season, however, regeneration averaged only 400 plants/m2 at Woorndoo and 640 plants/m2 at Glenthompson, both with and without grass. It appears that, when there is limited competition, Melilotus albus dominates in the first 2 years. However, as fertility and water use increase, other pasture species, which initially have a low rate of survival and are unproductive, begin to increase their presence in the sward at the expense of M. albus. These annual species germinate after the autumn rains dilute the salt on the surface of the soil and senesce in early summer as soil water deficits and/or evaporation increase the electrical conductivity again. We suggest that Melilotus albus is an excellent pasture legume to revegetate saline soils in southern Australia and represents an opportunity to obtain high levels of out-of-season pasture production from areas that are currently unproductive.
25
Turner, Neil C., e Senthold Asseng. "Productivity, sustainability, and rainfall-use efficiency in Australian rainfed Mediterranean agricultural systems". Australian Journal of Agricultural Research 56, n. 11 (2005): 1123. http://dx.doi.org/10.1071/ar05076.
Testo completoAbstract (sommario):
Mediterranean environments are characterised by hot, dry summers and cool, wet winters. The native vegetation in Mediterranean-climatic regions is predominantly perennial shrubs and trees intermixed with annual forbs. In south-western Australia, the spread of agriculture has seen the well adapted perennial vegetation replaced by rainfed annual crops and pastures. This has increased waterlogging and secondary salinity, thereby causing loss of productivity in ~10% of the cleared land area. To reduce deep drainage and make the agricultural systems environmentally sustainable requires the re-introduction of perennial vegetation in the form of belts of trees or shrubs, and phase-farming systems with perennials such as lucerne replacing annual pastures between the cropping years. To be economically viable, agricultural productivity needs to increase by at least 3% per annum. Yields of dryland wheat, the predominant crop in the Mediterranean agricultural regions of Australia, have increased at ~1%/year for the century preceding the 1980s and since then by nearly 4%/year. Increases have arisen from both genotypic and agronomic improvements. Genotypic increases have arisen from selection for earliness, early vigour, deep roots, osmotic adjustment, increased transpiration efficiency, improved disease resistance, and an improved harvest index from high ear weight (grain number) at flowering and high assimilate storage and remobilisation. Agronomic increases have arisen from early sowing that has been enabled by minimum tillage, increased fertiliser use, especially nitrogen, weed control, and rotations to improve weed control, minimise disease risk, and increase nitrogen availability. Evidence is presented suggesting that the rapid increase in yield of wheat in the last two decades has likely arisen from the rapid adoption of new technologies. For productivity to be maintained in the face of the increasing requirement to be environmentally sustainable will be a challenge and will require better integration of breeding and agronomy.
26
Calica, Phoebe N. "Nodulation and Nitrogen Fixation of Pongamia pinnata". Journal of Tropical Crop Science 4, n. 1 (1 febbraio 2017): 1–12. http://dx.doi.org/10.29244/jtcs.4.1.1-12.
Testo completoAbstract (sommario):
Nitrogen is one of the most important nutrients required by plants as a major component of all nucleic acids and proteins such as enzymes which control and enable their growth and reproduction. While much research has been conducted on the legume tree Pongamia (a candidate source for renewable biofuel), there is only a handful of studies on the mechanisms and regulation of nitrogen fixation, which is considered as one of the most important domestication traits that needs to be investigated. Steps to optimize the symbiotic nitrogen fixation of Pongamia is, firstly, to select the best rhizobial isolates as inoculum among the naturally-occurring pool of bacteria in soils across Queensland. There have been reports on rhizobia nodulating Pongamia isolated from Western Australia and India but not in Queensland, Australia. This study is the first to report such rhizobia isolates that nodulated Pongamia. Secondly, is to establish efficient nodulation by studying the factors such as nitrate and salinity. The published literature has provided extensive details on the effects of these factors in nodulation and their mechanisms in various legumes. However, only one preliminary study was published from our laboratory; the present study is the in-depth continuation of that effort. Lastly, nitrogen fixation in Pongamia must be assessed to determine if fixed nitrogen is sufficient to support its growth and reproduction. Acetylene reduction assay is the simplest and most common method of assessing fixed nitrogen but in this research, different methods were explored in order to compare both qualitative and quantitative results. This review summarises the current knowledge related to Pongamia, rhizobia, nodulation and nitrogen fixation.
27
McCaskill, M. R., e G. A. Kearney. "Control of water leakage from below the root zone by summer-active pastures is associated with persistence, density and deep rootedness". Crop and Pasture Science 67, n. 6 (2016): 679. http://dx.doi.org/10.1071/cp15337.
Testo completoAbstract (sommario):
Temperate pastures that leak water below the root zone have been linked to an increase in dryland salinity in southern Australia through their conservative use of stored water. An experiment was conducted at Hamilton in south-western Victoria to test the hypothesis that deep-rooted, summer-active perennial pasture species can substantially reduce leakage. On topographic crests the experiment compared lucerne and chicory with a traditional perennial ryegrass variety with low summer activity, whereas on the poorly drained valleys the comparison was between tall fescue, kikuyu and a perennial ryegrass variety with high summer activity. Lucerne developed a buffer of dry soil to a depth of at least 5 m. An empirical relationship with June–September rainfall indicated that with this dry buffer, leakage below the root zone would not occur even in the wettest of years. Chicory developed a dry buffer to the depth of measurement (3 m), but plant density gradually declined and leakage started to occur 5 years after sowing. The perennial ryegrass with low summer activity had leakage nearly every year. On the valleys kikuyu was initially the most effective at drying the soil in summer, but its density declined at the expense of annuals and 3 years after sowing it became wetter than the other treatments. None of the pasture options on the valley fully controlled leakage, but both the summer-active perennial ryegrass and tall fescue were persistent and there was little difference in their capacity to extract summer moisture. This study showed that four characteristics were associated with a pasture that controlled leakage – summer activity, persistence, adequate density and deep rootedness. Of the species tested only lucerne satisfied all these criteria.
28
Clarke, C. J., R. J. George, R. W. Bell e R. J. Hobbs. "Major faults and the development of dryland salinity in the western wheatbelt of Western Australia". Hydrology and Earth System Sciences 2, n. 1 (31 marzo 1998): 77–91. http://dx.doi.org/10.5194/hess-2-77-1998.
Testo completoAbstract (sommario):
Abstract. Dryland salinity poses a major threat to agricultural production in the wheatbelt of Western Australia and much time and effort is expended on understanding the mechanisms which cause it and on developing techniques to halt or reverse its development. Whilst the location of much dryland salinity can be explained by its topographic position, a significant proportion of it cannot. This study investigated the hypothesis that major faults in the Yilgarn Craton represented in aeromagnetic data by intense curvilinear lows explained the location of areas of dryland salinity not explained by topography. Moreover, the causal mechanisms that might underpin a spatial relationship between major faults and dryland salinity were sought. In one fourth order catchment, nearly 85% of the salinity that was not explained topographically was within 2km of the centre line of a major fault, the remaining 15% being in the other 12km of the catchment. Three groups of similar third order catchments in the western wheatbelt of Western Australia were also investigated; in each case the catchment that was underlain by a major fault had dryland salinity an order of magnitude more than the unfaulted catchment(s). This evidence demonstrates a strong spatial association between major faults and the development of dryland salinity. Other evidence suggests that the underlying mechanism is hydraulic conductivity 5.2 to 2.9 times higher inside the fault zone compared to outside it and shows that geomorphology, salt store, regolith thickness, and degree of clearing are not the underlying mechanisms. In one of the groups of catchments, it has been calculated that an amount of recharge, significant in relation to recharge from rainfall, was entering from an adjacent catchment along a major fault. The paper concludes that geological features such as major faults affect the development of dryland salinity in the wheatbelt of Western Australia because of permeability differences in the regolith and therefore computer models of salinity risk need to take these differences into account. Techniques need to be developed to map, quickly and relatively cheaply, the geology-related permeability differences over wide areas of the landscape.
29
Taylor, R. J., e G. Hoxley. "Dryland salinity in Western Australia: managing a changing water cycle". Water Science and Technology 47, n. 7-8 (1 aprile 2003): 201–7. http://dx.doi.org/10.2166/wst.2003.0690.
Testo completoAbstract (sommario):
Clearing of agricultural land has resulted in significant changes to the surface and groundwater hydrology. Currently about 10% of agricultural land in Western Australia is affected by dryland salinity and between a quarter and a third of the area is predicted to be lost to salinity before a new hydrological equilibrium is reached. This paper develops a general statement describing the changes to the surface and groundwater hydrology of the wheatbelt of Western Australia between preclearing, the year 2000 and into the future. For typical catchments in the wheatbelt it is estimated that average groundwater recharge and surface runoff have increased about tenfold when comparing the current hydrology to that preclearing. Saline groundwater discharge and flood volumes have also increased significantly. Saline groundwater discharge and associated salt load will probably double in the future in line with the predicted increase in the area of dryland salinity. In addition, future increases in the area of dryland salinity/permanent waterlogging will probably double the volumes in flood events and further increase surface runoff in average years. The outcomes of surface and groundwater management trials have been briefly described to estimate how the hydrology would be modified if the trials were implemented at a catchment scale. These results have been used to formulate possible integrated revegetation and drainage management strategies. The future hydrology and impacts with and without integrated management strategies have been compared.
30
Wilkes, Paul, Brett Harris e Anton Kepic. "Geoscience, Water and Salinity in Rural Towns of Western Australia". ASEG Extended Abstracts 2007, n. 1 (1 dicembre 2007): 1. http://dx.doi.org/10.1071/aseg2007ab161.
Testo completo
31
Pannell, David J., Donald J. McFarlane e Ruhi Ferdowsian. "Rethinking the externality issue for dryland salinity in Western Australia". Australian Journal of Agricultural and Resource Economics 45, n. 3 (settembre 2001): 459–75. http://dx.doi.org/10.1111/1467-8489.00152.
Testo completo
32
Schofield, N. J. "Tree planting for dryland salinity control in Australia". Agroforestry Systems 20, n. 1-2 (novembre 1992): 1–23. http://dx.doi.org/10.1007/bf00055303.
Testo completo
33
Halse, SA, MR Williams, RP Jaensch e JAK Lane. "Wetland characteristics and waterbird use of wetlands in south-western Australia". Wildlife Research 20, n. 1 (1993): 103. http://dx.doi.org/10.1071/wr9930103.
Testo completoAbstract (sommario):
The presence or absence of 61 waterbird species on 95 wetlands in south-western Australia was related to six wetland characteristics: salinity, emergent vegetation, water depth, pH, phosphorus level and wetland size. More species were associated with salinity and vegetation than with other wetland characteristics. There were more positive associations with brackish than with fresh or saline wetlands and few species occurred in hypersaline wetlands. Trees or shrubs and sedges were the vegetation with which most species were associated; few species were recorded on completely open wetlands or those with only samphire. The 95 wetlands were classified into five groups on the basis of waterbird use. All wetland characteristics differed between groups but larger differences occurred in salinity, vegetation and water depth. The wetland group that supported most species also supported the highest numbers of waterbirds and most breeding species.
34
Kimmerer, WJ, AD McKinnon, MJ Atkinson e JA Kessell. "Spatial distributions of plankton in Shark Bay, Western Australia". Marine and Freshwater Research 36, n. 3 (1985): 421. http://dx.doi.org/10.1071/mf9850421.
Testo completoAbstract (sommario):
The zooplankton of Shark Bay, Western Australia, shows an unusual pattern of abundance, with an initial increase from the ocean to the central bay, and a decrease of four orders of magnitude into the hypersaline region. The daytime zooplankton abundance in Hamelin Pool, at a salinity of >60 mg 1-1, is of a similar magnitude to that of the deep sea, and 100-fold below typical surface oceanic values. Night abundances are higher, but still well below surface oceanic values. The diverse oceanic community of net phytoplankton and zooplankton is replaced at intermediate salinities by a less diverse bay community, dominated by diatoms and several small copepods. At high salinities, the phytoplankton are mostly dinoflagellates and the zooplankton are mainly demersal forms. The abundance patterns for individual species can be attributed to intolerance of high salinity, although the pattern of total abun- dance is apparently due to extreme nutrient limitation in the hypersaline waters.
35
Kington, E. A., e D. J. Pannell. "Dryland salinity in the Upper Kent River catchment of Western Australia: farmer perceptions and practices". Australian Journal of Experimental Agriculture 43, n. 1 (2003): 19. http://dx.doi.org/10.1071/ea01058.
Testo completoAbstract (sommario):
Dryland salinity, resulting from extensive land clearing, has been increasingly recognised as a serious environmental and economic problem in Western Australia. Policy initiatives at the state and national level in Australia have attempted to influence farmers' choices of land management practices to reduce the threat of salinity. This study examines, for a particular catchment, what farmers' salinity management practices have been and are likely to be, how farmers view the salinity problem and its recommended treatments, and farmers' perceptions of why the salinity problem continues to worsen. We found that the farmers had high levels of knowledge about salinity and its treatment, although their perceptions appeared to be overly optimistic on a number of aspects of the problem. As a group they were highly uncertain about its extent and the rate of worsening, and they highlighted the complexity, modest effectiveness and relatively poor economic performance of available treatment options. It appears that the scale of salinity prevention practices in the catchment is insufficient for preventing ongoing increases in the area of saline land.
36
Barrett-Lennard, Edward G., Geoffrey C. Anderson, Karen W. Holmes e Aidan Sinnott. "High soil sodicity and alkalinity cause transient salinity in south-western Australia". Soil Research 54, n. 4 (2016): 407. http://dx.doi.org/10.1071/sr15052.
Testo completoAbstract (sommario):
Transient salinity associated with increased dispersion of clays is arguably one of the most economically important soil constraints in Australia because it occurs on land that is regularly cropped. However, this issue is rarely studied. This paper examines the occurrence of transient salinity on agricultural land in the south-west of Western Australia and the factors causing it. We analysed four soil datasets from the region, collected at scales varying from the entire south-west to a single paddock. A variety of soil parameters were correlated with increased electrical conductivity (EC1:5). The most significant relationships were invariably with measures of exchangeable sodium (Na+; 53–85% of variance accounted for), and this factor appears to be most responsible for transient salinity. Another parameter correlated with increased EC1:5 was alkalinity. This has been associated with the increased dispersion of kaolinite and consequent decreases in soil hydraulic conductivity; kaolinite is the most common clay mineral in the south-west of Western Australia. Other factors correlated with increased EC1:5 were increasing clay, increasing depth in the soil profile and decreasing rainfall. These factors are environmental indicators of transient salinity. Affected soils might be ameliorated by application of agents to increase soil hydraulic conductivity, such as gypsum and/or elemental sulfur.
37
Cresswell, GR, e JL Peterson. "The Leeuwin Current south of Western Australia". Marine and Freshwater Research 44, n. 2 (1993): 285. http://dx.doi.org/10.1071/mf9930285.
Testo completoAbstract (sommario):
Satellite images as well as data collected in situ were used to follow the seasonal changes of the Leeuwin Current south of Western Australia (WA) in 1986-87. The current has two major sources: salty subtropical water from west of WA, and fresher tropical water from north of WA. In summer, the tropical waters are excluded by the strong equatorward wind stress. In autumn and winter, this wind stress is reduced and tropical waters flood southward to dominate the flow. Nevertheless, salty subtropical water is entrained en route, and so, whatever the season, the Leeuwin Current is more saline than the 'local' subantarctic waters off southern WA. From a research vessel, observations were made on the current and one of its offshoots in June 1987. The Leeuwin Current had a maximum surface speed of more than 1 m s-1 just beyond the shelf edge. Its warm, low-salinity surface core rode on a sheath of higher-salinity subtropical water that it had entrained upstream. The first survey of the offshoot showed it to be 50 km across and 130 m deep (for water warmer than 17�C), and it extended 200 km seaward (as deduced from a satellite image). Velocities in the offshoot ranged up to 1 m s-1 southward and 1 m s-1 north-eastward on the western and eastern sides, respectively. Richardson numbers were, in places, as low as 0.25. On a second survey two days later, the offshoot was found to have pinched off and the remnant bulge on the edge of the parent stream to have moved 30 km eastward. The flow around this bulge reached 1.6 m s-'. The offshoot/bulge was possibly first formed in April, and it kept its identity at least until August. During this time, it moved eastward at speeds between 2 and 15 km day-1. In June, the offshoot was estimated to contain water equivalent to five days' transport of the parent current.
38
Pepper, R. G., e G. F. Craig. "Resistance of Selected Eucalptys Species to Soil Salinity in Western Australia". Journal of Applied Ecology 23, n. 3 (dicembre 1986): 977. http://dx.doi.org/10.2307/2403949.
Testo completo
39
Beresford, Quentin, Harry Phillips e Hugo Bekle. "The Salinity Crisis in Western Australia: A Case of Policy Paralysis". Australian Journal of Public Administration 60, n. 4 (dicembre 2001): 30–38. http://dx.doi.org/10.1111/1467-8500.00239.
Testo completo
40
George, Richard, Don McFarlane e Bob Nulsen. "Salinity Threatens the Viability of Agriculture and Ecosystems in Western Australia". Hydrogeology Journal 5, n. 1 (gennaio 1997): 6–21. http://dx.doi.org/10.1007/s100400050103.
Testo completo
41
Schofield, NJ. "Predicting the effects of land disturbances on stream salinity in southwest Western Australia". Soil Research 26, n. 2 (1988): 425. http://dx.doi.org/10.1071/sr9880425.
Testo completoAbstract (sommario):
A model developed by A. J. Peck to predict the effects of land disturbances on stream salinity has been extended to take account of increased stream runoff, and applied to the jarrah forest region with improved parameter estimates. Validation on Wights experimental catchment suggests that the model is capable of reliable predictions in the case of agricultural clearing. However, the extended model did not provide discernibly better predictions than the original model. When applied to rainfall zones of the northern jarrah forest of W.A., the model predicted that agricultural clearing would result in average stream salinity increases of -70 mg 1 for the high rainfall zone (> 1100 mm yr-1), of -270 mg L-1 for the intermediate rainfall zone (900-1100 mm yr-1), and of ~3400 mg L-1 for the low rainfall zone (<900 mm yr-1). In the case of bauxite mining followed by reforestation, the model was limited to consideration of long-term effects, and neglected transient effects. Predicted stream salinity increases were considerably smaller than for agricultural clearing, primarily because mining involves clearing smaller areas, and these areas are reforested. The model is sensitive to variations in parameter values which implies that a wide range of stream salinity increases could occur within any one rainfall zone, due to the variation of local conditions.
42
Paling, EI, AJ McComb e JS Pate. "Nitrogen fixation (acetylene reduction) in nonheterocystous cyanobacterial mats from the Dampier Archipelago, Western Australia". Marine and Freshwater Research 40, n. 2 (1989): 147. http://dx.doi.org/10.1071/mf9890147.
Testo completoAbstract (sommario):
Discs punched from non-heterocystous cyanobacterial mats, one containing Microcoleus chthonoplastes, Oscillatoria sp. and Phormidium sp., the other Phorrnidium sp. and Aphanocapsa sp., were incubated for 23 days in artificial sea-water of salinity 0 to 140 g L-1. The chlorophyll a content of both mats increased over this salinity range, with lower increases above 100 g L-1. There was little change in the species composition of mats at salinities 240 g L-1; ≥ 40 g L-1, mats produced essentially monospecific thalli containing small quantities of the other species. Acetylene reduction ranged from zero at the highest salinity to a maximum of 1100-1500 pmol C2H2 reduced m-2 h-1 at 20-60 g L-1. Maximum fixation rates were two orders of magnitude higher than in situ measurements (8-60, mean 16 pmol C2H2 reduced m-2 h-1). The salinity range observed in the field was 40-60 g L-1, but maximum fixation rates in the field (60 Fmol C2H2 reduced m-2 h-1) were much lower than those observed in the laboratory.
43
Musk, A. W., R. Shean, N. Walker e M. Swanson. "Progress on smoking control in Western Australia". BMJ 308, n. 6925 (5 febbraio 1994): 395–98. http://dx.doi.org/10.1136/bmj.308.6925.395.
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44
Musk, A. W., R. Shean e S. Woodward. "Legislation for smoking control in Western Australia." BMJ 290, n. 6481 (25 maggio 1985): 1562–65. http://dx.doi.org/10.1136/bmj.290.6481.1562.
Testo completo
45
Lymbery, A. J., R. G. Doupé e N. E. Pettit. "Effects of salinisation on riparian plant communities in experimental catchments on the Collie River, Western Australia". Australian Journal of Botany 51, n. 6 (2003): 667. http://dx.doi.org/10.1071/bt02119.
Testo completoAbstract (sommario):
Although the salinisation of streams has long been recognised as one of Western Australia's most serious environmental and resource problems, there is very little published information on the effects of salinisation on riparian flora and fauna. We studied riparian vegetation in three experimental catchments on the Collie River in Western Australia. The catchments are situated within a 5-km area of state forest and are geologically and botanically similar, but differ in the extent of clearing, groundwater levels and stream salinity. In each catchment, transects were taken perpendicular to the direction of streamflow, and 4-m2 quadrats taken along each transect. Within each quadrat, soil salinity was measured, all plants were identified to species level and percentage cover estimated. The catchments differed significantly in soil salinity, with salinity being greatest in the most extensively cleared catchment and increasing towards the floor of the valley. Plant-species richness, species diversity and species composition were significantly related to soil salinity, both among catchments and among quadrats within the most extensively cleared catchment. Plant-species richness and diversity decreased with increasing soil salinity, an effect that may be partly due to a decline in perennial herb and shrub species. This may have an impact on other components of the riparian ecosystem.
46
Furby, Suzanne, Peter Caccetta e Jeremy Wallace. "Salinity Monitoring in Western Australia using Remotely Sensed and Other Spatial Data". Journal of Environmental Quality 39, n. 1 (gennaio 2010): 16–25. http://dx.doi.org/10.2134/jeq2009.0036.
Testo completo
47
Robertson, M. J., R. J. George, M. H. O'Connor, W. Dawes, Y. M. Oliver e G. P. Raper. "Temporal and spatial patterns of salinity in a catchment of the central wheatbelt of Western Australia". Soil Research 48, n. 4 (2010): 326. http://dx.doi.org/10.1071/sr09126.
Testo completoAbstract (sommario):
Many estimates have been made of the future likely extent of salinity at regional and national scales in Australia; however, there are few detailed studies of changes in temporal and spatial patterns at catchment scale. This study was conducted in the Wallatin and O’Brien catchments in the low–medium rainfall zone of the central wheatbelt of Western Australia, where we examined the spatial trends in saline land over the last 18 years and related these to the likely rate and extent of future salinisation. The analysis showed that: (1) salinity has continued to expand post-1999 in landscape positions where there has been watertable rise and also in areas now at equilibrium even though rainfall has been below average; (2) increases in the area of salinity are still dominated by increases in the valley floor but there is now the emergence of many small, isolated outbreaks on the adjacent slopes; (3) widely available satellite-derived salinity maps (LandMonitor) derived in 1998 provide a reliable base-line for saline mapping but now underestimate the area of salt-affected land by 60%; (4) the trend in watertable levels and time since clearing and interactions with proximity to uncleared native vegetation provide reliable predictors of salinity risk; (5) episodic rainfall in areas of shallow watertables is proposed as a significant cause of the expansion in observed salinisation, even though some of this may be transient. These results are discussed in terms of management options for farmers and the likely long-term outlook for expansion of salinity in the catchment.
48
Dawes, W. R., M. Gilfedder, M. Stauffacher, J. Coram, S. Hajkowicz, G. R. Walker e M. Young. "Assessing the viability of recharge reduction fordryland salinity control: Wanilla, Eyre Peninsula". Soil Research 40, n. 8 (2002): 1407. http://dx.doi.org/10.1071/sr01044.
Testo completoAbstract (sommario):
The emerging paradigm to manage the spread of dryland salinity is the manipulation of farming practice to provide both a reduction in recharge and a commercial return to farm enterprises. Recent work has attempted to classify the groundwater systems across Australia into distinct provinces, with the implication that the flow processes, and therefore remediation strategies, of catchments within each province are similar. This paper presents a case study of the Wanilla catchment on the Eyre Peninsula in South Australia. This catchment is in the groundwater province that includes 60% of the dryland salinity expression in Australia. The results of conceptual and numerical modelling of the catchment suggest that the land management for reduced recharge paradigm may be less effective in this groundwater province than in others. The scale of expression and salinity history of such catchments provides further impediments to management options aimed at controlling or reversing existing dryland salinity.
49
Clarke, C. J., R. J. George, R. W. Bell e T. J. Hatton. "Dryland salinity in south-western Australia: its origins, remedies, and future research directions". Soil Research 40, n. 1 (2002): 93. http://dx.doi.org/10.1071/sr01028.
Testo completoAbstract (sommario):
Replacement of deep-rooted, perennial native vegetation with shallow-rooted, annual agricultural plants has resulted in increased recharge causing shallow saline water tables leading to dryland salinity and loss of agricultural production. Restoring the vegetation by regeneration or replanting lowers water levels locally but field evidence and computer modelling suggests this needs to be widespread for regional effects, which conflicts with the future of conventional agriculture. Alley farming allows agriculture to be continued in the bays between the rows, but needs as much perennial, preferably deep-rooted, vegetation as possible in the bays to achieve the required recharge reductions. Where the asset to be preserved is valuable and a means of safe saline effluent disposal exists, pumps and drains will be part of any salinity management system, but where these conditions are not met they will be of limited use on an economic basis. To limit the spread of dryland salinity substantial change in farming systems is required and farmers need assurance that the recommended strategies will have the desired effect. Computer modelling is the only timely way to do this. An operationally simple 1-dimensional model already exists, and a 2-dimensional one is under development and testing. Three-dimensional modelling is also probably required to support strategic, intensive interventions. computer modelling, revegetation, engineering, perennial.
50
Halse, S. A., J. K. Ruprecht e A. M. Pinder. "Salinisation and prospects for biodiversity in rivers and wetlands of south-west Western Australia". Australian Journal of Botany 51, n. 6 (2003): 673. http://dx.doi.org/10.1071/bt02113.
Testo completoAbstract (sommario):
Saline water was common in south-west Western Australian aquatic systems prior to land-clearing because most streams and wetlands were ephemeral and evapo-concentrated as they dried, and there were high concentrations of stored salt in groundwater and soil profiles. Nevertheless, a 1998 review of salinity trends in rivers of south-west Western Australia showed that 20-fold increases in salinity concentrations had occurred since clearing in the medium-rainfall zone (300–700 mm). More recent data confirm these trends and show that elevated salinities have already caused substantial changes to the biological communities of aquatic ecosystems. Further substantial changes will occur, despite the flora and fauna of the south-west being comparatively well adapted to the presence of salinity in the landscape. Up to one-third of wetland and river invertebrate species, large numbers of plants and a substantial proportion of the waterbird fauna will disappear from the wheatbelt, a region that has high biodiversity value and endemism. Increased salinities are not the only threat associated with salinisation: increased water volumes, longer periods of inundation and more widespread acidity are also likely to be detrimental to the biota.