Soil and Land Systems
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The Soil and Land Systems discipline was part of the School of Earth and Environmental Sciences until 2013. Since then Soil Science has become part of the School of Agriculture, Food and Wine.
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Item Open Access 3D-visualization and analysis of macro- and meso-porosity of the upper horizons of a sodic, texture-contrast soil(Blackwell Publishing Ltd, 2007) Jassogne, L.; McNeill, A.; Chittleborough, D.The lower E and upper B horizons of sodic, texture-contrast soils are a formidable barrier to most annual and many perennial crops. The research presented here is part of a wider study into the nature of subsoil constraints to root exploration. The aim of this study was to characterize in three dimensions the macro- and meso-porosity across the E horizon–Btn horizon interface of a sodic, texture-contrast soil using X-ray computed tomography (CT). Intact soil cores of 50-cm length and 15-cm diameter were scanned with a medical CT X-ray machine. The pore volume reconstructed from these scans had a resolution of 0.3 × 0.3 × 0.4 cm (in the x, y, z dimensions, respectively). This resolution allowed visualization and quantification of the macroporosity of the intact cores. Undisturbed samples of 1.5-cm diameter and 4-cm length were carefully excised from the interface and scanned with micro-CT X-ray equipment. The reconstructed pore volumes had an isotropic resolution of 19 μm that allowed analysis of the mesoporosity just on the boundary between the E and Btn horizons. Mesoporosity decreased across the interface and increased lower in the Btn horizon. The distribution of the pores at the macro- and meso-scales showed the importance of the smaller pores in the A and E horizons, whereas most of the porosity in the Btn horizon was attributed to the larger pores. Pores in this sodic, texture-contrast soil were not distributed homogeneously at either the macro- or meso-scale. A greater proportion of the pores in the E–B interface were horizontal than in the upper A1, upper E and lower Btn horizons. Some ‘coiling’ of the pores was also apparent in the interface. The shape of some pores (long tubular pores) suggested formation by roots as they drilled through the soil. The orientation of these pores was a function of physical (and possibly chemical) impedance at the interface.Item Metadata only A model linking organic matter decomposition, chemistry and aggregate dynamics(CRC Press, 1998) Golchin, A.; Baldock, J.; Oades, J.; Lal, R.; Kimble, J.M.; Follett, R.F.; Stewart, B.A.The interaction of organic materials with mineral particles is a fundamental process in the surface horizons of most soils. Organo-mineral interactions not only influence the dynamics of soil organic matter (Oades, 1988; Amato and Ladd, 1992; Golchin et al., 1995a; Oades, 1995; Chenu et al., 1996), but also contribute to the formation and stabilization of soil aggregates (Tisdall and Oades, 1982; Oades, 1993). Interactions between small organic molecules and clay surfaces have been described and reviewed at length (Mortland, 1970; Theng, 1974) and interactions of organic polymers with clays are reasonably well understood (Theng, 1979; 1982). Interaction of particulate organic matter (POM) with mineral particles, however, has received less attention and the turnover, composition, and distribution of POM within the soil matrix are not well known. In classical fractionation schemes, SOM has been extracted from soils using alkaline solutions and the unextractable fraction or humin, which includes POM, has not been studied extensively. In this chapter we will focus on the interaction of POM with mineral particles and consider the role of POM in the formation of aggregates of different sizes. We present a conceptual model describing the involvement of POM and microbial metabolites derived from its decomposition in soil aggregation. The importance of biological processes associated with the decomposition of POM and the associated chemical changes will be identified and discussed with respect to their involvement in the proposed model of aggregation. The conceptual model, which is based on our previous works and selected literature results, may be applied generally to soils where organic matter is an important agent responsible for binding soil mineral particles together creating an aggregate hierarchy (Oades and Waters, 1991; Oades, 1993). In the model, we proposed the existence of three levels of aggregation (< 20 µm, 20-250 µm, and > 250 µm) in which the mechanisms of stabilization differ.Item Metadata only A mutant in Lycopersicon esculentum Mill. with highly reduced VA mycorrhizal colonization: isolation and preliminary characterisation(Blackwell Science, 1998) Barker, S.; Stummer, B.; Gao, L.; Dispain, I.; O'Connor, P.; Smith, S.This paper reports the successful isolation and preliminary characterisation of a mutant ofLycopersicon esculentumMill. with highly reduced vesicular-arbuscular (VA) mycorrhizal colonization. The mutation is recessive and has been designatedrmc. Colonization byG. mosseaeis characterised by poor development of external mycelium and a few abnormal appressoria. Vesicles were never formed by this fungus in association with the mutant.Gi. margaritaformed large amounts of external mycelium, complex branched structures and occasional auxiliary cells. Small amounts of internal colonization also occurred. Laser scanning confocal microscopy (LSCM) gave a clear picture of the differences in development ofG. intraradicesandGi. margaritain mutant and wild-type roots and confirmed that the fungus is restricted to the root surface of the mutants. The amenability of tomato for molecular genetic characterisation should enable us to map and clone the mutated gene, and thus identify one of the biochemical bases for inability to establish a normal mycorrhizal symbiosis. The mutant represents a key advance in molecular research on VA mycorrhizal symbiosis.Item Metadata only A new procedure to determine soil water availability(C S I R O Publishing, 2001) Groenevelt, P.; Grant, C.; Semetsa, S.The integral water capacity is first introduced as a flexible method to quantify various soil physical limitations when calculating available water in non-swelling soils. ‘Weighting’ functions that account for hydraulic conductivity, aeration, and soil resistance to penetration are applied to the wet and dry ends of the differential water capacity, and then integration is performed. The concept is extended to swelling soils by applying the theory of Groenevelt and Bolt (1972), which enables overburden pressures to be taken into account. A set of shrinkage lines measured by Talsma (1977) is analysed using this theory, which enables precise values of overburden potentials to be calculated as a function of the moisture ratio for different load pressures. The addition of the overburden potential to the unloaded matric potential causes minor shifts in the classical limits of plant-available water (viz. –1/3 bar and –15 bar). However, when other soil physical restrictions are taken into account (such as in the concept of the least limiting water range), the consequence for available water deeper in the root-zone (due to an overburden pressure) is far more serious. This is primarily because the matric potential at which aeration begins to be satisfied shifts to a considerably lower value, making a large quantity of water at the wet end no longer available. Examples of weighting functions derived from the literature are applied and their implications for available water in swelling soils are discussed.Item Metadata only A simplified incubation method using chip-trays as incubation vessels to identify sulphidic materials in acid sulphate soils(C A B International, 2012) Creeper, N.; Fitzpatrick, R.; Shand, P.Acid sulphate soils (ASS) can pose a significant hazard to natural ecosystems and developed areas situated within ASS landscapes. Management techniques used to minimize these hazards rely on methods that can classify ASS materials. These methods have traditionally required complex and time-consuming techniques. A new simplified incubation method, modified from existing ones, was therefore developed to classify ASS materials in a timely manner. The simplified incubation method was found to be a viable alternative where samples cannot be incubated to a stable pH because of logistical or time constraints, but where there is still a need to classify slowly acidifying sulphidic materials. The use of chip-trays as incubation vessels was also examined. Chip-trays offer many advantages in terms of transport, storage and analysis of soil samples compared with soil-slabs. This study establishes an acceptable level of precision (x ± 0.1 pH units with 95% confidence) for pH measurements in the incubation method and confirms that an acceptable level of precision is obtainable when using chiptrays in the pH incubation method.Item Metadata only A solid state 13C-NMR study of kerogen degradation during black shale weathering(Pergamon-Elsevier Science Ltd, 2001) Petsch, S.; Smernik, R.; Eglinton, T.; Oades, J.Solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy is used to examine kerogen composition in weathering profiles of the Monterey, Green River, Woodford, and New Albany formations. Techniques include cross polarization (CP) and Bloch decay (BD) spectral acquisition, dipolar dephasing (DD), spin counting, experiments to provide estimates of relaxation times (T₁ρH and T₁H), and proton spin relaxation editing (PSRE). It is demonstrated that CP/MAS (cross polarization/magic angle spinning) spectra obtained on isolated kerogens provide reliable characterization of kerogen composition (compared with BD spectra and whole-rock samples). Highly aliphatic (polymethylenic) kerogens are not appreciably altered during weathering. Aromatic and/or branched aliphatic kerogens accumulate oxidation products and preferentially lose aliphatic relative to aromatic carbon during weathering. No relation is observed between T₁ρH times and either kerogen composition or degree of weathering; T₁H times correlate with aromaticity. Two distinct components within kerogens are discerned by PSRE: one highly aliphatic (largely polymethylenic) component and one mixed aliphatic/aromatic component. During weathering, the highly aliphatic component remains largely unaltered, while the mixed component loses aliphatic carbon and accumulates carbonyl oxidation products. Thus it appears that kerogen weathering is dominated by two separate processes: Linear alkyl fragments are cleaved without oxidation, and aromatic/branched alkyl fragments are oxidized while attached to the kerogen macromolecule and then cleaved.Item Metadata only Acid drainage at mine sites(Geological Society of Australia, 2001) Taylor, G. F.; School of Earth and Environmental Sciences : Soil and Land SystemsItem Metadata only Adaptive agents simulation of freshwater ecosystems(THE MODELLING & SIMULATION SOCIETY OF AUSTRALIA & NEW ZEALAND, 2001) Recknagel, F.; International Congress on Modelling and Simulation (14th : 2001 : Canberra, A.C.T.); Ghassemi, F.; White, D.; Caddy, S.; Nakanishi, T.Item Metadata only Aggregation of soil by fungal hyphae(CSIRO PUBLISHING, 1997) Tisdall, J.; Smith, S.; Rengasamy, P.Several authors have proposed that soils are made up of aggregates of various sizes, stabilised by different organic and inorganic materials. Fungal hyphae have been shown to bind microaggregates (<250 µm diameter) into macroaggregates (>250 µm diameter). This paper examines the aggregation of soil clay by saprophytic (Rhizoctonia solani and Hyalodendron sp.) and mycorrhizal (Hymenoscyphus ericae and Hebeloma sp.) fungi. The results support the hypothesis that fungal hyphae bring mineral particles and organic materials together to form stable microaggregates at least <2µm, and enmesh microaggregates into stable aggregates >50 µm diameter.Item Open Access Allocating water and maintaining springs in the Great Artesian Basin. Volume IV. Spatial survey and remote sensing of artesian springs of the western Great Artesian Basin(National Water Commission, 2013) Lewis, M.; White, D.; Gotch, T.; Environment InstituteItem Metadata only Allocation of carbon to shoots, roots, soil and rhizosphere respiration by barrel medic (Medicago truncatula) before and after defoliation(Kluwer Academic Publ, 2000) Crawford, M.; Grace, P.; Oades, J.Item Metadata only Aluminium speciation and phytotoxicity in alkaline soils(Kluwer Academic Publ, 2012) Brautigan, D.; Rengasamy, P.; Chittleborough, D.AIM Highly alkaline soils (pH > 9.0) may adversely affect agricultural crop productivity. Problems encountered include poor structure and nutrient deficiency. Research based on solution cultures suggests that aluminium (Al) phytotoxicity may occur in soils with pH > 9.0, but little research has been undertaken on actual soils under controlled conditions. The nature of the Al species responsible and the pH regime of the soils when this occurs are unknown. METHODS The charge and species of Al responsible for this toxicity was investigated using Zeta Potential measurement, Nuclear Magnetic Resonance (NMR) spectroscopy, Al precipitation characteristics and electrical conductivity as a function of pH. An anion exchange resin was used to evaluate Al availability to plants at alkaline pH. To verify Al phytotoxicity, a pot experiment was performed with plants grown at near neutral and high pH, with and without Al. RESULTS The anionic aluminate species of aluminium was ubiquitous at highly alkaline pH, and was the dominant charged species at pH 9.2. Aluminium was phytotoxic at high pH, significantly reducing the stem and root development of field pea test plants over and above that caused by alkalinity alone. The effects of both alkalinity in general and aluminium in particular became noticeable at pH 9.0 and debilitating at pH > 9.2. CONCLUSION As this corresponds to the pH where aluminate becomes dominant, it is probably responsible for the phytotoxicity.Item Metadata only Amelioration of water repellency: application of slow-release fertilisers to stimulate microbial breakdown of waxes(Elsevier Science BV, 2000) Franco, C.; Michelsen, P.; Oades, J.Item Metadata only An algorithm to model mass balances quantitatively(PERGAMON-ELSEVIER SCIENCE LTD, 1998) Biddle, D.; Chittleborough, D.; Fitzpatrick, R.FLUX is an ANSI standard FORTRAN-77 numerical model for calculating physical and chemical changes resulting from the alteration of rock under Earth surface conditions. Long-term losses or gains of elements can be approximated from basic analytical data for the concentration of major elements and a stable constituent (e.g. Zr) contained in both soil and the parent material from which the soil was derived. Assumptions necessary to apply pedogenic formulae, techniques for assessing parent material uniformity and the method of choosing a stable constituent are discussed. Application of the numerical code is demonstrated using data for an Aqualf derived from weathering in an albite-muscovite-quartz gneiss system. The FLUX program offers a rapid technique, free of random errors for the assessment of element mobility. © 1998 Elsevier Science Ltd. All rights reserved.Item Metadata only An analysis of the fragmentation of remoulded soils with regard to self-mulching behaviour(CSIRO, 1995) Grant, C.; Watts, C.; Dexter, A.; Frahn, B.A power-law relation was used to analyse the (mass-derived) number-size distributions of fragments generated by wetting and drying remoulded soils. Various soils from Europe and Australia produced a range of values for the two fragmentation coefficients, d and k, generated by the power-law function. Both coefficients had physical significance with respect to self-mulching behaviour. Likened to a fractal dimension, the d coefficient varied directly with the tendency of the remoulded soil to fragment during wetting and drying. Assessment of the number of generated fragments >1 cm was made with the k coefficient. Consideration of both coefficients together in a plot of k v. d enabled similar soils to be grouped and falsely large values of d to be identified; k values were small for limited fragmentations even if the size distribution of the fragments that were produced gave large values of d. Most strongly self-mulching soils produced d values >1 . 5 after three wet/dry cycles, and k values that increased sharply after one cycle and declined with subsequent wetting and drying. Other soils with lesser abilities to self-mulch generally produced smaller d values and more variable k values. Reasonable correlations were found between these two coefficients and other measurements of self-mulching behaviour, particularly after three cycles of wetting/drying. Examination of the aggregate size distributions produced from remoulded soils in this way offers the potential to understand more clearly the dynamics of structure regeneration in soils exhibiting various degrees of self-mulching behaviour.Item Metadata only An Image-Based Diversity Index For Assessing Land Degradation in an Arid Environment in South Australia(ARSPC, 2006) Jafari, R.; Lewis, M.; Ostendorf, B.; The Australasian Remote Sensing and Photogrammetry Conference (20 Nov 2007 : Canberra, Australia)One of the major indirect effects of artificial watering points in a grazed landscape is the development around them of a zone of extreme degradation called a piosphere. To investigate the degradation status of such zone in an arid environment in South Australia, the Moving Standard Deviation Index (MSDI) was applied to Landsat TM band 3 data. We found that watering points had significantly higher MSDI values (p <0.001) than reference areas (non-degraded areas. The results of two vegetation indices, the Normalized Difference Vegetation Index (NDVI) and Perpendicular Distances vegetation index (PD54), which were used as reference indices showed that The PD54 was more appropriate than NDVI in this arid environment. Piospheres were found to be more heterogeneous (high MSDI values) than non-degraded areas and heterogeneity decreased by increasing distance from water points. This study confirms that MSDI can be used as an appropriate adjunct to PD54 for land degradation assessment in arid rangelands of South Australia, which are naturally heterogeneous.Item Metadata only An improved thermal oxidation method for the quantification of soot/graphitic black carbon in sediments and soils(Amer Chemical Soc, 2001) Gelinas, Y.; Prentice, K.; Baldock, J.; Hedges, J.Item Metadata only An inductive approach to ecological time series modelling by evolutionary computation(Elsevier Science BV, 2001) Wigham, P.; Recknagel, F.Building time series models for ecological systems that can be physically interpreted is important both for understanding the dynamics of these natural systems and the development of decision support systems. This work describes the application of an evolutionary computation framework for the discovery of predictive equations and rules for phytoplankton abundance in freshwater lakes from time series data. The suggested framework evolves several different equations and rules, based on limnological and climate variables. The results demonstrate that non-linear processes in natural systems may be successfully modelled through the use of evolutionary computation techniques. Further, it shows that a grammar based genetic programming system may be used as a tool for exploring the driving processes underlying freshwater system dynamics. © 2001 Elsevier Science B.V. All rights reserved.Item Metadata only An interdisciplinary approach for evaluation of temporal-spatial heterogeneity of colour distribution and canopy development on an alpine test site(Blackwell Publishers Inc, 2002) Tasser, E.; Walde, J.; Ostendorf, B.; Schmid, P.; Tappeiner, U.; Bottarin, R.; Tappeiner, U.Item Metadata only An overview of processes affecting the cycling of organic carbon in soils(John Wiley, 1995) Oades, J.