Dissertations / Theses on the topic 'Soil structure South Australia'

Plantations provide a range of benefits, including the potential to ameliorate salinity and soil erosion, enhance biodiversity, and provide timber and wood chips. They are increasingly important because of their role in carbon sequestration (Adolphson, 2000; Anonymous, 2005; Jones et al. , 2005; Kozlowski, 2002; Paul and Polglase, 2004). Recent research has highlighted the connection between plantation health and soil fertility (Johnston and Crossley Jr, 2002). Within an Australian context there is little published data on the composition of the soil and litter fauna and their contribution to litter decomposition under plantation systems (Adolphson, 2000). The Albany Effluent Irrigated Tree Farm provided an opportunity to research plantation (Eucalyptus globulus ) soil flora and fauna communities, rates of litter decomposition and to describe the impact of irrigation (both mains-water and effluent) on these communities.

The overall objective of this study was to evaluate the performance of selected furrow irrigation models for field conditions in south-east Australia. The other important aspects which were examined during this study include: developing a methodology for estimating of infiltrating characteristics, assessing the applicability of the Manning and other similar equations for flows in furrow irrigation, investigating the variation of shape factor during irrigation developing methodology for estimation of recession time and exploring the sensitivity of the models to the input parameters. Field experiments were conducted at Walla Park in northern N.S.W. and on two selected paddocks at the University Farm, Richmond, in western Sydney,Australia, over a period of three years. The validity of the assumption that the shape factor of advancing water front during furrow irrigation varies between 0.7 and 0.8 was investigated using field data collected from irrigation events monitored in the study. It was found that the average values of the shape factor varied from 0.96 to 1.80 at Walla Park site, from 0.56 to 0.80 at Field Services unit paddock site and from 0.78 to 0.84 at Horticulture Farm paddock site. The value of shape factor was affected by uniformity of furrow cross section along the length, the value and uniformity of furrow slope, furrow length and infiltration characteristics of soil. This means it is difficult to recommend a typical value for the shape factor for a given field situation.The performance of the models for prediction of advance and recession characteristics and runoff were evaluated using different indices of performance. In general, it was found that the Walker-HD and ZI model was the most satisfactory for the field conditions encountered in this study. This finding can provide a basis for initiating work on developing design criteria and management strategies for furrow irrigation in south-east Australia.
Doctor of Philosophy (PhD)

Thesis (Ph. D.)--University of Adelaide, Dept. of Botany, 1997.
Errata page is behind title page (p. i). Copies of author's previously published articles inserted. Includes bibliographical references (leaves 121-156).

The annual production of biosolids in the Perth region during the period of this study was approximately 13,800 t dry solids (DS), being supplied by three major wastewater treatment plants. Of this, 70% was typically used as a low-grade fertiliser in agriculture, representing an annual land use area of around 1,600 ha when spread between 5 and 7 t DS/ha. Loading rates of biosolids are typically based on the nitrogen (N) requirements of the crop to be grown, referred to as the N Limiting Biosolids Application Rate (NLBAR). A consequence of using the NLBAR to calculate loading rates is that phosphorus (P) is typically in excess of plant requirement. The resultant high loading rates of P are considered in the guidelines developed for the agricultural use of biosolids in Western Australia, but lack research data specific to local conditions and soil types. Regulatory changes throughout Australia and globally to protect the environment from wastewater pollution have created a need for more accountable and balanced nutrient data. Experiments presented in this thesis were undertaken to ascertain: the percentage relative effectiveness (RE) of biosolids as a source of plant available P compared with inorganic P fertiliser; loading rates to best supply P for optimum crop growth; P loading rates of risk to the environment; and the forms of P in local biosolids. Therefore, both the agronomic and environmental viewpoints were considered. Anaerobically digested and dewatered biosolids produced from Beenyup Wastewater Treatment Plant, Perth with a mean total P content of 2.97% dry weight basis (db) were used in a series of glasshouse, field and laboratory experiments. The biosolids were sequentially fractionated to identify the forms of P present and likewise in soil samples after applying biosolids or monocalcium phosphate (MCP).The biosolid P was predominantly inorganic (92%), and hence the organic fraction (8%) available for mineralisation at all times would be extremely low. The most common forms of biosolid P were water-soluble P and exchangeable inorganic P (66%), followed by bicarbonate extractable P (19%) and the remaining P as inorganic forms associated with Fe, Al and Ca (14%). Following the application of biosolids to a lateritic soil, the Fe and Al soil fractions sorbed large amounts of P, not unlike the distribution of P following the addition of MCP. Further investigation would be required to trace the cycling of biosolid P in the various soil pools. The growth response of wheat (Triticum aestivum L.) to increasing rates of biosolids and comparable rates of inorganic P as MCP, to a maximum of 150 mg P/kg soil was examined in the glasshouse. The percentage relative effectiveness (RE) of biosolids was calculated using fitted curve coefficients from the Mitscherlich equation: y = a (1-b exp–cx) for dry matter (DM) production and P uptake. The initial effectiveness of biosolid P was comparable to that of MCP with the percentage RE of biosolids averaging 106% for DM production of wheat shoots and 118% for shoot P uptake at 33 days after sowing (DAS) over three consecutive crops. The percentage residual value (RV) declined at similar rates for DM production in MCP and biosolids, decreasing to about 33% relative to freshly applied MCP in the second crop and to approximately 16% in the third crop. The effectiveness of biosolid P was reduced significantly compared with inorganic P when applied to a field site 80 km east of Perth (520 mm annual rainfall). An infertile lateritic podsolic soil, consistent with the glasshouse experiment and representative of a soil type typically used for the agricultural application of biosolids in Western Australia was used.Increasing rates of biosolids and comparable rates of triple superphosphate (TSP), to a maximum of 145 kg P/ha were applied to determine a P response curve. The percentage RE was calculated for seasonal DM production, final grain yield and P uptake in wheat followed by lupin (Lupinus angustifolius L.) rotation for the 2001 and 2002 growing seasons, respectively. In the first year of wheat, the RE for P uptake in biosolids compared with top-dressed TSP ranged from 33% to 55% over the season and by grain harvest was 67%. In the second year, and following incorporation with the disc plough at seeding, the RE for P uptake by lupins in biosolids averaged 79% over the growing season compared with top-dressed TSP, and by grain harvest the RE was 60%. The residual value (RV) of lupins at harvest in biosolids compared with freshly applied TSP was 47%. The non-uniform placement of biosolids (i.e. spatial heterogeneity) was primarily responsible for the decreased ability of plant roots to absorb P. The P was more effective where biosolids were finely dispersed throughout the soil, less so when roughly cultivated and least effective when placed on the soil surface without incorporation. The RE for grain harvest of wheat in the field decreased from 67% to 39% where biosolids were not incorporated (i.e. surface-applied). The RE could also be modified by factors such as soil moisture and N availability in the field, although it was possible to keep these variables constant in the glasshouse. Consequently, absolute values determined for the RE need to be treated judiciously. Calculations showed that typical loading rates of biosolids required to satisfy agronomic P requirements of wheat in Western Australia in the first season could vary from 0 to 8.1 t DS/ha, depending on soil factors such as the P Retention Index (PRI) and bicarbonate available P value.Loading rates of biosolids were inadequate for optimum P uptake by wheat at 5 t DS/ha (i.e. 145 kg P/ha) based on the NLBAR on high P sorbing soils with a low fertiliser history (i.e. PRI >15, Colwell bicarbonate extractable P <15 mg P/kg). On soils of PRI <2 mL/g however, biosolids applied at identical loading rates would result in high concentrations of available P. Further work on sites not P deficient would be necessary to validate these findings on farmed soils with a regular history of P fertiliser. The sieving of soil samples used in the field experiment to remove stones and coarse organic matter prior to chemical analysis inadvertently discarded biosolids particles >2 mm, and thus their was little relationship between soil bicarbonate extractable P and P uptake by plants in the field. The risk of P leaching in biosolids-amended soil was examined over a number of different soil types at comparable rates of P at 140 mg P/kg (as either biosolids or MCP) in a laboratory experiment. Given that biosolids are restricted on sites prone to water erosion, the study focussed on the movement of water-soluble P by leaching rather than by runoff of water-soluble P and particulate P. In general the percentage soluble reactive P recovered was lower in soils treated with biosolids than with MCP, as measured in leachate collected using a reverse soil leachate unit. This was particularly evident in acid washed sand with SRP measuring 14% for biosolids and 71% for MCP, respectively, although the differences were not as large in typical agricultural soils. Specific soil properties, such as the PRI, pH, organic carbon and reactive Fe content were negatively correlated to soluble reactive P in leachate and thus reduced the risk of P leaching in biosolids-amended soil.Conversely, the total P and bicarbonate extractable P status of the soils investigated were unreliable indicators as to the amount of P leached. On the basis of the experiments conducted, soils in Western Australia were categorised according to their ability to minimise P enrichment and provide P necessary for crop growth at loading rates determined by the NLBAR. Biosolids applied at the NLBAR to soils of PRI >2mL/g with reactive Fe >200 mg/kg were unlikely to necessitate P loading restrictions. Although specific to anaerobically digested biosolids cake applied to Western Australian soils, the results will be of relevance to any industry involved in the land application of biosolids, to prevent P contamination in water bodies and to make better use of P in crop production.

Diskette for IBM/PC in pocket on back end paper. Copies of author's previously published articles inserted. Bibliography: leaves 186-207. An evaluation of spatial and temporal variation in composition of soil solutions collected from a hydro-toposequence with seasonally saturated soils ranging from Xeralfs to Aqualfs. The sub-catchment is under native eucalyptus and is formed from granite gneiss. The study shows that mineral weathering under eucalypt vegetation contributes substantially to the quantity of elements measured in soil solution with some aeolian salts. Migration of soil solutions to low lying areas promotes dryland salinity in these landscapes.

Thesis (M. Sc.)--University of Adelaide, National Centre of Petroleum Geology & Geophysics, 1992.
Vol. 2 consists of 30 col. & folded maps & charts. Includes five overlays in vol. 1. Includes bibliographical references (leaves 152-162).

The annual production of biosolids in the Perth region during the period of this study was approximately 13,800 t dry solids (DS), being supplied by three major wastewater treatment plants. Of this, 70% was typically used as a low-grade fertiliser in agriculture, representing an annual land use area of around 1,600 ha when spread between 5 and 7 t DS/ha. Loading rates of biosolids are typically based on the nitrogen (N) requirements of the crop to be grown, referred to as the N Limiting Biosolids Application Rate (NLBAR). A consequence of using the NLBAR to calculate loading rates is that phosphorus (P) is typically in excess of plant requirement. The resultant high loading rates of P are considered in the guidelines developed for the agricultural use of biosolids in Western Australia, but lack research data specific to local conditions and soil types. Regulatory changes throughout Australia and globally to protect the environment from wastewater pollution have created a need for more accountable and balanced nutrient data. Experiments presented in this thesis were undertaken to ascertain: the percentage relative effectiveness (RE) of biosolids as a source of plant available P compared with inorganic P fertiliser; loading rates to best supply P for optimum crop growth; P loading rates of risk to the environment; and the forms of P in local biosolids. Therefore, both the agronomic and environmental viewpoints were considered. Anaerobically digested and dewatered biosolids produced from Beenyup Wastewater Treatment Plant, Perth with a mean total P content of 2.97% dry weight basis (db) were used in a series of glasshouse, field and laboratory experiments. The biosolids were sequentially fractionated to identify the forms of P present and likewise in soil samples after applying biosolids or monocalcium phosphate (MCP).
The biosolid P was predominantly inorganic (92%), and hence the organic fraction (8%) available for mineralisation at all times would be extremely low. The most common forms of biosolid P were water-soluble P and exchangeable inorganic P (66%), followed by bicarbonate extractable P (19%) and the remaining P as inorganic forms associated with Fe, Al and Ca (14%). Following the application of biosolids to a lateritic soil, the Fe and Al soil fractions sorbed large amounts of P, not unlike the distribution of P following the addition of MCP. Further investigation would be required to trace the cycling of biosolid P in the various soil pools. The growth response of wheat (Triticum aestivum L.) to increasing rates of biosolids and comparable rates of inorganic P as MCP, to a maximum of 150 mg P/kg soil was examined in the glasshouse. The percentage relative effectiveness (RE) of biosolids was calculated using fitted curve coefficients from the Mitscherlich equation: y = a (1-b exp–cx) for dry matter (DM) production and P uptake. The initial effectiveness of biosolid P was comparable to that of MCP with the percentage RE of biosolids averaging 106% for DM production of wheat shoots and 118% for shoot P uptake at 33 days after sowing (DAS) over three consecutive crops. The percentage residual value (RV) declined at similar rates for DM production in MCP and biosolids, decreasing to about 33% relative to freshly applied MCP in the second crop and to approximately 16% in the third crop. The effectiveness of biosolid P was reduced significantly compared with inorganic P when applied to a field site 80 km east of Perth (520 mm annual rainfall). An infertile lateritic podsolic soil, consistent with the glasshouse experiment and representative of a soil type typically used for the agricultural application of biosolids in Western Australia was used.
Increasing rates of biosolids and comparable rates of triple superphosphate (TSP), to a maximum of 145 kg P/ha were applied to determine a P response curve. The percentage RE was calculated for seasonal DM production, final grain yield and P uptake in wheat followed by lupin (Lupinus angustifolius L.) rotation for the 2001 and 2002 growing seasons, respectively. In the first year of wheat, the RE for P uptake in biosolids compared with top-dressed TSP ranged from 33% to 55% over the season and by grain harvest was 67%. In the second year, and following incorporation with the disc plough at seeding, the RE for P uptake by lupins in biosolids averaged 79% over the growing season compared with top-dressed TSP, and by grain harvest the RE was 60%. The residual value (RV) of lupins at harvest in biosolids compared with freshly applied TSP was 47%. The non-uniform placement of biosolids (i.e. spatial heterogeneity) was primarily responsible for the decreased ability of plant roots to absorb P. The P was more effective where biosolids were finely dispersed throughout the soil, less so when roughly cultivated and least effective when placed on the soil surface without incorporation. The RE for grain harvest of wheat in the field decreased from 67% to 39% where biosolids were not incorporated (i.e. surface-applied). The RE could also be modified by factors such as soil moisture and N availability in the field, although it was possible to keep these variables constant in the glasshouse. Consequently, absolute values determined for the RE need to be treated judiciously. Calculations showed that typical loading rates of biosolids required to satisfy agronomic P requirements of wheat in Western Australia in the first season could vary from 0 to 8.1 t DS/ha, depending on soil factors such as the P Retention Index (PRI) and bicarbonate available P value.
Loading rates of biosolids were inadequate for optimum P uptake by wheat at 5 t DS/ha (i.e. 145 kg P/ha) based on the NLBAR on high P sorbing soils with a low fertiliser history (i.e. PRI >15, Colwell bicarbonate extractable P <15 mg P/kg). On soils of PRI <2 mL/g however, biosolids applied at identical loading rates would result in high concentrations of available P. Further work on sites not P deficient would be necessary to validate these findings on farmed soils with a regular history of P fertiliser. The sieving of soil samples used in the field experiment to remove stones and coarse organic matter prior to chemical analysis inadvertently discarded biosolids particles >2 mm, and thus their was little relationship between soil bicarbonate extractable P and P uptake by plants in the field. The risk of P leaching in biosolids-amended soil was examined over a number of different soil types at comparable rates of P at 140 mg P/kg (as either biosolids or MCP) in a laboratory experiment. Given that biosolids are restricted on sites prone to water erosion, the study focussed on the movement of water-soluble P by leaching rather than by runoff of water-soluble P and particulate P. In general the percentage soluble reactive P recovered was lower in soils treated with biosolids than with MCP, as measured in leachate collected using a reverse soil leachate unit. This was particularly evident in acid washed sand with SRP measuring 14% for biosolids and 71% for MCP, respectively, although the differences were not as large in typical agricultural soils. Specific soil properties, such as the PRI, pH, organic carbon and reactive Fe content were negatively correlated to soluble reactive P in leachate and thus reduced the risk of P leaching in biosolids-amended soil.
Conversely, the total P and bicarbonate extractable P status of the soils investigated were unreliable indicators as to the amount of P leached. On the basis of the experiments conducted, soils in Western Australia were categorised according to their ability to minimise P enrichment and provide P necessary for crop growth at loading rates determined by the NLBAR. Biosolids applied at the NLBAR to soils of PRI >2mL/g with reactive Fe >200 mg/kg were unlikely to necessitate P loading restrictions. Although specific to anaerobically digested biosolids cake applied to Western Australian soils, the results will be of relevance to any industry involved in the land application of biosolids, to prevent P contamination in water bodies and to make better use of P in crop production.

Thesis (PhD) -- Stellenbosch University, 2003.
Please refer to full text to view abstract.
ENGLISH ABSTRACT: The effects of different land use practices on soil quality in South Africa were investigated in five contrasting biomes, with a particular emphasis on the tendency of soils to crust and soil C content. Soil quality is a nebulous concept and its applicability in the South African landscape is scrutinised. A wide range of chemical and physical soil properties were examined. The tendency of soils to crust was assessed using modulus of rupture, water dispersible clay and a new method of laboratory infiltration which was verified with rainfall simulation. Crusting was greater in bare, exposed soils than soils under vegetation and varied with soil parent material. Differences in crusting are explained by factors relating to clay dispersion such as clay mineralogy, soil C, labile or readily oxidisable C, concentration of soluble salts, soil texture and exchangeable Na percentage (ESP). Results from longterm bum plots in savanna and grassland revealed that annual burning can increase the tendency of soils to crust. Greater crusting in burnt plots is ascribed to greater dispersion of clay, which in tum is attributed to a decline in soil C, a decline in EC and an increase in ESP. The loss of nutrients from burnt plots over time is ascribed to removal of ash in surface runoff. Calcium, Mg, and K were lost more readily than Na probably because plants take up these nutrients in greater concentration than Na. The net effect was an increase in ESP. Crusting on burnt plots may be self-perpetuating, because increased runoff is likely to incsease the loss of soluble salts. Removal of vegetation due to cultivation, grazing or burning reduced soil C at all sites. Mean soil C in the 0-1 cm layer of unburnt plots in the Kruger National Park was more than three times greater than in burnt plots (2.7 vs 0.8%). The difference in soil C between treatments decreased with depth and illustrated that sampling to depths greater than a few centimetres can obscure effects of land use. The top few centimetres of soil have a disproportionate effect on soil infiltrability and nutrient cycling. This layer was named the pedoderm. Tree cover on burnt plots in the southern Kruger Nationa--l- Park is highly variable, and was hypothesised to be a function of herbivory pressure. Herbivores tended to congregate on plots with the greatest clay, Zn and Mn content and the lowest tree cover. It is suggested that soil properties determine the abundance of herbivores after fire, which in tum affects tree cover. In the Eastern Cape,intensive stocking with goats transforms dense thicket to an open savanna. Soils from goat-transformed sites had a greater tendency to crust than soils from intact thicket, probably due to aggregate weakening associated with a decline in soil C. Mean soil C content of intact thicket was almost double that of goat-transformed thicket (5.6 vs. 3% to a depth of 10 cm) and is exceptionally high for a semi-arid region. The potential to sequestrate carbon in degraded thicket landscapes is thus considerable. Managing the land for greater sequestration of C will have the added benefit of increasing soil aggregate stability, reducing the tendency of soils to crust and therefore increasing the rate of water infiltration through the pedoderm. The benefits of such an approach have been recognised by specialists in soil conservation and rural land use for many decades, based largely on empirical observation. The results of this thesis provide a more quantitative basis for appreciating the effects of soil C across a broad spectrum of South African biomes.
AFRIKAANSE OPSOMMING: Die invloed van verskillende landgebruikspraktyke op grondkwaliteit in Suid-Afrika is in vyf kontrasterende biome ondersoek met spesifieke klem op die neiging van gronde om korste te vorm en die grond koolstofinhoud. Grondkwaliteit is 'n vae konsep en die toepassing daarvan in die Suid-Afrikaanse grondlandskap is noukeurig ondersoek. 'n Wye reeks van chemiese en fisiese grondeienskappe is ondersoek. Die neiging van korsvorming by gronde is beraam deur die gebruik van breukmodulus, waterdispergeerbare klei en 'n nuwe metode van laboratorium-infiltrasie wat met behulp van reënvalsimulasie gekontroleer is. Korsvorming was groter in kaal, blootgestelde gronde as in gronde met 'n plantbedekking en het gewissel volgens moedermateriaal. Verskille in korsvorming word verklaar deur faktore wat verband hou met kleidispergering soos byvoorbeeld kleimineralogie, grondkoolstof, labiele of maklik oksideerbare koolstof, konsentrasie oplosbare soute, grondtekstuur en uitruilbare natriumpersentasie (UNP). Resultate van langtermyn brandpersele in savanna en grasland het getoon dat jaarlikse brand die neiging tot korsvorming kan verhoog. Meer korsvorming in brandpersele word toegeskryf aan groter kleidispergering, wat waarskynlik verband hou met 'n afname in grondkoolstof, 'n afname in elektriese geleiding (Be) en 'n toename in UNP. Plantvoedingstowwe gaan oor tyd verlore uit brandpersele, waarskynlik deur die verwydering van as in oppervlak afloop. Kalsium, Mg en K gaan meer geredelik verlore as Na, waarskynlik omdat plante hierdie voedingstowwe in groter hoeveelhede opneem as Na. Die netto effek is 'n toename in UNP. Korsvorming op brandpersele kan self instand gehou word omdat verhoogde afloop die moontlike verlies van oplosbare soute kan verhoog. Verwydering van plantegroei deur bewerking, beweiding of brand het grondkoolstof op alle plekke verlaag. Die gemiddelde grondkoolstof in die 0-1 cm laag van ongebrande persele in die Kruger Nasionale Park was meer as drie maal groter as in --.. brandpersele (2.7 vs 0.8 %). Die verskil in grondkoolstof tussen behandelings neem af met diepte wat daarop dui dat monsterneming tot dieptes groter as 'n paar sentimeters die effek van landgebruik kan verberg. Die boonste paar sentimeters van 'n grond het 'n oneweredige invloed op infiltrasie en voedingstofsirkulasie. Hierdie laag word die pedoderm genoem. Boombedekking op brandperseie in die suidelikeKruger Nasionale Park is hoogs variërend. Die hipotese was dat dit 'n funksie van druk deur planteters is. Planteters neig om op persele met die hoogste klei, Zn- en Mn-inhoud en die laagste boom bedekking te versamel. Daar word voorgestel dat grondeienskappe die hoeveelheid planteters na 'n brand bepaal. Dit beïnvloed op sy beurt weer die boombedekking. In die Oos-Kaap het intensiewe bokboerdery digte bosruigtes verander na oop savannas. Gronde van bok-veranderde lokaliteite het 'n groter neiging tot korsvorming as gronde van onveranderde bosruigtes, vermoedelik as gevolg van verswakking van aggregate met 'n. afname in grondkoolstof. Die gemiddelde grondkoolstof van onveranderde bosruigtes was byna dubbel soveel as die koolstof van bok-veranderde bosruigtes (5.6 vs 3 % tot 'n diepte van 10 cm) en buitengewoon hoog vir 'n semi-ariede streek. Die potensiaal vir koolstof sekwestrasie in degradeerde bosruigte landskappe is dus aansienlik. Bestuur van land vir groter sekwestrasie van koolstof het die bykomende voordeel van verhoogde grond aggregaatstabilteit, verlaging van die neiging tot korsvorming en daardeur 'n verhoging in die tempo van waterinfiltrasie deur die pedoderm. Die voordele van so 'n benadering is vir baie dekades deur spesialiste in grondbewaring en landelike landgebruik herken. Dit was grootliks gebaseer op empiriese waarneming. Die resultate van hierdie tesis bied 'n meer kwantitatiewe basis tot die verstaan van die invloed van grondkoolstof oor 'n breë spektrum van Suid-Afrikaanse biorne.

Thesis (MScAgric)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Soil is a fundamental, non-renewable resource in any ecosystem. To uphold food production for increasing global human populations, it is imperative to develop ways in which to sustain healthy biological productivity and sustainability of agricultural soils. Nematodes are one of the most abundant groups of Metazoa occurring in all soils, and form an integral part of the soil food web at several trophic levels. They respond rapidly to changes within their environments, and can easily be extracted from soil, identified and characterised into functional guilds. Nematodes thus have the potential to impart insight into the condition of the soil food web. This study aims to establish whether nematodes will be suitable bio-indicators of soil health for the deciduous fruit industry in the Western Cape. Three different objectives have been set to determine the practical use of nematode community structures as a tool for the measurement of soil health. The objectives include describing the nematode community structure, biodiversity and functionality within Fynbos soils; the characterization of organic and conventional orchards; and the differences in nematode soil communities in differently managed soils in an apple orchard. The number of nematodes in each soil sample was quantified and identified to family level. The nematode biodiversity and functionality for each site was determined by evaluating the nematode food webs for trophic group distribution, as enumerated by the Maturity Index (MI), the Enrichment Index (EI), the Structure Index (SI), the Basal Index (BI) and the Channel Index (CI), based on the weighted abundance of coloniser-persister guilds. The functional guild analysis of Fynbos samples indicated that the enrichment and the structure of any given sample were not bound to a certain area, but it was representative of each of the four quadrats within the faunal analysis. Different geographic areas were found to differ in nematode diversity and functionality, which was mainly associated with dominant plant families and species (such as strong associations between Fynbos families Fabaceae, Solanaceae and Celestraceae with the nematode family Pratylenchidae). The most abundant nematode families present in the Fynbos were Tylenchidae, which are plant-feeding nematodes, and Cephalobidae which are bacterial-feeding nematodes. Despite Tylenchidae and Cephalobidae both having coloniser-persister values (cp-values) of two, they are split up into different feeding types. Cp-2 nematodes are tolerant to disturbances, and occur in all environments. Only one omnivorous family, the Dorylaimida, was identified in Fynbos samples. The average MI value for Fynbos was found to be very low, with a mean value of 1.26. The value obtained indicated the presence of taxa with tolerance to disturbance, which, in turn, indicated the presence of a disturbed soil, in general. The number of plant-parasitic nematodes within the Fynbos soils was low, which was supported by the low plant-parasitic index (PPI) of 0.85. The diversity, richness and evenness values were low, indicating low nematode diversity, but a distribution of abundances amongst the families. The average Hill’s N0 index value was 8.0, indicating that, in general, eight nematode families would have been present in a Fynbos soil sample. A study was done to determine the biodiversity and the functionality of the nematodes associated with deciduous fruit orchards that were conventionally, or organically, managed. Herbivores were dominant in all the orchards. The organic apple orchard had the lowest numbers of herbivores and fungivores, with the highest number of carnivores. When comparing organic and conventional apricot orchards, higher numbers of plant-parasitic nematodes were found in the organic orchard. Criconematidae occurred in higher numbers in conventional apricot orchard soil. When comparing organic apricots and apples, higher numbers of Criconematidae occurred within the organic apple soil. Overall, higher levels of plant-parasitic nematodes occurred in the organic apricot orchard. The MI indicated that all orchard soils had values below 1.5, indicating disturbance. Conventionally managed apricot orchard soil had the highest MI value of 1.48. The PPI value was highest in organically managed apricot orchards. All orchard soils were located within Quadrat B of the faunal analysis, indicating enrichment and structure. Regarding the diversity, richness and evenness of the distribution, conventional apricot soil had the highest species richness, while organic apple soil had the most even family distribution. Different management practices did not show marked differences in community composition and structure. The species richness of Fynbos soils was comparable to those of deciduous fruit orchards. Soil samples from eight different soil surface treatments were collected from an apple orchard in the Grabouw area. Treatments were combined according to the soil surface treatments received (chemical control of cover crops and weeds, mulch and mulch + effective micro-organism spray). Bacterivores were dominant in all soil treatments, with the least number being present in the chemical control (of cover crops and weeds) treatment. Sites which received chemical control of cover crops and weeds had higher levels of fungivores, compared to the levels at the other sites. High numbers of Rhabditidae occurred within mulch and mulch + effective micro-organism (EM) treatment sites, while high numbers of Aphelenchidae occurred in chemical control sites. The carnivorous family Ironidae only occurred in mulch + EM sites. Strong associations were found between soil surface applications and nematode families present within the soil. Chemical control (of cover crops and weeds) applications had the highest MI value, while values were equal for the other soil applications. The faunal analysis indicated that the mulch and the chemical control fell within Quadrat A, indicating enriched, but unstructured, soil, while the mulch + EM treatment fell within Quadrat B, indicating enrichment and structure, as well as good overall soil conditions. All the systems were dominated by bacterial decomposition pathways. Controversially, sites that received chemical control of the cover crops and weeds had the highest species richness of all three applications, as well as the highest level of diversity, according to the Simpson Index. As only the cover crops and the weeds were chemically controlled, the soil can be regarded as undisturbed, which explains the results obtained in this study. Clear differences in nematode community structure and composition were observed between the different soil applications in the apple orchard.
AFRIKAANSE OPSOMMING: Grond is 'n fundamentele, nie-hernubare hulpbron binne enige ekosisteem. Ten einde voedselproduksie vir die toenemende globale menslike bevolking te handhaaf, is dit noodsaaklik om maniere te ontwikkel om gesonde biologiese produktiwiteit en volhoubaarheid van landbougrond in stand te hou. Nematodes is een van die volopste Metazoa in alle gronde en vorm 'n integrale deel van die grond voedsel-web op verskeie trofiese vlakke. Hulle reageer vinnig op veranderinge binne hul omgewings, kan maklik ekstraheer en identifiseer word; en ook maklik in funksionele gildes ingedeel word. Nematodes het ook die potensiaal om insig oor te dra ten opsigte van die toestand van die grond voedsel-web. Hierdie studie het ten doel om vas te stel of nematodes geskikte bio-indikatore van grond gesondheid kan wees spesifiek vir die sagtevrugte bedryf in die Wes-Kaap. Drie verskillende doelwitte is gestel om die praktiese gebruik van nematode populasie samestelling as 'n instrument vir die meting van grond gesondheid te gebruik. Die doelwitte sluit in die nematode populasie samestelling, biodiversiteit en funksionaliteit binne natuurlike Fynbos; organies verboude versus konvensionele boorde; en die verskil in nematode populasie samestelling tussen verskillend behandelde en bestuurde grondpersele binne ʼn appel boord. Die nematode biodiversiteit en funksionaliteit vir elke perseel was bepaal deur die evaluering van die nematode voedselweb vir trofiese groep verspreiding en enumerering deur die Maturity Index (MI) en die Enrichment Index (EI), Strukturele Indeks (SI), Basale Indeks (BI) en Channel Index (CI) wat gebaseer is op die geweegde oorvloed van koloniseerder-persister gildes. Die funksionele gilde vir Fynbos monsters het aangedui dat die verryking en struktuur van enige gegewe perseel nie gebonde is aan ʼn bepaalde gebied nie, aangesien dit verteenwoordig was in elk van die vier kwadrante van die Fauna Analiseerder. Daar is gevind dat verskillende areas verskil in nematode diversiteit en funksionaliteit, wat hoofsaaklik geassosieer was met die dominante plant families en spesies in die omgewing. Die volopste nematode familie wat teenwoordig was in die Fynbos was Tylenchidae, wat plant-voedende nematodes is, en Cephalobidae, wat bakterie-voedend is. Tylenchidae en Cephalobidae het beide ʼn cp-waarde van twee, maar is verdeel in verskillende VIII tipes voedingsgroepe. Die cp-2 nematodes is verdraagsaam vir versteurings en kom in alle omgewings voor. Slegs een omnivoor familie is geïdentifiseer in Fynbos monsters, nl. die Dorylaimidae. Die gemiddelde MI waarde vir Fynbos was laag, met 'n gemiddelde waarde van 1.26. Hierdie waarde is ʼn aanduiding van die teenwoordigheid van taxa met verdraagsaamheid tot versteuring, wat op sy beurt 'n versteurde grond in die algemeen aangedui het. Die aantal plant-parasitiese nematodes binne die Fynbos-gronde was laag, wat ondersteun word deur die lae PPI-waarde van 0.85. Die waardes vir die diversiteit, spesie-rykheid en egaligheid was laag, wat dui op 'n lae nematode diversiteit, maar 'n egalige verspreidings onder families. Die Hill’s N0 indeks waarde was gelyk aan 'n gemiddelde van 8.0 en dui daarop dat in die algemeen agt nematode families teenwoordig sal wees in 'n Fynbos grondmonster. 'n Studie is gedoen om die biodiversiteit en funksionaliteit van nematodes wat verband hou met vrugteboorde wat organies en konvensioneel bestuur is te bepaal. Herbivore was dominant in alle boorde. Organiese appels het die laagste aantal herbivore en fungivore gehad en die hoogste aantal karnivore. Wanneer organiese en konvensionele appelkoosboorde met mekaar vergelyk is, was hoër getalle van plant-parasitiese nematodes gevind in die organiese boord. Criconematidae was teen ʼn groter aantal in die grond van die konvensionele appelkoosboord gevind. Met die vergelyking van organiese appelkose en appels word, is ʼn hoër aantal Criconematidae binne die organiese appelgrond aangetref. In die algemeen was hoër vlakke van plant-parasitiese nematodes gevind in die organiese appelkoosboord. Die MI het getoon dat alle boord waardes laer as 1.5 gehad het, wat daarop dui dat die gronde versteurd is. Die konvensioneel bestuurde appelkoosboord het die hoogste MI waarde gehad met ʼn vlak van 1.48. Die waarde vir die PPI was die hoogste in organies bestuurde appelkoosboorde. Alle boord gronde is geleë binne kwadrant B van die Fauna Analiseerder, wat dui op verryking met struktuur. Met betrekking tot die diversiteit, spesie-rykheid en egaligheid van die verspreiding van families, het konvensionele appelkoos grond die hoogste spesierykheid, terwyl die gronde van die organiese appelboord die mees egalige familie verspreiding vertoon het. Verskillende bestuurspraktyke nie toon nie merkbare verskille in die gemeenskap samestelling en struktuur nie. Die spesie-rykheid van Fynbos gronde is vergelykbaar met dié van sagtevrugte-boorde. Monsters is geneem van agt verskillende grondeoppervlak-behandelings in ‘n appelboord in die Grabouw area. Die behandelings is gekombineer volgens die grond toediening wat dit ontvang het (chemiese beheer van dekgewasse en onkruid, deklaag en ‘n deklaag + effektiewe mikro- IX organismes). Bakterievoedende nematodes was dominant in elke grondoppervlak-behandeling, met die minste teenwoordig in die behandelings wat chemiese beheer van die dekgewasse en onkruid ontvang het. Behandelings wat chemiese beheer van die dekgewasse en onkruid ontvang het, het ook hoër vlakke van fungivore in vergelyking met die ander behandelings. ʼn Hoë aantal Rhabditidae het voorgekom in grondmonsters van die deklaag en die deklaag + EM (effektiewe mikro-organismes) behandeling persele, terwyl ʼn groot aantal Aphelenchidae voorgekom het in chemiese beheer persele. Die predatoriese familie, Ironidae, het slegs voorgekom in persele wat die deklaag + EM behandeling ontvang het. Sterk assosiasies bestaan tussen grond behandeling en nematode families wat in die grond teenwoordig was. Die chemiese beheer behandeling het die hoogste MI waarde getoon, terwyl waardes vir die ander behandelings laer en gelyk was. Die fauna analise het daarop gedui dat die deklaag en chemiese beheer binne kwadrant A is en dus verryk, maar ook ongestruktureerd is. Die deklaag + EM behandeling het binne kwadrant B geval wat aandui op toestande van verryking en struktuur wat 'n goeie algehele grondtoestand tot gevolg gehad het. Al die stelsels is oorbruggingsweë wat oorheers was deur bakteriële ontbinding. Kontroversieel, het persele wat chemiese beheer van die dekgewasse en onkruid ontvang het, die hoogste spesierykheid van al drie behandelings getoon asook die hoogste vlak van diversiteit volgens die Simpson-indeks. Slegs die dekgewasse en onkruid is chemies behandel, nie die grond nie, en dus kan die grond as onversteurd beskou word en die resultate wat verkry is in die studie verklaar. Duidelike verskille in die nematode gemeenskap struktuur en samestelling is waargeneem tussen die verskillende grond behandelings in appel boorde.

Bibliography: leaves 164-193. This study aims to quantify the belowground input of organic carbon by barrel medic using techniques that account for root death and decomposition as well as root secretion and exudation. It also investigates the effect of defoliation on carbon allocation within the plant so as to determine the potential for optimising carbon input to the soil through grazing management.

Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots. Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots.

Microtidal estuaries are prone to anthropogenic degradation, with natural features of those in south-western Australia making them more susceptible. However, the benthic ecological health of these systems is rarely assessed, despite the importance of the benthos and frequent application of benthic indices in estuaries elsewhere, particularly macrotidal systems in the northern hemisphere. The aim of this research was to assess the current status of the benthic macroinvertebrate community and its role in the function and management of the microtidal Peel-Harvey Estuary. After accounting for the effects of natural hydrological conditions (e.g. salinity, temperature), the benthic macroinvertebrate community was shown to respond to anthropogenic stress as represented by sediment condition (i.e. oxygenation, organic enrichment, mud content, sulphide presence), demonstrating its potential utility for assessing estuarine health. However, existing benthic indices commonly used in macrotidal estuaries (e.g. the multivariate AZTI Marine Biotic Index) yielded results inconsistent with sediment condition, demonstrating their limitations when applied to highly adaptive, stress-tolerant macroinvertebrate communities that are common in microtidal estuaries. A new multi-metric Estuarine Benthic Community Index was developed, following a multivariate approach to select community metrics that showed greater responses to sediment condition than natural stress. Overall, the benthic macroinvertebrate community in the Peel-Harvey Estuary was typically in good to fair health, with decreased health in the summer and deeper depositional areas. It is largely dominated by small-bodied, opportunistic species, and apparently retained in early succession due to chronic natural and anthropogenic stress. This was further reflected by the community’s limited impacts on solute fluxes of benthic metabolism, nutrient exchange and denitrification, with sediment condition being more influential. These findings demonstrate that these benthic faunal communities do not play a substantial role in estuarine function, with the application of resulting benthic indices restricted to assessing more structural aspects (e.g. diversity) of benthic ecological health.

This thesis examines the response to P fertiliser by wheat crops growing in the vertosol soils of the low rainfall areas of the northern grain zone of eastern Australia. Farmers in this region depend on water accumulated from rainfall over a fallow period and stored in the subsoil to increase wheat grain yield beyond that normally achievable from in-crop rainfall and to decrease the production risks due to rainfall variability. The large variability in stored water, seasonal rainfall and subsoil properties result in extremely varied yield and yield responses to P fertiliser between seasons and between sites. Finally, as a practical guide to predicting wheat response to P fertilizer: 1/. current sampling strategies of determining P only in the surface 10 cm appear to be adequate for soils with bicarbonate P concentrations greater than 15 mg/kg. 2/. For soils with lower concentrations in the surface, sampling of 80 cm is recommended. Crops with a mean concentration of bicarbonate P greater than 7 mg/kg between 10 - 80 cm are unlikely to respond to P fertiliser. 3/. No increase in profitable grain yield response was found for fertiliser applications greater than 10 kg P/ha.
Doctor of Philosophy (PhD)

Copy of author's previously published work inserted. Bibliography: leaves 261-306. The objectives of the project were: i. to determine whether there are competitive interactions between Aporrectodea trapezoides and A. caliginosa and A. rosea.--ii. to investigate compeditive interactions between A. calignosa, Microscolex dubius and A. trapezoides.--iii . to determine the likely impact of A. longa on soil fauna, especially the native earthworm, Gemascolex lateralis, in native ecosystems.

Spicers Creek catchment is located approximately 400 km west of Sydney in the Central West region of New South Wales, Australia. Dryland salinity has been recognised as a major environmental issue impacting soil and water resources in the Central West region of NSW for over 70 years. Due to the geological complexity of the catchment and the presence of high salt loads contained within the soils, groundwater and surface waters, the Spicers Creek catchment was identified as a large contributor of salinity to the Macquarie River catchment. Over fifty-two dryland salinity occurrences have been identified in the Spicers Creek catchment and it appears that dryland salinity is controlled by the presence of geological structures and permeability contrasts in the shallow aquifer system. Combinations of climatic, geological and agricultural factors are escalating salinity problems in the catchment. The main aim of this thesis was to identify the factors affecting salinisation processes in the Spicers Creek catchment. These include the role of geological structures, the source(s) of salts to the groundwater system and the geochemical processes influencing seepage zone development. To achieve these aims a multidisciplinary approach was untaken to understand the soils, geology, hydrogeology and hydrogeochemistry of the catchment. Investigative techniques employed in this project include the use of geophysics, soil chemistry, soil spectroscopy, hydrogeochemistry and environmental isotopes. Evaluation of high-resolution airborne magnetics data showed a major north-east to south-west trending shear zone. This structure dissects the catchment and several other minor faults were observed to be splays off this major structure. These structures were found to be conducive to groundwater flow and are influencing the groundwater chemistry in the fractured aquifer system. Two distinctive groundwater chemical types were identified in the catchment; the saline Na(Mg)-Cl-rich groundwaters associated with the fractured Oakdale Formation and the Na-HCO3-rich groundwaters associated with the intermediate groundwater system. The groundwater chemistry of other deep groundwaters in the catchment appears to be due to mixing between these end-member groundwaters within the fractured bedrock system. The spatial distribution of electrical conductivity, Cl-, Sr2+ and 87Sr/86Sr isotopic ratios showed the correlation between saline groundwaters and the location of faults. Elevated salinities were associated with the location of two crosscutting fault zones. The spatial distribution of HCO3-, K+, Li+ and ?????3CDIC highlighted the extent of Na-HCO3-rich groundwaters in the catchment and showed that these groundwaters are mixing further east than previously envisaged. These findings show that Na(Mg)-Cl-rich groundwaters are geochemically distinctive and have evolved due to extensive water-rock interaction processes within the fracture zones of the Oakdale Formation. These saline groundwaters contain elevated concentrations of trace elements such as As, V and Se, which pose a potential risk for water resources in the area. 87Sr/86Sr isotopic ratios indicated that the source of salinity to the Na(Mg)-Cl-rich groundwaters was not purely from marine or aerosol input. Salt is most likely contributed from various allochthonous and autochthonous sources. This research found that the main mechanism controlling the formation of dryland salinity seepage zones in the Spicers Creek catchment is due to the presence of geological structures. These groundwater seepage zones act as mixing zones for rainfall recharge and deeper groundwaters. The main sources of salt to the seepage zones are from deeper Na(Mg)-Cl-rich groundwaters and rainfall accession. The major importance of this research highlights the need for an integrated approach for the use of various geoscientific techniques in dryland salinity research within geologically complex environments.

This thesis is an evaluation of the use the USLE to estimate soil loss from two pastoral land uses - commercial properties and "hobby farms" in Murrumbateman. Sensitivity analysis was used to evaluate the USLE components. Sediment measurement in farm dams was taken to estimate sediment yield from several sites, as an alternative approach to study soil loss. The annual soil loss from entire study area was 0.25 t/ha/year whilst these figures from commercial properties and hobby farms were 0.29 t/ha/year and 0.21 t/ha/year, respectively. The annual average sediment yield from three catchments in hobby farms was 0.3 t/ha/year. The USLE was found to be highly sensitive to slope steepness, ground cover and stocking rates. The critical values were 16% for slopes, 35% for the ground cover and 19 Dry Sheep Equivalent/ha for stocking rate. I tentatively conclude that the USLE is sufficiently sensitive to detect differences in soil loss between the two land uses. There is, however, a need to improve the operation of the model in some respects. The use of farm dams for estimating sediment yield also shows promise.

Following over 100 years of agriculture and continuous phosphorus (P) fertilizer application in the south west of Western Australia, there is a growing risk of P transport from cropping and pasture land to streams. However, soil and landscape factors affecting the likelihood of P losses and of stream water contamination have not yet been assessed for the South coast region of Western Australia. The present investigation was conducted in the Fitzgerald River catchment located ~ 400 km south east of Perth, to identify risk of P losses from agricultural land to streams, through an understanding of how P is retained within complex landscapes and released via surface and subsurface flow paths. The 104,000 ha catchment is in a moderately dissected landscape (average annual rainfall 450 mm) and discharges into the World Heritage listed Fitzgerald Biosphere. The main use of cleared land in the catchment is broad-scale agriculture, primarily winter grain cropping and pasture for livestock. The aim of an initial study was to identify the areas with high soil P concentrations and their relationship to factors such as soil type, topography, management (e.g. fertilizer and manure inputs, and uptake by crops or forage) and how variations in soil P concentrations were related to soil physico-chemical properties, P fertilizer management and landscape position. A wide variation in P concentrations was observed across the catchment, but few of the samples exceeded Colwell extractable P levels of 30 mg/kg in the 0-10 cm layer which is regarded as a critical level for crop and pasture productivity. The western area of the catchment, which was cleared earlier (before 1966) than the eastern area had a greater prevalence of loam soils, and higher Colwell-extractable P concentrations (average)22 mg/kg vs. 13 mg P/kg) due to soil type effects and higher P accumulation over time. Risk of P loss from the east and west of the catchment is expected to vary due to textural and topographic differences and P history (P fertilizer input and uptake by crops). The CaCl2-extractable P in the catchment was negatively correlated with oxalate extractable Fe (Feox) in soils. This suggests that P may be transported as particulate P (PP) on loam and clay soils due to sorption of P on oxides surfaces, while on sand soil leaching losses may be more likely. On loam and clay soils, higher sodicity and the dispersive nature of subsoils may increase the risk of both dissolved P (DP) and PP loss due to the effects on hydraulic conductivity of the profile. Hedley's fractionation scheme was used to quantify P fractions in the order of decreasing lability, viz: resin-P > NaOH-Pi > NaOH-Po > acid-P (H2SO4-P) > residual-P. Surface soil had higher resin and NaOH-Pi, which are regarded as water-soluble and readily exchangeable P forms, respectively and expected to contribute to DP in the runoff losses. The residual P was the largest fraction followed by the hydroxide extractable organic-P fraction (NaOH-Po): the former was positively correlated (r) with clay content, organic carbon (OC) and pyrophosphate extractable Fe and Al (0.48**, 0.61**, 0.69** and 0.58**, P < 0.01). A relatively higher value of NaOH-Po in the subsurface layer and positive correlation with OC (r = 0.45**, P < 0.01) suggests potential mobility of P as soluble organic P in run-off, throughflow and leachate. Phosphorus sorption and its relationship to soil properties was used to assess the potential P release from the catchment soils. Values of P sorption maxima varied from 1111-3333 mg/kg for surface soils and 1010-2917 mg/kg for subsoils. The P sorption isotherms conformed better to the Freundlich equation than the Langmuir equation. A highly significant negative correlation between CaCl2 extractable P and Feox in surface soils (r = -0.65**, P < 0.01) suggests that P was bound to hydrated Fe oxide surfaces and this may determine the concentration and dynamics of loosely bound P equilibrating with leachates and eroded particulate materials. On the other hand, high surface organic matter and the high proportion of total dissolved P in organically bound form may inhibit P sorption on clays and sesquioxides, which would increase P mobility through leaching or runoff losses. The relationship between soil P concentration and degree of P stratification in the top 0-10 cm of soils along five toposequences was examined to predict the effect on runoff P losses. The total Colwell-P content of the 0-10 cm layer of soils in the catchment was very low in comparison to other studies on P losses from agricultural soils, but soils showed higher P concentration at 0-1 cm depth compared to 5-10 cm (average 37 mg/kg vs. 19 mg/kg). The higher extractable P concentration in the 0-1 cm layer will create a greater P mobilization risk in surface runoff and leachate than analysis of the 0-10 cm layer might suggest. Assessment of P risk using the 0-10 cm data would still be reliable as P concentration in the 0-1 cm layer was linearly related (R2 = 0.59) with concentration in the 0-10 cm layer. The sampling at varied soil depths will result in different critical P levels for estimating the risk of P enrichment in runoff. In a glasshouse study with intact soil columns, initial high P concentrations in leachate decreased with leaching events suggesting that macropore flow dominated in initial leaching events changing later to matrix flow. The hydraulic behavior of clay and loam soil below 10 cm depends largely on structure and the type of clay minerals and exchangeable Na. Higher levels of exchangeable Na in the subsoil might increase dispersion of clay particles resulting in low permeability leading to ponding of surface water or lateral movement of water at the interface of sand A and clay B horizons. Lateral water movements increase the risk of P losses in the form of DP, dissolved organic P (DOP) or PP. The P concentration in all the P forms (DRP, DOP and TDP) increased significantly with P rates of application (P < 0.01). The DRP concentration was < 2 mg/l in unfertilized columns but an increase to 11 mg/l was observed with P application at 40 kg P/ha. The higher proportion of DOP relative to DRP and its correlation with TDP indicates that the DOP was the major form of P in leachate. However, the estimation of DOP which was by subtraction of DRP from TDP generally overestimates OP concentration. The TDP load from unfertilized soil was < 0.20 mg/l in runoff and < 2.40 mg/l in throughflow but increased with P application (20, 40 kg P/ha) for both packed box and field studies. Under field conditions, higher P loss was found with broadcast P application compared to drill placement. The higher load of DOP as a proportion of TDP and its significant relationship with TDP in runoff (R2sand = 0.81; R2clay = 0.79) and throughflow (R2sand = 0.94; R2clay = 0.98) in field and box studies also suggests DOP was the major form of P loss from soil. Dissolved OP concentration increased significantly with increase in soluble organic carbon (SOC) in soil solution at 5 cm depth (P < 0.05). Consequently, the amount of organic matter dissolved in soil solution may influence P sorption and mobility. Relatively higher affinity of soil for sorption of DRP compared to DOP might allow DOP to be more mobile through the profile. Higher PP load in clay soil in throughflow indicates subsurface lateral flow along the interface with the horizon of dispersive clay might be an additional risk factor regarding P mobility in clay soils of the catchment. The runoff, throughflow and leachate were dominated by eroded particles of clay and colloidal organic materials. However, the soil solution collected though 0.1 m pores in the Rhizon samplers had a similar dominance of DOP to the < 0.45 jum filtered samples in runoff and throughflow. This reduces the likelihood that the so-called DOP fraction was mostly P associated with PP in the 0.1 to 0.45 jum size fraction. The composition of DOP in soil solution collected through Rhizon samplers (< 0.1 jum) might provide important insights for P mobility since this more effectively excluded PP than in the < 0.45 jum filtrate used for runoff and throughflow samples. The DOP in soil solution (< 0.1 jum) might be associated with fine colloidal compound such as silicates, metallic hydroxides, humic acids, polysaccharides, fulvic acids and proteins. If so, then most, but not all of the DOP fraction would be organically bound. However, this requires verification. In conclusion, soil P levels across the catchment were never very high when assessed in the 0-10 cm layer, but levels in the 0-1 cm layer were more than twice as high. Overall, < 1 % of land area of the upper Fitzgerald River catchment had Colwell-P levels > 30 mg/kg (0-10 cm) and hydrological connection to streams. In addition, another 7 % of land had Colwell-P levels > 15 mg/kg, which appears to be a change point in soils for the release of CaCl2 extractable P. These areas, which are predicted to represent critical source areas of the catchment, need careful management. The high proportions of TDP as DOP in runoff, throughflow and soil solution suggest DOP was the major form of P loss from soil. Phosphorus losses from the catchments are also likely in the form of PP in clay and loam soil but leaching losses are more likely in sand. High exchangeable Na in the subsoil of loam and clay soils increases dispersion of clay particles resulting in low permeability of subsoil and greater lateral P mobility as throughflow at the interface of sand and clay textured horizons. In general, soils of Fitzgerald River catchment had low soil P, but nevertheless significant risk of P loss at Colwell-P > 15 mg/kg. This study provides baseline information for P loss risks in the wheatbelt of WA. Stream water quality monitoring instruments were installed in the upper Fitzgerald River Catchment at 5 stream locations by CSIRO to measure base line concentrations of P. The measured P concentrations were higher than ANZECC trigger values (> 0.05 mg P/l) for management response over the three-year monitoring period (2005-07). Hence this and many other catchments on the south coast and wheatbelt of south west Western Australia need assessment for P loss risks. Previous emphasis in south west Western Australia on P losses from sandy coastal soils under pasture may need to be reconsidered. In the South coast region, cropping land in the medium rainfall zone may still represent a risk of P loss to waterways and risk to water quality. The present study evaluated the risk of P loss based on soil P forms and their mobility. It suggests greater attention needs to be given to the difference between clay and loam soils with dispersive or non-dispersive sub-soils, and to the composition and mobility of DOP. However, a more complete understanding of P loss risks depends on follow-up studies on hydrological flow and connectivity in the upper Fitzgerald River catchment and similar landscapes of south west Western Australia.

Following over 100 years of agriculture and continuous phosphorus (P) fertilizer application in the south west of Western Australia, there is a growing risk of P transport from cropping and pasture land to streams. However, soil and landscape factors affecting the likelihood of P losses and of stream water contamination have not yet been assessed for the South coast region of Western Australia. The present investigation was conducted in the Fitzgerald River catchment located ~ 400 km south east of Perth, to identify risk of P losses from agricultural land to streams, through an understanding of how P is retained within complex landscapes and released via surface and subsurface flow paths. The 104,000 ha catchment is in a moderately dissected landscape (average annual rainfall 450 mm) and discharges into the World Heritage listed Fitzgerald Biosphere. The main use of cleared land in the catchment is broad-scale agriculture, primarily winter grain cropping and pasture for livestock. The aim of an initial study was to identify the areas with high soil P concentrations and their relationship to factors such as soil type, topography, management (e.g. fertilizer and manure inputs, and uptake by crops or forage) and how variations in soil P concentrations were related to soil physico-chemical properties, P fertilizer management and landscape position. A wide variation in P concentrations was observed across the catchment, but few of the samples exceeded Colwell extractable P levels of 30 mg/kg in the 0-10 cm layer which is regarded as a critical level for crop and pasture productivity. The western area of the catchment, which was cleared earlier (before 1966) than the eastern area had a greater prevalence of loam soils, and higher Colwell-extractable P concentrations (average)22 mg/kg vs. 13 mg P/kg) due to soil type effects and higher P accumulation over time. Risk of P loss from the east and west of the catchment is expected to vary due to textural and topographic differences and P history (P fertilizer input and uptake by crops). The CaCl2-extractable P in the catchment was negatively correlated with oxalate extractable Fe (Feox) in soils. This suggests that P may be transported as particulate P (PP) on loam and clay soils due to sorption of P on oxides surfaces, while on sand soil leaching losses may be more likely. On loam and clay soils, higher sodicity and the dispersive nature of subsoils may increase the risk of both dissolved P (DP) and PP loss due to the effects on hydraulic conductivity of the profile. Hedley's fractionation scheme was used to quantify P fractions in the order of decreasing lability, viz: resin-P > NaOH-Pi > NaOH-Po > acid-P (H2SO4-P) > residual-P. Surface soil had higher resin and NaOH-Pi, which are regarded as water-soluble and readily exchangeable P forms, respectively and expected to contribute to DP in the runoff losses. The residual P was the largest fraction followed by the hydroxide extractable organic-P fraction (NaOH-Po): the former was positively correlated (r) with clay content, organic carbon (OC) and pyrophosphate extractable Fe and Al (0.48**, 0.61**, 0.69** and 0.58**, P < 0.01). A relatively higher value of NaOH-Po in the subsurface layer and positive correlation with OC (r = 0.45**, P < 0.01) suggests potential mobility of P as soluble organic P in run-off, throughflow and leachate. Phosphorus sorption and its relationship to soil properties was used to assess the potential P release from the catchment soils. Values of P sorption maxima varied from 1111-3333 mg/kg for surface soils and 1010-2917 mg/kg for subsoils. The P sorption isotherms conformed better to the Freundlich equation than the Langmuir equation. A highly significant negative correlation between CaCl2 extractable P and Feox in surface soils (r = -0.65**, P < 0.01) suggests that P was bound to hydrated Fe oxide surfaces and this may determine the concentration and dynamics of loosely bound P equilibrating with leachates and eroded particulate materials. On the other hand, high surface organic matter and the high proportion of total dissolved P in organically bound form may inhibit P sorption on clays and sesquioxides, which would increase P mobility through leaching or runoff losses. The relationship between soil P concentration and degree of P stratification in the top 0-10 cm of soils along five toposequences was examined to predict the effect on runoff P losses. The total Colwell-P content of the 0-10 cm layer of soils in the catchment was very low in comparison to other studies on P losses from agricultural soils, but soils showed higher P concentration at 0-1 cm depth compared to 5-10 cm (average 37 mg/kg vs. 19 mg/kg). The higher extractable P concentration in the 0-1 cm layer will create a greater P mobilization risk in surface runoff and leachate than analysis of the 0-10 cm layer might suggest. Assessment of P risk using the 0-10 cm data would still be reliable as P concentration in the 0-1 cm layer was linearly related (R2 = 0.59) with concentration in the 0-10 cm layer. The sampling at varied soil depths will result in different critical P levels for estimating the risk of P enrichment in runoff. In a glasshouse study with intact soil columns, initial high P concentrations in leachate decreased with leaching events suggesting that macropore flow dominated in initial leaching events changing later to matrix flow. The hydraulic behavior of clay and loam soil below 10 cm depends largely on structure and the type of clay minerals and exchangeable Na. Higher levels of exchangeable Na in the subsoil might increase dispersion of clay particles resulting in low permeability leading to ponding of surface water or lateral movement of water at the interface of sand A and clay B horizons. Lateral water movements increase the risk of P losses in the form of DP, dissolved organic P (DOP) or PP. The P concentration in all the P forms (DRP, DOP and TDP) increased significantly with P rates of application (P < 0.01). The DRP concentration was < 2 mg/l in unfertilized columns but an increase to 11 mg/l was observed with P application at 40 kg P/ha. The higher proportion of DOP relative to DRP and its correlation with TDP indicates that the DOP was the major form of P in leachate. However, the estimation of DOP which was by subtraction of DRP from TDP generally overestimates OP concentration. The TDP load from unfertilized soil was < 0.20 mg/l in runoff and < 2.40 mg/l in throughflow but increased with P application (20, 40 kg P/ha) for both packed box and field studies. Under field conditions, higher P loss was found with broadcast P application compared to drill placement. The higher load of DOP as a proportion of TDP and its significant relationship with TDP in runoff (R2sand = 0.81; R2clay = 0.79) and throughflow (R2sand = 0.94; R2clay = 0.98) in field and box studies also suggests DOP was the major form of P loss from soil. Dissolved OP concentration increased significantly with increase in soluble organic carbon (SOC) in soil solution at 5 cm depth (P < 0.05). Consequently, the amount of organic matter dissolved in soil solution may influence P sorption and mobility. Relatively higher affinity of soil for sorption of DRP compared to DOP might allow DOP to be more mobile through the profile. Higher PP load in clay soil in throughflow indicates subsurface lateral flow along the interface with the horizon of dispersive clay might be an additional risk factor regarding P mobility in clay soils of the catchment. The runoff, throughflow and leachate were dominated by eroded particles of clay and colloidal organic materials. However, the soil solution collected though 0.1 m pores in the Rhizon samplers had a similar dominance of DOP to the < 0.45 jum filtered samples in runoff and throughflow. This reduces the likelihood that the so-called DOP fraction was mostly P associated with PP in the 0.1 to 0.45 jum size fraction. The composition of DOP in soil solution collected through Rhizon samplers (< 0.1 jum) might provide important insights for P mobility since this more effectively excluded PP than in the < 0.45 jum filtrate used for runoff and throughflow samples. The DOP in soil solution (< 0.1 jum) might be associated with fine colloidal compound such as silicates, metallic hydroxides, humic acids, polysaccharides, fulvic acids and proteins. If so, then most, but not all of the DOP fraction would be organically bound. However, this requires verification. In conclusion, soil P levels across the catchment were never very high when assessed in the 0-10 cm layer, but levels in the 0-1 cm layer were more than twice as high. Overall, < 1 % of land area of the upper Fitzgerald River catchment had Colwell-P levels > 30 mg/kg (0-10 cm) and hydrological connection to streams. In addition, another 7 % of land had Colwell-P levels > 15 mg/kg, which appears to be a change point in soils for the release of CaCl2 extractable P. These areas, which are predicted to represent critical source areas of the catchment, need careful management. The high proportions of TDP as DOP in runoff, throughflow and soil solution suggest DOP was the major form of P loss from soil. Phosphorus losses from the catchments are also likely in the form of PP in clay and loam soil but leaching losses are more likely in sand. High exchangeable Na in the subsoil of loam and clay soils increases dispersion of clay particles resulting in low permeability of subsoil and greater lateral P mobility as throughflow at the interface of sand and clay textured horizons. In general, soils of Fitzgerald River catchment had low soil P, but nevertheless significant risk of P loss at Colwell-P > 15 mg/kg. This study provides baseline information for P loss risks in the wheatbelt of WA. Stream water quality monitoring instruments were installed in the upper Fitzgerald River Catchment at 5 stream locations by CSIRO to measure base line concentrations of P. The measured P concentrations were higher than ANZECC trigger values (> 0.05 mg P/l) for management response over the three-year monitoring period (2005-07). Hence this and many other catchments on the south coast and wheatbelt of south west Western Australia need assessment for P loss risks. Previous emphasis in south west Western Australia on P losses from sandy coastal soils under pasture may need to be reconsidered. In the South coast region, cropping land in the medium rainfall zone may still represent a risk of P loss to waterways and risk to water quality. The present study evaluated the risk of P loss based on soil P forms and their mobility. It suggests greater attention needs to be given to the difference between clay and loam soils with dispersive or non-dispersive sub-soils, and to the composition and mobility of DOP. However, a more complete understanding of P loss risks depends on follow-up studies on hydrological flow and connectivity in the upper Fitzgerald River catchment and similar landscapes of south west Western Australia.

Following over 100 years of agriculture and continuous phosphorus (P) fertilizer application in the south west of Western Australia, there is a growing risk of P transport from cropping and pasture land to streams. However, soil and landscape factors affecting the likelihood of P losses and of stream water contamination have not yet been assessed for the South coast region of Western Australia. The present investigation was conducted in the Fitzgerald River catchment located ~ 400 km south east of Perth, to identify risk of P losses from agricultural land to streams, through an understanding of how P is retained within complex landscapes and released via surface and subsurface flow paths. The 104,000 ha catchment is in a moderately dissected landscape (average annual rainfall 450 mm) and discharges into the World Heritage listed Fitzgerald Biosphere. The main use of cleared land in the catchment is broad-scale agriculture, primarily winter grain cropping and pasture for livestock. The aim of an initial study was to identify the areas with high soil P concentrations and their relationship to factors such as soil type, topography, management (e.g. fertilizer and manure inputs, and uptake by crops or forage) and how variations in soil P concentrations were related to soil physico-chemical properties, P fertilizer management and landscape position. A wide variation in P concentrations was observed across the catchment, but few of the samples exceeded Colwell extractable P levels of 30 mg/kg in the 0-10 cm layer which is regarded as a critical level for crop and pasture productivity. The western area of the catchment, which was cleared earlier (before 1966) than the eastern area had a greater prevalence of loam soils, and higher Colwell-extractable P concentrations (average)22 mg/kg vs. 13 mg P/kg) due to soil type effects and higher P accumulation over time. Risk of P loss from the east and west of the catchment is expected to vary due to textural and topographic differences and P history (P fertilizer input and uptake by crops). The CaCl2-extractable P in the catchment was negatively correlated with oxalate extractable Fe (Feox) in soils. This suggests that P may be transported as particulate P (PP) on loam and clay soils due to sorption of P on oxides surfaces, while on sand soil leaching losses may be more likely. On loam and clay soils, higher sodicity and the dispersive nature of subsoils may increase the risk of both dissolved P (DP) and PP loss due to the effects on hydraulic conductivity of the profile. Hedley's fractionation scheme was used to quantify P fractions in the order of decreasing lability, viz: resin-P > NaOH-Pi > NaOH-Po > acid-P (H2SO4-P) > residual-P. Surface soil had higher resin and NaOH-Pi, which are regarded as water-soluble and readily exchangeable P forms, respectively and expected to contribute to DP in the runoff losses. The residual P was the largest fraction followed by the hydroxide extractable organic-P fraction (NaOH-Po): the former was positively correlated (r) with clay content, organic carbon (OC) and pyrophosphate extractable Fe and Al (0.48**, 0.61**, 0.69** and 0.58**, P < 0.01). A relatively higher value of NaOH-Po in the subsurface layer and positive correlation with OC (r = 0.45**, P < 0.01) suggests potential mobility of P as soluble organic P in run-off, throughflow and leachate. Phosphorus sorption and its relationship to soil properties was used to assess the potential P release from the catchment soils. Values of P sorption maxima varied from 1111-3333 mg/kg for surface soils and 1010-2917 mg/kg for subsoils. The P sorption isotherms conformed better to the Freundlich equation than the Langmuir equation. A highly significant negative correlation between CaCl2 extractable P and Feox in surface soils (r = -0.65**, P < 0.01) suggests that P was bound to hydrated Fe oxide surfaces and this may determine the concentration and dynamics of loosely bound P equilibrating with leachates and eroded particulate materials. On the other hand, high surface organic matter and the high proportion of total dissolved P in organically bound form may inhibit P sorption on clays and sesquioxides, which would increase P mobility through leaching or runoff losses. The relationship between soil P concentration and degree of P stratification in the top 0-10 cm of soils along five toposequences was examined to predict the effect on runoff P losses. The total Colwell-P content of the 0-10 cm layer of soils in the catchment was very low in comparison to other studies on P losses from agricultural soils, but soils showed higher P concentration at 0-1 cm depth compared to 5-10 cm (average 37 mg/kg vs. 19 mg/kg). The higher extractable P concentration in the 0-1 cm layer will create a greater P mobilization risk in surface runoff and leachate than analysis of the 0-10 cm layer might suggest. Assessment of P risk using the 0-10 cm data would still be reliable as P concentration in the 0-1 cm layer was linearly related (R2 = 0.59) with concentration in the 0-10 cm layer. The sampling at varied soil depths will result in different critical P levels for estimating the risk of P enrichment in runoff. In a glasshouse study with intact soil columns, initial high P concentrations in leachate decreased with leaching events suggesting that macropore flow dominated in initial leaching events changing later to matrix flow. The hydraulic behavior of clay and loam soil below 10 cm depends largely on structure and the type of clay minerals and exchangeable Na. Higher levels of exchangeable Na in the subsoil might increase dispersion of clay particles resulting in low permeability leading to ponding of surface water or lateral movement of water at the interface of sand A and clay B horizons. Lateral water movements increase the risk of P losses in the form of DP, dissolved organic P (DOP) or PP. The P concentration in all the P forms (DRP, DOP and TDP) increased significantly with P rates of application (P < 0.01). The DRP concentration was < 2 mg/l in unfertilized columns but an increase to 11 mg/l was observed with P application at 40 kg P/ha. The higher proportion of DOP relative to DRP and its correlation with TDP indicates that the DOP was the major form of P in leachate. However, the estimation of DOP which was by subtraction of DRP from TDP generally overestimates OP concentration. The TDP load from unfertilized soil was < 0.20 mg/l in runoff and < 2.40 mg/l in throughflow but increased with P application (20, 40 kg P/ha) for both packed box and field studies. Under field conditions, higher P loss was found with broadcast P application compared to drill placement. The higher load of DOP as a proportion of TDP and its significant relationship with TDP in runoff (R2sand = 0.81; R2clay = 0.79) and throughflow (R2sand = 0.94; R2clay = 0.98) in field and box studies also suggests DOP was the major form of P loss from soil. Dissolved OP concentration increased significantly with increase in soluble organic carbon (SOC) in soil solution at 5 cm depth (P < 0.05). Consequently, the amount of organic matter dissolved in soil solution may influence P sorption and mobility. Relatively higher affinity of soil for sorption of DRP compared to DOP might allow DOP to be more mobile through the profile. Higher PP load in clay soil in throughflow indicates subsurface lateral flow along the interface with the horizon of dispersive clay might be an additional risk factor regarding P mobility in clay soils of the catchment. The runoff, throughflow and leachate were dominated by eroded particles of clay and colloidal organic materials. However, the soil solution collected though 0.1 m pores in the Rhizon samplers had a similar dominance of DOP to the < 0.45 jum filtered samples in runoff and throughflow. This reduces the likelihood that the so-called DOP fraction was mostly P associated with PP in the 0.1 to 0.45 jum size fraction. The composition of DOP in soil solution collected through Rhizon samplers (< 0.1 jum) might provide important insights for P mobility since this more effectively excluded PP than in the < 0.45 jum filtrate used for runoff and throughflow samples. The DOP in soil solution (< 0.1 jum) might be associated with fine colloidal compound such as silicates, metallic hydroxides, humic acids, polysaccharides, fulvic acids and proteins. If so, then most, but not all of the DOP fraction would be organically bound. However, this requires verification. In conclusion, soil P levels across the catchment were never very high when assessed in the 0-10 cm layer, but levels in the 0-1 cm layer were more than twice as high. Overall, < 1 % of land area of the upper Fitzgerald River catchment had Colwell-P levels > 30 mg/kg (0-10 cm) and hydrological connection to streams. In addition, another 7 % of land had Colwell-P levels > 15 mg/kg, which appears to be a change point in soils for the release of CaCl2 extractable P. These areas, which are predicted to represent critical source areas of the catchment, need careful management. The high proportions of TDP as DOP in runoff, throughflow and soil solution suggest DOP was the major form of P loss from soil. Phosphorus losses from the catchments are also likely in the form of PP in clay and loam soil but leaching losses are more likely in sand. High exchangeable Na in the subsoil of loam and clay soils increases dispersion of clay particles resulting in low permeability of subsoil and greater lateral P mobility as throughflow at the interface of sand and clay textured horizons. In general, soils of Fitzgerald River catchment had low soil P, but nevertheless significant risk of P loss at Colwell-P > 15 mg/kg. This study provides baseline information for P loss risks in the wheatbelt of WA. Stream water quality monitoring instruments were installed in the upper Fitzgerald River Catchment at 5 stream locations by CSIRO to measure base line concentrations of P. The measured P concentrations were higher than ANZECC trigger values (> 0.05 mg P/l) for management response over the three-year monitoring period (2005-07). Hence this and many other catchments on the south coast and wheatbelt of south west Western Australia need assessment for P loss risks. Previous emphasis in south west Western Australia on P losses from sandy coastal soils under pasture may need to be reconsidered. In the South coast region, cropping land in the medium rainfall zone may still represent a risk of P loss to waterways and risk to water quality. The present study evaluated the risk of P loss based on soil P forms and their mobility. It suggests greater attention needs to be given to the difference between clay and loam soils with dispersive or non-dispersive sub-soils, and to the composition and mobility of DOP. However, a more complete understanding of P loss risks depends on follow-up studies on hydrological flow and connectivity in the upper Fitzgerald River catchment and similar landscapes of south west Western Australia.

Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1996.
National Grid reference (SI 54) 6527-36 ; 44, 45, 36, 37 1:10 000 sheets. Includes bibliographical references.

The forests of south-eastern Australia, having evolved in one of the most fire-prone environments in the world, are characterized by many adaptations to recovery following burning. Thus forest ecosystems are characterized by rapid regenerative capacity, from either seed or re-sprouting, and mechanisms to recover nutrients volatilized, including an abundance of N2 fixing plants in natural assemblages. Soil physical, chemical and biological properties are directly altered during fire due to heating and oxidation of soil organic matter, and after fire due to changes in heat, light and moisture inputs. In natural ecosystems, carbon (C) and nitrogen (N) lost from soil due to fires are recovered through photosynthesis and biological N2 fixation (BNF) by regenerating vegetation and soil microbes.
This study investigated post-fire recovery of soil C and N in four structurally different sub-alpine plant communities (grassland, heathland, Snowgum and Alpine ash) of south-eastern Australia which were extensively burnt by landscape-scale fires in 2003. The amount and isotopic concentration of C and N in soils to a depth of 20 cm from Alpine ash forest were assessed five years after fire in 2008 and results were integrated with measurements taken immediately prior to burning (2002) and annually afterwards.
Because the historical data set, comprised of three soil samplings over the years 2002 to 2005, consisted of soil total C and N values which were determined as an adjunct to 13C and 15N isotopic studies, it was necessary to establish the accuracy of these IRMS-derived measurements prior to further analysis of the dataset. Two well-established and robust methods for determining soil C (total C by LECO and oxidizable C by the Walkley-Black method) were compared with the IRMS total C measurement in a one-off sampling to establish equivalence prior to assembling a time-course change in soil C from immediately pre-fire to five years post-fire. The LECO and IRMS dry combustion measurements were essentially the same (r2 >0.99), while soil oxidizable C recovery by the Walkley-Black method (wet digestion) was 68% compared to the LECO/IRMS measurements of total C. Thus the total C measurement derived from the much smaller sample size (approximately 15 mg) combusted during IRMS are equivalent to LECO measurement which require about 150 mg of sample.
Both total C and N in the soil of Alpine ash forests were significantly higher than soils from Snowgum, heathland and grassland communities. The ratio of soil NH4+ to NO3- concentration was greater for Alpine ash forest and Snow gum woodland but both N-fractions were similar for heathland and grassland soils. The abundance of soil 15N and 13C was significantly depleted in Alpine ash but both isotopes were enriched in the heathland compared to the other ecosystems. Abundance of both 15N and 13C increased with soil depth.
The natural abundance of 15N and 13C in the foliage of a subset of non-N2 fixing and N2 fixing plants was measured as a guide to estimate BNF inputs. Foliage N concentration was significantly greater in N2 fixers than non-N2 fixers while C content and 13C abundance were similar in both functional groups. Abundance of 15N was depleted in the N2 fixing species but was not significantly different from the non-N2 fixers to confidently calculate BNF inputs based on the 15N abundance in the leaves.
The total C pool in soil (to 20 cm depth) had not yet returned to the pre-fire levels in 2008 and it was estimated that such levels of C would be reached in another 6-7 years (about 12 years after the fire). The C and N of soil organic matter were significantly enriched in 15N and 13C isotopes after fire and had not returned to the pre-fire levels five years after the fire. It is concluded that the soil organic N pool can recover faster than the total C pool after the fire in the Alpine ash forests.

A field-based project was undertaken to develop and test a mechanism which would allow for the correlation of the health of vegetation surrounding playa lakes in south-west Australia with the natural variation in salinity and waterlogging that occurs spatially and temporally in natural systems. The study was designed to determine threshold ranges of vegetation communities using moderately extensive data over short temporal periods which will guide the design of potential engineering solutions that manipulate hydrological regimes to ultimately conserve and protect native vegetation. A pair of playa lake ecosystems, surrounded by primary production land, was modelled with hydro-geological data collected from March 2006 to March 2007. The data was used to determine the hydroperiods of vegetation communities fringing playa lakes and provide insight into the areas and species that are most affected by extreme rainfall events which are hypothesised to have a significant, rapid deleterious effect on the ecosystems. The methodology was multi-faceted and included; a detailed topographical survey; vegetation surveys; hydrological and hydro-geological monitoring over a 12 month period. 4 The hydro-geological data and vegetation data was linked with the topographical survey at a high resolution for spatial analysis in a Geographic Information System (GIS) to determine the degree of waterlogging experienced by vegetation communities over the monitoring period. The study has found that the spatial and temporal variability of hydroperiods has been reduced by rising groundwater levels, a result of extensive clearing of native vegetation. Consequently populations are becoming extinct locally resulting in a shift in community composition. Extreme summer rainfall events also have a significant impact on the health of vegetation communities by increasing the duration of waterlogging over an annual cycle and in some areas expanding the littoral zone. Vegetation is most degraded at lower positions in the landscape where communities are becoming less diverse and dominated by salt tolerant halophytic species as a result of altered hydrological regimes. Some species appear to be able to tolerate groundwater depths of less than 2.0 m from the surface, however there are thresholds related to the duration at which groundwater is maintained at this depth. Potential engineering solutions include groundwater pumping and diverting water through drains to maintain sustainable hydroperiods for vegetation in areas with conservation value. The effectiveness and efficiency of the engineering solutions can be maximised by quantifying thresholds for vegetation that include sustainable durations of waterlogging. The study has quantified tolerance ranges to salinity and waterlogging with data collected over 12 months but species may be experiencing a transition period where they have 5 sustained irreversible damage that will result in their eventual mortality. With long-term monitoring, the methodology developed and tested in the study can be used to quantify the long-term tolerance ranges that are important for the application of conservation approaches that include engineering solutions.

Soil structure and its associated physical properties are essential soil components. Soil texture and mineralogy are inherent soil properties that influence soil management. This study assessed the implication of tillage, texture and mineralogy on soil sieving, aggregate stability indices and physical fractions of organic matter in soils of Eastern Cape Province of South Africa. An Iris FTLVH – 0200 digital electromagnetic sieve shaker (Filtra Vibraciόn SL Spain), was used to determine settings for sieving efficiency. Mean weight diameter (MWD), water stable aggregate (WSA), state of aggregation (SA), dispersion ratio (DR), water dispersible clay (WDC), clay dispersion ratio (CDR), clay flocculation index (CFI), and potential structural deformation index (PSDI) were aggregate stability indices evaluated to check for sensitivity in evaluating aggregate stability of soils under two tillage systems and physical fractions of carbon and nitrogen in soils of Eastern Cape Province. The T4I3P2 and T4I4P3 settings were sensitive under tillage and T4I1P4, T3I4P3 and T4I4P3 were sensitive under mineralogical considerations for sieving efficiency. The total carbon in soils under conventional tillage (CT) was 17.7 g/kg and in soils under no tillage (NT) it was 15.8 g/kg. The total carbon content in the clay fraction of soils under CT was 24.1 percent higher than the total carbon content in the clay fraction of soils under NT. The total nitrogen content in the clay fraction of soils under CT was 5.4 percent higher than the total nitrogen content in the soils under NT. The total carbon in the sandy loam (SL) textured soils was 17.4 g/kg and in the sandy clay loam (SCL) textured soils it was 17.1 g/kg. The total nitrogen in SL soils was 3.7 g/kg and in SCL soils it was 3.7 g/kg. The clay fraction had higher total carbon than other fractions in Sl and SCL soils. The higher values of nitrogen were observed in the silt fraction for SL soils and clay fraction for SCL soils. The total carbon in the soils dominated with kaolinite was 17.3 g/kg and in quartz dominated soils the value was 16.9 g/kg. The total nitrogen in the soils dominated with kaolinite was 3.7 g/kg and in the soils dominated with quartz the value was 3.7 g/kg. For soils under NT the WDC was 135.8 g/kg and for soils under CT it was 139.7 g/kg. The ASC was 72.5 for soils under NT and 92.0for soils under CT. The DR was 0.9 for soils under NT and 0.8 for soils under CT. The CFI was 0.5 for soils under NT and 0.5 for soils under CT. The CDR was 0.5 for soils under NT and 0.5 for soils under CT. The MWDw was 1.6 mm for soils under NT and 1.4 mm for soils under CT. The MWDd was 4.0 mm for soils under NT and 4.0 for soils under CT. The percent WSA > 0.25 mm was 61.7 percent for soils under NT and 56.2 percent for soils under CT. The PSDI was 55.2 percent for soils under NT and 61.15 percent for soils under CT. The SA was 43.2 percent for soils under NT and 37.89 percent for soils under CT. The WDC was 125.7 g/kg for SCL soils and 151.4 g/kg for SL soils. The CDR was 0.5 for both SCL and SL soils. The DR was 0.9 for SCL soils and 0.8 for SL soils. The CFI was 0.5 for both SCL and SL soils. The ASC was 56.2 g/kg for SCL soils and 115 g/kg for SL soils. The MWDw was 1.5 mm for SCL soils and 1.4 mm for SL soils. The MWDd was 3.6 mm for SCL soils and 3.6 mm for SL soils. The percent WSA > 0.25 mm was 53.0 percent for SCL soils and 62.5 percent for SL soils. The PSDI was 59.2 percent for SCL soils and 59.7 percent for SL soils. The SA was 33.6 percent for SCL soils and 45.2 percent for SL soils. The WDC was 313.3 g/kg for kaolinitic soils and 120.7 g/kg for quartz dominated soils. The CDR was 0.5 for kaolinitic soils and 0.5 for quartz dominated soils. The DR was 0.9 for kaolinitic soils and 0.8 for quartz dominated soils. The CFI was 0.5 for kaolinitic soils and 0.5 for quartz dominated soils. The ASC was 110.0 g/kg for kaolinitic soils and 101.7 g/kg for quartz dominated soils. The WSA > 0.25 mm was 57.3 percent for quartz dominated soils and 68.4 percent for kaolinitic soils. The MWDw was 1.6 mm for quartz dominated soils and 0.8 mm for kaolinitic soils. The MWDd was 3.6 mm for quartz dominated soils and 3.4 mm for kaolinitic soils. The PSDI was 56.3 for quartz dominated soils and 76.0 for kaolinitic soils.

Bibliography: p. 182-197. The objectives of this study are: selection and construction of four narrow sowing points, evaluation of these points in terms of draught requirements and wear rates, comparison of the points in direct drilling systems and their effects on soil physical properties.

Includes bibliographical references (leaves 78-86) In the Herrmanns sub-catchment in the Mt. Lofty Ranges (near Mt. Torrens) soil sodicity was the dominant factor in causing clay to disperse in the eroded area along the foot slopes, wheras in non-eroded areas of the mid-slopes and on the stream banks, the dispersive power of sodicity was attenuated by the flocculative power of other soil properties.

In many parts of the world, the increasing demand for timber and other forest products has led to loss, fragmentation, degradation or modification of natural forest habitats. The consequences of such habitat changes have been well studied for some animal groups, however not much is known of their effects on bats. In Australia, logging of native forests is a major threat to the continent‘s biodiversity and while logging practices have undergone great changes in the past three decades to selective logging (including ecologically sustainable forest management), which is more sympathetic to wildlife, there is still concern about the effects of logging on the habitat of many forest-dwelling animals. The goal of this thesis was to investigate the effects of logging on the bat species assemblages at both community and individual species levels in terms of their foraging and roosting ecology in jarrah forests of south-western Australia. This information is necessary to strengthen the scientific basis for ecologically sustainable forest management in production forests. The outcome of this research may help in the formulation of policy and management decisions to ensure the long-term maintenance and survival of viable populations of forest-dwelling bats in these altered environments. Bats were selected because they comprise more than 25% of Australia‘s mammal species and constitute a major component of Australia‘s biodiversity. In addition, bats play key roles in forest dynamics and may act as indicators of disturbance. In the jarrah forests, bats are a significant proportion of the mammal fauna (9 of around 30 native extant species). As a basis of understanding how bats use modified habitats, nine species of bats were investigated by assessing their foraging and commuting habits (measured as bat activity) in different forest types (logged, young regrowth and old regrowth forest). To assess patterns of habitat use across a gradient of managed forest conditions, and to help predict impacts of logging on bats, four replicates were selected from each of three distinct post-harvest management treatments, recently logged forest or gaps (<6 years since logging), young regrowth forest (12–30 years since logging) and old regrowth forest (> 30 years old). Sites were monitored for bat activity on two nights, with Anabat detectors placed on track and off-track positions. The relationships between bat species assemblages in terms of their relative use and foraging activity and various forest structural variables, and the relationship between bats and the insect biomass were examined in order to identify the effects on the bat fauna of historical logging practices. Overall, 12 sites were sampled (four sites for each forest type) with bat activity and vegetation structure conducted on-track and off-track at each site and insect abundance sampled only at off-track sites. Secondly, because roosts are an important resource for bats, and may be a limiting factor in modified landscapes, we investigated the roosting requirements of two sympatric species of jarrah forest-dwelling vespertilionid bats, the Southern forest bat Vespadelus regulus and Gould‘s long-eared bat Nyctophilus gouldi. Their sensitivity to the loss of roost sites from logging and the effectiveness of current management practices at conserving appropriate roost sites were examined. As part of the research, tree (age, size, type, condition, presence of hollows, loose bark) and landscape characteristics (elevation, logging history, distance to water holes and creeklines, etc) of roosting sites were compared with random trees and their surrounding forest structure at local roost tree and broader landscape scales to determine whether bats selected roost trees and sites with particular characteristics. The fieldwork was carried out during 2007 – 2009 and information was gathered through capture, radiotelemetry and passive monitoring using echolocation call detectors. Specifically, harp traps and radiotelemetry were used for roost-selection studies while Anabat bat detectors were used to assess bat activity (commuting, foraging) among different logging histories and in response to forest structural attributes and insect activity. Light traps were used to assess insect availability in relation to bat activity and forest structure. The activity of different bat species related in different ways to the structural vegetation parameters, generally reflecting bat echolocation ability and manoeuvrability. Bats tended to use tracks more than off-track locations, thereby avoiding clutter at off-track locations. At the same time, tracks recorded similar activity across logging histories. However, off-track activity in old regrowth was significantly greater than either young regrowth or recently logged forest. Two taxa, Vespadelus regulus and Nyctophilus spp. were more active in old regrowth than other logging histories. Similarly, V. regulus, Nyctophilus spp., Chalinolobus gouldii, C. morio and Falsistrellus mackenziei activity was significantly greater on-track than off-track, but this activity was similar on-track across forest types, suggesting bats‘ use of forest tracks was unaffected by logging. As an indication of the association of low bat activity off-track with clutter, negative relationships of under-storey clutter were the most consistent predictors of bat habitat use. Conversely, reduced clutter and abundant roost resources seemed the most likely explanations for greater activity at old regrowth sites. There were both inter-specific similarities and differences in the selection and location of roost trees and roost sites between V. regulus and N. gouldi. Both species were highly selective, preferring old large trees (> 80 cm diameter at breast height over bark – DBHOB) at intermediate or advanced stages of decay, crown senescence and deterioration with a lower percent bark cover compared to random trees. Both species also selected hollows for roosting, with V. regulus roosting exclusively in hollows but a few N. gouldi also used roosts under decorticating bark, cracks and under balga (Xanthorrhoea preissii) skirts. V. regulus preferred tall trees in the canopy with roost entrances high above the ground with little surrounding vegetation while N. gouldi preferred roosting closer to the ground and in dense clutter. In general, little evidence was found of bats roosting in either shelterwood creation or gap release silvicultural treatments, although a few N. gouldi bats roosted in retained habitat, or remnant, trees in these silvicultural treatments. Only riparian buffers and structurally mature forests appeared to provide multiple alternate roosts, containing a higher density of trees with hollows required by bats for roosting. In contrast, gap release and shelterwood creation sites contained substantially lower densities of hollow bearing trees. Pockets of mature forest that were previously only lightly and selectively logged before the introduction of Ecologically Sustainable Forest Management (ESFM) were important roosting sites for bats. However, although some N. gouldi bats selected roosts in retained or remnant trees in gap release and shelterwood creation silvicultural treatments, it remains unclear if bats can successfully breed in such regrowth forests in the absence of older forest stands and this should be a priority for future studies. This study demonstrated that unharvested buffer strips surrounding ephemeral streams, and more open mature forests, with reduced midstoreys, were important roosting habitats for bats because they provided a large pool of older and mature trees in a variety of decay classes as roost sites. With short logging rotations in the jarrah forests and with only approximately 39 % total forest area currently reserved from logging in the study area, the roosting requirements of bats may be affected negatively as the abundance of old trees with hollows, exfoliating bark and other forms of senescence may be reduced. Thus, although this study demonstrated the importance of mature forest and buffers as mitigating measures on bat roost sites, it was unclear whether the area of retained habitat is adequate for for roosting bats given the dynamics of logging regimes in the jarrah forests, and this should be a priority to address in future research. As the only mammals capable of true flight, bats may persist in selectively logged forests. However, as this study showed, bats are specialised in their foraging and roosting requirements. Therefore, the maintenance of forest tracks and the protection, and sustained recruitment, of hollow-bearing trees are essential for the conservation of these animals in such modified landscapes. Current management practices in the jarrah forests have created a mosaic of successional stages within logged landscapes that may satisfy the foraging requirements of many bat species. This is especially true because tracks and unlogged buffers and structurally mature forest with reduced clutter provided access to post-disturbance forests such as regrowth areas. The study also demonstrated that habitat retention, as provided by adjacent streamside buffers and mature forest in the jarrah forests were important roost sites for bats, and could mitigate against logging impacts in the long term. However, retained habitat trees in logged coupes were avoided by roosting bats and further studies are required to demonstrate if these can be used effectively by viable bat populations, especially in the absence mature unlogged forest and unlogged riparian buffers nearby. In addition, further research is required to shed light on bat overwintering and maternity roost sites that are important for the survival of bat populations. In addition, a long-term study to clarify temporal/seasonal and intra-specific variation in bat distribution and roost site selection needs to be undertaken in the jarrah forests of south-western Australia to better determine if current ESFM practices are effective at maintaining bat populations in logged forests.

Thesis (MSc)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: Bush encroachment in savannas leads to reduced diversity, productivity and profitability of rangelands. This holds important implications for the livestock and eco-tourism industries, as well as for subsistence ranchers in the South African semi-arid savannas, who depend on this vegetation type for economic and livelihood purposes. Soil moisture, nutrients, rue and herbivory are generally regarded as the principal factors determining vegetation structure and function within savannas. The factors and processes involved in the determination of the tree:grass ratio within savannas are, however, not clearly understood. We investigated the role of soil type and management strategy (cattle, game and communal grazing) in the determination of the presence and distribution of plant species in general, and on the presence and distribution of the encroaching tree species, Acacia mellifera, specifically. Both shortand long-term trends were investigated. The study area, the Kimberley Triangle, (Northern Cape Province, South Africa), was ideal for this kind of study because it has different management strategies practised on several soil types, and bush encroachment is a widespread phenomenon. Contrary to the belief that heavy livestock grazing is the main cause of increases in the tree:grass ratio, we found that soil type, through its effects on plant growth and on the presence and availability of soil moisture and nutrients, is more important in determining vegetation composition than management strategy. It was found that the various types of grazing management mainly influenced vegetation structure and function by affecting the competitive interactions between Ns-fixing woody species and non-Ns-fixing grasses. Of the soil factors affecting vegetation composition, soil texture was a good indicator of the physical conditions for plant growth in an area, and also of the presence and availability of soil moisture and nutrients. We found that sand and clay soils are relatively resistant to bush encroachment as compared to loamy-sand and -clay mixes. This is because woody growth is impaired in the first-mentioned habitats by soil texture, soil moisture regimes and heavy utilisation. In soils with combinations of loam, sand and clay, soil texture and moisture are not limiting to woody growth and if the repressive competitive effect of grasses on woody vegetation is removed, opportunities are created for recruitment of woody species and encroachment. Additionally, rockiness increases soil moisture infiltration. In the study area, woody species, and specifically A. mellifera, are associated with these areas. We suggest that in the study area, rocky areas are naturally encroached. This is in agreement with the patchdynamic approach to savanna vegetation dynamics. Because soil moisture is such an important factor in the determination of the tree:grass ratio in the study area, we further suggest that in above-average rainfall years, when soil moisture conditions are optimal for woody seed germination, establishment and growth, heavy grazing should be avoided, as it would provide the opportunity for encroachment. Keywords: Bush encroachment; N2-fixing species; game, cattle, communal grazing; soil texture; soil moisture; soil nutrients; Acacia mellifera; tree-grass competition.
AFRIKAANSE OPSOMMING: Bosindringing in savanna gebiede het verlaagde diversiteit, produktiwiteit en winsgewendheid van natuurlike weivelde tot gevolg. Behalwe dat dit die Suid-Afrikaanse vee- en ekotoerisme bedrywe raak, is verskeie bestaansboerderye afhanklik van die plantegroei-tipe vir oorlewing. Grondvog, grondvoedingstowwe, vuur en beweiding word algemeen aanvaar as die belangrikste faktore wat die struktuur en funksie van savannas bepaal. Daar is egter nog nie duidelikheid oor die prosesse wat betrokke is in die bepaling van die boom-gras verhouding in savannas nie. In dié studie het ons ondersoek ingestel na die invloed van grond tipe en beweidingstrategieë (beweiding deur beeste, wild, of kommunale beweiding) op die algemene verspreiding van verskillende plant spesies, en ook op die van die indringer spesie, Acacia mellifera. Beide kort- en lang-termyn patrone is ondersoek. Die studiegebied, die Kimberley Driehoek in die Noord-Kaap, Suid-Afrika, was ideaal vir so 'n ondersoek omdat verskillende beweiding strategieë op verskeie grond-tipes beoefen word maar bosindringing steeds 'n algemene verskynsel in die gebied is. Ons bevinding was dat, ten spyte van die feit dat daar oor die algemeen geglo word dat swaar beweiding die hoof oorsaak van bosindringing is, grond-tipe belangriker is in die bepaling van die spesie-samestelling van 'n gebied. Dit is as gevolg van die feit dat grond-tipe die groei van plante beïnvloed deur die teenwoordigheid en beskikbaarheid van grondvog en -nutriënte te bepaal. Die verskillende beweidingstrategieë beïnvloed meerendeels die kompetatiewe interaksies tussen N2-bindende hout-agtige spesies teenoor nie-Nj-bindende gras-agtige spesies. Grond-tekstuur was 'n goeie aanduiding van die algemene toestande vir plantegroei en ook van die teenwoordigheid en beskikbaarheid van grondvog en -nutriënte. Ons het bevind dat sand en klei grond, relatief tot leem, sand en klei kombinasies, weerstandbiedend is teen bosindringing as gevolg van die tekstuur, water-regimes en swaar beweidings vlakke wat op die grond-tipes voorkom. Omdat grond-tekstuur en grondvog nie beperkend is op die leem-, sand- en klei-grond kombinasies nie, kan bosindringing maklik hier voorkom as die onderdrukkende effek wat grasse op houtagtige plantegroei het, deur swaar beweiding verwyder word. A. mellifera is ook oor die algemeen met klipperige gebiede geassosieer omdat klipperigheid lei tot verhoogde infiltrasie van grondvog. In die studie-gebied is klipperige areas dan ook van nature ingedring deur A. mellifera. Dit stem ooreen met die siening dat savannas bestaan uit "laslappe" van verskillende plantegroei (patch-dynamic approach). Dit was duidelik dat grondvog 'n belangrike bepalende faktor is in die bepaling van die boom-gras verhouding in die studiegebied. Ons stel dus voor dat in bo-gemiddelde reënval jare, swaar beweiding vermy moet word, omdat houtagtige saailinge gedurende die tydperke maklik kan ontkiem en vestig juis omdat grondvog dan nie beperkend is nie. Sleutelwoorde: Bosindringing; N2-bindende spesies; bees, wild, kommunale beweiding; grond tekstuur; grond-vog; grond-nutriënte; Acacia mellifera; boom-gras kompetisie.

With the increased planting of E. globulus monoculture plantations, concerns surround the impact these mass plantings will have on the soil environment and wider ecosystem. Soil and litter mites are the dominant saprophages of terrestrial ecosystems, contributing to decomposition processes through their comminution and grazing activities. Despite the importance of mites to decomposition processes, there have been no investigations to date of the litter and soil communities under these plantations within Australia. This study investigated the impact of Eucalyptus globulus subsp. globulus (Tasmanian bluegum) monoculture plantations on the diversity and abundance of the soil and litter acarine (mite) fauna. Mite communities under three 8 year-old E. globulus plantations sited on reclaimed pastureland were compared with an adjacent native E. marginata (jarrah) forest and a grazed pasture in the mediterranean-type region of southwest Western Australia. Sites were sampled in spring 1997 and new sites randomly selected in autumn 1998. Large seasona1 variations in abundance and diversity were found between the sampling periods of spring 1997 and autumn 1998, influenced considerably by soil moisture. Species richness was consistently higher in both the soil and litter layers under native jarrah forest, with the E. globulus plantations intermediate in species richness between the native forest and grazed pasture. A total of 114 mite species/morphospecies was recognized; 16 Mesostigmata, 52 Prostigmata, 45 Oribatida (Cryptostigmata) and 1Astigmata. Species diversity in the surface litter was higher under the native forest, reflecting the greater heterogeneity of the litter. Diversity in the underlying soil was similar for the native forest and E. globulus plantation, although there were considerable differences in species richness. Soil diversity in the pasture was very poor in comparison to the two forest systems, reflecting the absence of a litter layer and reduced niche dimensions. The monospecific E. globulus litter possibly reduced niche variety by simplifying the physical habitat and reducing the variety of resources available for the saprophagous fauna, of which the oribatid mites are a major component. Consequently, the number of families represented in the microphytophagous, phytophagous and predator functional groups under the E. globulus plantation may have been reduced. The most common oribatid families under the plantation were those often reported from disturbed habitats, Oppiidae and Tectocepheidae, and those common in many habitats, Oppiinae and Oppiellinae. An important management implication arising from this study is that these plantations would harbour a more diverse mite fauna if planted as a mixed tree stratum.

Thesis (B. Sc.(Hons.)--University of Adelaide, Dept. of Geology and Geophysics, 1993.
On title page: National Grid reference (51-53) 6326-4 (1-50,000). Includes bibliographical references (leaves 45-50).

Comprised of the author's previously published works
Includes bibliographical references
1 v. (various pagings) :
Thesis (D. Sc.)--University of Adelaide, Dept. of Soil Science, Waite Agricultural Research Institute, 1988

Drip irrigation is the most common method of water application used in Australian vineyards. However it places physical and chemical stress upon soil structure, which may affect soil physical properties, soil water availability and grapevine functioning. Common soil types within Australian vineyards appear vulnerable to soil degradation and there is emerging evidence of such degradation occurring. Two South Australian vineyards (one located at Nuriootpa in the Barossa Valley, the other in the McLaren Vale winegrowing region) were used to examine evidence of altered soil physical properties due to irrigation. Significantly higher soil strength and lower permeability was found under or near the dripper in irrigated soils. There was also evidence that irrigation increased subsoil bulk density at Nuriootpa. It was uncertain how irrigation caused these changes. While sodicity was present at Nuriootpa, it appeared the physical pressures exerted by irrigation, such as rapid wetting and prolonged wetness, also contributed. To gauge the severity of the degradation at Nuriootpa, a modelling study assessed the impact of higher soil strength and salinity on grapevine transpiration. The SWAP model (Soil- Water-Atmosphere-Plant) was modified and then calibrated using soil moisture data from Nuriootpa. Simulations were conducted for different irrigation regimes and the model output indicated that degradation led to a reduction in cumulative transpiration, which was almost entirely due to higher soil strength. However the reduction was relatively minor and there was evidence of water extraction by roots in all soil layers. Hence the degradation, in terms of higher soil strength and salinity, was not considered a significant management problem in the short - term. Evidence of increased waterlogging and its consequences require further investigation. Roots were observed in soils at Nuriootpa with penetration resistance (PR) much greater than 2 MPa, which was thought to completely impede grapevine root growth. It was hypothesised that roots avoided the physically hostile matrix by using biopores or structural cracks. A pot experiment tested this hypothesis and examined the relationship between soil strength, biopores and root growth for grapevines. Grapevine rootlings (cv. Cabernet Sauvignon) were grown into pots with varying degrees of soil compaction, with and without artificial biopores. No root growth occurred when PR>2 MPa unless biopores were present. Pores also improved root growth in non-compacted soil when PR approached 1 MPa, which suggested biopores influence root growth in soils regardless of compaction levels. Therefore PR should not be the only tool used to examine the rooting-potential of a vineyard soil. An assessment of soil structure, such as biopore density and size, should be incorporated. In drip-irrigated vineyards, there is a possibility that degraded clayey subsoils could be ameliorated by manipulating zones of soil drying. At distances away from the dripper, drying events could generate shrinkage cracks that improve drainage and provide opportunities for root growth. From a practical perspective, drying events could be manipulated by moving the dripper laterally or by changing the irrigation frequency and intensity. The potential of this simple, non-invasive, ameliorative approach was investigated. Large, intact cores were sampled from Nuriootpa subsoil where degradation had been identified. Individual core bulk density was calculated using a formula that was derived by solving two common soil physics equations simultaneously. This proved to be an accurate and non - invasive method. Half the cores were leached with a calcium solution, and the saturated hydraulic conductivity (K [subscript s] ) was measured on all cores before and after drying to a matric potential of -1500 kPa. Soil drying led to a significant increase in K [subscript s], which indicated an improvement in structure through the creation of shrinkage cracks and heaving. Calcium treatment had no impact on K [subscript s], but that could change with more wetting and drying cycles. Results indicated the need for further investigation in the field, where different compressive and tensile forces operate. Harnessing this mechanism may provide an attractive soil management option for growers. The soil physical degradation identified is concerning for sustainable production in irrigated vineyards. Given the sites were representative of typical irrigation practices, such degradation may be widespread. While modelling suggested the impact of higher soil strength and salinity was minimal, these properties should be monitored because they may worsen with continuing irrigation. Furthermore, the impact of irrigation on subsoil permeability needs to be defined more accurately. An increased incidence of waterlogging could significantly restrict production, which was evident when overly wet growing seasons were modelled. If subsoil permeability was found to be significantly lower in irrigated soils, amelioration may be required. In this instance, the use of drying events to generate structure provides an option. Ultimately, the impact of drip irrigation on soil physical quality warrants further attention, and it is imperative to monitor the physical quality of vineyard soils to ensure sustainable production.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007.