Thesis (Ph.D)--Murdoch University, 2003. / Thesis submitted to the Division of Science and Engineering. Bibliography: leaves 219-235.

The quokka (Setonix brachyurus Quoy & Gaimard 1830) is a medium-sized, macropodid marsupial that is endemic to the mesic, south-western corner of Australia. While being a tourist icon on Rottnest Island, the species is threatened with extinction. It has been intensively studied on Rottnest Island in the 1960s and 1970s, however very little is known of its ecology on the mainland. Additionally the insular and mainland environments are extremely different suggesting that ecological differences between the two populations are likely. Consequently, this study sought to determine the basic autecology of the quokka and identify what factors have attributed to its threatened conservation status. The northern jarrah forest of Western Australia was selected as the study region due to it being at the northern limit of extant quokka distribution and because it was thought that the factors threatening the quokka would be exacerbated there. Fossil deposits suggest that the quokka originally occupied an area of approximately 49,000 km2 in the south-western corner of Australia. Historical literature show that they were widespread and abundant when Europeans colonised the region in 1829 but a noticeable and dramatic decline occurred a century later. The arrival of the red fox to the region coincided almost exactly with this decline and so it was probably ultimately responsible. Continued predation by both it and the feral cat are likely to have continued the decline, along with habitat destruction and modification through altered fire regimes. Specific surveys and literature searches show that since the 1950s, the area occupied by the quokka has declined by 45% and since 1990 by 29%. Based on the criteria of the IUCN (Hilton-Taylor 2000), the conservation status of the quokka should remain as vulnerable. An endangered status may be more applicable if the quokkas restriction to patches through its existence as a metapopulation is considered. Trapping of eight sites supporting quokka populations in the mid-1990s revealed three sites now locally extinct despite the ongoing, six year old, fox control programme. Another three are at serious risk of extinction. Extant population sizes ranged from one to 36 and population density ranged from 0.07 to 4.3 individuals per hectare. This is considered to be below the carrying capacity of each site. The overall quokka population size in the northern jarrah forest may be as low as 150 adult individuals, of which half are likely to be female. Even the largest extant populations are highly susceptible to stochastic extinction events. This small size was surprising considering the six year old, introduced predator control programme. Historically, the restriction to discrete habitat patches, the occasional inter-patch movement, the lack of correlation between the dynamics of each population and reports of frequent localised extinctions and colonisations suggest that the quokka population once existed as part of a classic metapopulation. The massive decline of the quokka in the 1930s pushed the metapopulation structure into a non-equilibrium state such that today, the extant populations are the terminal remnants of the original classic metapopulation. Wild mainland quokkas breed throughout the year. A significant reduction in the number of births occurs over summer and this coincides with a decline in female body weight. Despite this, the mainland quokka is relatively fecund and is able to wean two offspring per year. The level of recruitment from pouch young to independence was low and this may explain the apparent lack of population increase following the initiation of fox control. A total of 56 trapped quokkas were fitted with a radio collar. Mean home range size for quokkas was 6.39 ha with a core range of 1.21 ha and this was negatively related to population density. Male home ranges were larger than females but not significantly when the sexual size dimorphism was considered. Nocturnal ranges were larger than diurnal ranges reflecting nocturnal departures from the swamp refugia. Home range sizes varied seasonally, probably due to changes in the distance required to move to obtain sufficient nutrients and water over the dry summer compared to the wet winter and spring. Telemetry confirmed trapping results that showed no movement between swamps or populations. Home range centres shifted to the periphery of the swamp following the winter inundation and this may increase the species susceptibility to predation. The lack of dispersal is probably caused by quokka populations existing below carrying capacity and following selection for philopatry under the threat of predation for dispersing individuals. Without dispersal to recolonise or rescue unpopulated patches, the collapse of the original quokka metapopulation appears to have occurred. On a macrohabitat scale, the quokka in the northern jarrah forest is restricted to Agonis swamp shrubland habitats that form in the open, upper reaches of creek systems on the western side of the forest. This restriction was probably initially due to the high water requirements of the quokka but is likely to have been exacerbated by increased predation pressure since the arrival of the fox. On a microhabitat scale, the quokka is a habitat specialist, preferring early seral stage swamp habitats, probably for foraging, as part of a mosaic of old age swamp that provides refuge. Despite the six year old, introduced predator control programme, foxes and cats are still the major cause of mortality to quokkas. Road kills was the other identifiable cause. Individuals alive at the start of the study had an 81% chance of staying alive until the end. The likelihood of dying was minimised by grouping together with conspecifics, maximising home range size and maximising the time spent within the swampy refuge. Current rates of adult and juvenile survivorship should allow population recovery and so it seems pouch young mortality, reflected by low recruitment, has inhibited the anticipated population increase following predator control. The confounding effect of inadequate unbaited controls meant that little statistical evidence was available on the impact of introduced predators on the quokka, however the models provided support for earlier hypotheses of these. The presence of a quokka population at a site was related to the amount of poison baits delivered ??? reflecting predation pressure, the average age of the swamp and a mosaic of early and late seral stages within the swamp habitat. Recently burnt habitat is thought to provide food for quokkas and long unburnt habitat provides refuge from predation.

The quokka (Setonix brachyurus Quoy & Gaimard 1830) is a medium-sized, macropodid marsupial that is endemic to the mesic, south-western corner of Australia. While being a tourist icon on Rottnest Island, the species is threatened with extinction. It has been intensively studied on Rottnest Island in the 1960s and 1970s, however very little is known of its ecology on the mainland. Additionally the insular and mainland environments are extremely different suggesting that ecological differences between the two populations are likely. Consequently, this study sought to determine the basic autecology of the quokka and identify what factors have attributed to its threatened conservation status. The northern jarrah forest of Western Australia was selected as the study region due to it being at the northern limit of extant quokka distribution and because it was thought that the factors threatening the quokka would be exacerbated there. Fossil deposits suggest that the quokka originally occupied an area of approximately 49,000 km2 in the south-western corner of Australia. Historical literature show that they were widespread and abundant when Europeans colonised the region in 1829 but a noticeable and dramatic decline occurred a century later. The arrival of the red fox to the region coincided almost exactly with this decline and so it was probably ultimately responsible. Continued predation by both it and the feral cat are likely to have continued the decline, along with habitat destruction and modification through altered fire regimes. Specific surveys and literature searches show that since the 1950s, the area occupied by the quokka has declined by 45% and since 1990 by 29%. Based on the criteria of the IUCN (Hilton-Taylor 2000), the conservation status of the quokka should remain as vulnerable. An endangered status may be more applicable if the quokkas restriction to patches through its existence as a metapopulation is considered. Trapping of eight sites supporting quokka populations in the mid-1990s revealed three sites now locally extinct despite the ongoing, six year old, fox control programme. Another three are at serious risk of extinction. Extant population sizes ranged from one to 36 and population density ranged from 0.07 to 4.3 individuals per hectare. This is considered to be below the carrying capacity of each site. The overall quokka population size in the northern jarrah forest may be as low as 150 adult individuals, of which half are likely to be female. Even the largest extant populations are highly susceptible to stochastic extinction events. This small size was surprising considering the six year old, introduced predator control programme. Historically, the restriction to discrete habitat patches, the occasional inter-patch movement, the lack of correlation between the dynamics of each population and reports of frequent localised extinctions and colonisations suggest that the quokka population once existed as part of a classic metapopulation. The massive decline of the quokka in the 1930s pushed the metapopulation structure into a non-equilibrium state such that today, the extant populations are the terminal remnants of the original classic metapopulation. Wild mainland quokkas breed throughout the year. A significant reduction in the number of births occurs over summer and this coincides with a decline in female body weight. Despite this, the mainland quokka is relatively fecund and is able to wean two offspring per year. The level of recruitment from pouch young to independence was low and this may explain the apparent lack of population increase following the initiation of fox control. A total of 56 trapped quokkas were fitted with a radio collar. Mean home range size for quokkas was 6.39 ha with a core range of 1.21 ha and this was negatively related to population density. Male home ranges were larger than females but not significantly when the sexual size dimorphism was considered. Nocturnal ranges were larger than diurnal ranges reflecting nocturnal departures from the swamp refugia. Home range sizes varied seasonally, probably due to changes in the distance required to move to obtain sufficient nutrients and water over the dry summer compared to the wet winter and spring. Telemetry confirmed trapping results that showed no movement between swamps or populations. Home range centres shifted to the periphery of the swamp following the winter inundation and this may increase the species susceptibility to predation. The lack of dispersal is probably caused by quokka populations existing below carrying capacity and following selection for philopatry under the threat of predation for dispersing individuals. Without dispersal to recolonise or rescue unpopulated patches, the collapse of the original quokka metapopulation appears to have occurred. On a macrohabitat scale, the quokka in the northern jarrah forest is restricted to Agonis swamp shrubland habitats that form in the open, upper reaches of creek systems on the western side of the forest. This restriction was probably initially due to the high water requirements of the quokka but is likely to have been exacerbated by increased predation pressure since the arrival of the fox. On a microhabitat scale, the quokka is a habitat specialist, preferring early seral stage swamp habitats, probably for foraging, as part of a mosaic of old age swamp that provides refuge. Despite the six year old, introduced predator control programme, foxes and cats are still the major cause of mortality to quokkas. Road kills was the other identifiable cause. Individuals alive at the start of the study had an 81% chance of staying alive until the end. The likelihood of dying was minimised by grouping together with conspecifics, maximising home range size and maximising the time spent within the swampy refuge. Current rates of adult and juvenile survivorship should allow population recovery and so it seems pouch young mortality, reflected by low recruitment, has inhibited the anticipated population increase following predator control. The confounding effect of inadequate unbaited controls meant that little statistical evidence was available on the impact of introduced predators on the quokka, however the models provided support for earlier hypotheses of these. The presence of a quokka population at a site was related to the amount of poison baits delivered ??? reflecting predation pressure, the average age of the swamp and a mosaic of early and late seral stages within the swamp habitat. Recently burnt habitat is thought to provide food for quokkas and long unburnt habitat provides refuge from predation.

The quokka (Setonix brachyurus Quoy & Gaimard 1830) is a medium-sized, macropodid marsupial that is endemic to the mesic, south-western corner of Australia. While being a tourist icon on Rottnest Island, the species is threatened with extinction. It has been intensively studied on Rottnest Island in the 1960s and 1970s, however very little is known of its ecology on the mainland. Additionally the insular and mainland environments are extremely different suggesting that ecological differences between the two populations are likely. Consequently, this study sought to determine the basic autecology of the quokka and identify what factors have attributed to its threatened conservation status. The northern jarrah forest of Western Australia was selected as the study region due to it being at the northern limit of extant quokka distribution and because it was thought that the factors threatening the quokka would be exacerbated there. Fossil deposits suggest that the quokka originally occupied an area of approximately 49,000 km2 in the south-western corner of Australia. Historical literature show that they were widespread and abundant when Europeans colonised the region in 1829 but a noticeable and dramatic decline occurred a century later. The arrival of the red fox to the region coincided almost exactly with this decline and so it was probably ultimately responsible. Continued predation by both it and the feral cat are likely to have continued the decline, along with habitat destruction and modification through altered fire regimes. Specific surveys and literature searches show that since the 1950s, the area occupied by the quokka has declined by 45% and since 1990 by 29%. Based on the criteria of the IUCN (Hilton-Taylor 2000), the conservation status of the quokka should remain as vulnerable. An endangered status may be more applicable if the quokkas restriction to patches through its existence as a metapopulation is considered. Trapping of eight sites supporting quokka populations in the mid-1990s revealed three sites now locally extinct despite the ongoing, six year old, fox control programme. Another three are at serious risk of extinction. Extant population sizes ranged from one to 36 and population density ranged from 0.07 to 4.3 individuals per hectare. This is considered to be below the carrying capacity of each site. The overall quokka population size in the northern jarrah forest may be as low as 150 adult individuals, of which half are likely to be female. Even the largest extant populations are highly susceptible to stochastic extinction events. This small size was surprising considering the six year old, introduced predator control programme. Historically, the restriction to discrete habitat patches, the occasional inter-patch movement, the lack of correlation between the dynamics of each population and reports of frequent localised extinctions and colonisations suggest that the quokka population once existed as part of a classic metapopulation. The massive decline of the quokka in the 1930s pushed the metapopulation structure into a non-equilibrium state such that today, the extant populations are the terminal remnants of the original classic metapopulation. Wild mainland quokkas breed throughout the year. A significant reduction in the number of births occurs over summer and this coincides with a decline in female body weight. Despite this, the mainland quokka is relatively fecund and is able to wean two offspring per year. The level of recruitment from pouch young to independence was low and this may explain the apparent lack of population increase following the initiation of fox control. A total of 56 trapped quokkas were fitted with a radio collar. Mean home range size for quokkas was 6.39 ha with a core range of 1.21 ha and this was negatively related to population density. Male home ranges were larger than females but not significantly when the sexual size dimorphism was considered. Nocturnal ranges were larger than diurnal ranges reflecting nocturnal departures from the swamp refugia. Home range sizes varied seasonally, probably due to changes in the distance required to move to obtain sufficient nutrients and water over the dry summer compared to the wet winter and spring. Telemetry confirmed trapping results that showed no movement between swamps or populations. Home range centres shifted to the periphery of the swamp following the winter inundation and this may increase the species susceptibility to predation. The lack of dispersal is probably caused by quokka populations existing below carrying capacity and following selection for philopatry under the threat of predation for dispersing individuals. Without dispersal to recolonise or rescue unpopulated patches, the collapse of the original quokka metapopulation appears to have occurred. On a macrohabitat scale, the quokka in the northern jarrah forest is restricted to Agonis swamp shrubland habitats that form in the open, upper reaches of creek systems on the western side of the forest. This restriction was probably initially due to the high water requirements of the quokka but is likely to have been exacerbated by increased predation pressure since the arrival of the fox. On a microhabitat scale, the quokka is a habitat specialist, preferring early seral stage swamp habitats, probably for foraging, as part of a mosaic of old age swamp that provides refuge. Despite the six year old, introduced predator control programme, foxes and cats are still the major cause of mortality to quokkas. Road kills was the other identifiable cause. Individuals alive at the start of the study had an 81% chance of staying alive until the end. The likelihood of dying was minimised by grouping together with conspecifics, maximising home range size and maximising the time spent within the swampy refuge. Current rates of adult and juvenile survivorship should allow population recovery and so it seems pouch young mortality, reflected by low recruitment, has inhibited the anticipated population increase following predator control. The confounding effect of inadequate unbaited controls meant that little statistical evidence was available on the impact of introduced predators on the quokka, however the models provided support for earlier hypotheses of these. The presence of a quokka population at a site was related to the amount of poison baits delivered ??? reflecting predation pressure, the average age of the swamp and a mosaic of early and late seral stages within the swamp habitat. Recently burnt habitat is thought to provide food for quokkas and long unburnt habitat provides refuge from predation.

The quokka (Setonix brachyurus Quoy & Gaimard 1830) is a medium-sized, macropodid marsupial that is endemic to the mesic, south-western corner of Australia. While being a tourist icon on Rottnest Island, the species is threatened with extinction. It has been intensively studied on Rottnest Island in the 1960s and 1970s, however very little is known of its ecology on the mainland. Additionally the insular and mainland environments are extremely different suggesting that ecological differences between the two populations are likely. Consequently, this study sought to determine the basic autecology of the quokka and identify what factors have attributed to its threatened conservation status. The northern jarrah forest of Western Australia was selected as the study region due to it being at the northern limit of extant quokka distribution and because it was thought that the factors threatening the quokka would be exacerbated there. Fossil deposits suggest that the quokka originally occupied an area of approximately 49,000 km2 in the south-western corner of Australia. Historical literature show that they were widespread and abundant when Europeans colonised the region in 1829 but a noticeable and dramatic decline occurred a century later. The arrival of the red fox to the region coincided almost exactly with this decline and so it was probably ultimately responsible. Continued predation by both it and the feral cat are likely to have continued the decline, along with habitat destruction and modification through altered fire regimes. Specific surveys and literature searches show that since the 1950s, the area occupied by the quokka has declined by 45% and since 1990 by 29%. Based on the criteria of the IUCN (Hilton-Taylor 2000), the conservation status of the quokka should remain as vulnerable. An endangered status may be more applicable if the quokkas restriction to patches through its existence as a metapopulation is considered. Trapping of eight sites supporting quokka populations in the mid-1990s revealed three sites now locally extinct despite the ongoing, six year old, fox control programme. Another three are at serious risk of extinction. Extant population sizes ranged from one to 36 and population density ranged from 0.07 to 4.3 individuals per hectare. This is considered to be below the carrying capacity of each site. The overall quokka population size in the northern jarrah forest may be as low as 150 adult individuals, of which half are likely to be female. Even the largest extant populations are highly susceptible to stochastic extinction events. This small size was surprising considering the six year old, introduced predator control programme. Historically, the restriction to discrete habitat patches, the occasional inter-patch movement, the lack of correlation between the dynamics of each population and reports of frequent localised extinctions and colonisations suggest that the quokka population once existed as part of a classic metapopulation. The massive decline of the quokka in the 1930s pushed the metapopulation structure into a non-equilibrium state such that today, the extant populations are the terminal remnants of the original classic metapopulation. Wild mainland quokkas breed throughout the year. A significant reduction in the number of births occurs over summer and this coincides with a decline in female body weight. Despite this, the mainland quokka is relatively fecund and is able to wean two offspring per year. The level of recruitment from pouch young to independence was low and this may explain the apparent lack of population increase following the initiation of fox control. A total of 56 trapped quokkas were fitted with a radio collar. Mean home range size for quokkas was 6.39 ha with a core range of 1.21 ha and this was negatively related to population density. Male home ranges were larger than females but not significantly when the sexual size dimorphism was considered. Nocturnal ranges were larger than diurnal ranges reflecting nocturnal departures from the swamp refugia. Home range sizes varied seasonally, probably due to changes in the distance required to move to obtain sufficient nutrients and water over the dry summer compared to the wet winter and spring. Telemetry confirmed trapping results that showed no movement between swamps or populations. Home range centres shifted to the periphery of the swamp following the winter inundation and this may increase the species susceptibility to predation. The lack of dispersal is probably caused by quokka populations existing below carrying capacity and following selection for philopatry under the threat of predation for dispersing individuals. Without dispersal to recolonise or rescue unpopulated patches, the collapse of the original quokka metapopulation appears to have occurred. On a macrohabitat scale, the quokka in the northern jarrah forest is restricted to Agonis swamp shrubland habitats that form in the open, upper reaches of creek systems on the western side of the forest. This restriction was probably initially due to the high water requirements of the quokka but is likely to have been exacerbated by increased predation pressure since the arrival of the fox. On a microhabitat scale, the quokka is a habitat specialist, preferring early seral stage swamp habitats, probably for foraging, as part of a mosaic of old age swamp that provides refuge. Despite the six year old, introduced predator control programme, foxes and cats are still the major cause of mortality to quokkas. Road kills was the other identifiable cause. Individuals alive at the start of the study had an 81% chance of staying alive until the end. The likelihood of dying was minimised by grouping together with conspecifics, maximising home range size and maximising the time spent within the swampy refuge. Current rates of adult and juvenile survivorship should allow population recovery and so it seems pouch young mortality, reflected by low recruitment, has inhibited the anticipated population increase following predator control. The confounding effect of inadequate unbaited controls meant that little statistical evidence was available on the impact of introduced predators on the quokka, however the models provided support for earlier hypotheses of these. The presence of a quokka population at a site was related to the amount of poison baits delivered ??? reflecting predation pressure, the average age of the swamp and a mosaic of early and late seral stages within the swamp habitat. Recently burnt habitat is thought to provide food for quokkas and long unburnt habitat provides refuge from predation.

This thesis examined aspects of the reproductive and molecular biology of Eucalyptus marginata (jarrah). The aims were to develop protocols for controlled pollination, that could be used in clonal orchard trees to breed jarrah seedlings that have a known genetic resistance to Phytophthora cinnamomi (dieback), for use in rehabilitation after mining and logging. An intimate knowledge of the breeding biology of jarrah was necessary to achieve this aim. The project also aimed to increase knowledge of the genetic diversity and structure of jarrah, in order to make informed decisions regarding the collection of material to be used for clonal propagation. Previous research has had little success in producing viable seed from any controlled pollinations, but clonal material resistant to P. cinnamomi has been produced using tissue culture. The question posed in this thesis was ‘Can we improve breeding and propagation techniques of jarrah?’ Techniques were developed for testing of in vitro pollen viability and pollen storage, pollination and fertilisation success after controlled pollinations, including determination of stigma receptivity and development of bud isolation techniques using alfoil. The variation in female fertility between genotypes was examined. The use of paclobutrazol was explored as a method of increasing the level of viable seed production in clonal orchard trees. The use of fertiliser as well as the growth retardant was also explored to see if it increased the level of seed production even more. Genetic diversity, genetic differentiation and phylogeny within Eucalyptus marginata were examined using nuclear and chloroplast DNA analysis with Restricted Fragment Length Polymorphisms. While it was first thought that the fertilisation rate was quite low, it was confirmed that the fertilisation rate is similar to other eucalypt species. The zygote abortion rate was quite high in one clone, but one wild tree had a similar seed production rate to other eucalypt species. The zygote and endosperm appeared to be different in the clone and the wild tree observed. The level of seed production was examined in clones and wild trees and it was found that the level was often quite low, particularly in the clones (0 – 13% in clones, 0 – 18% in wild trees) in comparison with other Eucalyptus species, and varied between genotypes. The use of a growth retardant such as paclobutrazol may increase the production of viable seed, if it is applied during autumn. The results were inconclusive for the fertiliser/paclobutrazol experiment, since the paclobutrazol was applied during spring which was the worst time of year for increasing seed production. There were differences between genotypes in reaction to both the paclobutrazol and the fertiliser/paclobutrazol. Genetic diversity was moderate in comparison with other Eucalyptus species, and there was a low level of genetic differentiation between populations in the nuclear genome. No differentiation was observed between the morphologically recognised subspecies in the nuclear genome, but differentiation between the populations on the Swan Coastal Plain and populations on the Darling Plateau was seen in the chloroplast genome, indicating that there was historical separation of these two areas. The conclusions arising from this work are that while controlled pollinations are possible in Eucalyptus marginata the clones that were used in these experiments have often behaved differently to the wild trees in the time of anthesis and levels of viable seed production, and in one clone (5J119) the zygote and endosperm nuclei appeared to be very different to the zygote and endosperm nuclei of a wild tree. Further investigation is necessary to see if these differences are related to the low level of seed production observed in the clonal populations. Paclobutrazol may be worth exploring further as a means of increasing seed production. Material to be used for rehabilitation and seed orchards can be collected from a wide area in the main distribution of the species, although trees on the Swan Coastal Plain are distinct from the trees in the main forest area in the chloroplast genome.

Thesis (MDes) - National School of Design, Swinburne University of Technology, 2008. / [Thesis submitted for degree of] Master of Design, to the [Faculty of Design], Swinburne University of Technology, 2008. Typescript. Bibliography: p. 159-165.

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.

Thesis submitted to the Division of Science and Engineering. Bibliography: leaves 219-235.

[Truncated abstract] Recovery of soil nutrients, microbial populations and carbon (C) and nitrogen (N) cycling processes are critical to the success of rehabilitation following major ecosystem disturbance. Bauxite mining represents a major ecosystem disturbance to the jarrah (Eucalyptus marginata) forest in the south-west of Western Australia. Mining has created a mosaic of mined areas in various stages of succession surrounded by non-mined forest areas. Initial site preparations within rehabilitation areas such as contour ripping alter soil structure (creation of mound and furrows) and over time also influence the distribution of vegetation and litter. Current performance criteria developed by industry, government and other stakeholders have determined that before post-bauxite mined areas of jarrah forest can be integrated back into normal forest management practises they should be functional and demonstrate resilience to normal forest disturbances such as fire. Furthermore, resilience should be of a manner comparable to non-mined analogue forest sites. Currently little is known of the resilience of microbial communities and C and N cycling in rehabilitation sites to normal forest disturbances such as prescription burning. As such, before rehabilitated jarrah forests can be successfully integrated into broad scale forest management regimes, a more thorough knowledge of the potential impacts of burning practises on the soil microbial community and C and N cycling processes in these systems is required. ... While there are similar rates of C and N cycling the underlying microbial community structure was distinctly different; implying a high degree of functional redundancy with respect to C and N cycling. Differences in the C and N cycling and structure of the microbial communities were likely to be due to differences in soil environmental conditions (i.e. soil alkalinity/acidity, soil moisture) and C substrate availability which influence the physiological status of the microbial community and in turn are related to successional age of the forests. Results also suggest that the measurement of CLPP can be a useful approach for assessment of changes in the functional ability of microbial communities. However, the interpretation of how well these rehabilitation forests have recovered heterotrophic abilities was greatly affected by the methodological approach used (e.g. MicroRespTM or Degens and Harris, 1997). Importantly, results from Chapter 4 and 5 suggested that the effects of a moderate prescription fire on C and N processes, CLPP and microbial community structure of 18 year old rehabilitation forests are likely to be short-lived (< 2 years). Furthermore, the effects of the moderate spring prescription fire were not large enough to decouple C and N cycling processes over the short-term (< 1 years) which suggests that by 18 years of age rehabilitation forests demonstrate comparable functional resilience to a moderate prescription burn.