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Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Science, Environment, Engineering and Technology, Outbreaks of insect pests pose a serious threat to local economies and global food production, with as much as 15% of global crop production lost to herbivorous insects annually. Outbreaks of transboundary pests and diseases that affect food crops have increased in frequency in conjunction with globalization, international trade and the impacts of climate change. Indeed, increasing global temperatures are predicted to increase the distribution, rate of development, survival and population density of many pest insects. Such changes have important ramifications for host plant exploitation. The Queensland fruit fly (Bactrocera tryoni) is Australia’s worst horticultural pest, and is feared by international buyers of Australian produce. Like other Tephritid fruit fly species, B. tryoni has the potential to breach quarantine barriers via human mediated transport, and can rapidly establish in ‘new’ environments. This pest species is responsible for an estimated AU$28.5 million in annual yield loss, management costs and loss to domestic and international markets. Increasing and ongoing outbreaks of B. tryoni in Australia’s major growing regions has put international trade in jeopardy.

Prescribed burning has been widely used in the management of forests for reducing wildfire risk, and can have significant effects on soil carbon (C) and nitrogen (N) pools and their temporal changes. This study aimed to investigate the impacts of different burning frequency regimes on the temporal dynamics of C and N in the topsoil and forest floors. The experimental site was a 39 year old wet scherophyll forest prescribed burning trial at Peachester, southeast Queensland, Australia, with treatments of no burning (NB) since 1969, 2 yearly burning (2yrB) and 4 yearly burning (4yrB) since 1972. Each of three burning treatments had four replications and these plots were randomly distributed over an area of the forest with similar vegetation and soil characteristics. Soil (0–10 cm) and forest floors were sampled monthly for 6 months prior to the next scheduled burning for both burning treatments to minimize the effects of fire recency. Prescribed burning significantly (P < 0.01) affected most C and N variables in both soils and forest floors. The 2yrB treatment had significantly lower (P < 0.01) soil total C, total C:N ratio, microbial biomass C (MBC) and N (MBN), MBC:MBN ratio, dissolved organic C (DOC) and N (DON), NO3−-N, inorganic N and L layer total N, DON and NO3−-N, compared with the NB and 4yrB treatments. However, there were no overall significant differences in these variables between the NB and 4yrB treatments. Sampling month significantly (P < 0.01) affected C and N variable in both soils and forest floors except for soil total C and N and F layer MBC. Temporal dynamics of most of these labile C and N variables were highly related to soil and forest floor moisture content, seven day mean air temperature (MAT) and cumulative rainfall prior to sampling date. However, fire effects were independent of sampling month, as there were no significant interactions between them for most response variables measured. This study has clearly demonstrated that more

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Science, Environment, Engineering and Technology, There is a general consensus among scientists that climate change poses a severe threat to organisms with little tolerance for higher temperatures than those in their current environmental niche. The effects of increased environmental temperature will be of significance in those organisms combining reduced thermal tolerance and limited mobility across the environment to allow shifts to more optimal habitat. The relict populations of the freshwater crayfish genus, Euastacus, in Queensland are generally restricted to cooler mountain-top streams and are at significant extinction risk due to these factors. While noted as threatened by increases in environmental temperature, key knowledge gaps exist regarding the thermal biology of these crayfish. This project sought to answer the underlying question; Are species of Euastacus in Queensland, some with severely restricted distributions, currently experiencing thermal stress in warmer parts of the year? It was anticipated that evidence of fitness reducing temperatures in these crayfish would give an indication of the future effect of climate change, primarily increased temperature, and initiate further research into this vulnerable genus. A minimally-intrusive assessment of physiological and biochemical indicators of tissue damage in response to an imposed thermal stressor were initially developed using a model organism, Cherax quadricarinatus. The data provided “proof of concept” for a validated method to contrast the level of thermal stress experienced between individuals of the same species, conditioned to different temperatures. Additionally, the results indicated that the physiological and biochemical indicators gave some defined effects of higher temperature on the model organism, and opened up the potential for a suite of non invasive assays to be used within the genus Euastacus.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Science, Environment, Engineering and Technology, The overall aim of this thesis was to investigate the morphological and molecular diversity within Tenuibranchiurus, and to utilise these data to further the understanding of the evolution of this freshwater crayfish and the other genera of the Australian burrowing clade from both a phylogenetic and biogeographic perspective. The genus Tenuibranchiurus occurs within coastal eastern Australia and currently represents the largest gap in knowledge within this clade of crayfish. It is also the only monotypic parastacid genus, containing the single species T. glypticus. Additionally, it has morphological, phylogenetic, and geographical attributes that are not exhibited by other members of the burrowing clade, or by other freshwater fauna found throughout its distributional range. Examination and clarification of these unique features has the potential to elucidate evolutionary processes determining the distribution and genetic structure of the genus, the burrowing clade, and the freshwater fauna of coastal eastern Australia.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Science, Environment, Engineering and Technology, Australia has 155 million hectares of native forests. Trees in Australia's native forests hold about 6.56 billion tonnes of carbon (C) in their biomass, with eucalypt woodlands and open forests containing the most biomass. Historically, fire has been a distinct feature of Australian forests. It is predicted that the frequency and severity of fire in Australia would be increased due to reduced rainfall and high temperature in the near future. Prescribed burning (generally low density fires) has been used as a tool in forest management around the world to reduce fuel load and to protect many of the landscapes from wildfires. However, there are concerns that prescribed fires cause a reduction in soil fertility at sites where the intervals between fires are too short. The extent of fire effects on aboveground ecosystem components and soil varies greatly with fire intensity and frequency. Most studies have been focused on the short-term/immediate effects of fires on soil. The effects of frequency of the long-term repeated fires are largely unknown. The objectives of this study were to examine the effects of different repeated prescribed-burning regimes on a) C and nitrogen (N) storage and b) temporal dynamics of C and N in an Australian forest (Peachester State Forest), using a 39 year-old repeated prescribed burning trial with three treatments: no burning (NB) since 1969, 2 yearly burning (2yrB) and 4 yearly burning (4yrB).

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Science, Environment, Engineering and Technology, The incursion of the globally notorious pest, red imported fire ant Solenopsis invicta (Buren) (Hymenoptera: Formicidae: Myrmicinae) in Brisbane, Australia necessitated the prompt design and implementation of an integrated pest eradication solution. The solution included the broad-scale application of the insect growth regulators Methoprene and Pyriproxyfen. Known for high efficacy and low toxicity to selected non-target taxa in the laboratory, these chemicals have received scant attention to identify real non-target species impacts in the field. It was the purpose of this study to provide a real-time assessment of the impacts of Methoprene on the soil ecosystem, examining both its chemical and biological composition. This was achieved by constructing a Before-After, Control-Impact (BACI) experiment, where Methoprene was applied to ‘treated’ (i.e. impact) sites following Fire Ant Control Centre (FACC) protocols. A series of soil samples were collected over repeated Methoprene applications, and analysed to determine mite diversity, community structure and chemical composition of the soil. A comparison of these characteristics at ‘control’ and ‘treated’ sites over repeated Methoprene applications enabled the assessment of the non-target impacts of Methoprene on soil mites and soil function.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Biomolecular and Physical Sciences, Science, Environment, Engineering and Technology, Revegetation schemes are increasing in Australia and are part of strategy to restore cleared lands, enhance biodiversity and alleviate global climate change. Site preparation practices play a pivotal role in the successful establishment of revegetation projects in tropical and sub-tropical Australia. However, site preparation practices are costly and there is great interest to develop cost-effective establishment methods. The most common site preparation practices, in Australia, include weed control and fertilisation. Reduced weed competition is a crucial factor in the successful establishment of revegetation projects. Herbicide application is the most commonly used method of weed control but need for repeated site visits and sequential applications greatly increase establishment costs. Alternative methods are sought to reduce the reliance on herbicide application. One such method is scalping, the removal of the top 100 mm of soil from the planting area which effectively removes the soil seed bank. Both herbicide and scalping have implications for soil properties which could in turn affect early plant growth and establishment. This study aimed to investigate the dynamics of soil organic matter (SOM), carbon (C) and nitrogen (N) pools under differing site preparation practices and the associated effects on plant survival, growth and eco-physiological status in tropical and sub-tropical Australia. Two experimental sites located at Rockhampton (23º31'24 S, 150º18'14 E) and Laidley (27º40'31 S, 152º24'04 E) were established in this study. The treatment layout was randomised complete block split plot. Treatments included topsoil removal (scalping) and herbicide application for weed control. Other treatments included the use of fertiliser to overcome the potentially negative effects of scalping and to give a competitive advantage to seedlings.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Science, Environment, Engineering and Technology, Calyptorhynchus lathami, the Glossy-black Cockatoo, is a highly specialized monophagous bird feeding only on the cones of Allocasuarina species. Studies elsewhere have shown that C. lathami are restricted by a tight energy budget, forcing them to select high quality food sources, thereby minimizing effort and time in feeding, and resulting in the birds feeding in some trees and ignoring other apparently suitable trees. This specialized feeding habit, in conjunction with recent and ongoing habitat loss, is expected to cause a decline in their population in many localities. This study examined the abundance and distribution of C. l. lathami on the Gold Coast, Queensland. The feeding status and stability of feed trees was examined, comparing between feed and non-feed trees within a site, and between sites, determining why some trees and sites are fed upon, whilst others are ignored. The results indicate that many areas containing Allocasuarinas had little to no current potential as a food source due to low cone production. Ultimately, it was found that many birds were feeding in few suitable sites, with most sites being unsuitable. Where trees with adequate cones crops were observed, it was found that C. lathami would feed in the areas with abundant cones. Within these areas, the birds were feeding on trees with large cone crops. This study also used the number of chewings (pieces of cones: C. lathami feeding residue) to estimate bird abundance. The population size was calculated using the quantity and age of C. lathami feeding in the study area, and their daily food requirements. It was calculated that between 250 and 690 C. lathami were been feeding on the Gold Coast. On-going habitat loss on the Gold Coast may suggests that this population is not stable.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Science, Environment, Engineering and Technology, In the mountains of the Gold Coast Hinterland (Queensland, Australia), Euastacus sulcatus (Decapoda: Parastacidae) is the largest aquatic invertebrate, largest member of the aquatic shredder guild, and probably plays a key role in the area’s stream ecology. The objective of this study was to investigate the ecological effects of E. sulcatus in the streams of the Gold Coast Hinterland, but in particular to assess the species’ capacity to act as an effective ecosystem engineer, obtain measures of the ecosystem services provided by the species, and evaluate the likely impacts of the crayfish on downstream water quality. To achieve this objective, an estimate of the population size of E. sulcatus was obtained; a series of experiments measured the species’ capacity to liberate nutrients from leaf litter, reduce the particle-size of the leaf litter, and mobilise and redistribute organic and inorganic materials in a flowing stream environment. This information allowed estimation of the species’ ecological impact(s) per unit time as a measure of the ecosystem services provided by E. sulcatus in the headwater streams of the study area. During this study E. sulcatus was common and abundant with a within-stream density of ~0.5 crayfish m-2. The total population of E. sulcatus in the study area was estimated at >860,000 crayfish. Correction for strong seasonal variation in activity was required for ecological impact calculations, and the “ecologically effective” population was estimated at >570,000 crayfish (biomass ~12 tonnes wet weight (WWT)). Crayfish significantly liberated nitrogen and phosphorus from leaf litter into the water column via consuming leaf litter and excreting nutrients. The phosphorus dynamic was complex, however the overall effect of crayfish was to facilitate eventual “loss” of phosphorus from the system with binding/absorption to substrates, particularly leaf litter, evident as the mechanism. The ecologically effective population was estimated to liberate

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Large tracts of brigalow (Acacia harpophylla F. Muell. ex Benth. Mimosaceae) vegetation once covered the Queensland Brigalow Belt. Over the last century, a significant reduction in brigalow coverage has taken place (> 90%), primarily a result of land clearing for agricultural development. Despite significant loss of brigalow and its associated biodiversity, potential exists for reversing the loss, avoiding further land degradation and promoting sustainable agricultural production, through the establishment of brigalow-cropping systems. Such land-use systems are characterised by deliberate integration of stands of regrowth and remnant brigalow vegetation with areas of dryland cropping. This landscape ecology study increased knowledge and understanding of brigalow-cropping systems using two complementary investigative approaches: (1) a conventional, reductionist, quantitative approach; and (2) a holistic, qualitative approach. The first approach was used to investigate brigalow-cropping systems from agronomic, hydrological and ecological perspectives. These perspectives provided insight into aspects of brigalow-cropping system function, structure and composition. The second approach looked at brigalow-cropping systems from the Goethean perspective. This latter perspective sought to understand brigalow-cropping systems on a ‘whole-of-paddock’ basis. Each perspective constituted a discrete study, with the studies done on properties located in the Tara Shire of south-east Queensland. Specifically, the agronomic perspective looked at tree-crop competition adjacent to stands of regrowth and remnant brigalow. It found that young brigalow regrowth (< 5 years since last disturbance) did not have a negative impact on adjacent cropping. However, older brigalow regrowth (> 10 years since last disturbance) and remnant brigalow vegetation had a significant, detrimental impact on adjacent production, with tree-crop competition zones ranging from 12–47 m. Both field measurements and

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environmental and Applied Science, Exotic plants are a threat to natural areas world wide including the Australian Alps, one of the largest relatively undisturbed natural areas remaining in Australia. This thesis examines the diversity, abundance and distribution of exotic plants in the Australian Alps, including Kosciuszko National Park and then focuses on Achillea millefolium (L.) (Asteraceae) as a case study of the biology and ecology of an important environmental weed. To determine the diversity and abundance of exotics in the Australian Alps published records of exotic species were reviewed. A total of 175 exotic taxa were recorded in the alpine and subalpine areas representing 41 families and 122 genera. The distribution of exotics was associated with human activities with 80% of exotic taxa found along roads and tracks and nearly 60% around ski resorts. Just over 20% of exotic species were naturalised with some species presenting an environmental threat to the region. To examine the relationship between human disturbance and exotics, vegetation was surveyed and soil analysed on road verges, in runoff areas and in adjacent vegetation along a gravel road in the subalpine zone of Kosciuszko National Park. The road verge was dominated by exotics, the area 10 m from the road verge was dominated by natives and the road drainage areas were dominated by the exotic, A. millefolium. There were also clear differences in the soils, with coarse nutrient poor soils on the road verge, highly organic fine soils in the areas 10 m from the road, and soils with high nutrients and water content in the road drainage areas. The potential for exotics to colonise areas adjacent to roads after disturbance was examined in an experiment conducted along a subalpine road. The composition of plants colonising small gaps created in the existing vegetation (50 cm x 100 cm) was dependant on the distance from the road. In general, gaps one metre from the road verge were recolonised by exotic species while gaps five or ten metr

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environmental and Applied Science, Lantana Lantana camara L. is a highly aggressive exotic environmental weed that is weestablished throughout eastern Australia and is reportedly able to displace native vegetation under a range of conditions. Whether lantana is able to displace native vegetation in the absence of anthropogenic disturbance is subject of some disagreement in the literature. The question remains, however, as to what is the future for the Gold Coast hinterland rainforests in the face of invasion by lantana? This study is mainly directed at addressing the dynamics at the lantana/rainforest interface, especially lantana's capacity to invade and ability to compete with the wetter subtropical rainforests of the MacPherson Ranges of southeast Queensland, where the studies are centered on the Springbrook Plateau and the Springbrook and Lamington National Parks. The aims of this research are to determine: whether lantana can displace rainforest; whether rainforest can reclaim the space lost to lantana; and what are the mechanisms and processes involved. To investigate these questions a conceptual framework was determined where key processes at the rainforest/lantana interface were determined and set in a logical context. A wide variety of possible processes whereby lantana could resist or displace rainforest or forest could resist or replace lantana were identified. The framework questions were addressed by observations made at lantana patches in Springbrook and Lamington National Parks in southeast Queensland. These answers/conclusions indicate that lantana is not invading further into intact rainforest and is seemingly isolated to canopy gaps, suggesting that rainforest is suppressing further expansion of lantana. Even though lantana may not commonly occur thriving in subtropical rainforest, it was determined that the issues/interactions that need to be pursued via experimentation were as follows: (i) how common is lantana in the national parks of southeast Queensland; (ii) what limits lantan

Full Text, Thesis (Masters), Master of Philosophy (MPhil), School of Environmental and Applied Science, Culicoides molestus (Skuse) is the major species of biting midge that plagues human comfort in the estuarine Gold Coast region of southeast Queensland. Local authorities have initiated a search for an effective, non-chemical means of control, that would minimize human-midge interaction. The effectiveness of a program to control an organism, such as a biting midge, is dependent upon knowledge of the biology of the particular organism of interest. This project revolved examines the lifecycle of C. molestus in detail. It addresses questions regarding the location, seasonal distribution, and dispersal of its juvenile stages in the sand of infested beaches, and their response to chemical treatment, the monthly and annual cycles of the adult midge, and the possibilities of achieving laboratory oviposition, as a first step to laboratory colonisation. The distribution of eggs, larvae and pupae of C. molestus was found to be mostly concentrated around, but below, mean tide level. They also occurred well below the mean tide level. Eggs and larvae have been recovered from as deep as 10 cm in the sand. A seasonal study of the juveniles of this species indicated that they were more strongly influenced by tides than seasons. After a routine pest-control larviciding treatment, a beach recolonisation study revealed that beaches become suitable for oviposition approximately two months after treatment. Large larvae invaded the sprayed areas within days of treatment, which suggests the existence of a refuge outside of the reach of the insecticide. Larvae found in clean (egg- and larva-free), isolated sand containers, placed on the study beach, indicated that larvae could swim in or on the water as a way of moving around the beach. Extended bite-rate studies highlighted the existence of four peaks in adult midge biting activity during the course of a year, around the mid seasons. The strongest peaks of activity were found to be in autumn and spring, but the data suggest that the specie

Full Text, Thesis (Masters), Master of Philosophy (MPhil), School of Environmental and Applied Science, The main objective of this study was to examine the abundance and diversity of ants in suburban sites following vegetation removal or modification for development. This research examines the capacity of suburban sites to support ant diversity, which is dependent on the site characteristics and their surrounding environment. The study focused on 29 suburban garden and 3 suburban reserve sites on the Gold Coast, Queensland, Australia. This region, through continuing land development, undergoes ongoing habitat disturbance and modification. Ground-dwelling ants were collected by pitfall trapping in study sites over three summers between 1997 and 1999. In total, 28,512 ants from 60 species in 31 genera were collected. Garden sites that maintain vegetation structural diversity were found to be most similar to reserve sites in terms of ant community composition. These sites were highest in ant richness and diversity and contained particularly high proportions of specialized ant species. Sites in close proximity to remnants of native vegetation contained higher species diversity and a greater proportion of specialized ant species. The introduced tramp ant, Pheidole megacephala was found in 28 of the 32 sites and was found to significantly reduce ant species richness and diversity and displace the dominant ant Iridomyrmex sp. 1 in suburban environments. This ant poses a serious threat to the recovery of a diverse ant fauna to suburban environments. Ant community composition was shown to vary significantly among suburban sites. The ant functional groups commonly found in disturbed sites were abundant in open sites with little canopy cover in this study. Sites that provided vegetation structural diversity and areas of closed canopy supported similar functional groups to natural vegetation remnants. These results indicate that ant communities in suburban environments respond to disturbance in a similar manner to ant communities in tropical forests and rainforests. The dominance

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environmental and Applied Science, Science, Environment, Engineering and Technology, There are many real world assignment, scheduling and planning tasks which can be classified as combinatorial optimisation problems (COPs). These are usually formulated as a mathematical problem of minimising or maximising some cost function subject to a number of constraints. Usually, such problems are NP hard, and thus, whilst it is possible to find exact solutions to specific problems, in general only approximate solutions can be found. There are many algorithms that have been proposed for finding approximate solutions to COPs, ranging from special purpose heuristics to general search meta-heuristics such as simulated annealing and tabu search. General meta-heuristic algorithms like simulated annealing have been applied to a wide range of problems. In most cases, the designer must choose an appropriate data structure and a set of local operators that define a search neighbourhood. The variability in representation techniques, and suitable neighbourhood transition operators, has meant that it is usually necessary to develop new code for each problem. Toolkits like the one developed by Ingber's Adaptive Simulated Annealing (Ingber 1993, 1996) have been applied to assist rapid prototyping of simulated annealing codes, however, these still require the development of new programs for each type of problem. There have been very few attempts to develop a general meta-heuristic solver, with the notable exception being Connolly's General Purpose Simulated Annealing (Connolly 1992). In this research, a general meta-heuristic based system is presented that is suitable for a wide range of COPs. The main goal of this work is to build an environment in which it is possible to specify a range of COPs using an algebraic formulation, and to produce a tailored solver automatically. This removes the need for the development of specific software, allowing very rapid prototyping. Similar techniques have been available for linear programming based solvers for some years in the form of t