Thesis (DTech (Tourism and Hospitality Management))--Cape Peninsula University of Technology, 2009. / Includes bibliographical references. Also available online.

This thesis reports on research that examines the early stage invasion process of Asparagus asparagoides (L.) W. Wight (bridal creeper), primarily a bird-dispersed weed, in a remnant vegetation patch. The study site is on Phillip Island, approximately 100 kilometres south east of Melbourne, Victoria. Asparagus asparagoides invasion of the remnant vegetation reserve is a relatively recent phenomenon. Landscape elements that affect bird dispersal and vegetation types that affect seedling establishment may be important factors that limit or enhance the spread of A. asparagoides. A systematic sampling strategy was adopted and data collected for a variety of landscape and vegetative variables including cover and abundance of A. asparagoides and the data were presented in a Geographic Information System (GIS). Preliminary results show that the distribution of A. asparagoides within a remnant vegetation patch is not random. It appears to have entered the reserve from two boundaries, spreading toward the centre, which to date remains sparsely colonised despite the capacity of this weed to spread rapidly over long distances by birds. A number of other outcomes are noted. Asparagus asparagoides establishment is prevented in pasture where sheep and cattle graze, and paddocks subjected to tillage practices. The exclusion of grazing in fenced off vegetation in pastures demonstrates rapid weed establishment and colonisation several hundred metres from main infestation. Field observation and visual inspection of temporal progress of invasion (using above ground weed density with tuber appearance to infer age) appear to suggest that invasion into remnant is associated with the track network. This age/density assumption is strengthened when spatial distribution is examined using a data set where low-density values for A. asparagoides are removed and compared with a data set using all A. asparagoides density values. The mapping of A. asparagoides in fenced off farm remnants suggests that velocity of spread at 191m/yr is a considerable underestimate. Subsequent analysis shows that the spatial distribution of A. asparagoides is not completely spatially random while intensity surface analysis highlights regions of low and high intensity located near track network. Mapping a density surface within GIS provided confirmatory evidence for the establishment of satellite clusters along the track network. The change in the intensity surface observed using the two data sets (lowdensity values and all density values) is also consistent with an expanding invasion occurring between two time periods. Spatial point pattern analysis using K-function statistics shows that xxii the clustering observed using GIS appears to be occurring at two scales or distances (130m- 160m and 195m-205m). The association between tracks and the invasion process observed in the initial stages of the study is examined. There is a change in density as a function of distance from a track where the density of A. asparagoides appears to reduce the further away from the track a site is and this relationship holds regardless of track width. The final stages of the study look at the development of a predictive model. Visual exploration of the data through mapping in a GIS and field observation made during data collection provide the starting point for the development of logistic models to estimate the probability of A. asparagoides presence. Finally the best overall logistic model is applied to a second independent site to determine the general applicability of the model. A number of variables that impact on the presence of A. asparagoides, particularly during the initial stages of the invasion process, are identified. While all the identified variables and the overall model are statistically significant, the model is found to correctly predict presence/absence in only 67% of cases overall. The model however could be expected to correctly predict the presence of A. asparagoides in 74% of cases and has a false positive rate of 40%. The model is applied at a second independent site and found to have an overall percent correct rate of 80% and correctly predicted A. asparagoides presence in 94% of cases. The variables identified as influential in the early stage of invasion are relatively easy to acquire by simple field survey that does not require specialist skills. When considering the model as a tool for the management of remnant vegetation communities, high false positive rates may lead to limited resources being spent on searching sites where there is no weed. However, a high false negative rate would have a larger impact on the management of the weed since the undetected infestations would form sources for new propagules. The model performs well from this point of view in that it provided low false negative rates at both sites. The value of the predictive model is its ability to provide managers with information regarding specific areas to target for weed eradication and management can use the model to assess the effectiveness of any control measures by going back to obtain new cover density data, then using the model to examine the changes over time. The model also provides a starting point for the development of a generic model of A. asparagoides invasion at sites outside of Phillip Island and could also provide the starting point for developing models that could be used for other bird-dispersed fleshy-fruited weed species.

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This study is concerned with programs to conserve remnant stands of native vegetation in the agricultural regions of South Australia and concentrates on the development of explicit evaluation procedures which reflect stated conservation objectives. As botanical data are available for stands of native vegetation in most of the agricultural regions, stands in a particular region are able to be compared rather than assessed in isolation. Based on a review of conservation evaluation schemes in Australia and overseas, a hierarchical evaluation procedure using multiple criteria to compare stands was applied to stands of vegetation in the Mount Lofty Ranges. The conservation objective, of preserving samples of all plant communities in a region, led to the analysis of existing botanical data from two surveys of the Mount Lofty Ranges, to provide the basis for an inventory of regional plant communities. These surveys included 52 remnant stands of native vegetation and employed a point-centred quarter plotless sampling technique to summarise the vegetation. Numerical classificatory analysis of the raw sampling point data produced a more comprehensive floristic summary than the results from the plotless sampling. These floristic groups were correlated with physical environmental variables to produce an inventory of 45 regional vegetation types, as the first stage in the conservation evaluation of stands. Evaluation criteria of size, species richness and species rarity were quantified and used to select examples of each vegetation type on the basis of overall satisfaction of the criteria. In addition, the smallest suite of stands, in which all the vegetation types were represented, was determined, and was shown to be 24 stands. All of these were included in the 37 stands chosen using the three criteria. A third evaluation stage used stand parameters such as plant community richness to give a priority ranking of the 37 stands. A polythetic divisive classification of the vegetation types was developed to provide a means of evaluating communities in stands of native vegetation yet to be sampled in the region, and of comparing the vegetation types with communities in existing reservesr Examination of species-sampling area relationships led to recommended plot sizes for such future vegetation surveys in the Mount Lofty Ranges. The ease of collecting floristic data and the extensive time involved in quantitative measurements suggest that all perennial plant species be recorded and only estimations be made of vegetation quantity and structure for each sampling plot. This study demonstrates the usefulness of numerical classification techniques for conservation evaluation, and of continuous variables to quantify criteria of conservation value; and the application of those criteria in an explicit, hierarchical conservation evaluation procedure.

No description available.

Thesis (Ph.D.)--University of Adelaide, Dept. of Geographical and Environmental Studies, 2001. / Includes bibliographical references (p. 301-319).

Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 153-172.

Thesis (Ph. D.)--University of Waikato, 2004. / Title from PDF t.p. (viewed Feb. 7, 2006). Includes bibliographical references (p. [349]-374).

Revegetation of bauxite residue is hampered by a lack of understanding of the limitations imposed on plant growth in highly saline and alkaline growth mediums. In this study, several of these growth limiting factors were investigated. The toxicity of the hydroxyl ion (OH-) was examined using a solution culture system developed to allow studies at high pH without nutritional limitations. Also using this solution culture system, the effect of the high Na and Mg concentrations of bauxite residue on the Ca nutrition of plants was investigated. As the toxicity of Al at high pH is not known, a study was conducted to examine the rhizotoxicity of aluminate (Al(OH)4-) and polycationic Al at high pH. The ability of plant roots to reduce rhizosphere pH in bauxite residue was also considered. A novel gypsum application method was assessed for its efficiency at improving the Ca status of bauxite residue. Manual adjustment, ion exchange resins and automated titration were examined for their suitability for nutrient solution pH control in alkaline conditions. For short-term studies, it was found that a solution without supply of Cu, Fe, Mn and Zn, and aerated with CO2 depleted air, greatly reduced nutrient precipitation at high pH, thus eliminating nutritional differences between treatments. Manual pH adjustment and the use of ion exchange resins as pH buffers were unsuitable methods of pH control. In contrast, pH control by automated titration had little effect on solution composition while maintaining constant pH. The solution culture system was used to examine OH- toxicity in mungbeans (Vigna radiata (L.) Wilczek cv. Emerald), with root length reduced at a bulk solution pH of 8.5 and greater. The effect of Ca activity ratio (CAR) and pH on Ca uptake by mungbeans and Rhodes grass (Chloris gayana cv. Pioneer) in Na dominated solution cultures and in soil was investigated. Changes in pH in the alkaline range were shown to have no effect on the critical CAR of 0.024 (corresponding to 90 % relative root length) for mungbeans grown in solution culture. Results from soil grown mungbeans confirmed those from solution culture, with a critical CAR of 0.025. A critical CAR of 0.034 was also established for soil grown Rhodes grass. However, using dilute nutrient solutions dominated by Mg at pH 9.0, root growth was found to be more limited than had been observed for Na solutions, with growth reduced beneath a critical CAR of 0.050. Using a CAR equation modified with plasma membrane binding constants (to incorporate the differing antagonistic effects of Mg and Na), new critical CAR values were calculated for Na (0.56) and Mg (0.44) dominated solutions. This modified CAR equation permits the calculation of CAR irrespective of the dominant salt present. Solubilities of various gypsum sources and size fractions in seawater were studied to investigate the effectiveness of gypsum addition to the residue sand pipeline, rather than as a direct field application. The dissolution rate constant varied with gypsum source (analytical grade (AR) > phosphogypsum (PG) > mined gypsum (MG)) due to reactivity and surface area differences, generally reaching saturation within 15 s (AR) to 30 min (MG > 2.0). The ability of bauxite residue to remove Ca from solution (due to cation exchange and precipitation) was also examined; the quantity of the total solution Ca adsorbed was found to be small (5 %). These low rates of solution Ca adsorption, comparatively rapid dissolution rates, and long pumping times (20 min), preclude the application of gypsum to the residue sand/seawater slurry as a method for residue amelioration. Dilute, alkaline (pH 9.5) nutrient solutions were used to investigate the effects of aluminate (Al(OH)4-) on mungbean root growth. Although root growth in Al(OH)4- solutions was slightly limited, the symptoms associated with this growth reduction were observed to be similar to those caused by the Al13 polycation at concentrations lower than that which can be detected. Also, when roots displaying these symptoms were transferred to fresh Al(OH)4- solutions, no root tip lesions were observed, and root hair growth on the lateral roots improved. Thus, Al(OH)4- is considered to be non-toxic, with the observed reduction in root growth in solutions containing Al(OH)4- due to the gradual formation of toxic Al13 in the bulk nutrient solution resulting from the acidification of the alkaline nutrient solution by the plant roots. The effect of Mn deficiency in Rhodes grass and of legume inoculation in lucerne (Medicago sativa L. cv. Hunter River), on the rhizosphere pH of plants grown in highly alkaline bauxite residue was investigated. In response to Mn deficiency in residue sand, Rhodes grass was observed to increase acidification of its rhizosphere (being up to 1.22 pH units lower than the bulk soil). Due to its ability to fix atmospheric N2 rather than relying on soil N (NO3-) reserves, inoculated lucerne (1.75 pH unit decrease) was also found to acidify its rhizosphere to a greater extent than non-inoculated lucerne (1.16 pH unit decrease).

Revegetation of bauxite residue is hampered by a lack of understanding of the limitations imposed on plant growth in highly saline and alkaline growth mediums. In this study, several of these growth limiting factors were investigated. The toxicity of the hydroxyl ion (OH-) was examined using a solution culture system developed to allow studies at high pH without nutritional limitations. Also using this solution culture system, the effect of the high Na and Mg concentrations of bauxite residue on the Ca nutrition of plants was investigated. As the toxicity of Al at high pH is not known, a study was conducted to examine the rhizotoxicity of aluminate (Al(OH)4-) and polycationic Al at high pH. The ability of plant roots to reduce rhizosphere pH in bauxite residue was also considered. A novel gypsum application method was assessed for its efficiency at improving the Ca status of bauxite residue. Manual adjustment, ion exchange resins and automated titration were examined for their suitability for nutrient solution pH control in alkaline conditions. For short-term studies, it was found that a solution without supply of Cu, Fe, Mn and Zn, and aerated with CO2 depleted air, greatly reduced nutrient precipitation at high pH, thus eliminating nutritional differences between treatments. Manual pH adjustment and the use of ion exchange resins as pH buffers were unsuitable methods of pH control. In contrast, pH control by automated titration had little effect on solution composition while maintaining constant pH. The solution culture system was used to examine OH- toxicity in mungbeans (Vigna radiata (L.) Wilczek cv. Emerald), with root length reduced at a bulk solution pH of 8.5 and greater. The effect of Ca activity ratio (CAR) and pH on Ca uptake by mungbeans and Rhodes grass (Chloris gayana cv. Pioneer) in Na dominated solution cultures and in soil was investigated. Changes in pH in the alkaline range were shown to have no effect on the critical CAR of 0.024 (corresponding to 90 % relative root length) for mungbeans grown in solution culture. Results from soil grown mungbeans confirmed those from solution culture, with a critical CAR of 0.025. A critical CAR of 0.034 was also established for soil grown Rhodes grass. However, using dilute nutrient solutions dominated by Mg at pH 9.0, root growth was found to be more limited than had been observed for Na solutions, with growth reduced beneath a critical CAR of 0.050. Using a CAR equation modified with plasma membrane binding constants (to incorporate the differing antagonistic effects of Mg and Na), new critical CAR values were calculated for Na (0.56) and Mg (0.44) dominated solutions. This modified CAR equation permits the calculation of CAR irrespective of the dominant salt present. Solubilities of various gypsum sources and size fractions in seawater were studied to investigate the effectiveness of gypsum addition to the residue sand pipeline, rather than as a direct field application. The dissolution rate constant varied with gypsum source (analytical grade (AR) > phosphogypsum (PG) > mined gypsum (MG)) due to reactivity and surface area differences, generally reaching saturation within 15 s (AR) to 30 min (MG > 2.0). The ability of bauxite residue to remove Ca from solution (due to cation exchange and precipitation) was also examined; the quantity of the total solution Ca adsorbed was found to be small (5 %). These low rates of solution Ca adsorption, comparatively rapid dissolution rates, and long pumping times (20 min), preclude the application of gypsum to the residue sand/seawater slurry as a method for residue amelioration. Dilute, alkaline (pH 9.5) nutrient solutions were used to investigate the effects of aluminate (Al(OH)4-) on mungbean root growth. Although root growth in Al(OH)4- solutions was slightly limited, the symptoms associated with this growth reduction were observed to be similar to those caused by the Al13 polycation at concentrations lower than that which can be detected. Also, when roots displaying these symptoms were transferred to fresh Al(OH)4- solutions, no root tip lesions were observed, and root hair growth on the lateral roots improved. Thus, Al(OH)4- is considered to be non-toxic, with the observed reduction in root growth in solutions containing Al(OH)4- due to the gradual formation of toxic Al13 in the bulk nutrient solution resulting from the acidification of the alkaline nutrient solution by the plant roots. The effect of Mn deficiency in Rhodes grass and of legume inoculation in lucerne (Medicago sativa L. cv. Hunter River), on the rhizosphere pH of plants grown in highly alkaline bauxite residue was investigated. In response to Mn deficiency in residue sand, Rhodes grass was observed to increase acidification of its rhizosphere (being up to 1.22 pH units lower than the bulk soil). Due to its ability to fix atmospheric N2 rather than relying on soil N (NO3-) reserves, inoculated lucerne (1.75 pH unit decrease) was also found to acidify its rhizosphere to a greater extent than non-inoculated lucerne (1.16 pH unit decrease).