School of Botany - Theses
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ItemThe roosting and foraging requirements of insectivorous bats in an urban environment( 2013)Most urban areas around the world are continuing to increase in size and density. Urbanisation results in extensive loss and fragmentation of habitat and is a key process threatening the conservation of biodiversity worldwide. Many populations of insectivorous bats (hereafter bats) have declined in urban areas, for reasons that are poorly understood. In order to predict future trends in the distribution and abundance of bats in urban areas, and design cities to provide habitat for bats, a better knowledge is needed of their preferences and requirements for particular habitat elements within the urban mosaic. This project aims to determine the roosting and foraging requirements of bats across Melbourne, Australia. To identify bat roosts and roosting behaviour, I radio-tracked 95 Gould’s wattled bats Chalinolobus gouldii at three sites in Melbourne which represented two urban habitat types: open parkland (Royal Botanic Gardens (RBG)) and regenerated bushland reserves (Valley Reserve and Blackburn Lake (bushland sites)). Large hollow-bearing trees were limited at these sites, which is typical of much of the urban landscape. Chalinolobus gouldii roosted within a range of native and exotic tree species, but showed preference for certain roost tree characteristics (greater DBH, height and decay stage) compared to available trees, as well as certain tree types (e.g. small dead trees). Chalinolobus gouldii used a greater range of cavity types (including dead leaves and loose bark) in Melbourne compared to rural areas (fragmented farmland and extensive forest); possibly in response to a paucity of large hollow-bearing trees. Some evidence was found suggesting bats modified their roosting behaviour in urban environments; this included the greater reuse of roosts at the RBG compared to the bushland sites and in forested areas where more hollow-bearing trees were available. Radio-telemetry was also used to investigate the foraging habitat selection and foraging behaviour of C. gouldii within open parkland (RBG) and a bushland reserve (Valley Reserve). A total of 21 C. gouldii were radio-tracked at night. Bats displayed a preference for foraging in areas with relatively high levels of tree cover and in close proximity to water. Chalinolobus gouldii foraged within the urban matrix, especially around Valley Reserve, where there was less impervious surface in the matrix compared to the RBG. Bats typically foraged within 1 km of their roosts, which is considerably less than what they are capable (Individuals of C. gouldii can forage up to 21 km from their roosts). This suggests that there were sufficient foraging resources close to roosts in this study, which could be attributed to the amount of edges and linear strips of vegetation in urban areas. The provision and protection of trees across the urban landscape will benefit C. gouldii and other bat species which rely on high levels of tree cover. Nocturnal aerial insects and bats were sampled at 60 study sites distributed along an urban-rural gradient. Ten sites each were located within six land-use categories (industrial areas, residential areas, golf courses, recreational parks, remnant bush reserves and riparian vegetation), representing varying levels of human modification. I found that insect abundance and biomass was negatively influenced by urbanisation and positively influenced by number of trees and tree cover. Insect abundance and biomass was greater in riparian and remnant areas than in golf courses, recreational parks and industrial areas. These habitat types also had a higher density of trees than golf courses, recreational parks and industrial areas. A positive relationship was found between insect abundance and biomass and the activity and species richness of bats. Results suggest that managing urban areas to maximise insect abundance, by maintaining diverse and structurally varied habitats, would benefit bat populations. This study highlights the importance of trees as roosting and foraging habitat for bats. The protection of dead, decayed and large old trees is essential for providing roosting habitat. Tree planting and measures to ensure regeneration (i.e. reducing mowing in urban parks) will also provide foraging resources for bats and an ongoing replacement of hollow-bearing trees for roosting. The findings from this study will assist in the formulation of policy and management decisions to ensure the long-term survival of bats in urban environments.
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ItemUrban landscape structure and the provision of ecosystem services at multiple scales: understanding socio-ecological patterns shaping the development of sustainable cities( 2013)Urbanisation poses a variety of threats to natural resources, especially vegetation which becomes dispersed, fragmented and less abundant, in turn affecting ecological processes and ecosystem services. Vegetation in urban areas is one of the main suppliers of ecosystem services linked to the enhancement of human well-being. Little is known about the quantification of ecosystem services and its linkages to the vegetation structure of urban areas. This research explores some of the key linkages existing between the structure of the urban vegetation and their ecosystem services provision at different scales to test if previous findings at local scale repeat at larger scales and in urban areas that have been less explored. The study hypothesised that the supply of ecosystem services depends on the structure of vegetation which is likely to be a reflection of biophysical, social, political and demographic factors. The understanding of these relationships is critical for enabling informed decision making towards developing sustainable cities. At the local scale, nine ecosystem services maps were produced detecting areas of low and high supply of ecosystem services, as well as their trade-offs and synergies. Fragmentation, population and diversity of languages were found to be the strongest drivers for the provision of ecosystem services. At the regional scale, the provision of recreation potential, carbon mitigation and habitat provision in Melbourne, Perth and Sydney were assessed. Differences between cities were found as a result of a climate gradient that affects both habitat provision and carbon mitigation. Higher temperature and precipitation tended to be related to areas with high provision of habitat and carbon mitigation. Differences within cities were related to fragmentation and shape of the vegetation patches and the strongest drivers were population and temperature. Once again this showed how increased population creates more fragmented landscapes. At the global scale, the study of one hundred cities revealed that recreation potential and habitat provision were related to development and governance, while carbon mitigation was primarily influenced by climate. Recreation potential and carbon mitigation have a synergistic relationship while tradeoffs occurred with both these services and habitat provision. Similar patterns were found when exploring the relationships between vegetation structure and ecosystem services, where more populated, wealthier and more democratic cities are providing more services and better vegetation structure within a certain climatic envelope, confirming results from the broader literature for a wider range of cities. The research represents one of the first attempts to establish linkages between ecosystem services and vegetation structure at multiple scales to increase our understanding of patterns in socio-ecological systems. The findings showed differences according to the level of development, as a reflection of income and education, and constrained by the climate in which the city is located. These results suggest that when establishing targets to achieve sustainable development goals, it is necessary to base them on a city’s climate and available economic resources.