School of Botany - Theses
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ItemThe sanitisation of urban ecosystems: simplification of the ground layer in eucalypt woodlands and the effects on arthropod communities( 2011)Green spaces in urban environments can provide valuable habitat for maintaining local and regional biodiversity. Many urban green spaces are, however, managed for human recreation, where the vegetation structure is reduced, and critical resources such as leaf litter and woody debris are removed. Reductions in ground layer resources have been implicated in the decline of urban vertebrate biodiversity, but the effects of this process on arthropod communities is poorly understood. The response of the ground-active arthropod community to differences in ground layer resources was studied in green spaces managed for human recreation compared to areas maintained in a ‘natural’ state, at 21 field sites in Melbourne, Australia. Sites were separated into two categories: 1) areas with high leaf litter levels (remnant woodland patches) and 2) areas with reduced leaf litter layers, which were regularly mown (public parks). All sites had overstoreys of Eucalyptus camaldulensis. Site assessments confirmed litter layers were greatly reduced in abundance and extent in public parks, and also showed that these sites had less vegetation in the mid- and over-storey, and fewer dead wood resources. The arthropod communities at the sites were examined at order level, and millipede (Diplopoda), slater (Isopoda: Oniscidea), ant (Hymenoptera: Formicidae) and beetle (Coleoptera) communities were examined at species-level. The millipede and slater (macrodetritivores) communities were made up almost exclusively of introduced species from Europe. Although they were able to persist in both Parks and Remnants, their abundance was greatest where there was more leaf litter and shrub cover. In contrast, the ant fauna was diverse, abundant and native at all sites, but had a different community composition at Parks compared to Remnants. These differences were associated with both local- and landscape-scale features of the sites. The beetle community showed strong changes in composition and diversity in response to differences in the leaf litter layer as well as to the composition of the ground layer species. The response of the invertebrate fauna to small-scale manipulations of common urban ground covers – bare ground, leaf litter, woodchips and grass – was investigated experimentally at a semi-field site. Diverse arthropods rapidly colonised previously cleared plots under all four ground covers and were most abundant in grass plots. This is likely to be related to the landscape context of the experiment and has important implications for small-scale landscape management for biodiversity conservation. This thesis provides information on the role of urban, managed green spaces for arthropod biodiversity conservation, and contributes to our understanding of the effects of management practices that influence the arthropod community composition and diversity in these areas. Green open spaces (parks) were not found to provide the same resources for ground-dwelling arthropods as woodland remnants, and this was associated with marked changes in their community composition. The findings have important implications for biodiversity conservation in an urbanising world.