Abstracts - Posters

Cilliers, Sarel*, J-P Smith, Ryan Jonas, Nikki Smith, Henk Bouwman, Ernst Drewes, Pieter Theron and Leon Van Rensburg
A PROPOSED STRUCTURAL FRAMEWORK FOR INTEGRATED URBAN ECOLOGICAL RESEARCH IN POTCHEFSTROOM, SOUTH AFRICA

A growing need for urban employment in South African cities, have witnessed an increase in informal settlements on urban fringes, leading to fragmentation and sprawling. This in turn, increases the strain on the natural environment and immense areas of significant ecological open space are cleared for persistent lateral growth. Conservation-orientated spatial planning and land-use management are, therefore, important. All these issues should, however, operate successfully in the arena of poverty, as well as privilege, if it is truly to function as an integral component of urban development. In this poster a conceptual framework integrating social and biophysical studies in a South African context, is discussed. A long-term objective of this program is to improve our understanding of the concept of biological diversity in urban areas in terms of the variability of human impacts and social issues. Another objective is to co-ordinate opportunities for continuity and long-term research in urban ecology involving inventories and characterizing of habitats as a benchmark for monitoring trends, identification of ecological indicators and state-of-environment reporting. Emphasis will be placed on urbanization gradient studies focusing on birds, epigeal arthropods, plants and soil properties. Limitations on the application of urbanization gradient studies in South African cities will also be discussed.

The introduced European Red Fox (Vulpes vulpes) and the Domestic Cat (Felis catus) are widely recognised as major threats to the indigenous vertebrate fauna of Australia. Foxes and cats are common in urban areas but present a serious problem in the outer urban fringe where they occur in high densities and prey on remnant populations of ground-dwelling species. Many of these populations now persist only in a few small, isolated patches of indigenous vegetation. The Royal Botanic Gardens Cranbourne contains one of the largest remaining patches of indigenous vegetation in Melbourne's south eastern suburbs and supports 26 species of threatened fauna including a number of rare terrestrial mammals, birds and lizards. An innovative and adaptive approach to fox control was been undertaken in an attempt to substantially reduce the potential impact of fox predation on biodiversity at the site. Fox activity at the site was monitored during a two-year period while control trials were implemented and have resulted in a sustained reduction in fox activity.

This presentation aims at the integration of spatial planning at Local Municipal level with the zoning of land in terms of ecological aspects, including biodiversity. Spatial Development Frameworks are currently being compiled at Local and District Municipal levels as a legal instrument to guide future spatial development. Although it is an integrated approach, i.e. most relevant sectors provide their input in this regard (through the IDP-process), it has shortcomings specifically with regard to environmental matters. Greenfield developments are subjected to environmental impact assessments (EIA's) in most cases where agricultural land is redeveloped. In brown field developments, however, the land only needs to be rezoned properly - in most cases without an EIA. The EIA is, therefore, a reactive instrument to protect the environment. Strategic environmental assessment (SEA) guidelines, i.e. a pro-active instrument, has been compiled in South Africa, but has no legal status at the moment. Biotope mapping is used in many European countries as an effective instrument to guide land-use planning and control on Local and District Municipal levels. These two instruments have been used successfully in the Potchefstroom Local Municipality as part of the formulation and promulgation of the Spatial Development Framework. This poster shows the process and results of the integration process.

Remnant patches of river red gum (Eucalyptus camaldulensis) woodland occur along a 30 kilometre urban-rural gradient in northern Melbourne. We explored the influence of sub-patch, patch and landscape features on the composition of the plant community. Ordinations of the vegetation community were compared with characteristics of the sample plot (edge or interior placement; soil characteristics), remnant patch (patch area, local annual rainfall, current management practice, local patch history) and landscape type (urban, urban-rural fringe, agricultural, agriculture/forest mix). Characteristics of the remnant patch appear to have a greater influence on the vegetation than sample plot or landscape type. Smaller remnant patches (<5 ha) tend to have lower species richness and fewer indigenous plant species than larger patches (5 - 50 ha). The species composition in smaller patches is not unique, and tends to be a subset of the species recorded in larger patches. The similarity of the vegetation communities at both ends of the urban-rural gradient indicates that the red gum woodland communities can survive and persist in urban landscapes.

Urban development fragments previously more uniform landscapes, which produces changes in the ecosystem remnants. Furthermore, smaller scale fragmentation is caused by different use and management of urban green areas. The changes and dynamics in remnant ecosystems should be understood in order to maintain indigenous nature within the urban setting. Our previous results suggest changes in the flora, soil microbes and invertebrates in relation to fragmentation and recreational use. We will present a multi-taxa approach to quantify the effects of fragmentation and recreational use, aiming to collaborate with people all over the world interested in using the same design. We take the typical Scandinavian urban indigenous ecosystems, forests, as an example, and will use the distance to the nearest forest edge, and size of the woodland patch as measures of fragmentation. The set-up within forest fragments will take into account direct and indirect effects of wear. Spontaneous walking paths will be quantified from heavily trampled to lightly trampled and samples will be taken on the paths, right beside them and further away in the seemingly untrampled spots. Vegetation and soil sampling, and pitfall trapping of epigaeic invertebrates will be carried out from May to August 2003, during the northern hemisphere summer.

The new EU Directive concerning the assessment of effects of certain plans and programmes on the environment raises demands on the integration of environmental concerns in planning and decision-making. The implementation of the Directive calls for adequate tools and methods to evaluate alternative planning scenarios. In order to integrate nature conservation considerations among these issues, a landscape ecological assessment (LEA) tool was developed through the focal species' approach. A case study was conducted in the Stockholm region, where scenarios of future urban development were evaluated. Focal species were selected that were considered to be sensitive to the threatening process, in this case to habitat fragmentation and disturbances caused by urbanisation. From predicted habitat networks of focal species, impacts of the development scenarios were evaluated. The LEA tool was shown to be useful for assessing impacts on sensitive species on a landscape scale, at a strategic level in the planning process. There is also a potential to develop effective mitigation and restoration measures, which will be explored in further research.

Metapopulation theory is useful for understanding the dynamics of pond-breeding frogs, as wetlands and ponds are naturally patchy and interspersed with terrestrial habitats of varying suitability for frogs. The theory suggests that large ponds (habitat patches) are more likely to be occupied than small ponds, because of a lower probability of local extinction, while isolated ponds are less likely to be occupied than ponds close to other suitable habitat, because of a lower probability of colonisation. During a field study of 104 ponds across greater Melbourne, Australia, I found that the size, isolation (measured by the average density of roads in a 500 m radius) and habitat quality of a pond all influenced the probability of occurrence of frog species and the diversity and composition of assemblages. For example, species richness at an otherwise average pond was predicted to decrease from 3 to 0.33 as the surrounding density of roads increased from 0 to 0.25. Three of four species modelled individually were more likely to occur at larger ponds, while only the southern brown treefrog Litoria ewingii was regularly detected at ponds with a vertical stone wall. Conservation of pond-breeding frogs in urban areas such as Melbourne may require both improvement of the habitat at ponds and reintroduction of species that have gone locally extinct.

Increasing urbanization leads to a decrease in job opportunities and a need for self-provision of food using entrepreneurial skills. People are discouraged by the huge effort and expense that gone into conventional vegetable growing. In Potchefstroom we established a low-cost program in relatively small areas which aspires small farmers to prove their ability within short periods of time. This program follows the eco-circle approach that claims to be ecologically sound. Only recycled and organic materials are used. This program enables people to feed their families and to generate an income for sustainable growth as a profitable enterprise. Vegetables are cultivated in circles with a diameter of 1m, directly surrounded by ruderal or natural vegetation. The advantages of this approach include conservation of water, reduction in rain run-off, less desertification and erosion, conservation of existing vegetation, cost-effectiveness, planned and maintained production and less labor. Currently there are 4800 of these agro-ecosystems operating in Potchefstroom under the direct supervision of the Municipal Authority, as part of a community-upliftment project. In this poster the methodology, social and ecological difficulties in the establishment of this approach and important ecological questions that need to addressed, are discussed.

Urban trees and parks provide important ecosystem services such as improved air quality, reduced run-off, removal of atmospheric carbon dioxide, reduced air temperatures, and enhanced energy use efficiency. Urban vegetation contributes to communities at risk from urban development by reducing air pollution. A spatial analysis of Jefferson County, KY correlated individual trees and parks to socio-demographics. This study examined which ethnic groups have the most access to local parks, and based on increasing proportion of Caucasian inhabitants, which neighborhoods contain the majority of Jefferson County's urban trees. Within one kilometer surrounding the local parks, over 60% of the population was Caucasian. However, the African American population had greater access to parks in comparison to their proportion of the county population. The >80% Caucasian neighborhoods have the greatest total number of trees and area, and contain more trees per person than the county average, but have less trees per square kilometer than the <20% Caucasian neighborhoods. The Caucasian inhabitants of Jefferson County have the most urban trees and access to local parks. However, more detailed analysis of tree species, tree age, size and morbidity is needed to truly assess the ability of the urban vegetation to filter pollutants in these neighborhoods.

Forest remnants surrounded by urban land use may experience altered soil nitrogen cycling caused by warmer temperatures, increased nitrogen deposition, and altered organic matter quality. An urban-rural gradient was established in Louisville, KY within oak forest stands on the same soil series. Urban forest plots received five times more nitrogen deposition than the rural plots. Urban mean surface soil temperatures (two week period in July 2002) were 1.0°C warmer than rural forests. However, field mineralization rates from March-September 2002 were not higher in the urban stands as anticipated (urban Nmin: 53.2 mg kg-1 DW soil; rural Nmin: 62.1 mg kg-1 DW soil). To separate effects of exogeneous influences on nitrogen mineralization, we conducted a three-month soil incubation experiment in the lab. Replicate cores were removed simultaneously with field-incubated cores from urban and rural plots. Temperature and soil moisture were held constant during the lab incubation to determine whether urban and rural organic matter quality differences existed. Soil cores were incubated at 2 and 4 °C higher than mean daily urban soil temperatures to discover whether soil warming may interact with urban organic matter quality to decrease nitrogen mineralization rates.

The ecological condition of streams as indicated by the composition of biotic assemblages and ecological function has been demonstrated to decline with increasing density of catchment urbanization in cities around the world. While some researchers have focused on density (indicated by catchment imperviousness) as the driving factor, the wide variation in condition that is common among sites with similar, low levels of imperviousness remains unexplained. Urban stormwater managers are increasingly looking to low-impact design (LID) to minimize the impacts of stormwater on receiving streams, but links between LID and improved stream condition have remained elusive. Studies seeking to detect such links have so far failed to find a catchment-scale indicator that integrates the effectiveness of specific stormwater treatment measures. In streams in the east of Melbourne, drainage connection (the proportion of impervious surfaces connected to streams by pipes) has proven to be a very good indicator of stream condition. As stormwater treatment measures associated with LID reduce drainage connection, this indicator has great potential for assessing the effectiveness of LID in improving stream condition. A new project will make a comparative assessment of this approach in three Australian cities.

Williams, Nick*, Mark J. McDonnell, and Emma Seager
THE CONTRIBUTION OF LANDSCAPE AND SOCIETAL FACTORS TO THE DESTRUCTION AND DEGRADATION OF MELBOURNE'S GRASSLANDS

Over the past two decades, the decline and destruction of native grasslands in Australian cities has intensified. In Melbourne large remnants of this endangered ecosystem have been subdivided and destroyed by urban development while linear reserves are being degraded by changes to management practices. To analyse fragmentation patterns we developed a temporal dataset recording the extent and distribution of native grassland patches in western Melbourne. Of the 7,230 ha of native grassland present in 1985, 1,670 ha (23%) were destroyed by development and 1,469 ha (21%) were degraded to non-native grassland by 2000. There were fewer patches and greater distance between patches in 2000 than in 1985, indicating that significant fragmentation has occurred. Logistic regression models were created to determine the probabilities that a patch would be destroyed, degraded or remain as native grassland. Patches that were privately or government owned, close to major roads and close to Melbourne were more likely to be destroyed while patches close to streams or on railway land had a lower probability of destruction. Patches with high perimeter to area ratios had a higher probability of being degraded. Biological significance ranking was also an important explanatory variable determining

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