Urban Ecology最新文献

Forty vacant lots within the City of Montreal were studied during summer of 1983 for floristic composition. Despite a low floristic diversity per site — number of species per site varies around 23 — the whole sampling allowed us to record 136 taxa. Among these taxa, very few appear in more than 50% of the stands, suggesting a good discrimination between the 40 vacant lots. The data were analysed using principal coordinate analysis and hierarchic agglomeration cluster analysis. A study of the ordination and the dendrogram reveals eight phytosociological groups among which the most important are those dominated by Agropyron repens, Ambrosia artemisiifolia, Hordeum jubatum, Melilotus alba and Poa pratensis. Finally, dynamic relationships were identified between these groups which go from annual-dominated communities towards perennial-dominated communities.

The paper describes the ecology and nature conservation interest of the aquatic ecosystems of urban Britain. The paucity of published information is attributed to the historical lack of interest by the government's ecological and nature conservation agencies, research workers, and those concerned with the management of urban green space.

Urban water bodies are classified according to their origins and use, as modified by age, size, water quality and level of public use. The plants and animals to be found in each category are described. Most of the information relates to London and to birds. However, London is atypical in many respects because of its size, large estuary, large parks, an active natural history society, and because it is the capital city. Apart from Milton Keynes (a new town) and some areas of the West Midlands, there is very little information about the ecosystems of other British towns and cities.

The data indicate the importance of urban water bodies for the conservation of wildlife in Britain. The potential for improving the value for nature by ecological engineering is demonstrated. The diffused management responsibilities are described together with the need to impose a discipline on the maintenance authorities by the preparation of management plans in order to ensure continuity and consistency of treatment.

A programme of research is advocated on the basis of the re-allocation of existing funds. The prime objective of such a programme is the acquisition of pragmatic information that will allow planning, design and maintenance operations to respond to inevitable development whilst maintaining a high-quality environment.

Corticolous (bark-inhibiting) lichens and bryophytes were studied in several deciduous forest study area as biological indicators of urban impact and as microhabitats for meiofaunal invertebrate colonizers. Bryophyte and lichen species richness are greatest in high-humidity, ‘clean air’ sites. Urban environmental conditions were characterized by decreased humidity, rapid humidity depression and decreased air quality. Differences in the bryophyte community at study sites best reflect their openness to light penetration and patchiness of microhabitats. Reduction in the number of lichen species found in sites is best explained by the study area's proximity to the city and ambient air quality.

Variation in the frequency of occurrence of tardigrade species living on corticolous mosses and lichens indicates differential tolerances to aspects of climate altered by urbanization. Tardigrade species richness is greatest in high-humidity, ‘clean air’ sites. Correlation methods were utilized to illustrate the relative effects of habitat conditions on the representation of species within epiphytes collected in these monitored study areas. Tardigrade species richness was best explained by site humidity regime; however, the frequency with which some species were found in sites appears to be related to air quality. Two common species are characterized by different environmental preferences. Diphascon scoticum Murray predominates in urban park sites, characterized by low air quality and reduced humidity. The prevalence of D. scoticum may be related to this protococcal algae feeder's adaptation to low pH substrates. Such low pH conditions are more frequent in urban moss habitats. Minibiotus intermedius Plate is found more often in humid, rural sites, and is apparently intolerant of faster evaporation rates which may occur in more xeric environments.

Recent publications have dealt with the subject of urban renewal in Western Europe. In this paper we attempt to extend this discussion by describing recent experiences in urban revitalization in Australian cities. To begin, a brief outline is made of the characteristic features of the urbanization process in Australia. Among the challenges facing Australian cities as a result of their particular pattern of urban development are the heavy demands for the use of private vehicles due to low-density suburban growth, and a relative decline in the commercial importance of central city areas. The paper canvasses a number of solutions proposed for these developments and their manifestations. In particular, three foci emerge: planning and design of residential streetscapes, pedestrianization in commercial and shopping areas, and the conflict between calls for redevelopment or preservation of old buildings.