This thesis aims to present some investigation aspects of urban ecology giving examples related to Kolozsvár. The first chapter deals with the notion of 'urban ecology' and gives a short history of this science. In order to urban areas, they represent a mosaic of different biotope types and can not be regarded as ecologically homogenous ones due to climate, soil, vegetation and buildings. Each chapter deals with one of these environmental elements (soil, climate, vegetation).
The word of "urban ecology'" is used in the natural science referring to that field of biology which concerns with urban areas. Ecology does mean an interdisciplinary scientific study of the living conditions of organisms in interaction with each other and their surroundings, organic as well as inorganic. On the other hand, urban ecology is concerned to the Chicago School of urban ecology that and its theories of urban social ecology were strongly influenced by Social Darwinist thought. Such theories were originally part of social ecology. The members of the school viewed the city as an object of detached sociological analysis and sought to explain the complexities of the urban community and to discover the pattern of regularity. They thought that ecological processes are similar to those which determine the structure of plant and animal communities.
Urban ecology as natural science is the third interpretation, and it is a young discipline. It was thought for a long time that urban areas were not worth studying with regard to ecology. Cities were seen as non-life zones, and this view began to change in the sixties. Since then, ecological aspects of the cities have been intensively researched. It was necessary to rediscover the cities through the insights that the natural sciences provide the nature of the familiar places we live in. Basically, urban ecology has been developed from landscape ecology and environmental geography through intensive research in inhabited areas down to the biotop level, and it has become established as a landscape ecological specialisation par excellence.
Kolozsvár is situated in the valley of the Kis-Szamos river between 323 and 711 m above the sea level. The surface of the city extends on ten geomorphological levels, which are as follows: the floodplain of Szamos and its tributary, the seven river terraces and the surface of Felek hill (it is the highest geomorphological level, generated in the Messinian stage). Each level has its own environmental and ecological characteristics.
In climatically point of view, urban ecosystems differ from non-urban areas in several ways: the combined influence of the greenhouse effect, the high heat capacity of the buildings and of urban ground. The actual heating of buildings leads to warmer annual average air temperature by 2-3oC than the normal one of the region, and it is proved by measurements and model analysis. It means that the growth season for plants in the inner-city area is extended, blossoming and leaf formation occurs 6-7 days earlier, and in the same time thermophilous plants migrate into the city (Hordeum murinum can be used as indicator species for the inner-cities heat-island). Basically, the city heat-island covers the same area like the built-up ones, especially the very densely built-up territory and the areas without gardens.
The selected areas for urban climatical investigation are located in such representatives urban structures which are typical of Kolozsvár. The influence of different built-up territories on the spatial distribution of numbers of summer, winter, hot and frost days depend on the built-up environment index as well as on the density and the building materials and geomorphological levels. Regarding the temperature surplus during the daytime the spatial distribution shows the highest temperature in the centre and the territories built of concrete slabs. The housing estates appear as the second warmest area. Cold areas are the mainly vegetated open spaces e. g. encapsulated countryside's, cemeteries. The difference between the two extremities reaches 4-6 degrees daytime, and 2-3 degrees night-time in summer, and 2-3 degrees in winter.
The diurnal courses of bioclimatical indices show spatial differences of the inside and outside of urban areas too. It can be confirmed that there is a correspondence between the degree of the increase of uncomfortable days, the urban morphological type and the geomorphological level. The most comfortable territories of the city which are the highest geomorphological levels and they are featured by stimulating bioclimate: the bioclimate indices are quite moderate with long thermal comfort period during the day in the summer. On the other hand, the centre presents comfort periods with gentle and mild evenings during the summer. The increasing number of winter and frost days from the inner town to the suburbs is advantageous in order to ensure a lower cold stress effect, and to present a spare in the heating of flats.
The city should be considered as a whole system which includes not only buildings and streets but also greenery and energy webs. Urban buildings do not affect only the urban topography, but they have ecological effects too. Building surfaces resemble natural rock faces for many plants in urban habitats. Microclimatic effects have also ecological importance: depending on their exposure, the building walls and the street pavage can be subject to high temperatures which can be maintained over longer periods.
Material inputs into cities have meant that the ground level has risen by several meters in the older districts. Surface sealing and the resulted consequences reduced infiltration capacity as well as extraction of groundwater for human usage. The urban soil of the city has become considerably dryer step by step with the exception of parks and gardens that often have become moisterfull through extensive watering. They are generally altered, eutrophicated and over-compacted. The eastern industrial area, the waste deposits and the roadsides places are heavily polluted in general. Heavy metal exploration by using EDTA-solutions is an appropriate method for monitoring the so called "Chemical Time Bombs". I have measured great concentrations of Mn, Pb and Cu at several sites. The abnormally high concentration of Mn were revealed in all samples, the Pb and Cu pollution pattern of the soil is rather fragmented. The main part of the pollution covers the industrial zone in the eastern part of the city which is situated on the floodplain, and along of the main wayrouts. The natural ecological conditions are outweighed and modified by the type of land use and by the cities' built-up index. The ecological mapping is based on land use types.
The proportion of species which are ecologically indifferent to soil reaction and continentality is always higher in the cities than in their vicinity. The number of fern and flowering plant species correlates with population at the same time. Regarding Kolozsvár, the number of flowering plant species were 934 in 1971, and it was 1,019 in 1998. There are various reasons for this growth of this number:
The ecological communities in Kolozsvár and generally in the human settlements have some characteristics: low diversity, low rate of primary production, poor stratification, strong desertification, low stability. The succession is under external influence, and in most cases it is under anthropological control. The climax stage is rare, the majority of plant populations have wide ecological tolerance, and the dominating species have a wide geographical distribution.
The urban ecosystems differ completely from those which are situated in their surroundings. Eight types of habitats can be recognised in the city: strongly built-up territories, open spaces, green corridors, parks and cemeteries, industrial sites, railroad embankments and dumps.
Specific urban-industrial environmental effects have been investigated using lichen on tree bark. The distribution pattern of various lichen species differs from each other according to their sensitivity to the air pollution. The inner city and the eastern industrial area are lichen-free-zones. The highest geomorphological levels belong to the normal zone where the number of species, their extend and their combination correspond with the conditions in the "hinterland".
The increase of human influence on urban areas is represented by using the so called hemerobic index (scale) which is the degree of antropological influence on environment. The natural state can be obtained using the data of spreading degree of ruderal plant species, land use and the degree of soil compactness. Generally speaking, the hemeroby level i.e. the influence of human activity is the highest in the centre and in the eastern industrial zone, and the lowest on the highest terraces which are dominated by open spaces and garden city areas.
Some possible conflicts could arise concerning the limitation of land use, e.g. conflict between (1) the so called "Handkerchief Construction" in the inner city and in the green spaces, (2) the pedigreed and nurtured landscape and the fortuitous one, (3) the naturalised plant community and the old urban woodland community, (4) the continuous demand of living spaces and the reduction of household's sides. A few of them can be handled, others depend on ecological technologies and the environmental and social policy of the local authorities.
25th November, 1999.