G. Profous and R. Rowntree
George Profous is Senior Forester of the New York State Department of Environmental Conservation, New Paltz, New York. Rowan Rowntree is with the United States Department of Agriculture Forest Service, Northeastern Forest Experiment Station, College of Environmental Sciences and Forestry, State University of New York, Syracuse.
A study of Prague's urban forests, based on a 16-neighbourhood sample, conducted in 1987 and updated in 1990.
Robinia pseudoacacia in Jagellononska Street In Vinohrady. Locusts are the most common street trees in many older neighbourhoods
Prague, the capital of the Czech Republic, is located on gently rolling hills along the Vltava River at 50°N latitude and 14°E longitude. Elevations in the metropolitan area range from 176 m along the river to 390 m on the surrounding hills. The average temperature in summer is 20°C, dropping to 5°C in winter. A little more than 1200000 people live within the 497 km2 metropolitan area.
There are an estimated 10155 ha of green space in Prague, of which 4060 ha are in parks managed by the Department of Parks, Forests and Horticulture (SLZ) (Tichy, 1981). Prague has more vegetation than most European cities of a comparable size, although access to and the distribution of green space varies widely from neighbourhood to neighbourhood.
The vegetation of Prague has been influenced by agriculture since neolithic times. Forests, except those protected by private landowners, were removed from virtually all areas suitable for agriculture. Historical records from the thirteenth century describe a wood shortage which led King Jan to establish a wood marketplace near the city. In 1350, King Charles IV ordered the preparation of strict regulations controlling the use of forest lands. Although never enacted, the regulations indicate the degraded state of the forest lands around Prague during that period.
The Hussite Wars in the fifteenth century crippled agricultural production, allowing natural reforestation to alleviate wood shortages, but an acceleration in mining and housing construction in the mid-sixteenth century again created a high demand. The Thirty Years' War (1618-1648) so depleted the population that the threat of wood shortages was removed until the eighteenth century.
In 1740, King Charles VI ordered the planting of trees along roadsides; nobles owning land abutting on roads were to care for and profit from the trees. In 1752, Empress Maria Theresa broadened the decree to include the planting of trees on all new roads in order to orient travellers in fog and snow, increase wood production and enhance the appearance of the landscape. A space of 11.4 m was required between trees, quality standards were prescribed for planting stock and causing damage to trees became an offence punishable by law.
The first major reforestation of Prague was undertaken in 1854 and, between 1897 and 1908, substantial efforts were made by public beautification commissions to revegetate open spaces and eroded hillsides throughout the city. It is noteworthy that air pollution was already so severe in the Vltava valley that the use of conifers was avoided in favour of the more resistent black locust (Robinia pseudoacacia) (Valesova, 1985).
Today, the Czech Republic has one of Europe's highest pollution rates (Supuka. 1985). Within the past decade or so, Prague's air pollution has tripled, primarily because of a tremendous increase in the number of private vehicles (Tomek, personal communication). Another important source of pollution is the high concentration of small, coal-fired heating systems in the dense urban centre. The deteriorating urban environment has substantially reduced the successful establishment of new plantings and has placed new stresses on older trees. Particulate fallout over the city in 1977 was 244 tonnes/km: and even higher in some industrial areas (Poleno, 1977). The largest fallout was recorded in the city centre and the industrial districts.
The period 1860-1920 also marked the establishment of most of the city's formal parks. Landscaping in many parks and gardens reflects the reconstruction which was carried out at the turn of the century and which was spearheaded by the famous Czech gardener and landscape architect, Frantisek Thomayer (Svoboda, 1985a). He is known as the founder of the Prague municipal park system and his designs a" still studied.
Until the early twentieth century, most the Prague's forest land was owned by the nobility, church or other institutions. In 1919, just prior to the first land reform, the municipality owned only 100 ha of forest land.
After the First World War, an inadequate workforce curtailed park maintenance and ended the development of new public areas. During the First Republic (1918-1938), especially following land reform, the upkeep of castle gardens declined. Although park area continued to increase, a growing interest in ornamental horticulture by the newly affluent middle class shifted the efforts of landscape gardeners to the private sector. Emphasis shifted back to the management of public green space after the establishment of the Czechoslovak Socialist Republic in 1948 (Stepanek, 1973).
A view across the Vltava River towards Mala Strana, showing the growing space in the palace gardens end courtyards
Today, fully 10 percent of metropolitan Prague is covered with forest vegetation. There are marked differences among the tree compositions of streets, parks, private yards and courtyards. Vegetation structure is influenced by several factors but the age and structure of buildings appear to have had the greatest influence. The density and type of tree tends to reflect the management choices and species preferences at the time of neighbourhood establishment. In Stare Mesto (the old town), which retains a medieval character, vegetation is almost absent, but in sections of another old zone, Mala Strana (the lesser side), where palace gardens are common, green space may be as high as 20 percent of total land area. The densely constructed apartment blocks which were common at the turn of the century also have very little green space, while newly constructed residential areas may have as much as 60 percent, largely because of the presence of undeveloped city blocks (Jelen, 1985).
Species composition has also been influenced by the date and style of architectural design. For example, ornamental cherries (Prunus spp.) were a popular planting choice during the First Republic and mature specimens can be seen throughout Prague, especially in the dense multifamily housing zones of that period.
Lindens (Tilia spp.) in Parizska Street, the central boulevard of Josefov
Wherever land is under private or semiprivate control, fruit-trees are a substantial component of the green space. Suburbs and villages recently incorporated into the city have a substantial fruit-tree component, representing between 50 and 75 percent of all trees.
The use of poplars (Populus spp.) to screen industrial sites is reflected in the inventory results for Kobylysy and Liben. These fast-growing, pyramidal trees are also seen alongside sports stadiums, large institutional structures and certain parklands.
On public lands outside parks and forests, linden (Tilia spp.), black locust (Robinia pseudoacacia), maple (Acer platanoides, A. pseudoplatanus) and black poplar (Populus nigra) comprise more than 65 percent of all tree species. The Czech national tree is linden and, as a historical symbol of freedom and independence, it has often been planted and even overplanted along major boulevards, streets and squares throughout the city. Unfortunately, lindens are susceptible to damage in areas with temperature extremes, salting and heavy air pollution. Extensive street planting carried out between 1900 and 1940 has caused gaps in the intermediate size classes of trees, particularly in multifamily residential neighbourhoods.
Fruit-trees often predominate in sideyards and backyards
Today, the most frequently planted street trees in Prague are lindens and maples. However, the Division of Road Maintenance in the Department of Transportation (TSK) now avoids the use of lindens because of their sensitivity to salt. Along the Vltava River, trees are planted in containers below street level to reduce salt damage. The containers, which are separated from the surrounding soil by an air gap, range from 8 to 12 m in diameter and are designed to last for at least 30 years. A 5 cm diameter perforated pipe is built into the root area to allow thorough watering. Hedgerow rose (Rosa rugosa), firethorn (Pyracantha spp.), common privet (Ligustrum vulgare L.) sea buckthorn (Hippophae spp.) and tamarisk (Tamarix spp.) are frequently recommended shrubs for salt-resistant planting. Trees and shrubs are being tested under urban conditions for growth rate, hardiness, flowering and fruiting characteristics, leaf fall, nutrient demand and resistance to insect pests and pollution (Businsky, personal communication).
Poplars are also being reduced because of their increasing brittleness with age, while horse-chestnuts (Aesculus spp. L.) are not recommended because their large leaves are skid hazards on roads. The preferred species of the TSK are black locust (Robinia pseudoacacia) and honey locust (Gleditisia triancanthos L.) but there are problems regarding their availability from nurseries (Kolebaba, 1986). Therefore, the TSK primarily plants oaks (Quercus spp. L.) and maples (Acer spp. L.), with maples more common in the city itself and oak on suburban roads.
Parks and formal gardens
The origins of many of the city's public parks can be traced back to King Josef II's social reforms which included a 1780 edict closing cemeteries within the city limits. These cemeteries were replaced by publicly accessible green space which often evolved into parkland. The first public park, Chotkovy Gardens, was created in 1833. The early parks were built at a time when exotic species were at the height of their popularity and they still reflect these species choices. As a result, species diversity in Prague parks is high. Over 700 species were identified in a study of 17 parks (Svoboda, 1985a; 1985b). Today, wherever possible, park management emphasizes the maintenance of existing species composition and design. If a tree appears likely to die within the next decade, a replacement is planted nearby. People are very protective of trees and often react strongly to removal. The SLZ estimates that more than 2000 trees need to be removed from Stromovka Park (the former royal hunting ground) but adverse public reaction has stopped the work (Tomek, personal communication).
The first gardens of Prague were created in the sixteenth century and garden size soon became a status symbol for the nobility, church and, later, wealthy townspeople. Although garden architecture was at first only for the aristocracy, during the eighteenth century, gardens became popular with affluent town families and were eventually opened to the public (Stepanek, 1973). The natural park concept created an opportunity for the introduction of exotic species, following the European trend that had begun in the eighteenth century. Since then, new parks and gardens have been built or rebuilt following the natural landscape style. Historically accurate reconstruction, designed to recreate several Baroque terrace gardens, is currently under way.
Robinia pseudoacacia alongside an industrial site
Private yards and courtyards
The trees in courtyards tend to volunteer species or remnants of pre-war plantings. About 80 percent of the trees are at least 40 years old and less than 1 percent have been established over the past decade (Soucek, Stencel and Kreslova, 1985). A study by these authors of 226 street blocks in six Prague neighbourhoods found that fruit-trees were in more than 80 percent of the courtyards surveyed and that they were the dominant species in more than 18 percent of these courtyards. The city housing department lacks the resources necessary to maintain courtyards, so this significant urban green space continues to deteriorate. In nearly 50 percent of the courtyards surveyed, vegetation was completely absent while functional green space survives on only 8 percent of the courtyards.
State Law 142,-passed in 1980, set guidelines on the management and protection of trees outside forest lands (Ministry of Culture, 1980). Local or district national committees are responsible for administering the law with the assistance of other agencies. Under the law, "significant" trees are to be identified and mapped. Responsibility for categorizing and inventorying trees in Prague lies with the Prague National Committee but, because of insufficient funding, the task has been transferred to the Prague Centre for the Reconstruction of Historic Monuments and Protection of Nature (PSPPOP) (Pacakova, personal communication). Eventually, tree inventories will be computerized and ownership information added to facilitate management decisions.
Fruit-trees are common along Stalinova Street, formerly a suburb but now surrounded by newer housing complexes
Local Law No. 2 (1981) of the Prague National Committee sets out guidelines for the design, maintenance and protection of public green space (Prague National Committee, 1981). The Prague Department of Transportation's Division of Road Maintenance is responsible for planting street trees but the Department of Parks, Forests and Horticulture carries out the maintenance. Requests for new street trees may go through the Office of the Chief Architect of Prague, the PSPPOP or the district national committees. Most often, district national committees propose projects and express community needs to the Prague National Committee which then supervises design projects that are submitted for funding to the national government. Once permission is granted, planting is usually delayed by the profusion of underground utility lines which preclude the use of power tools. A new programme was recently designed to coordinate the activities of the Parks, Forests and Horticulture Department and utility services (Tomek, personal communication).
Housing construction is usually the responsibility of the Prague Construction Department which, on completion, turns the buildings and landscaping over to the Department of Building Maintenance. Project plans are required to address project impacts on trees and shrubs and must include a map showing the location, size and species of all affected trees.
Species diversity in landscaping around the Jizny Mesto I housing complex
Special conditions, including replanting and changes in project design, may be required before tree removal is permitted. In practice, landscaping associated with public housing developments in Prague is often a mosaic of publicly and privately planted species. As landscaping by government agencies is often delayed for months or even years after buildings are completed and occupied, local residents frequently plant various species, including conifers and many varieties of rose. The resulting mosaic is often initially pleasing in appearance but is very difficult to maintain. Long-term survival may be as low as 20 percent.
Squares and public places other than parks are also maintained by the Department of Public Green Space. A labour shortage has forced city agencies to rely heavily on volunteers for tree-planting.
Street trees in the larger diameter classes predominate in Prague. The historic inner city and areas with older housing have very few new or replacement plantings. Courtyard vegetation is mainly composed of pre-1945 plantings. Most new trees are planted along roads and in housing complexes away from the urban core.
Over the past decade Prague has lost several important open spaces and parklands to development, but awareness of the importance of protecting these areas is growing. Courtyards, often located in the most densely populated sections of the city, have great potential to improve the quality of human life with appropriate tree-planting and management. Positive steps have been taken to preserve urban vegetation through legislation and research. Czech popular and scientific literature frequently focuses on Prague's environmental dilemmas caused by the city's rapid expansion and housing shortage. However, the battle between rational and sensitive environmental planning and economic and political development continues.
Public attitudes towards green space in Prague are changing as a more active recreational use replaces the passive use for which most of the older and larger parks were designed. Active recreation has not been as popular in the Czech Republic as in the United States or Western Europe but it is increasing in popularity and hence placing new pressures on urban green space (Subr, personal communication). Fiscal constraints and labour shortages have limited the ability of the Department of Parks, Forests and Horticulture to maintain the larger parks, thereby spurring further deterioration. Past neglect has endangered the survival of historic gardens despite the government's strong commitment to restoration and protection. Public awareness of the importance of trees in modifying pollution and temperature conditions as well as in creating pleasing urban environments has increased substantially over the past decade.
Recent changes leading to democratization and the adoption of a form of market economy may initially lead to a further deterioration in the condition of Prague's urban forest as already scarce revenue is diverted to other uses. It will be a significant challenge for the new government to choose the best management techniques, harnessing the country's long forest management tradition and experience with both socialist and democratic systems. Economic factors will now play an even larger and more direct role in the management of Prague's urban forest.
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