Long-term changes in indigenous vegetation preserved in urban areas

摘要

During the last decades models for an 'ecological approach' to physical planning of towns and cities have been discussed. Part of such an ecological approach is to utilize existing indigenous vegetation (natural and semi-natural forests, meadows, pasture land, heaths) and trees in parks and other green areas in future developed areas. This planning approach includes many economical, social and other advantages. In 1972, a research project was started at Jarvafaltet, situated 15 km north of downtown Stockholm, Sweden. Investigation plots were established at locations in proposed green areas within development zones. During construction and subsequent use, changes in vegetation and habitat (soil, ground water, climate, air and water pollution. impacts from the inhabitants) were studied annually from 1972 to 1981. Vegetation analysis in most plots is still (2000) being maintained. Trees were damaged during construction. Damage was mainly caused by increased wind velocity when surrounding trees were felled and by damage to root systems due to excavation and adding landfill. Damage during later use was much less. Vegetation field and bottom layer were Little damaged during construction. During later use plant communities on shallow poor dry soils were damaged by wear and tear caused by trampling. There was much less damage to other plant communities during the 27-year study. Damage through other habitat changes during this period was not detected. A schedule showing interactions between planning, construction, use, habitat changes and vegetation is presented. Despite some damage to the preserved vegetation that has occurred, the local residents highly appreciate it as a recreation area.