Browsing by Author "Tommila, Tero"

The herbaceous vegetation of Viikinoja naturalistic rain garden in Viikinojanpuisto, Helsinki, was mapped about 10 years after construction. Viikinoja garden is a brooklike reworking of a part of an old main ditch and can be classified as an enhanced wetland. In the garden area, 28 species of herbaceous perennials were planted in 1999, 23 of them within the actual wetland area. The aim of the study was to evaluate the success of planted herbaceous perennials in the wetland area and to compare this data to the life history traits of these species. In addition, the spontaneous herbaceous vegetation in the area was surveyed and the success of some of these species was compared to their life history traits. Species' success was assessed by their proportional presence, general coverage and local coverage. Of the 23 species planted in the wetland area, 19 had survived and of these, ten can be called succesfull. Spontaneous species were identified from over 80 genera. The combined coverage of the planted species in the study area was 57 %, while that of spontaneous species exceeded 90 %. Both groups were dominated by graminoid species (Phragmites australis and other grasses, Typha latifolia, Scirpus sylvaticus and Carex species). Of the life history traits, competitiviness, maximum height and lateral spreading ability had a positive effect on species' success, especially with respect to perennials at their planting sites. Ruderality had a negative effect on the success of perennials. It was concluded that the vegetation of Viikinoja is entering competitor-dominated phase. Future long-term development depends largely on park management practices regarding mowing, dredging and cutting of willows.