Current issue: 53(4)
Draining of peatlands to improve forest growth started to increase in Finland in the beginning of 1900s. The aim of the study was to find out which kind of peatlands are suitable for draining. The peatlands examined in this study had been drained earlier in 1800s for other purposes, and the original peatland type was deduced afterwards. When the peatland is drained, its vegetation changes gradually towards that of mineral soil sites, depending on the original peatland type. The article includes detailed description of the vegetation on different drained peatland sites. Best represented in the study were different types of pine swamps, which change towards Calluna or Vaccinium forest site type depending on the original peatland type. The Sphangnum species and brushwood disappear gradually and Cladina sp. become common in some drained pine swamp types. Scots pine (Pinus sylvestris L.) regenerates well on most drained pine swamps, and also Betula sp may grow as dominant species. The richer pine swamp types develop to Vaccinium-myrtillus forest site type, which may grow also Norway spruce (Picea abies (L.) H. Karst). Drained treeless bogs change first towards pine swamps. However, trees regenerate poorly on these sites and the growth is low. Flark-bogs develop typically to treeless lichen heaths. Drained spruce swamps develop to forest with grass-herb vegetation or Myrtillus site type.
The PDF includes a summary in German.
The hummocky peatlands are fairly common in Finland. Peatlands with hummock ridges are rare in southern Finland but become more common in northern parts of the country.
In the incompletely drained flark fens the development of the hummocks can be studied particularly well because they can be found in different development phases there. The phenomenon is more common in drained peatlands than in the peatland on their natural state.
The development of the hummock ridges is close related to development of the hummocks. The hummock ridges are formed only under certain circumstances.
Height increment of the hummock ridges is restricted by the same factors that prevent the unrestricted height increment of the hummocks. The hummock ridge may sink due to its own weight in unfrozen swamp, it may be eroded by frost, wind, flowing water or ice. Dead trees, shading or other detriments may prevent the growth of secondary peat.