The herb-rich forests of Ruissalo
Herb-rich forests are among the most typical habitats found on Ruissalo. Only 1% of Finnish forests consist of herb-rich forests, and yet they are the primary habitat of approximately half of the endangered forest species in Finland. When people started to clear away forests, a large proportion of herb-rich forests were harnessed for agricultural use. Some patches unsuitable for cultivation were also transformed into wooded pastures. Only small patches of herb-rich forests that were difficult to reach and clear for agricultural use survived this period. Thus, the extensive, continuous herb-rich forests found on Ruissalo are unique in Finland.
The most obvious difference between herb-rich and coniferous forests is that the soil in the former consists of mull. This is due to rapid decomposition of organic matter, i.e. efficient nutrient recycling, which lends the soils of herb-rich forests their characteristic fertility. Characterised by the diversity of its deciduous trees, herbaceous plants and the shrub layer, herb-rich forests support a wide range of species. The diverse vegetation is complemented by a wide variety of mosses, lichen, fungi and insects. Herb-rich forests are thus notably lusher, more layered and more diverse in terms of the range of species inhabiting them than the surrounding habitats.
The rarest subtype of Finnish herb-rich forests is deciduous herb-rich forest. As such, the deciduous herb-rich forests of Ruissalo are the most valuable habitats on the island. In Finland, these types of forests are found only in a narrow band by the southern and south-western coast. Temperate deciduous trees – primarily English oak and lime – and the species that are dependent on them, are characteristic to deciduous herb-rich forests. Together they form a very diverse biotic community that is otherwise rare in Finland. Temperate deciduous trees are common in the temperate deciduous forest zone of Central Europe. In Finland, they only occur in sites with optimal growing conditions. They include English oak, small-leaved lime, wych elm, white elm, common ash, Norway maple and common hazel. On Ruissalo, extensive deciduous herb-rich forests can be found in particular in the area between the bridge leading to the island and Honkapirtti.
