Birch-dominated slash-and-burn forests, clearings and steep cliffs are examples of Koli's diverse natural features. If you venture to the forest, you will encounter dark, mysterious spruce forests on the eastern side of Lake Pielinen and lush herb-rich forests along the brooks. When snow covers the landscape in the winter, the spruces with crown snow loads create peculiar shapes on the hilltops. On the summits and western slopes you can also roam in rugged pine forests.
The natural features are also found in the Koli National Park emblem, symbolising the area's old and valuable slash-and-burn agriculture. In the emblem, white birches glow and slash-and-burn fires blaze against the backdrop of a black hill ("Hill with Black Slopes", or "Mustarintainen", was the old name for Ukko-Koli Hill).
Ancient Mountain Chain
The hills of Koli are remnants of the ancient Karelides mountain chain that formed almost two billion years ago when the tectonic plates pushed against each other. The hard quartzite rocks created by the collision have endured the erosion and weathering caused by the ice ages better than the surrounding areas. You can read more about the area's geology here.
Ukko-Koli Hill, the hill chain's highest peak and also the highest point in Southern Finland, rises to 347 metres above sea level and 253 metres above the surface of Lake Pielinen. Even an uninitiated visitor will notice the unique geological formations created by the ice age, such as the rocks with ripple marks or the narrow chain of the Purjesaaret Islands.
Koli's climate is different from that in the surrounding area. Adjacent to the hills, Lake Pielinen warms its surroundings, especially in the autumn, and in the summer the moisture rising from the lake condenses into fog and rain over the eastern hill slopes. As you climb up the hills, the temperature drops. Due to the cool climate, the northern forest types thrive in the summit areas, and in the winter you will see gorgeous crown snow loads on the trees.
Flowers in the Fields, Plant Treasures in the Forests
There are numerous clearings within Koli National Park that came about during the time of slash-and-burn and meadow agriculture. They are nationally significant protected areas as they are important habitats for some rare plant and butterfly species. In the summer you can walk there and admire the unusual moonworts (Botrychium species) or the stiff-strawed mat-grass (Nardus stricta).
Each clearing has its typical species, slightly different from the others. In sunny clearings, such as Havukanaho, you can see the mountain everlasting (Antennaria dioica) and the mouse-ear hawkweed (Pilosella officinarum) for example. In the more humid Mustanaho Clearing you can find plants like the marsh thistle (Cirsium palustre) and the meadowsweet (Filipendula ulmaria). Other clearings worth visiting include Mäkränaho, Purolanaho, Ikolanaho and Vaaralanaho. The demanding species of the clearings require annual mowing in order to survive.
On the whole, the vegetation in Koli National Park is rich and diverse. By climbing up and down the hill slopes you can see many types of habitats from lush herb-rich forests to rocky Cladina-type forests. In the herb-rich forests you might spot the rare, vanilla-smelling calypso (Calypso bulbosa). The Koli area is home to both northern and southern species, many of which grow there at the extreme edge of their range.
Bulgarica cana and Other Rarities of the Animal World
The fauna of Koli includes species of the natural and cultural environment that find suitable habitats in the park's old-growth forests, slash-and-burn areas and clearings. In the old mixed forests you might be lucky enough to see a glimpse of the big-eyed Siberian flying squirrel (Pteromys volans). On your walk you may also spot the tracks of a lynx (Lynx lynx) or hear a beaver (Castor canadensis) splashing its tail. There are also a lot of elks (Alces alces) in the national park.
Forest birdlife is especially abundant in the northern parts of the park. The choir of small birds hold their lively concerts in the summer. Forests of varying ages are also favoured by capercaillies (Tetrao urogallus), black grouses (Tetrao tetrix) and hazel grouses (Tetrastes bonasia). Koli is home to many endangered invertebrates, such as the flat bug Aradus laeviusculus that thrives on burnt wood and the grey snail species Bulgarica cana whose only habitat in Finland is the Koli region.
At Koli, clearings are mowed and slashing and burning is carried out every year. By felling spruces, the old forests that remind us of the era of slash-and-burn agriculture are preserved as forests dominated by deciduous trees. Animals also contribute to preserving the cultural landscape: summertime landscape maintenance in the park's heritage farms is done by both Finnish sheep and "kyyttö", the rare Eastern Finnish cattle breed.
Herb-rich forests dominated by deciduous trees are managed by removing shrub-layer and planted spruces to prevent the spruces from shading and acidifying the soil. In addition, some former commercial forests and drained mires located in the national park have been restored (www.metsa.fi). Ennallistajan polku (Nature restoration Trail), located in the southern part of the park, gives an introduction to the secrets of forest restoration.