A cold early summer can rob a forest of its berries
Dwarf shrubs – the bilberry and the lingonberry – thrive in coniferous forests. The bilberry, which prefers young coniferous forests, flowers in late May, producing small, reddish and pitcher-like flowers. The crop of berries produced each summer depends on successful flowering; a cold period reduces the number of pollinators, and if worst comes to worst, the flowers themselves may end up dying of frost. However, there is hardly ever a risk of this happening on islands, as a result of which there always are plenty of bilberries to be found on Ruissalo from July onwards. The lingonberry, which prefers dryer coniferous forests, doesn’t flower until June, by which time the weather is usually more summery, as a result of which lingonberry harvests are more consistent than bilberry ones.
The coniferous forests of Ruissalo
Coniferous forest is the dominant forest type of the cold climate zone, which is why the vast majority of Finnish forests, 99% of them in fact, are coniferous forests. The type of a coniferous forest depends on the nutrient content of the soil and on moisture levels. On Ruissalo, the most common types are young and herb-rich coniferous forests, which are more humid and nutrient-rich habitats than dry coniferous forests. The dominant tree-species of young and herb-rich coniferous forests is Norway spruce, but they also contain birches and Scots pine. One of Ruissalo’s unique characteristics is coniferous forests consisting primarily of Scots pines and English oaks. Coniferous forests are also characterised by dwarf shrub vegetation, with bilberry being the dominant species, and a forest floor covered in mosses.
Forest management for the preservation of natural values
Forestry, meaning the felling of trees for commercial utilisation, is not practised on Ruissalo. Instead, certain small sites on the island are managed to preserve natural biodiversity and threatened species. For example, the branches of old lime trees that are in poor condition are cut to protect the rare East European hermit beetle. This ensures that the trees do not fall over during autumn storms and that the beetle larvae, which are dependent on decaying wood, have plenty of food and shelter available. The practice also protects other fungi and insect species that live in standing decaying trees. Norway spruces that threaten the renewal of English oaks by shading are also removed, as necessary. However, often the best form of forest management is simply letting the forest develop in peace.
The field layers of herb-rich coniferous forests, in which the conditions are slightly more humid, are also home to hepatica (Hepatica nobilis), wood cranesbill (Geranium sylvaticum), small cow-wheat (Melampyrum sylvaticum) and spring vetch (Lathyrus vernus). Herb-rich coniferous forest can also support a variety of mosses, such as rose moss (Rhodobryum roseum), which grows in beautiful rosettes.
May lily is a common flowering plant that grows in the shade of Scots pines in coniferous forests. The species’ red berries are poisonous, and nobody knows why they are called ‘squirrel’s berries’ (oravanmarja) in Finnish. The plant’s scientific name (Maianthemum bifolium), on the other hand, is much more informative, with the genus Maianthemum, or ‘May flower,’ telling us when the plant flowers and the species name bifolium, or ‘two-leaved,’ detailing the plant’s most common structure.
Chickweed wintergreen (Trientalis europaea) is another common resident of coniferous forests. It is found everywhere in Finland, from the Archipelago Sea all the way to the northern fells. Its white flowers come into their own in the dark forest, where they shine like small stars. No wonder that the species is also known as Arctic starflower! Despite their impressive appearance, the flowers attract hardly any insects, and in fact chickweed wintergreen spreads vegetatively, with the help of subterraneous runners.
May lily, chickweed wintergreen and the other beauties of coniferous forests
The majority Ruissalo’s coniferous forests are herb-rich and young coniferous forests. Beside bilberry, species that thrive in the field layer of young coniferous forests include may lily (Maianthemum bifolium), chickweed wintergreen (Trientalis europaea), wood sorrel (Oxalis acetosella) and common wintergreen (Pyrola minor).
Decaying wood is an essential part of natural forests. There can be as much of 100 cubic metres of decaying wood in the form of dead standing and fallen trees in a hectare of forest, accounting for approximately one third of all tree matter. In commercial forests, efficient forestry has reduced the proportion of decaying wood to a mere fraction of this, making species that are dependent on decaying wood increasingly rare. It has been estimated that decaying wood offers food and habitats to approximately 5,000 different species in Finland. These species simply cannot survive without decaying wood.
A tree’s life after death
In time, even the most imposing tree grows old, weakens and eventually dies. Although dead trees can stay standing for decades, at some point they are inevitably felled by gale winds. However, dead standing or fallen tree trunks are by no means lifeless. Quite the opposite, in fact: they are teeming with life. There are countless insect and fungus species that specialise in feeding on and decomposing dead tree matter. Fungal mycelium penetrates deep into the tree trunk while hymenoptera and beetle larvae excavate tunnels under the bark and in decaying wood. Little by little, the trunk breaks apart and the nutrients contained within are recycled and made available for other life forms. This slow and relatively invisible decomposition process is one of the prerequisites for the functioning of the entire forest ecosystem.