The last time the forest was thinned was some 20 years ago. Both spruce and birch grew on the lush soil, and where the terrain rose to a rugged mound, pine trees were dominant.
Jorma Pietikäinen from Tornio in northern Finland had become a forest owner a couple of years earlier, when his mother’s estate was dissolved, and the forest assets were divided between Pietikäinen and his siblings.
Now Pietikäinen wandered in the forest side by side with Metsä Group’s forest specialist Tuomas Hookana to determine felling needs in his forest.
Hookana sketched a felling plan for Pietikäinen. It included shelterwood felling to promote natural regeneration on an area of around 12 hectares dominated by spruce. The plan was to leave 100–300 trees per hectare as shelterwood to protect the seedlings growing beneath them. Seed-tree cutting was planned for a pine-dominated forest of just over three hectares, where 50–100 good quality pine trees were to be left as seed trees.
A mixed forest of roughly three hectares, predominantly spruce and birch, was to be thinned using a selection cutting approach.
Selection cutting is a good option in peatlands
As one of the methods used in continuous cover forestry, selection cutting aims to promote natural forest regeneration. It means removing many of the largest trees in the forest and making room for small vibrant trees as well as new seedlings.
Some of the large trees that are of a high quality are left in the forest to produce seeds. Poor-quality trees are removed from the lower canopy layers, and overly dense groups of trees are thinned.
The method is well suited for spruce- and pine-dominated forests and peatlands in northern Finland. Pietikäinen’s forest also falls in this category.
Pietikäinen liked the plan, and the wood trade was concluded in spring 2023. The first sections were cut in September the same year, and the rest around Easter the following year.
In all, peatland forests cover around 5 million hectares in Finland. For the forest industry, peatlands are a huge wood reserve, as they are home to roughly a quarter of the overall growing stock. In some Finnish regions, peatlands account for 30–40% of the forest area.
In the past, peatlands were actively drained. Drainage improved tree growth, but also caused environmental burden, the extent of which was not discovered until the 1990s. As a result of drainage, nutrients and suspended solids leaked into waterbodies. At first, it was thought that the load was of a short-term nature, but later research revealed that it continued for decades.
Water resources are managed with continuous cover forestry
The use of peatland forests also affects the climate in ways that have been better understood in recent years. The key is the water level of the peatland. When peatland is drained, the water level drops, causing the peat to dry and begin decomposing into carbon dioxide. If all the trees are removed at once, their transpiration ceases. With the water level close to the surface, the soil begins to release methane.
“Final felling and ditch network maintenance have traditionally been used in peatlands, but nowadays, water resources are managed with continuous cover methods,” says Hookana.
The goal is to keep the water level as stable as possible at about 30–40 centimetres. This ensures the root system of trees gets enough oxygen, but the peat layer remains under water, preventing its decomposition.
Natural Resources Institute Finland, which has studied different felling intensities, has proposed that transpiration in spruce-dominated peatlands remains at a suitable level when the basal area of trees after selection cutting is 10–12 square metres per hectare.
Selection cutting requires professional skills
Especially in lush peatlands, continuous cover forestry often makes financial sense as well. Although the stumpage earnings from selection cutting are lower than in final felling, there are no costs for ditch network maintenance and regeneration.
Financial profitability requires that seedlings emerge naturally in the area. This condition is met in Pietikäinen’s forest.
“After the previous thinning, a new generation of trees has begun to develop in the forest. The prerequisites for continuous cover felling are in place,” says Hookana.
Technically, selection cutting is more demanding than final felling and requires the harvester operator to be a real professional. Metsä Pirttimaa, in charge of felling in Pietikäinen’s forest, is an experienced contractor, and Pietikäinen is very pleased with their work.
“If you didn’t know, you wouldn’t notice that any cutting had taken place in the forest. That’s how neat it is.”
Now, the forest will be left to grow at its own pace for 15–20 years, after which there will be another selection cutting.
“I don't think I’ll be here to deal with it though. It will be something for the next generation to decide. However, I doubt they’ll make it into a ballpark.”
This text was published in Metsä Group’s Viesti 3/2024.
Text Maria Latokartano
Photo Nina Susi