When the aim is to grow high-quality pine logs, you must visit the forest with a clearing saw at least twice during the sapling phase, says Teppo Oijala, Resource Manager at Metsä Forest.
The young stand management is called early clearing and pre-commercial thinning. The purpose of this is to guarantee the saplings have the best possible environment for growth.
“In early clearing, the hardwood trees that shadow the saplings are cleaned outclean out the hardwood trees that shadow the saplings. As a tree that demands light, pine is sensitive to shade. In pre-commercial thinning more growth space is created for the saplings, which improves their diameter growth,” says Oijala.
The forest is thinned before regeneration
When the pines are 13–15 metres tall, it is time for the first thinning. Primarily poor-quality trees are removed from the pine stand, focusing the growth on the best individuals.
“The right time for the first thinning is estimated from the tree crowns. The living tree crown must be at least 40 per cent of the height of the trunk. In a dense forest, the lower branches die from the lack of light, reducing the size of the tree crown. This leads to slower growth and increases the risk of snow damage after the thinning.”
After the first thinning, the pine stand is thinned out 1 to 2 times before a regeneration cut. This is usually carried out when the trees are approximately 80 years old in southern Finland and 100 years old in northern Finland.
Quality and diversity in the same forest
Growing high-quality pine logs and retaining the diversity of forest nature do not need to be mutually exclusive. Regenerative forestry, a concept launched by Metsä Group in the spring of 2023, sees raw wood material as an ecosystem service offered by the forest. In addition, forests provide berries and mushrooms and the opportunity to refresh oneself. They also function as a carbon sink, purify water and air, and control soil erosion.
The purpose of forest management is not to maximise tree production but to strengthen the state of the entire forest ecosystem. Oijala lists a few ways to achieve this goal:
“We prefer mixed forests, as they are more diverse in terms of species. We leave retention trees and high biodiversity stumps for species that need decaying wood. We offer nutrition and shelter for birds and mammals by leaving unmanaged protective thickets in the forests.”
Different parts of the trunk have different end users
A single pine trunk can turn into branchless butt logs, dry-branched middle logs and healthy-branched top logs. The logs are refined into various sawn timber dimensions, each of which has its own end use.
“Sawn timber made from butt logs is refined into glued laminated timber and pillars and used in construction projects, where you need strong and stiff materials. Middle logs are used by producers of timber houses as well as door and window components. Top logs with healthy branches are perfect for visually demanding locations such as internal and external cladding panels and glulam,” says Niko Öhman, Product Manager, Sawn Timber at Metsä Fibre.
The core of a mature pine turns into heartwood, which is a dense and dark wood material. Heartwood is naturally resistant to decay due to its extractives, so it is particularly well suited for uses such as outdoor construction. More than half of the trunk’s volume can be heartwood, and its rot resistance can be further improved with heat treatment.
Only once the technical and visual quality of the sawn timber corresponds to the requirements, can the package be delivered to the customer.
Niko Öhman, Product Manager, Sawn Timber at Metsä Fibre
Collaboration leads to the right kind of sawn timber
Metsä Group’s wood procurement, delivery chain, sales and production collaborate to ensure that the client gets the right kind of sawn timber. Planning, however, begins before even one trunk is harvested.
“Our wood procurement sends information about the ordered measurements to the harvester operator, who then cuts the logs according to the end user’s needs,” says Öhman.
The right kind of cutting has a significant impact on the trunk’s processing value.
“When assessing the quality of the trunk, the harvester operator plays an important role. Once a trunk has been cut, cannot extend the length of the logs.”
The sawmill uses a log sorting X-ray to sort the logs into batches which are similar in size and quality. The final sawn timber is sorted in both a fresh and a dried state. The sorting considers both the technical and visual features.
“Only once the technical and visual quality of the sawn timber corresponds to the requirements, can the package be delivered to the customer.”