Acts to improve biodiversity
Forest owners and forest professionals work daily to preserve the biodiversity of forests. Forest Specialist Piia Jyväs and forest machine contractor Petteri Liiri are experts of the practical side of commercial forest’s nature management. Accounting for biodiversity in forest handling is demanding work. There’s a lot to remember: retention trees, high stumps, buffer zones as well as the preservation of standing and fallen decayed wood. In addition, you must remember the requirements of the Forest Act and the Nature Conservation Act. You must also be careful not to damage either the standing or fallen decayed wood during harvesting and forest management work.
It is the job of Piia Jyväs and Petteri Liiri to carry out the measures required by law, certifications and voluntary biodiversity acts in the forests of forest owners.
High stumps are an indication of forest owners’ will to improve the biodiversity of forests. Metsä Group has been leaving high stumps in forests for more than three years. They are made for the diversification of decayed wood and, in growing stocks, for increasing decayed wood. Groups of retention trees and protective thickets are good locations for high stumps.
As of the beginning of 2020, the number of high stumps left per hectare on our thinning or regeneration felling sites increased from two to four. The practice is voluntary for forest owners. A high stump is usually made from a pulpwood-sized broad-leaved tree by cutting its trunk at a height of 2–4 metres. The stump begins to decay in a few years.
High stumps have been received well
Forest owners have welcomed the practice of making high stumps. “High stumps serve as nesting cavity trees for woodpeckers and willow tits, among others, and this is one of the aspects that encourages people to leave them,” says Jyväs.
“A healthy and diverse forest also serves the interests of forest owners themselves. The species living on decaying trunks keep pest insects at bay.”
Jyväs says that forest owners are also motivated by the fact that a small concrete act that increases biodiversity can influence opinions on forest use. In addition to a forest’s commercial value, biodiversity is extremely important for many forest owners.
Biodiversity work is visible in many ways in the work of a forest specialist. Cooperation with the harvester operators is one of the most concrete examples of this. Jyväs has confidence in operators’ skills. “I give them a pretty free hand. Sometimes the forest owner has wishes about the location of retention trees and high stumps. That’s when I mark them in stands beforehand.” The trust stems from long-term cooperation with the same machine contractors. “The trust grows when everything works. Forest owners have been happy with the results of the work.”
The importance of preserving decayed wood
Decayed wood is important for many forest-dwelling species – a quarter of them depend on it. In addition to high stumps, the volume of decayed wood in commercial forests is increased with the retention trees left in the regeneration felling of a certified forest, to provide it with different-aged trees. Retention trees and decayed wood safeguard biodiversity.
A group of retention trees is a natural location for a high stump. If it is left in a highly visible location, it is more likely to attract the forest owner’s attention.
In a thinning, high stumps are often left within stands, due to which they are not as visible as in a regeneration felling. The same selection criteria apply to both handling options. The increase of biodiversity is often planned before the harvesting.
“Forest owners should also consider the possible location of a group of retention trees in any preliminary clearing they do themselves, and leave this location uncleared, so that the group will have layers and provide protection to animals,” says Jyväs.
Retention trees are left in groups and, if possible, within or next to an important habitat. Regarding biodiversity, beneficial retention trees are trees that decay rapidly. Aspen, for instance, is a good choice.
“Largish trees of lesser commercial value within a stand are selected to serve as retention trees. Protective thickets left in various stages of forest management can form future groups of retention trees. This provides the forest with decayed wood of varying ages and sizes. This continuum of decayed wood secures living conditions for many species dependent on decayed wood.”
Aspen and broad-leaved trees are the best retention trees
According to machine contractor Petteri Liiri, the selection of which trees to leave in a forest can be challenging. This is only increased by the abundance and variety of the sites.
“When I’m choosing a group of retention trees, I pay attention to the aspens and white birches as well as the undergrowth,” says Liiri. “They provide animals with natural hiding places and the forest with decayed broad-leaved wood.”
“High stumps and retention trees shouldn’t be left on hilltops, where they can fall down too early. They’ll have a better chance to remain upright in a sheltered location, such as a hollow or depression,” says Liiri. “Common sense can take you far, and years of work experience provide you with confidence.”
Liiri says that the making of high stumps has become routine over the past three years. “Experience has made me able to spot suitable locations for group of retention trees, a high stump and also a protective thicket.”
Retention trees in favourite spots
Both Liiri and Jyväs are forest owners in their own right. Ensuring biodiversity in their respective forests is important for both. “The groups of retention trees in your own forest are like oases in the middle of a seedling stand,” says Jyväs. “They’re great locations for picnics. But most importantly, they’re important for biodiversity.”
A forest owner’s own wishes are important in forest handling. “If you have a favourite spot in your own forest that would work well as a group of retention trees, for example, you should mention it to the forest specialist,” says Jyväs.
Text: Annamari Heikkinen