High stumps increase diversity

High stumps increase diversity

​We add decaying wood and holed trees to forests with every felling

As of October 2016, every hectare of forest subject to Metsä Group's thinning and regeneration felling will come to include two high stumps. The practice is voluntary for forest owners and will be discussed in connection with each wood sale.

Forest owners and the forest industry work daily for the cherishing of Finnish forest nature. One of the most visible examples of this effort are retention trees, left at felling sites in the context of regeneration felling.

While retention trees introduce more diversity in tree ages to forests, their primary purpose is to die over time, and thereby provide commercial forests with decaying wood, which is important for many species. While our forests now have more dead or decaying wood than a century ago, we still need more. Trees with holes, on the other hand, benefit hole-nesting birds.

Of our commercial forests, young and mature thinning forests are the ones that have the least decaying wood. Making high stumps is an easy and cost-effective way to increase the amount of decaying wood and trees with holes within these forests.

The forest owner decides

So far, high stumps have been made whenever a forest owner has asked for them. As of October, forest owners will be asked, in connection with each new wood sale and with regard to both thinning and regeneration stands, whether or not they would like to have two stumps per hectare on their forestland.

As far as we know, Metsä Group is the first operator in Finland to begin systematically making high stumps at all felling sites. The high stumps made during felling represent a forest owner's voluntary contribution to safeguarding forest nature.

We believe that a majority of forest owners want to work towards securing the habitats of endangered species by, for instance, making high stumps. The volume of wood used by Metsä Group is growing strongly, and we want to bear increased responsibility for the sustainable use of forests.

Hole-nesting birds, such as the Ural owl, benefit from high stumps. Image: Juha Ollila/Vastavalo

Hundreds of new trees with holes every day

A high stump is made by cutting the trunk of a tree at a height of 2–4 metres. When selecting candidates for high stumps, we favour pulpwood-sized deciduous trees. If there are none, the high stump can be from softwood fibre trees. In regeneration fellings, sturdy aspens and poor-grade white birches are also good alternatives for high stumps.

Thinnings aim to keep the forest a mixed one. Rather than selecting the only deciduous trees on a felling site to become high stumps, our selection in such situations falls on softwood fibre trees. A high stump is usually made from a normal, living tree, but a tree freshly felled by wind or snow can also be considered a high stump. A birch bent over by the weight of snow makes for an ideal half-finished high stump.

High stumps have often been called ugly and unnecessary. High stumps nevertheless provide us with decaying stumps that do not usually appear in forests as a result of windfall. The humidity of a decaying stump varies at different heights, thereby providing the species living in the dead tree with very diverse conditions.

A high stump begins to decay in a few years, at which point woodpeckers and tits can start making nesting holes in it. While the nesting density of birds varies a great deal, the average number of bird pairs nesting in a hectare of Finnish forest ranges from one to four. Therefore, two high stumps per hectare provide a good amount of additional holes in which to nest. 

Metsä Group is the biggest single buyer of wood in Finland, and we operate over large areas. This means that we will be making hundreds of future nesting trees every day, around the year, provided that all of our forest owner customers are willing to take part in making high stumps.

To a game thicket or a group of retention trees

Game thickets provide ideal spots for high stumps. Thickets like this are created when undergrowth and root sprouse whose growing stock is left, for the most part, untouched, is retained here and there during clearing and thinning.

The retention of thickets in managed forests creates the shelters necessary for game and particularly game birds. Thickets also have an impact on a forest stand's microclimate by increasing shade and abating windiness. Although preliminary clearing is very necessary at many felling sites, a few game thickets here and there will not make felling more difficult.

In regeneration felling, it is advisable to leave a high stump within a group of retention trees, given that a high stump sticking out from the middle of a seedling stand may look unattractive to some people. On the other hand, it provides birds of prey with a fine lookout spot. A high stump in the middle of a thinning forest, however, is not as visible.

Only a few years from now, we will have made hundreds of thousands of future nesting trees in forests.

Cost approximately a euro per hectare

When a tree's trunk is cut at a height of four metres to make a high stump, what is left in the forest is a tall stump. The forest owner does not receive money for this part of the tree. The forest owner's lost wood sales income due to two high stumps left in a hectare of forest will range from a few dozen cents to slightly over a euro, depending on the species of tree.

It would be a good idea to think about the location of the retention tree group as early as during the first thinning and to leave more deciduous trees in the relevant spots. A forest that includes deciduous trees throughout its life cycle benefits both nature and the forest owner's wallet: deciduous trees with low financial value make valuable high stump or retention trees.

While current forest certification criteria do not call for high stumps, fresh high stumps can be counted as retention trees in the PEFC certification. The new PEFC criteria require retention trees and decaying wood to be left in forests starting from intermediate felling. In practice, this means the retention of some individuals of the previous generation of trees in the context of a thinning, for example, if there are any.

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