About 5,000 species in Finnish forests are dependent on deadwood. One solution is to leave high stumps, and instructions on how to make them have now been published.
By making a high stump a live tree is transformed into deadwood in the blink of an eye, and at the same time, the process of decay starts. A high stump is simply a tree cut halfway up its trunk and left standing to decay.
According to the recently published instructions, the best high stumps are tall and stout, providing space for a greater number of species. The best locations for high stumps are, for example, both in the middle and at the edges of felling sites.
’Varying the location of stumps will also ensure variation in how the decay proceeds,’ says Salla Pitkänen on an instructional video published by the Tekopöly project. Pitkänen is a postgraduate student at the University of Jyväskylä and specializes on fungi.
The video, complemented by written material, is published by the Finnish Museum of Natural History Luomus, on the web pages of its Tekopöly project (in Finnish). The instructions are particularly directed to forest owners and other actors in the forest sector.
’The instructions are needed since there is no previous research-based instruction on the making of high stumps in Finland,’ says Heidi Björklund, coordinator of the project, in a bulletin.
According to the instructions, it is important to ensure the presence of deadwood in different types of environment. The species using high stumps are somewhat different in semi-shady, thinned commercial forests and on open felling sites.
On an open, sunny regeneration site, for example, high stumps are particularly useful for many beetles, bees and some fungi. On the edges of forests, high stumps are more likely to host nesting birds.
In the boreal conifer forests of the North, species particularly suitable as high stumps are spruce and birch.
5,000 species benefit from deadwood
The Tekopöly project studied the range of species using high stumps for a few years. The groups of species studied were birds, fungi and Hymenoptera (for example, wasps, ants and bees). The aim was to find out what the high stumps should be like and where they should be placed so as to be most beneficial to pollinator species living in forests and to biodiversity in commercial forests in general.
The number of species dependent on deadwood in Finland is about 5,000. The majority of them are insects and wood-decomposing fungi. The ecosystem services they provide include pollination and decomposition, for example.
High stumps were found to host the red-belted conk and Chondrostereum purpureum fungi. Among birds, particularly the great spotted woodpecker was found to visit the stumps. As for Hymenoptera, species like the bee species Hylaeus annulatus and Megachile lapponica had discovered the stumps.
The use of high stumps is included in the recommendations for forestry and in certification criteria. The PEFC certificate, for example, requires leaving 2 to 3 high stumps per hectare if the volume of deadwood on the felling site is otherwise insufficient. Individual forest companies have set different targets, up to ten stumps per hectare.
Ideally, the continuum of both standing and fallen or felled deadwood is ensured in the forest.
Salla Pitkänen stresses the benefits of making high stumps at all stages of tending the stands, to ensure that the stands also contain younger standing deadwood. After cutting the tree, the top section should be left lying as fallen deadwood, which is a good host for conks, for example.
How to make a high stump
- Choose mainly spruces and birches, but in pine-dominated forests, birches and pines. Leave rowans, aspens, goat willows and other less common broadleaves standing as retention trees. In regeneration fellings, also spare some stout pines, which will age into standing deadwood important for biodiversity.
- Select live and healthy trees for high stumps. Weakened and dead trees are more useful as natural deadwood.
- Select stout trees and leave tall stumps.
- Over time, the high stumps will become more beneficial for many species.
- To ensure a deadwood continuum, make high stumps at different stages of forest growth.
- After cutting the tree, leave the top lying as fallen deadwood.