Nyckelbiotoper - urskogsrester eller kulturprodukter?

Since 1993 the Swedish Forestry Administration conducts a nation-wide inventory of wood-land key habitats covering all forest land in Sweden. The inventory aims at mapping and describing habitats where redlisted species occur or can be expected to occur. According to the inventory stand history is crucial to the presence of red-listed species. However, the current knowledge of stand history in woodland key habitats is very limited. The purpose of this work is to describe stand history in woodland key habitats, i.e. fire history, human activities - mainly cuttings - and structural changes. The survey has been carried out on forest land owned by the forest company Assi-Domän within the parish of Lycksele in the county of Västerbotten, northern Sweden. The forest history in twelve key habitats were reconstructed through an analysis of forest surveys from the 1880s till the 1980s, and also by investigations in the field. Eight of the key habitats consisted of mature conifer stands of which one half was dominated by Scotch pine and the other half by Norway spruce. In the other four key habitats deciduous trees, mainly hairy birch, were dominating. Five of the eight conifer stands showed evident traces from logging. The first loggings were performed in the second half of the 19th century as high-grading of the largest pines. During the 20th century, mainly at the time of world war two, four of these five stands have been affected by further cuttings. These were, apart from large pines, aimed at spruce, birch and dead trees. The most intensively logged key-habitat consisted in the beginning of the century of a clear-cut with scattered seed-trees of pine. In three of the conifer-dominated stands no traces of cuttings were found. However, stumps in the vicinity and blazing marks in the stands makes it likely that also these key habitats have been affected by cuttings. Heavy cuttings have been carried out in all of the four key habitats dominated by deciduous trees. Three of them originate from old-growth spruce forests that were clear-cut in the 1930s. Thereafter hairy birch regenerated abundantly and became the dominant species. All investigated key habitats with pine trees have burnt several times during the last 400 years. However, due to the successful fire-protection during the 20th century, fire is no longer a disturbance factor in the key habitats. As a consequence, in combination with former high-grading, spruce is now regenerating abundantly and will gradually replace other tree species. The same development takes place in the key habitats dominated by deciduous trees. Prescribed burning or specially designed cuttings are therefore necessary in order to conserve the ecological values connected to pine and deciduous trees. The investigated key habitats share the fact that the cuttings were performed more than 50 years ago. During the following period, which is characterised by little human impact, some old-growth characteristics have developed. This is probably the most important reason for the stands' present status as woodland key habitats. The analysis of the old forest surveys have contributed a lot of information that cannot be achieved only by work in the field. The conclusion is that a combination of studies of historical records and analyses in the field provides the most useful information for understanding the origin of the woodland key habitats, their status of today, and their future development.

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