Att återställa en naturlig ordning : skogshistoria och restaureringsbränning i Långsidbergets naturreservat

Abstract: During the late 1800s fire suppression became increasingly effective in northern Sweden which led to decreased areas of fire-disturbed woodland and successive changes in the structure of forests. In the long run this can pose a serious threat to fire-dependent and fire-favored species. Today some fire-prone forest reserves are burned as a nature conservation act. Often partial cuttings are made before burning, with somewhat different motives. The purpose of the study in Långsidberget nature reserve was to give a general picture of forest history and its affect on today's forest condition, and to show how partial cuttings affect burning conditions and results. Långsidberget is located close to areas that were colonized during the Middle Ages. The closest village, Känne was established during the 18th century and the reserve should at least since then have been used for pasture and probably intentional burning to promote grazing conditions. In 1852 cutting rights for large pine timber were sold by the Känne farmers to a sawmill for a period of 50 years. The sawmill sold the rights on to another sawmill in 1858 but cutting probably did not start until after 1877, when the upper reaches of Fåssjöån had bin prepared for timber flotation. During the late 19th century the forest company Essvik bought both rights and land but sold it all on to the state in 1899. The forest was by then described as "exhausted", but no detailed forest taxation has been found. In June 1920 large parts of the woodland which today represents the reservation burned. A forest taxation in 1926 shows that most of the forest had very low volume, but that there also was older trees within most of the area. The average standing volume was 32 m³/ha but it has since then increased to 220 m³/ha. The volume consists mostly of trees established during the late 19th century or after the fire in 1920. Within parts of the reserve there is however very old trees left with five or more fire scars. The fire interval from the early 16th century until the fire in 1920 was on average 31 years. In the summer of 2006 about 50 ha of the 300 ha reserve was burnt. Before the burning, moisture sampling was done in six sample areas with varying forest structure. There were large variations in the moisture of surface fuel (moss/litter) and humus between the different sample areas. A big part of this variation was explained by differences in forest density and other forest variables. There was however no correlation between moisture in fuel (moss/litter) and fire intensity, which was due to the fact that the ignition pattern was continuously adjusted during the burning to regulate the intensity. In addition the burning was started late in the day and was not finished until after midnight. The fine fuel moisture should by then have changed considerably from the situation during mid-day, when the samples were collected. Concerning impact on the humus layer there was only a relatively weak relationship between moisture and burning depth.