Mängden död ved i värdekärnor i Söderåsens nationalpark

Abstract: There is a lack of knowledge about the development of the dead wood in former production beech (Fagus sylvatica) forests that have been protected. The present study has been carried out in Söderåsen National Park to compare the distribution of dead wood in relatively unaffected beech forests that have been protected for a long time (A-value cores) and older, previously managed beech forest that has only been protected for 20-30 years (B-value cores). The basic hypothesis was that the amount of dead wood is larger in A-value compared with areas that have been previously managed (B-value cores and other old growth beech forest). In April 2021, the amount of dead wood in 50 sample plots was inventoried, from which 25 plots are randomly distributed within areas of the respective value class. The inventory of dead wood followed the field instruction of the Swedish National Forest Inventory. All deadwood was recorded that was ≥ 10 cm in diameter and judged to have grown within a circular sample plot of 10-meter radius (314 m2). The following variables for each separate piece of dead wood were collected: status (standing dead tree, tall stump, laying tree/stem), tree species, height/length, diameter, and degree of decomposition. The results for all 50 sample plots (value classes A and B) show an average volume for standing dead wood of 10.9 m3/ha and for downed dead wood of 9.6 m3/ha, which gives a total volume of 20.5 m3/ha on average. Sample plots in value class A contained lying dead wood of 11.2 m3/ha and standing dead wood of 3.6 m3/ha, and thus 14.8 m3/ha in total. The average volumes for value class B were 15.6 m3/ha for standing dead wood and 10.6 m3/ha for lying dead wood, a total of 26.1 m3/ha. The differences were not statistically significant due to large variation between the sample plots and the hypothesis of the study could not be confirmed. Regarding the number of elements of dead wood, A plots had a higher mean number of logs per hectare (51.0) compared to B plots (34.4), while B plots had a higher number of high stumps (B plots 19.1 and A plots 8.9), and number of standing dead trees (B plots 19.1, A plots 6.4). However, none of these differences were statistically significant. The downed dead wood was more decomposed than the standing wood. The results indicate that the conservation core areas in Söderåsen National Park contain approx. 20 m3/ha of dead wood, which corresponds to the average amount in key habitats in Swedish deciduous forests. This is roughly twice as much as in Swedish forests on average, but several times lower than the volume in old natural beech forests. The value cores in Söderåsen National Park are thus still far from a natural state. With the available data, it is not possible to determine whether the amount of dead wood differs between different value classes. In hindsight, both the number and the size of the sample areas were probably too small to give a reliable estimate of the dead wood. This inventory should be supplemented with more sample areas as soon as possible and a re-inventory on a larger scale should be carried out after 10 years, in order to be able to follow the development of the amount and quality of the dead wood in Söderåsen National Park.