Mortalitet av bok i Biskopstorp och Frodeparken naturreservat, Halland
The aim with this study was to investigate mortality in older respectively younger beech
stands (Fagus sylvatica), the different types of dead wood in the forest and the availability of coarse woody debris (CWD). The research was carried out in previously managed and seminatural stands in Biskopstorp and Frodeparken, located north of Halinstad in Halland,Sweden. Data were collected from 22 stands with at least 50 % beech and with a minimum age of 5 1 years, ranging in size from 0,67 to 19,9 ha. A transect was placed in each stand, in which the diaineter on both dead and living trees with a minimum diameter of 50 mm was recorded. On seven to 13 dead trees, depending on the size of each stand, decomposition stage, primary and secondary cause of death, amount of fungi and the type of the dead wood was noted. In stands dominated by larger trees, breast height diameter (dbh) 220 cm, there was a higher amount of dead trees as compared to stands with thinner trees. The diameter of dead trees was larger than the dbh of living trees in stands with thicker trees. Consequently they are more easily blown down by wind, since they have thicker limbs. In stands with thinner trees there are more living than dead trees (dbh up to 19 cm). Dead trees, most often snags or whole standing trees, in the same stands are thinner than the living trees. This is probably due to strong competition during self-thinning. The diameter distribution for the
dead trees, in the stands with large trees, are steadily increasing from diameter 40 cm and larger. This can be an indication that the mortality is not abruptly increasing and that the trees are probably dying gradually. The amount of snags in the stands with large trees is large, probably since the risk for the steins to break is larger for large trees. The large amount of fungi on trees with dbh 220 cm, placed close to where the trees often break, makes the trees weaker and therefore increases the amount of snags. Most of the dead trees are in the early stage of decomposition. In a natural stand there would probably be a continuous supply of dead wood, and therefore about the same amount in each decomposing stage. The studied stands have been thinned earlier and have probably too short continuity for this to be the case today.