Verjüngungsdynamik nach Großflächigem Borkenkä ferbefall in den Fichtenwäldern der Hochlagen des Bayerischen Waldes

Following local storm events in 1983/84 bark beetle (Ips typographus) spread in the mountain spruce forests at the higher altitudes of the Bavarian Forest National Park. On large areas stands of Norway spruce died. By 1997, about 97% of the high altitude spruce stands were dead. From 1998 to 2000 we studied tree regeneration during and immediately after the dy-back process of spruce stands. The experiment included 24 permanent plots, which were randomly selected at the high altitudes in both the old part (since 1970) and the extended part (since 1997) of the national park. The recorded regeneration plants were almost exclusively Norway spruce (Picea abies). Seeds originated mainly from fructification in 1995. Most of the individuals were therefore rather small (three-quarters less than 4 cm in 1998). In 1998, the average density of saplings less than 0.5 m height was 29,200 per hectare. This density decreased to around 12,800 per hectare in 2000. In 1998 regeneration individuals higher than 0.5 m were very low in number (33 per hectare). This number, however, increased to 53 per hectare in 2000. The dominating species within this height class was Sorbus aucuparia. The survival rate of saplings is strongly dependant on total plant height, with taller saplings having significantly higher odds of survival than smaller plants. Surviving saplings are mainly found in grass-free areas, at the foot of trees, or on dead wood. In areas densely covered with grasses or ferns, regeneration has a very low survival rate. The near future development of tree regeneration was estimated by using a simple prediction model. It calculates several thousand saplings per hectare with more than 10 cm height. In the field the spatial distribution of seedlings and saplings, however, is rather irregular and characterised by large spatial variation. For large areas regeneration density can be considered sufficient for regenerating forest stands, but there will be some areas with rather sparse tree density. The study shows that in the high mountain areas of the Bavarian Forest National Park, a new layer of young tress is going to grow up. In some areas, however, its spatial structure will be different from the former stands.