Bark beetles kills spruce forests in the Bavarian Forest, Germany: did humans play a role? Evidence from pollen and macrofossils
The Bavarian Forest, a middle-high mountain in SE Germany, experienced after two severe windstorms in 1983/84 intense and widespread infestations by the bark beetle Ips typographus. In the area of the Bavarian Forest National Park, the beetle killed over 6000 ha of spruce stands (Picea abies). The National Park adheres since 1983 to the policy of „let nature be nature“, which means not to interfere with the natural processes, so it does not control the beetle infestation by logging or other management activities within the inner core of the park. This practice has been intensively debated for and against. In this study we address the question to what extent the forest dynamics were influenced in earlier centuries by infestations of Ips typographus.
Pollen and macrofossils from Stangenfilz mire (1 ha in size) show that spruce immigrated about 10’000 years ago (calibrated), followed by beech and fir about 6000 years ago. Spruce, fir (Abies alba) and beech (Fagus sylvatica) were co-dominants until the sixteenth century when large-scale charcoal production for the glass industry began, while a second phase of heavy logging took place in the early twentieth century. Spruce suffered less from the logging and recovered well, also through plantation, in contrast to fir and beech that remained sub-ordinate until now, which resulted in extensive spruce-dominated forests. Later, however, bark beetles killed off large stretches of pure spruce forests, and stretches of mixed forest have lost much of their spruce. We postulate that the human-induced shift to spruce dominance is the main cause for the large scale of the bark-beetle infestations. The forest trees regenerate well in the beetle-infested areas, thus crediting the intentional no-intervention management – a sustainable pathway, supported by learning from the past for shaping the future.