Effects of microhabitat and space limitation on Norway spruce regeneration in bark beetle affected areas of Bavarian Forest National Park
Philipp Kohler (01/2018-07/2018)
Support: Carl Beierkuhnlein, David Kienle
Secondary forest succession caused by large-scaled bark beetle infestations is determined by several anthropogenic and natural parameters. Recent studies indicate self-replacement of Norway spruce (Picea abies) forests, although the effect sizes of particular drivers are unknown. In line with the current state of research, this study states that lying dead wood positively influences Norway spruce regeneration, whereas the cover of the hairy reed grass (Calamagrostis villosa) is antithetic to the frequency of woody microhabitats. Within Bavarian Forest National Park, research areas were established in both, non- intervention and management zone after large-scale bark beetle infestations. For 49 systematically distributed plots, a set of 16 plot- microhabitat- deadwood- vegetation- soil- and time-related parameters were analyzed. The plots were characterized by a four times higher C. villosa mean cover compared to the cover of Norway spruce recruits. Time since disturbance had a large positive effect on both, Norway spruce and C. villosa cover (R²= 0,32 and 0,16). Furthermore, C. villosa showed little negative influence on Norway spruce cover whereas C. villosa cover was primary explained by the negative influence of other graminoids and secondary by lying dead wood characteristics as vegetation cover and ground contact and Norway spruce cover. For the first time, this study proves positive temporal effects to be more influential on Norway spruce cover than spatial aspects such as the amount of woody microhabitats or graminoid cover. These findings suggest a state shift in secondary succession from graminoid induced delayed tree regeneration towards a closed canopy stage.