Woody species-specific disturbance regimes and strategies in mixed mountain temperate forests in the Šumava Mts., Czech Republic

The disturbance regime of mountain spruce–beech temperate forests has not yet been sufficiently elucidated. We hypothesized that spruce and beech express completely different disturbance histories and behavioural strategies, potentially causing exceptionally complex disturbance regimes. We further hypothesized that the spontaneous development of mountain forests can temporarily result in a simplification of the forest's spatial structure. We wanted to discover how the disturbance history and growth plasticity of the main tree species differ, and whether some old managed forests arose from primeval forest remnants. We compared dendrochronological records of the unmanaged Boubin Primeval Forest and 30 sites with current forestry records. Using this comparison, we categorized all sites into three categories. In the disturbance history of all evaluated forest sites, there was clear evidence of the presence of severe disturbances in the nineteenth century. However, the regeneration of beech was more continuous and less dependent on the presence of severe disturbances than the regeneration of spruce, which depended on the presence of severe disturbances of low frequency. Human-induced changes at some sites were manifested in changes in the initial growth of both species and disrupted their mutual competition and also led to a higher growth plasticity of beech. Despite human impacts in the region since the end of the nineteenth century, about 30% of analysed trees were older than the severe disturbances in the nineteenth century; therefore, some studies sites preserved the characteristics of primeval forest. Our results revealed three main forest development trajectories since the end of the nineteenth century.