The recent increase in extreme weather events has made the progressing climate change clearly noticeable globally. With regard to forest ecosystems, abiotic and biotic influences often interact, which significantly increases the extent of damage, especially in monocultures. This development has become very clear in Germany and some neighbouring countries since 2018. Storms and dry periods enabled the large spruce bark beetle (Ips typographus L.) to spread on a massive scale. The enormous amount of damaged timber quickly pushed forestry operations and service providers, as well as the softwood processing industry, to their capacity limits. As a result, the dead spruce trees (Picea abies [L.] Karst.) remained in the stands in many places. This condition sometimes persisted for years, raising the question of how the spruce wood stored standing would change over time with a view to later use. In addition to possible changes in the properties of the wood, which can only be determined through complex investigations, the external appearance of the spruce trees changes considerably after infestation with bark-breeding beetles – needles become discoloured, bark detaches from the trunk, cracks form, other insect species infest the trees, fungi grow and form fruiting bodies or the trees break off at different heights.
The aim of the study, which was carried out in the Harz National Park, was to find out whether there is a correlation between the changing external appearance of beetle-infested spruce and the duration of standing storage.
The approach of this work stems from the NUKAFI project, the aim of which is to research the possible uses of spruce wood infested with bark beetles and to make this knowledge available to forest owners and the interested public.
Our research has shown that the structural factor of fungal fruiting bodies appears to be the main driver of development in terms of tree condition and demolition intensity. In addition, the occurrence of fungal fruiting bodies correlates significantly with a higher demolition intensity and the longer the standing storage period, the more individual trees have fungal fruiting bodies. The structural factor of fine brushwood can be regarded as a quick and visually easily detectable characteristic for drawing conclusions about the standing storage period.
The opportunity to use my own research to make a contribution to supporting the forestry industry with regard to future calamity situations and thus to be able to better meet the challenges of climate change is a great incentive for me to carry out this research work.
Keywords: drought spruce stand, standing storage, year of mortality, Picea abies ([L.] Karst.), Ips typographus (L.), Harz Mountains National Park, stem breakage
Authors
Jan-Frederik Trautwein
Wood Biology and Wood Products, Faculty of Forest Sciences and Forest Ecology, University of Goettingen, Germany
Laurenz Rudolf Rohde
Wood Biology and Wood Products, Faculty of Forest Sciences and Forest Ecology, University of Goettingen, Germany
Holger Militz
Wood Biology and Wood Products, Faculty of Forest Sciences and Forest Ecology, University of Goettingen, Germany
Christian Brischke
Thünen Institute of Wood Research
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