Abstract: Norway spruce (Picea abies (L.) Karst.) in the Harz Mountains National Park (Germany) has experienced widespread mortality (> 97% of trees in the study stands) due to infestation with the large spruce bark beetle (Ips typographus L.). The dead trees (snags) remain standing in the forest for 2–5 years before harvesting. It is important to identify trees that can still produce quality timber, which may be achieved by examining their outer appearance using selected characteristics. The aim of this study was to identify possible correlations between the standing storage duration and defined external characteristics of the snags. The mean tree height at compartment level was calculated using a vegetation height model, based on light detection and ranging data from 2018, to derive the stem breakage proportion. The condition of the crown and the bark and presence of fungi, wood rot, stem cracks and bark stripping damage were also assessed. The majority of the snags were broken at least once. Windthrows were less likely compared to living spruce trees because of reduced resistance to the wind as a result of needle loss and breakage. The mean stem breakage proportion increased significantly with the duration of the standing storage; however, prolonged storage durations did not always lead to complete breakage. The occurrence of fungal fruiting bodies was significantly correlated with a higher proportion of stem breakage, and the longer the storage, the more snags had fungal fruiting bodies. The condition of the crown, assessed by the presence of branchlets, was a good indicator of the duration of the standing storage. If trees had few or no branchlets, they had been standing for at least 4 years. Overall, this initial description of the external appearance of spruce trees that have been stored standing for many years suggests that time significantly influences the tree condition and breakage intensity, which is reflected by certain tree characteristics. Future studies should examine these aspects in greater depth, particularly with regard to utilization options and safety during timber harvesting.

Key words: Snag, Stem breakage proportion, Ips typographus