High-stumps and wood living beetles in the Swedish production forest landscape

The amount of dead wood in Swedish production forests is low compared to natural forests. This has resulted in a high proportion of red-listed and threatened wood living beetle species. Different actions are taken to increase the amount of dead wood and one such action is to artificially create high-stumps (snags), i.e. living trees cut between 3 and 5 meters height. This thesis focuses on whether high-stumps on clearcuts in southern Sweden increase beetle diversity. One study focus on whether a high-stump offers a different substrate compared to ordinary low-stumps. Another study investigates if beetle species are affected if the high-stumps are pre-rotten or not. Finally, the beetle species number and composition between high-stumps of spruce and birch in biodiversity hotspots and production forest (matrix), respectively. High-stumps have a somewhat different beetle species composition compared to low-stumps (normal cutting stumps), and several species were primarily associated with high-stumps. This justifies the making of high-stumps even though the amount of dead wood they add to a clearcut is low. The pre-rotten spruce high-stumps (infected by Heterobasidion spp.) had a negative effect on some beetle species and none of the analyzed species showed positive associations with Heterobasidion spp. This suggests that increasing the proportion of rotten spruce high-stumps could have a small but negative effect on beetle diversity. The number of beetle species did not differ between high-stumps on hotspot and matrix clearcuts, suggesting that concentrating high-stumps to hotspot areas will not benefit more beetle species. However, the amount of broadleaved forest in the surroundings of clearcuts was important for explaining species composition on high-stumps. The amount of coniferous forest only explained a small part of the beetle species composition, possibly because coniferous forests are dominating the entire forested landscape in southern Sweden. The high-stumps in these studies were four years old at most. This means that, as the wood decay progress, the properties of high-stumps change and potentially they become even more important.