Overvåking av insekter i hule eiker 2023

One hundred oak trees were selected from a set of 600 veteran oaks registered in the national oak survey. These oaks were divided into two sets of 50 oaks, where insects can be sampled every second year in each oak. For practical reasons, these two sets represent two different geographical regions; region East (Oslo, Akershus, Buskerud, Østfold, Telemark & Vestfold) and region West (Agder, Rogaland og Vestland). The oaks for each set were selected at random, with the exception of a doubled likelihood of selecting oaks with a visible cavity in addition to diameter at breast height larger than 200 cm, and a few criteria relating to the number of trees in each plot. The distribution of oaks between counties and with-in/outside of forest was controlled after the selection was made and was considered adequately balanced. Insects were sampled from the 50 selected oaks in region East in June and July in 2023. Two window traps were mounted at each tree, one in the canopy and one at the trunk, next to a cavity if the tree had any. Beetles were identified.