Oaks in Norway: Hotspots for red-listed beetles (Coleoptera)

Old, hollow oaks are important for biodiversity all over Europe. The present paper sums up the results of a study on 14 sites of old, hollow oaks in Nor-way. At each site, 5 hollow oaks, each containing 2 traps, were sampled in order to gather information on the abundance and composition of red-listed species of beetles. With an average of > 4 red-listed species per tree, the results confirm that hollow oaks are hotspots for saproxylic beetles, especially west of the Oslo Fjord in southern Norway. Trap placement within the tree seems to strongly influence the species composition. In general, there is a high heterogeneity in species composition in the samples for beetles sampled in traps on the same tree, beetles sampled on different trees at the same site, and those sampled from different sites. In order to monitor oak-associated beetles, a combination of species sampling and indirect monitoring (surrogate inventories) is a realistic solution.