Assemblages of flower-visiting insects in clear-cuts are rich and dynamic

Clear-cuts in production forests provide an open, sunny environment, with an abundance of nectar, as well as exposed soil and woody debris. This makes them a potential habitat for several groups of insects that typically use open habitats like grassland, including those species that visit flowers. In the current study, we used colour pan traps to catch flower-visiting species. Study sites were selected according to age (2-8 yrs since clear-cut) and land-use history (forest or meadow 150 yrs ago). We caught and identified solitary bees (395 specimens belonging to 59 species), social bees (831/16), other Hymenoptera (367/66), Syrphidae (256/31), and beetles (Lepturinae & Cetoniinae; 11,409/12). Age of the clear-cut strongly affected species composition as well as several of the groups and species, with most species caught mainly in the younger clear-cuts. Flower abundance statistically affected several groups and species, but such effects are potentially suspect due to the flower-richness bias in pan trap catches. Bare soil and woody debris seemed irrelevant were important for the insect assemblage sampled, while bare rock sometimes positively affected flower-visiting insectswas not. Although the majority of the insects caught were forest species, about one third of the species were associated with open, agricultural sites and hence seem to be able to locate and exploit resources in clear-cuts.