| Summary: | Forestry affects most of the forest-covered land in Sweden. In the landscape, the most common stream type is headwaters, which are important sites for many processes and organisms in both the terrestrial and the aquatic ecosystems. The aim of this study was to investigate how the abundance of benthic invertebrate functional feeding groups in headwater streams develops after clear-cutting and if it also is possible to detect a change in the composition of feeding groups. The study also attempts to determine what factors have an effect on temporal changes in abundance of these groups. For the study, 11 sites in northern Sweden were sampled for benthic invertebrates using a Surber-sampler, and for each site canopy-cover and pH was obtained. Further, the age of the surrounding forest at each was visually assessed and created a 100-year gradient along which temporal changes in abundance of the functional feeding groups were investigated. The results revealed that the total abundance of organisms was the highest short after clear-cutting and afterward decreased to the lowest level in streams with the highest age of surrounding forest. Significant results for the functional feeding groups were found for predators, shredders and scrapers, which also had the highest levels of abundance early after clear-cutting and thereafter decreased. The result shows that clear-cutting, not only changes the fundamental terrestrial conditions, but also has an impact on the abundance of different benthic functional feeding group.
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