| Summary: | Wood can be added to streams to create microhabitats that provide macroinvertebrates with an opportunity for re-colonization by making the stream more heterogeneous. I examined colonization on wood substrate by macroinvertebrates in semi-natural streams in northern Finland during a three month period. Each of the streams was divided in three sections A, B and C, half of which were provided with wood. The focus has been on whether the density of macroinvertebrates changes with time, along an upstream-downstream direction in the streams, or in streams with two wood sections if macroinvertebrates will colonize the first section with wood that they come in contact with (upstream section) or if they continue downstream to the second section with wood. Wood from Salix sp. was placed in nine of the 18 enclosures during mid-June. Samples of wood were removed from the streams on three different occasions from August to October 2014. A total of 32 taxa were identified from the wood and assigned to functional feeding groups: shredders, scrapers, active filter feeders, passive filter feeders, collectors, miners, piercers and predators. The results showed that collectors, miners and piercers increased in density during the month of October and the abundance of scrapers was higher in the upstream location than in the downstream location. Total number of macroinvertebrates, collectors, passive filter feeders and predators had a higher colonization on the first substrate they came into contact with. Ved i homogena vattendrag skapar mikrohabitat och ger evertebrater en möjlighet att återkolonisera vattendraget genom att göra vattendraget mer heterogent. Jag har undersökt makroevertebraters kolonisation på ved i semi-naturliga bäckar under en tre månaders-period i norra Finland. Bäckarna var uppdelade i tre sektioner upp-, mellan- och nedströms respektive A, B och C. Av 18 sektioner var nio ved försedda. Jag har fokuserat på om tätheten av evertebrater och diversiteten förändras med tiden, längs bäckarna dvs. uppströms – ...
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