DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 11-12/2013 str. 45     <-- 45 -->        PDF

total drift densities exceeded 1000 individuals/100 m3 in two of the drift traps in the upstream part. In Lötbergstjärnbäcken, which had the lowest catches, no animals were caught in one of the traps in the upstream part. In Kroktjärnbäcken the family Leptophlebiidae was very abundant. The Ephemeropteran dominance was not that pronounced in the other streams. Among the pelagic group, Cladocera on average was very dominant, but most of them were found in Rismyrbäcken. In the other streams the number of Cladocera was low.
The drift differed significantly between the streams for most of the variables, and that the interaction between stream and the part analyzed was significantly different in most cases (Table 4). No significant difference between the upstream and downstream area was noted in the total drift densities (Fig. 5). The drift densities of benthic species were however significantly higher at the sites upstream of the dams. In this study no significant difference in the drift density of pelagic species was observed.
The drift densities of Ephemeroptera (Fig. 6) were significantly higher upstream of the beaver dams. For Diptera, Trichoptera and Plecoptera no significant difference was observed.
Diversity was studied as the number of aquatic genera identified. A total of 45 taxa were identified across all sites (table 5). No significant difference was observed in total diversity or in diversity of benthic and pelagic species. There was no significant difference in dry weight (Fig. 5).