lnvertebrate fauna on Norwegian spruce (Picea abies) branches in northern Finland

The invertebrate fauna living on old Norwegian spruce (Picea abies) branches was studied in the years 1986 and 1987 in four localities in northern Finland. Three of the study areas, Linnanmaa, Sanginjoki and Muhos, were located close to the coast of the Bothnian Bay. The fourth area, Taivalkoski, lays inland, in the most easterly location of the four. The numbers of invertebrates living on spruce branches varied seasonally, as well as between the individual branches of a sample. They were highest at Linnanmaa, near the city of Oulu, and lowest at Taivalkoski. The most abundant taxa were mites (Acarina), spiders (Araneae) and springtails (Collembola). As regards the total invertebrate index Linnanmaa differed significantly from the other areas. Most of the animal groups showed a similar trend as well. In addition to a geographical cline (from coast to inland), the level of pollution is considered a possible cause of the observed uneven distribution in invertebrate numbers.