DECAYING WOOD AND SAPROXYLIC COLEOPTERA IN 2 OLD SPRUCE FORESTS - A COMPARISON BASED ON 2 SAMPLING METHODS

The saproxylic beetle fauna was compared in two old spruce dominated f orests in northern Finland. The volume of decaying wood in the forests was 32 m3 and 8 m3 per hectare. The beetles were sampled by carefully peeling the bark off all the dead trees within twenty circular sample plots of 100 m2, and by window flight trapping. The pooled sample com prised 7184 individuals of 207 saproxylic species. According to both s ampling methods, common generalist species were equally abundant in bo th forests, whereas specialists living either on decaying spruce or bi rch were more abundant in the forest with a larger supply of decaying wood. The set of dominant species was, however, almost completely diff erent with the two methods. Bark peeling yielded mostly sub-corticulou s species. Window flight trapping yielded, in addition, many species l iving inside decaying trees, on microfungi on dead trees or on polypor ous fungi. The amount of decaying wood around the traps did not affect the number of species or specimens caught. The problems involved in t he sampling methods are discussed.