Markberedningens påverkan på blåbärsris och dess pollinerare

Sammanfattning: The young forest stands that are generated from clear cutting have been proven to be suitable habitats for aculeates. It is, however, uncertain how soil scarification, which is a very common procedure before planting, affects the flowering dwarf shrubs and its pollinators. The aim of this survey was to examine how the bilberry coverage is affected by soil scarification and how the occurrence of floral visiting hymenopterans that is depending on bilberry for foraging in May are affected by soil scarification. I compared bilberry cover and occurrence of floral visiting hymenopterans in five scarified and five unscarified cutting areas in Uppsala County. Cover of bilberry was assessed by visual estimates and occurrences of floral visiting hymenopterans were estimated by white pan traps. One cutting area was inventoried both before and after scarification and the bilberry coverage was compared. The analysis showed that scarification leads to 3-4 percent-units less bilberry coverage which means that scarification reduce bilberry cover by 30-40 %. There was no significant difference in the numbers of captured hymenopterans on the different kind of cutting areas during the blooming season of bilberry. The biggest reduction on bilberry coverage is caused by clear cutting but scarification is reducing the coverage further. It is uncertain whether fresh clear cut areas are suitable habitats for floral visiting hymenopterans in May. Few caught hymenopterans can be explained by few nectar- and pollen producing flowers or cold weather during the study period.