Coarse woody debris, polyporous fungi and saproxylic insects in an old-growth spruce forest in Vodlozero National Park, Russian Karelia

摘要

We measured the amount and quality of coarse woody debris, and surveyed polypores and threatened saproxylic insects in a spruce-dominated old-growth forest in Vodlozero National Park, Russian Karelia - one of the largest remaining areas of virgin forest in northern Europe. The inventory area was 1 km~2. We compared the polypore data from Vodlozero to data that was previously collected in 12 old-growth forest areas (sizes 600— 9100 ha) in eastern Finland using the same inventory method. The average volume of coarse woody debris was 87 m~3ha~(-1) in Vodlozero, and the variation between sites was 52—128 m~3ha~(-1). The number of red-listed polypore species recorded was higher in Vodlozero (23 species) than in any of the areas in eastern Finland (3-20 species, median = 11.5 species). The abundances of red-listed, indicator, and successor polypore species were each over three times higher in Vodlozero than in eastern Finland. The number of red-listed saproxylic insect species found (18) was also strikingly high considering the short inventory period. Since the biogeographic region, climate, and vegetation zone did not differ significantly between the areas, we suggest that the high species richness and abundance of rare species in Vodlozero could be a result of unhindered dispersal and colonization between habitats in a continuous old-growth area as compared with the more fragmented landscape in Finland. The proportion of old-growth forest of the whole landscape was 41% in Vodlozero, whereas in eastern Finland the mean proportion around the inventory areas was 19.4% within a radius of 10 km and 8.6% within 30 km.