Habitat requirements and conservation of Pytho kolwensis, a beetle species of old-growth boreal forest

Abstract

The host-tree and habitat requirements of an endangered saproxylic beetle species, Pytho kolwensis, which inhabits fallen spruce ( Picea abies) trunks were studied. Host-tree quality of 150 potential host trees, 60 of which were inhabited, and stand characteristics were measured at six sites in eastern Finland. All of the P. kolwensis habitats were virgin spruce-mire forests with a stand continuity of at least 170–300 years, and a high volume of dead wood (73–111 m 3/ha). Decay-class distribution of large-diameter logs was very even, indicating that the recruitment rate of large, fallen trunks had remained nearly constant for at least 100 years. Microclimate and host-tree quality were not likely factors explaining the habitat confinement of the species. We suggest that P. kolwensis is mainly restricted to spruce-mire forests because of the long-term continuous availability of suitable host trees in these habitats.