Xylophagous insect species composition and patterns of substratum use on fire-killed black spruce in central Quebec

Abstract

Several xylophagous insect species have adapted to recurrent fires in boreal forests and use high-quality habitats created by these disturbances. To characterize the xylophagous insect assemblages of fire-killed black spruce and their patterns of substratum use, eighty-four 40 cm long bole segments were cut in 2000 and 2001 according to tree diameter, segment height, and fire severity criteria in a 1999 burn in the Grands-Jardins provincial park, Quebec, Canada. The segments were suspended in rearing cages, and neonates were collected until November 2001. The cerambycid Mono chamus scutellatus (Say) and the scolytids Dryocoetes affaber (Mann.) and Polygraphus rufipennis (Kirby) were the most common beetles collected. For all common taxa, more neonates emerged from larger-diameter trees. Few neonates emerged from the upper parts of the trees, and none of the species were specialist of the upper parts of the tree. Fire severity had a drastic effect, and heavily charred trees yielded very few insects. The effect of fire severity on insect colonization density varies widely among tree species. This effect may be linked to varying bark thickness and to bark's insulating potential against water loss during the fire. The host's vigor before its death, measured from growth rings of the last 10 years, had a positive effect on cerambycid emergence, but no effect on scolytids.