The amplitude of dead wood resource pulses produced by plantation thinning mediates the assembly of wood-boring beetles

The commercial thinning of forests creates a dead wood resource pulse in the form of tree tops, branches, and stumps that are used by many organisms as a substrate but are also increasingly coveted as a source of bioenergy. To evaluate the effects of commercial thinning, as well as those of woody debris (WD) harvest, retention or supplementation on communities of cerambycids (Coleoptera: Cerambycidae), a family of saprophagous wood-boring beetles, a 3-yr study was carried out in white spruce plantations subjected to three contrasting thinning regimes. The regimes included a standard commercial thinning, a thinning with biomass removal, and a thinning with added standing dead wood. Beetles were captured starting the first summer following treatment using flight intercept traps, and the volume of standing and downed WD was estimated using quadrats. The results indicated that the complex of 25 cerambycid species was influenced by commercial thinning, by the time elapsed since thinning treatments were carried out, and by the abundance of fresh WD. A higher abundance and species richness of cerambycids was documented in thinning treatments yielding greater volumes of dead wood; compared to unthinned areas, cerambycid beetle richness was 116% higher in thinned areas where woody biomass was harvested, while it was 200-233% higher in thinned areas with dead wood retention or supplementation. This suggests that dead wood resource pulses caused by plantation thinning have a strong, beneficial effect on cerambycid communities that wanes as the amount of harvesting debris remaining on site decreases.