Canadian Forest Service Publications
Succession of saproxylic beetles associated with decomposition of boreal white spruce logs. 2014. Lee, S.-I.; Spence, J.R.; Langor, D.W. Agricultural and Forest Entomology 16(4):391-405.
Issued by: Northern Forestry Centre
Catalog ID: 35832
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We reared saproxylic beetles from 54 white spruce [Picea glauca (Moench) Voss] logs collected in northwestern Alberta, Canada. Logs represented six decay classes, ranging from freshly dead to well decayed.
Beetle assemblages were indicated mainly by phloeophagous and predaceous species in early decay stages, although indicator species were mainly predaceous in later stages of decay. No indicator species were identified for intermediate decay stages.
Larvae from rearings were disproportionately predaceous. Thus, movement of juveniles within and among coarse woody debris (CWD) substrates is likely an important aspect of the life history for these species.
Beetle assemblages changed progressively with increasing stages of decomposition. Assemblages of adjacent decay classes were highly similar, although similarity decreased with increasing difference in decay classes. Therefore, the retention of all decay classes of white spruce downed CWD on post-harvest landscapes is necessary to conserve the associated saproxylic beetle fauna.
Retention of CWD in advanced decay stages, which contains species not found in earlier decay classes, presents a particular challenge in forest management because of the long times required to develop CWD in the later stages of decomposition.
Plain Language Summary
We sought to understand how the diverse community of beetles that inhabits dead wood change as wood decays and whether there are unique species associated with various degrees of decay (decay “classes”). We wanted to determine whether there are decay classes that provide unique habitat and should be the target of conservation efforts in landscapes where forestry is taking place. Beetles were reared from wood of a range of decay classes, and their species were identified. Wood with little decay, moderate decay and advanced decay all had species that were unique to that decay class. Therefore, it is important that the forest industry leave dead wood of a variety of decay classes on landscapes where wood harvesting has been carried out. Wood of little-to-moderate decay is very common on such landscapes, so it is unlikely that these habitats and the species associated with them will be adversely affected by current harvesting practices. However, as it takes a long time for dead wood to develop into advanced decay classes, we recommend that the forest industry take steps to ensure that patches of forest with wood of advanced decay be conserved.