Succession of saproxylic beetles associated with decomposition of boreal white spruce logs

Abstract

1 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. 2 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. 3 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. 4 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. 5 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.

Forest management strategy affects saproxylic beetle assemblages: A comparison of even and uneven-aged silviculture using direct and indirect sampling

“…We also fitted linear models to test for management strategy effects on tree species composition, basal area and log-transformed deadwood volume. Since the quality of deadwood might have a higher impact than the quantity on beetles assemblages [ 31 , 52 ], we divided deadwood into decay stages and substrate types to compare effects of management strategy on deadwood type using the R package ‘nlme’. A principal component analyses (PCA) were performed to assist in the interpretation of effects from management of stand characteristic using the R-package ‘ factoextra’ [ 53 ].…”

“…As decay progresses, the chemical composition and nutrient availability change [ 29 ] and decay stages last longer, e.g., it can take up to 50 years for a spruce log to reach the advanced stages of decay [ 30 ]. This means that rapid recolonization becomes less important for species dependent on late decay stages [ 31 , 32 ], but that resources may be much rarer following silviculture, increasing the vulnerability of these species. Previous research from our study system indicated that even-aged forest management has limited impacts on beetle assemblages compared with uneven-aged forest management [ 24 , 25 ].…”

Stump‐harvesting for bioenergy probably has transient impacts on abundance, richness and community structure of beetle assemblages

“…However, we also separately analyzed saproxylic species that we caught (even though pitfall trapping is not a recommended method of collection for such species, although it has been used to look at certain species such as pine weevil). We would expect saproxylic abundance to be highest in the first year and diversity to increase with stump age (Jonsell et al ., ; Stenbacka et al ., ; Lee et al ., ). Stump‐harvesting is a two‐three stage process: once stumps are removed from the soil, they are temporarily left on site in wind‐rows to undergo a ‘weathering period’.…”

Effects of Post-Fire Deadwood Management on Soil Macroarthropod Communities

“…The enhancement of soil macroarthropod communities in the PC treatment can be related to several non-mutually exclusive mechanisms, several of which are related to how dead wood can enhance soil biota. First, as the logs decompose, they lose integrity, causing the wood to crumble and increasing the amount and heterogeneity of resources available for taxa involved in wood decay, such as wood-boring beetles (Coleoptera) [78] and termites (Termitoidae) [79]. Logs had lost an overall 23% of their mass at the time of the present study, and they showed a high degree of fragmentation and many tunnels bored by insects [80].…”