Saproxylic Beetles in Standing Dead Wood Density in Relation to Substrate Sun-exposure and Diameter

Abstract

Species-specific densities of saproxylic beetles in cut 4-m high, medium to large diameter stumps of spruce, birch, aspen and oak were monitored for 7 years after cutting, by trapping emerging insects within seasonally applied net enclosures. A total of 47,038 individuals, representing 316 saproxylic beetle species including 40 red-listed species, were recorded. Densities of 86 species were modelled in relation to stump diameter and measured levels of sun-exposure. Two thirds of the species favoured semi-or fully exposed substrates, while one third performed better in shade. Few species seemed to be specifically adapted to semi-exposed conditions. Diameter was generally of less importance than exposure, and similar numbers of species favoured medium and large diameter substrates. Group mean diameter and exposure calculated from means per individual and species were similar for groups of modelled and non-modelled species, and for groups of red-listed and non-red-listed species, respectively. This indicates that the proportions found in the models are representative for the diverse regional fauna of saproxylic beetles that utilise high stumps of spruce, birch, aspen and oak in early stages of decay. The results suggest that sunexposed dead wood substrates generated and retained in managed forest landscapes are potentially important for many species. However, stands of unmanaged self-thinning successions of deciduous trees, as well as substantial areas of old-growth spruce-forests are also necessary to address the wide spectrum of saproxylic beetles.

Bark- and wood-boring beetles on Scots pine logging residues from final felling: effects of felling date, deposition location and diameter of logging residues

“…LR type had a greater explanatory power than LR diameter, possibly because LR type was more strongly correlated with unstudied variables, such as the presence or absence of needles on particular LR fragments. Substrate diameter has previously been shown to affect saproxylic beetle occurrence (Schiegg 2001, Lindhe & Lindelöw 2004, Lindhe et al 2005, Jonsell et al 2007, Maňák 2007, Jonsell 2008b, Foit 2010, Brin et al 2011. Thus, nine taxa were signifi cantly associated with LR diameter in the present study ( Table 2).…”

“…In general, the occurrence of saproxylic beetles on LRs or dead wood is affected by substrate characteristics, including substrate metric parameters, such as bark thickness (Zhang et al 1993, Foit 2010 and diameter (Schiegg 2001, Lindhe & Lindelöw 2004, Lindhe et al 2005, Jonsell et al 2007, Maňák 2007, Jonsell 2008b, Foit 2010. Sun exposure (Jonsell et al 2004, Lindhe & Lindelöw 2004, Lindhe et al 2005, Jonsell 2008b), moisture (Wallace 1953, Larkin & Elbourn 1964, decomposition stage (Wallace 1953, Vanderwel et al 2006, Jonsell 2008b and the presence of other organisms (Jonsell et al 2005, Abrahamsson et al 2008, Weslien et al 2011) are of remarkable signifi cance for the occurrence of saproxylic beetles in various substrates. Because of these associations, known breeding substrate requirements and timing of mating and egg laying of particular BWBB species (Schwenke 1972), it is possible that the colonisation of LRs by BWBBs is infl uenced by the date of LR production (felling date).…”

Aftermath of Mountain Pine Beetle Outbreak in British Columbia: Stand Dynamics, Management Response and Ecosystem Resilience

“…In another study, Perovich and Sibold [60] reported that stands with MPB outbreak had greater diversity in age classes and species composition. In addition, natural disturbances generate tremendous amounts of dead wood, which can be used as habitats for many saproxylic (i.e., organisms that depend, during at least part of their life cycle, upon the dead or dying wood of moribund or dead trees, or upon other saproxylic organisms) species [147]. Based on a study by Müller et al [148], European spruce bark beetle (Ips typographus) infestations improved the habitat of several endangered saproxylic beetles.…”

Boxes mimicking tree hollows can help conservation of saproxylic beetles

“…However, more sun-exposed oaks do on average host more species than more shaded ones (Ranius and Jansson 2000;Lindhe et al 2005;Buse et al 2007). Thus, to favour a larger number of species it might be advisable to place the boxes so that a variation in sun exposure is obtained.…”