Effects of landscape composition and substrate availability on saproxylic beetles in boreal forests: a study using experimental logs for monitoring assemblages

Abstract

K. 2006. Effects of landscape composition and substrate availability on saproxylic beetles in boreal forests: a study using experimental logs for monitoring assemblages. Á/ Ecography 29: 191 Á/204.Intensive forestry practises in the Swedish landscape have led to the loss and fragmentation of stable old-growth habitats. We investigated relationships between landscape composition at multiple scales and the composition of saproxylic beetle assemblages in nine clear-cut, mature managed and old-growth spruce-dominated forest stands in the central boreal zone of Sweden. We set out fresh spruce and birch logs and created spruce snags in 2001 Á/2002 to experimentally test the effects of coarse woody debris (CWD) type and forest management on the composition of early and late successional, and red-listed saproxylic beetle assemblages. We examined effects of CWD availability at 100 m, and landscape composition at 1 and 10 km on saproxylic beetle abundances. Additionally, we tested whether assemblage similarity decreased with increasing distance between sites. We collected beetles from the experimental logs using eclector and window traps in four periods during 2003. CWD was measured and landscape composition data was obtained from maps of remotely sensed data. The composition of saproxylic beetles differed among different CWD substrates and between clear-cuts and the older stand types, however differences between mature managed and old-growth forests were significant only for red-listed species. Assemblage similarities for red-listed species on clear-cuts were more different at greater distances apart, indicating that they have more localised distributions. CWD availability within 100 m of the study sites was rarely important in determining the abundance of species, suggesting that early successional saproxylic beetles can disperse further than this distance. At a larger scale, a large area of suitable stand types within both 1 and 10 km resulted in greater abundances in the study sites for several common and habitatspecific species. The availability of suitable habitat at scales of 1 Á/10 km is thus likely to be important in the survival of many saproxylic species in forestry-fragmented areas.

Can Airborne Laser Scanning (ALS) and Forest Estimates Derived from Satellite Images Be Used to Predict Abundance and Species Richness of Birds and Beetles in Boreal Forest?

“…Other bird studies indicate that local stand variables are important predictors of bird species richness, although some also highlight the importance of the broader landscape context [50,73]. As such, our results do not contradict previous findings, highlighting the importance of the landscape context for explaining local biodiversity patterns (e.g., [14,74]), because we did not specifically evaluate additional effects of the landscape context after accounting for local-scale conditions. Additionally, although 50 m performed better, it is not necessarily the optimal radius, and more research would be needed to determine the best radius.…”

Responses of parasitoids to saproxylic hosts and habitat: a multi-scale study using experimental logs

“…While the volume of CWD appeared in the best-Wt models for species richness and Rhimphoctona spp., it was not a signiWcant predictor. A similar lack of dependence on small-scale variation in substrate availability has commonly been found in studies examining the eVects of landscape variables on saproxylic beetles (Siitonen 1994;Økland et al 1996;Gibb et al 2006). This lack of relationship between the abundance of their hosts and the volume of CWD in close proximity suggests that parasitoids would not Wnd prey more easily by searching in areas with locally higher volumes of CWD.…”

“…Previous studies have tested the relationship between features of forestry-dominated landscapes and assemblages of saproxylic beetles (Økland et al 1996;Gibb et al 2006), but little is known about how host and landscape responses interact to aVect their parasitoids. Species belonging to higher trophic levels are particularly vulnerable to changes in landscape structure and composition, as a result of their reliance on intact trophic chains (Roland and Taylor 1997;Kruess and Tscharntke 2000).…”

Application of Semiochemicals to Assess the Biodiversity of Subcortical Insects following an Ecosystem Disturbance in a Sub-boreal Forest

“…Although we caught a greater number of beetles in our traps, we had lower species richness than these other studies on subcortical insects. Possible reasons include: 1) inclusion of latesuccessional beetle taxa (e.g., Colydiidae, Elateridae, Passalidae, and Stapylinidae) by previous researchers in their analyses in contrast to inclusion of only earlysuccessional taxa in our study (Savely 1939;Gibb et al 2005); 2) the use of window-traps attached directly to the trees by previous researchers in contrast to baited Lindgren funnel traps hung from poles in our study (e.g., SverdrupThygeson and Birkemoe (2008) found that window traps hung directly on aspen trees caught more beetles associated with aspen than traps hanging freely); and 3) some of the highly specific semiochemical baits that we used attracted large numbers of target species, but captured far fewer taxa than did unbaited traps or more generically baited traps. The subcortical insect guild that we have characterized likely originated primarily from jack pine (P. banksiana) [e.g., I. grandicollis, I. perroti, I. pini, Pityogenes plagiatus plagiatus (LeConte) (all Scolytidae) and M. s. scutellatus (Cerambycidae)], with identifiable components from L. laricina, Picea glauca, P. resinosa, and P. strobus.…”