Numerical responses of saproxylic beetles to rapid increases in dead wood availability following geometrid moth outbreaks in sub-arctic mountain birch forest

• Published in: PLoS ONE
• Main Authors: Vindstad, Ole Petter Laksforsmo, Schultze, Sabrina, Jepsen, Jane Uhd, Biuw, Martin, Kapari, Lauri, Sverdrup-Thygeson, Anne, Ims, Rolf Anker
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2014
• Subjects: /dk/atira/pure/core/keywords/559922418; Biology; birch; community structure; dead wood; Denticollis borealis; Enicmus lundbladi; epidemic; Epirrita autumnata; forest; larval development; litter decomposition; mortality; moth; nonhuman; Norway; Operophtera brumata; organisms by habitat; population abundance; saproxylic species; species difference; species diversity; wood; animal; Arctic; ecosystem; forest; geography; moth; population density; Atheta taxiceroides; betula pubescens; /dk/atira/pure/core/keywords/biology; Ecosystems Research; beetle; Arctic; Norway; Northern Norway
• Online Access: http://fox.leuphana.de/portal/de/publications/numerical-responses-of-saproxylic-beetles-to-rapid-increases-in-dead-wood-availability-following-geometrid-moth-outbreaks-in-subarctic-mountain-birch-forest(8c575f8f-1f00-445c-9497-e2e3d98b5862).html; https://doi.org/10.1371/journal.pone.0099624; https://pure.leuphana.de/ws/files/14247287/10.1371_2Fjournal.pone.0099624.PDF; http://www.scopus.com/inward/record.url?scp=84902602814&partnerID=8YFLogxK

Saproxylic insects play an important part in decomposing dead wood in healthy forest ecosystems, but little is known about their role in the aftermath of large-scale forest mortality caused by pest insect outbreaks. We used window traps to study short-term changes in the abundance and community structure of saproxylic beetles following extensive mortality of mountain birch in sub-arctic northern Norway caused by an outbreak of geometrid moths. Three to five years after the outbreak, the proportion of obligate saproxylic individuals in the beetle community was roughly 10% higher in forest damaged by the outbreak than in undamaged forest. This was mainly due to two early-successional saproxylic beetle species. Facultative saproxylic beetles showed no consistent differences between damaged and undamaged forest. These findings would suggest a weak numerical response of the saproxylic beetle community to the dead wood left by the outbreak. We suggest that species-specific preferences for certain wood decay stages may limit the number of saproxylic species that respond numerically to an outbreak at a particular time, and that increases in responding species may be constrained by limitations to the amount of dead wood that can be exploited within a given timeframe (i.e. satiation effects). Low diversity of beetle species or slow development of larvae in our cold sub-arctic study region may also limit numerical responses. Our study suggests that saproxylic beetles, owing to weak numerical responses, may so far have played a minor role in decomposing the vast quantities of dead wood left by the moth outbreak.