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Stump extraction in the surrounding landscape: Predatory saproxylic beetles are more negatively affected than lower trophic levels

Ranlund, Åsa, Victorsson, Jonas
Forest ecology and management 2018 v.408 pp. 75-86
Coleoptera, bark, biofuels, clearcutting, dead wood, forest management, forests, habitat destruction, harvesting, landscapes, long term effects, monitoring, predators, sieving, stump extraction, stumps, trophic levels, Sweden
To harvest more biofuel from forests, tree stumps are sometimes extracted after clearcutting. Species in different organism groups rely on deadwood, and biofuel extraction reduces their substrate. Our aim was to investigate the potential landscape effects of stump extraction, and compare the effects among trophic levels of deadwood-dependent (saproxylic) beetles. We sampled saproxylic beetle species in clearcut stumps using bark sieving. We did the study in 2013 in 49 clearcuts (1–4 years old) in three regions in central Sweden where stump extraction had been performed for six years prior to sampling. We selected landscape buffers with 500 m, 1000 m, and 2000 m radius with different intensities of stump extraction (0–100%). We show for the first time, based on empirical data, that increasing stump extraction can affect deadwood-dependent species at the landscape level. On average, obligate predators were more negatively affected than cambivores and facultative predators. The 34 studied saproxylic beetle species showed varied responses to stump extraction in the surrounding landscape, including stable (no response), negative, or positive responses. Positive responses could be due to a crowding effect, indicating a time-lagged response to habitat loss. Since stump extraction in the study area started just six years prior to sampling, time-lags in population-level responses could be expected. The age of the sampled clearcuts influenced the abundance of eleven species, but other local factors had little effect on abundance.Our results suggest that if stump extraction is widely introduced, deadwood retention—planned for both spatial and temporal continuity—should be an integrated part of intensified forest management. We suggest monitoring the long-term effects of stump extraction.