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Modelling the predisposition of Norway spruce to Ips typographus L. infestation by means of environmental factors in southern Finland


New measures for effective monitoring and controlling of bark beetle infestations are needed as a response to intensified outbreaks caused by the climate change. Various environmental factors affect tree health and susceptibility, as well as stand predisposition to bark beetles. European spruce bark beetle Ips typographus L. abundance and outbreak frequency in Finland has significantly increased during the last decade. The ability to identify sites under a high risk of infestation would facilitate adaptation to this new situation and help target limited forest health management resources. Accordingly, our goal was to investigate the importance of various stand, soil and topographic characteristics in the assessing predisposition of Norway spruce dominated urban forest in southern Finland to I. typographus infestations. Information on the environmental factors was assessed in the field in 2014 and derived from a digital elevation model. Ips typographus infestation intensity was classified into three infestation index classes based on tree-wise symptoms of resin flow, discoloration and defoliation. Cumulative logit link models were utilized for investigating stand-level infestation probability. The best explanatory factors were aspect, slope, site type and soil texture. Models with the highest cumulative probabilities for severe infestation were linked with eastern aspect, moderate steep slope and rich site type fertility (0.72) and eastern aspect, shallow soil and rich site type fertility (0.71). Higher soil C/N ratios with east aspect and rich site type fertility was associated with an increased risk of severe infestation in a third model. The lowest risk was associated with southern and southwestern aspects, fine soil texture, moderate site fertility and gentle slopes.

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This study was funded by Maj and Tor Nessling Foundation, Niemi Foundation, the Finnish Society of Forest Sciences and the Finnish Cultural Foundation. Many thanks are due to Anna-Maaria Särkkä, head of the forestry unit of the city of Lahti, for her cooperation. In addition, we would like to express our thanks to Raimo Asikainen, former head of the forestry unit of the city of Lahti, who enabled an onset of the study. We wish to thank Jarkko Isotalo for statistical advice and Sini Keinänen for her help in the field and laboratory. In addition, we thank Elina Peuhu and the three anonymous reviewers for their comments in improving the paper.

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Correspondence to Minna Blomqvist.

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The authors declare that they have no conflict of interest.

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Communicated by Claus Bässler.

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Blomqvist, M., Kosunen, M., Starr, M. et al. Modelling the predisposition of Norway spruce to Ips typographus L. infestation by means of environmental factors in southern Finland. Eur J Forest Res 137, 675–691 (2018).

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  • Cumulative link model
  • European spruce bark beetle
  • Infestation risk
  • Norway spruce
  • Soil properties
  • Topography