Colonisation, par les coléoptères phloéophages et xylophages, de sapins baumiers défoliés par l'arpenteuse de la pruche

Authors: Béland, Jean-Michel
Advisor: Bauce, ÉricCloutier, ConradHébert, Christian
Abstract: The aim of this study was to characterise the impact of a hemlock looper outbreak, in the balsam fir-white birch forest, on the community of primary saproxylic beetles. To this end, we first compared different approaches in order to determine which of them could profile easily and efficiently the defoliation status of the trees affected by the hemlock looper. Then, the early response of the phloeo- and xylophagous beetles was assessed with flight-interception multidirectional and trunk-window traps along with emergence cages. Results show that an upper crown overall estimation method is optimal to determine the defoliation status of the balsam fir following hemlock looper. They as well show that a change in the beetle assemblage occurred only in 2014 and in the most defoliated stands. An assemblage characterised by polyphagous species often associated to undisturbed forests shifted to the predominance of a xylomycetophagous and dying conifer feeder: the striped ambrosia beetle. This scolytid alone was positively associated with the increase of defoliation and death of balsam firs but also with the presence of salvage logging nearby the study plots. Results have then showed a dichotomic response of the beetle, thus exhibiting massive colonization only when fir trees reached 95% of defoliation. At last, the flight-interception traps were found to be useful to detect variations in beetle visit frequencies of stands and trees along the defoliation gradient. The striped ambrosia beetle is therefore the first and almost the only saproxylic to initiate the decomposition process of post-hemlock looper firs trees two years after the detection of the outbreak. However, this colonization may raise concerns because its fungal symbiont stains the galleries throughout the sapwood of infested trees.
Document Type: Mémoire de maîtrise
Issue Date: 2017
Open Access Date: 24 April 2018
Grantor: Université Laval
Collection:Thèses et mémoires

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