Associations of secondary bark beetles with dying and live lodgepole pine in the post-outbreak phase of mountain pine beetle, Dendroctonus ponderosae (Hopkins), in the central interior of British Columbia, Canada.

Abstract

The author has granted a non exclusive license allowing Library and Archives Canada to reproduce, publish, archive, preserve, conserve, communicate to the public by telecommunication or on the Internet, loan, distrbute and sell theses worldwide, for commercial or non commercial purposes, in microform, paper, electronic and/or any other formats. AVIS: L'auteur a accorde une licence non exclusive permettant a la Bibliotheque et Archives Canada de reproduire, publier, archiver, sauvegarder, conserver, transmettre au public par telecommunication ou par I'lnternet, preter, distribuer et vendre des theses partout dans le monde, a des fins commerciales ou autres, sur support microforme, papier, electronique et/ou autres formats. Bien que ces formulaires aient inclus dans la pagination, il n'y aura aucun contenu manquant. Canada Dendroctonus ponderosae (Hopkins) or mountain pine beetle is a native bark beetle (Coleoptera: Curculionidae: Scolytinae) that feeds on more than 20 species of pine in western North America. In British Columbia, its principal host is lodgepole pine (Pinus contorta var. latifolia Engelmann). As a "primary" bark beetle, D. ponderosae kills its host at epidemic stages, exerting profound landscape-level mortality. As of 2012, D. ponderosae has caused the loss of 726 million cubic meters of timber, covering an area of 17.5 million hectares of mature pine forest in British Columbia and Alberta. Small diameter hosts are not suitable for D. ponderosae, however, creating a niche for the "secondary" bark beetles, including Ips pini (Say), Pseudips mexicanus (Hopkins), and Orthotomicus latidens (LeConte). At the post-epidemic stage of D. ponderosae, we found the rate of new mortality was approximately 4%, which 1% of the mortality was associated with a complex of secondary bark beetles, and not D. ponderosae, as the principal mortality agent in those stands. This finding suggests that at high population densities, secondary bark beetles are potential mortality agents of residual pines, sustaining the apparent outbreak of D. ponderosae by killing smaller diameter trees, with the highest rate of mortality among younger stands.