Characteristics of forest legacies following two mountain pine beetle outbreaks in British Columbia, Canada

Abstract

Abstract:The mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera, Curculionidae), a native insect of North America, periodically reaches population sizes that cause serious economic impact to the forest industry in western North America. The most recent outbreak in British Columbia (BC), Canada, which began in the late 1990s, is only now (2015) abating, after causing unprecedented tree mortality in lodgepole pine (Pinus contorta Douglas ex. Loudon) forests. In this paper, we make use of permanent research plots to report on the condition of lodgepole pine forests in the Chilcotin Plateau of central BC, which underwent two fully documented mountain pine beetle outbreaks. In this region, the first outbreak started in the late 1970s and lasted until the mid-1980s; the second outbreak began in the early 2000s and ended in 2010. We measured the impacts of these outbreaks in terms of tree mortality and describe the characteristics of the legacies that remain following these outbreaks, including survivors in various canopy layers and levels of existing and new regeneration. We provide evidence in support of the existence of postdisturbance legacies that classify into five distinct stand structure types. Abundant regeneration and surviving intermediate canopy layers in most stands indicate that management actions to restock pine stands in this area will not likely be necessary. The information provided by this study is important for estimating future forest development and timber supply and for forest planning and management.Key words: mountain pine beetle, forest disturbance, forest dynamics.Résumé : L'explosion périodique des populations de dendroctone du pin ponderosa, Dendroctonus ponderosae Hopkins (Coléoptères, Curculionidées), un insecte indigène de l'Amérique du Nord, a de sérieux impacts économiques sur l'industrie forestière dans l'ouest de l'Amérique du Nord. L'épidémie la plus récente en Colombie-Britannique (C.-B.), qui a débuté à la fin des années 1990, commence seulement maintenant (2015) à régresser après avoir causé une mortalité sans précédent dans les forêts de pin tordu (Pinus contorta Douglas ex Loudon). Dans cet article, nous avons utilisé des placettes permanentes de recherche pour produire un rapport sur l'état des forêts de pin tordu sur le plateau Chilcotin dans le centre de la C.-B. qui ont subi deux épidémies bien documentées de dendroctone du pin ponderosa. Dans cette région, la première épidémie a débuté à la fin des années 1970 et s'est poursuivie jusqu'au milieu des années 1980; la seconde épidémie a débuté au début des années 2000 pour se terminer en 2010. Nous avons mesuré les impacts de ces épidémies en termes de mortalité des arbres et nous décrivons les caractéristiques des répercussions qui persistent à la suite de ces épidémies, incluant les survivants dans différentes strates du couvert forestier ainsi que les niveaux de régénération, nouvelle et existante. Nous apportons des preuves à l'appui de l'existence de répercussions des perturbations qui auraient engendré ci...

Use and selection at two spatial scales by female moose (alces alces) across central British Columbia following a mountain pine beetle outbreak

“…Balsom et al (1996) hypothesized that the removal of mature cover would lead to lower moose densities because of lower forage availability and malnutrition. In our study, moose selection for the Pine cover class did not decrease as cover quality declined (in response to canopy die-off after MPB), perhaps because blowdown provided lateral cover and restricted access by hunters and predators, and there was more preferred regenerating browse (Timmermann and McNicol 1988, Rempel et al 1997, Alfaro et al 2015. Salvage logging in central BC removed the Pine cover class, which may be important for moose as a source of cover and forage, and therefore could leave moose more vulnerable by creating large forest clearings.…”

“…Our results emphasize that female moose utilize forest cover, heterogeneous landscapes, and areas with browse abundance in large clearcut landscapes. Other researchers have shown that following large-scale bark beetle outbreaks, without the intervention of clear-cutting practices, forests maintain heterogeneity in vertical and horizontal structure, diversity of understory species, and high stocking standards (Alfaro et al 2015, Winter et al 2015). Our work also highlights that if clear-cutting of MPB-killed pine stands continues in these study areas, the effective carrying capacity of the landscape for female moose may continually decrease if forest harvesting occurs at a rate that exceeds the regrowth of forestry plantations that produce adequate moose habitat.…”

“…They do, however, represent the relative weight of selection or avoidance of area under the receiver-operating curve (ROC), and k-fold cross validation value. Model numbers are described in Table 3 A large-scale MPB outbreak significantly changed the landscape in a short time, followed by high intensity salvage logging (Alfaro et al 2015) in all three study areas (Appendix E), but the landscapes and proportions of the landscape harvested differed.…”

“…Pine forests that were not cut following the MPB outbreak are highly utilized by female moose. I propose leaving the remaining MPB-killed Pine stands intact as they maintain forest heterogeneity in vertical and horizontal structure, diversity of understory species, and high stocking standards (Alfaro et al 2015, Winter et al 2015. I believe if forest harvesting of MPB-killed Pine stands continues in these study areas, moose populations will continue to decline as the rate of deforestation greatly exceeds the regrowth needed to provide adequate moose habitat.…”

“…We examined home-range (HR) selection of female moose (Alces alces) in three landscapes differing in disturbance intensities 15 years after a mountain pine beetle (Dendroctonus ponderosae; MPB) outbreak in central British Columbia (BC; Alfaro et al 2015). Our objectives were to test a landscape-change hypothesis (Kuzyk and Heard 2014) by: determining if selection of HRs by female moose differed in relation to the intensity of MPB salvage and associated logging operations; and determining if movement rates and seasonal HR size differed by study area.…”