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R.A Fleming et al. 2010. Forest management and climate, through landscape structure, affect the potential for insect outbreak
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Forest management and climate, through landscape structure, affect
the potential for insect outbreak
Richard A Fleming 1* , Allan L. Carroll 2 , Jean-Noël Candau 1 & Philippe Dreyfus 3
1 Canadian Forest Service, Natural Resources Canada, P.O. Box 490, Sault Ste. Marie,
P6A 4C8, Canada
2 Department of Forest Sciences, Faculty of Forestry, University of British Columbia,
2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
3 Institut National de la Recherche Agronomique (INRA), Recherches Forestières
Méditerranéennes (Mediterranean Forest Research), Avenue A. Vivaldi, 84000,
Avignon, France
Abstract
The mountain pine beetle (MPB) is endemic to western North American pine forests and is
currently causing a very destructive outbreak in western Canada. Historically, expansion further
north and east was limited by mountains and winter cold, but during recent warm winters the
insect crossed the mountains and it now threatens Canada’s eastern forests.
This concern has motivated our study of how landscape structure affects outbreak development
and spread. As part of this study, we describe a model of MPB-stand dynamics. Based on recent
field work, the model includes a threshold at low density which the local beetle population must
overcome to become eruptive. We show how, from the MPB perspective, landscape structure
responds to climate and forest management and has strong, indirect affects on the likelihood of
eruption. We discuss the recent under-estimation of MPB spread in Alberta by much more
complex models.
Keywords: mountain pine beetle, stand density management diagram, Dendroctonus
ponderosae, forest landscape structure, outbreak spread
1. Introduction
Besides timber, healthy forests provide a variety of non-timber products and many ecosystem
services including maintenance of biodiversity, clean water, and carbon storage. In Canada’s
forests, change comes primarily in the form of "disturbances". Disturbances occur in many
forms (e.g., storms, fire, insects, disease, and logging) and over a wide range of scales (Ayres
and Lombardero 2000; Dale et al. 2001). Disturbances leave ecological legacies which
determine future species composition, age structure, and spatial heterogeneity of the area
(Radeloff et al. 2000) and consequently, facilitate or impede the occurrence of future
disturbances (Kulakowski et al. 2003).
Insects are the most diverse class of organisms on earth and the major natural cause of depletion
from Canada’s forest productivity. Past outbreaks have engulfed extensive areas (Volney and
Fleming 2000). Canada’s western forests are now experiencing “the largest insect outbreak in
* Corresponding author.
Email address: rfleming@nrcan.gc.ca
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.