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Impact of Forest Fragmentation on Patterns of Mountain Pine Beetle-Caused Tree Mortality
Department of Geography, University of Oregon, Eugene, OR 97403, USA
Canadian Forest Service (Pacific Forestry Centre), Natural Resources Canada,506 West Burnside Road, Victoria BC V8Z 1M5, Canada
Department of Geography & Environmental Studies, Wilfrid Laurier University,75 University Avenue West, Waterloo ONT N2L 3C5, Canada
Spatial Pattern Analysis & Research (SPAR) Laboratory, Department of Geography,University of Victoria, P.O. Box 3060, Victoria BC V8W 3R4, Canada
* Author to whom correspondence should be addressed.
Received: 1 March 2013; in revised form: 10 April 2013 / Accepted: 17 April 2013 / Published: 29 April 2013
Abstract: The current outbreak of mountain pine beetle, Dendroctonus ponderosae Hopkins, has led to extensive tree mortality in British Columbia and the western United States. While the greatest impacts of the outbreak have been in British Columbia, ongoing impacts are expected as the outbreak continues to spread eastward towards Canada’s boreal and eastern pine forests. Successful mitigation of this outbreak is dependent on understanding how the beetle’s host selection behaviour is influenced by the patchwork of tree mortality across the landscape. While several studies have shown that selective mechanisms operate at the individual tree level, less attention has been given to beetles’ preference for variation in spatial forest patterns, namely forest fragmentation, and if such preference changes with changing population conditions. The objective of this study is to explore the influence of fragmentation on the location of mountain pine beetle caused mortality. Using a negative binomial regression model, we tested the significance of a fragmentation measure called the Aggregation Index for predicting beetle-caused tree mortality in the central interior of British Columbia, Canada in 2000 and 2005. The results explain that mountain pine beetle OPEN ACCESS Forests 2013, 4 280 exhibit a density-dependent dynamic behaviour related to forest patterns, with fragmented forests experiencing greater tree mortality when beetle populations are low (2000). Conversely, more contiguous forests are preferred when populations reach epidemic levels (2005). These results reinforce existing findings that bark beetles exhibit a strong host configuration preference at low population levels and that such pressures are relaxed when beetle densities are high.
Keywords: mountain pine beetle; forest fragmentation; density dependent; insect outbreak
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Bone, C.; White, J.C.; Wulder, M.A.; Robertson, C.; Nelson, T.A. Impact of Forest Fragmentation on Patterns of Mountain Pine Beetle-Caused Tree Mortality. Forests 2013, 4, 279-295.
Bone C, White JC, Wulder MA, Robertson C, Nelson TA. Impact of Forest Fragmentation on Patterns of Mountain Pine Beetle-Caused Tree Mortality. Forests. 2013; 4(2):279-295.
Bone, Christopher; White, Joanne C.; Wulder, Michael A.; Robertson, Colin; Nelson, Trisalyn A. 2013. "Impact of Forest Fragmentation on Patterns of Mountain Pine Beetle-Caused Tree Mortality." Forests 4, no. 2: 279-295.