Canadian Forest Service Publications

A multi-scale analysis of western spruce budworm outbreak dynamics. 2017. Senf, C., Campbell, E.M., Pflugmacher, D., Wulder, M.A., Hostert, P. Landscape Ecology. Vol. 32, pp. 501–514.

Year: 2017

Available from: Pacific Forestry Centre

Catalog ID: 39003

Language: English

CFS Availability: PDF (download)

Available from the Journal's Web site.
DOI: 10.1007/s10980-016-0460-0

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Abstract

Context - Forest insect outbreaks are influenced by ecological processes operating at multiple spatial scales, including host-insect interactions within stands and across landscapes that are modified by regional-scale variations in climate. These drivers of outbreak dynamics are not well understood for the western spruce budworm, a defoliator that is native to forests of western North America. Objectives - Our aim was to assess how processes across multiple spatial scales drive western spruce budworm outbreak dynamics. Our objective was to assess the relative importance and influence of a set of factors covering the stand, landscape, and regional scales for explaining spatiotemporal outbreak patterns in British Columbia, Canada. Methods - We used generalized linear mixed effect models within a multi-model interference framework to relate annual budworm infestation mapped from Landsat time series (1996–2012) to sets of stand-, landscape-, and regional-scale factors derived from forest inventory data, GIS analyses, and climate models. Results - Outbreak patterns were explained well by our model (R2 = 93%). The most important predictors of infestation probability were the proximity to infestations in the previous year, landscape-scale host abundance, and dry autumn conditions. While stand characteristics were overall less important predictors, we did find infestations were more likely amongst pure Douglas-fir stands with low site indices and high crown closure. Conclusions - Our findings add to growing empirical evidence that insect outbreak dynamics are driven by multi-scaled processes. Forest management planning to mitigate the impacts of budworm outbreaks should thus consider landscape- and regional-scale factors in addition to stand-scale factors.

Plain Language Summary

Forest insect outbreaks are influenced by ecological processes operating at multiple spatial scales, including host-insect interactions within stands and across landscapes that are modified by regional-scale variations in climate. These drivers of outbreak dynamics are not well understood for the western spruce budworm Landscape- to regional-scale variations in climate and forest composition/structure are important drivers of insect outbreak dynamics. Regional weather variability, in particular moisture deficits, governs budworm population dynamics through synchronizing budworm and host phenology and through determining the quantity and quality of food. Weather variability can thus trigger and synchronize the eruption of localized outbreaks Our aim was to assess how processes across multiple spatial scales drive western spruce budworm outbreak dynamics. Our objective was to assess the relative importance and influence of a set of factors covering the stand, landscape, and regional scales for explaining spatiotemporal western spruce budworm outbreak patterns in British Columbia, Canada.

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