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Open AccessArticle

Landscape Topoedaphic Features Create Refugia from Drought and Insect Disturbance in a Lodgepole and Whitebark Pine Forest

U.S. Geological Survey, Lower Mississippi-Gulf Water Science Center, 640 Grassmere Park, Suite 100, Nashville, TN 37211, USA
Forests 2018, 9(11), 715; https://doi.org/10.3390/f9110715
Received: 24 October 2018 / Revised: 14 November 2018 / Accepted: 16 November 2018 / Published: 18 November 2018
(This article belongs to the Special Issue Ecology and Restoration of Whitebark Pine)
Droughts and insect outbreaks are primary disturbance processes linking climate change to tree mortality in western North America. Refugia from these disturbances—locations where impacts are less severe relative to the surrounding landscape—may be priorities for conservation, restoration, and monitoring. In this study, hypotheses concerning physical and biological processes supporting refugia were investigated by modelling the landscape controls on disturbance refugia that were identified using remotely sensed vegetation indicators. Refugia were identified at 30-m resolution using anomalies of Landsat-derived Normalized Difference Moisture Index in lodgepole and whitebark pine forests in southern Oregon, USA, in 2001 (a single-year drought with no insect outbreak) and 2009 (during a multi-year drought and severe outbreak of mountain pine beetle). Landscape controls on refugia (topographic, soil, and forest characteristics) were modeled using boosted regression trees. Landscape characteristics better explained and predicted refugia locations in 2009, when forest impacts were greater, than in 2001. Refugia in lodgepole and whitebark pine forests were generally associated with topographically shaded slopes, convergent environments such as valleys, areas of relatively low soil bulk density, and in thinner forest stands. In whitebark pine forest, refugia were associated with riparian areas along headwater streams. Spatial patterns in evapotranspiration, snowmelt dynamics, soil water storage, and drought-tolerance and insect-resistance abilities may help create refugia from drought and mountain pine beetle. Identification of the landscape characteristics supporting refugia can help forest managers target conservation resources in an era of climate-change exacerbation of droughts and insect outbreaks. View Full-Text
Keywords: Dendroctonus ponderosae; drought; forest disturbance; lodgepole pine; mountain pine beetle; Pinus albicaulis Engelm.; Pinus contorta Dougl. ex. Loud.; refugia; whitebark pine Dendroctonus ponderosae; drought; forest disturbance; lodgepole pine; mountain pine beetle; Pinus albicaulis Engelm.; Pinus contorta Dougl. ex. Loud.; refugia; whitebark pine
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Cartwright, J. Landscape Topoedaphic Features Create Refugia from Drought and Insect Disturbance in a Lodgepole and Whitebark Pine Forest. Forests 2018, 9, 715.

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