Table of Contents
ISRN Forestry
Volume 2013, Article ID 542380, 10 pages
http://dx.doi.org/10.1155/2013/542380
Research Article

Spatial Dispersal of Douglas-Fir Beetle Populations in Colorado and Wyoming

1Anadarko Industries, LLC, 500 Dallas, Suite 2750, Houston, TX 77002, USA
2USDA Forest Service, Rocky Mountain Research Station, 240 West Prospect Road, Fort Collins, CO 80525, USA
3Softec Solutions, Inc., 384 Inverness Parkwy, Ste 211, Englewood, CO 80112, USA
4USDA-FS Forest Health Technology Enterprise Team, NRRC Building A, Suite 331, 2150 Centre Avenue, Fort Collins, CO 80526, USA
5USDA Forest Service, Region 10 Forest Health Protection and Pacific Northwest Research Station, 3301 C Street, Suite 202 Anchorage, AK 99503, USA

Received 1 October 2012; Accepted 10 December 2012

Academic Editors: D. Huber and G. Martinez Pastur

Copyright © 2013 John R. Withrow et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Bark beetles (Coleoptera: Curculionidae: Scolytinae) are mortality agents to multiple tree species throughout North America. Understanding spatiotemporal dynamics of these insects can assist management, prediction of outbreaks, and development of “real time” assessments of forest susceptibility incorporating insect population data. Here, dispersal of Douglas-fir beetle (Dendroctonus pseudotsugae Hopk.) is estimated over four regions within Colorado and Wyoming from 1994 to 2010. Infestations mapped from aerial insect surveys are utilized as a proxy variable for Douglas-fir beetle (DFB) activity and analyzed via a novel GIS technique that co-locates infestations from adjacent years quantifying distances between them. Dispersal distances of DFB infestations were modeled with a cumulative Gaussian function and expressed as a standard dispersal distance (SDD), the distance at which 68% of infestations dispersed in a given flight season. Average values of SDD ranged from under 1 kilometer for the region of northwestern Colorado to over 2.5 kilometers for infestations in Wyoming. A statistically significant relationship was detected between SDD and infestation area in the parent year, suggesting that host depletion and density-dependent factors may influence dispersal. Findings can potentially provide insight for managers—namely, likelihood of DFB infestation increase for locations within two to five kilometers of an existing infestation.