Mountain pine beetle dispersal: spatiotemporal patterns and role in the spread and expansion of the present outbreak

Abstract

Abstract. Dispersal has been least understood in mountain pine beetle ecology. We developed a novel regional dynamic conceptual model of mountain pine beetle infestation using the tree mortality estimated from the British Columbia annual aerial overview survey to quantitatively determine short-distance dispersal (SDD) and long-distance dispersal (LDD) at local (forest district) and regional (provincial) scales. The dispersal patterns were characterized based on distances between a sink patch to its nearest source patch. At the regional scale, SDD accounted for 85.3% of mountain pine beetle dispersal to non-infested areas and 96.8% of beetle dispersal to infested areas. Although SDD was a dominant dispersal mode, LDD played a more important role in the early stage of the current mountain pine beetle outbreak. At the local scale, three patterns of dispersal to non-infested areas were identified. First, LDD dominated in the forest districts where only sparse infestations occurred. Second, LDD was a dominant or important factor in the early stages of the infestations in some districts. Third, SDD dominated throughout the infestations in more severely infested forest districts. However, for dispersal to infested areas, SDD was a dominant mode in most of the forest districts. We conclude from the spatiotemporal patterns of dispersal observed at local and regional scales that LDD is a key factor in the initiation and early stage of the infestations in new remote areas, and SDD dominate in the spread and expansion of the outbreak as the infestations intensify and reach epidemic levels. However, it should be conscious that there is uncertainty that LDD might have been over emphasized in the dispersal before local dynamics is fully taken into account.

Pest and Disease Management: Why We Shouldn't Go against the Grain

“…In recent years, changes in forest demography and favorable weather conditions have opened the door to outbreak conditions, and the mountain pine beetle has become one of the most damaging of all forest–disturbance agents in the United States [28], [29]. Mountain pine beetles generally disperse over short distances (∼50 m) within the forest canopy [30] and the D. ponderosae model was based on Eq. 1 with a two–dimensional Gaussian dispersal kernel (Eq.…”

“…This kernel has been used previously to simulate within-canopy dispersal of this and other species of bark beetle [29], [31]. The model was parameterized using empirically derived values from the literature for the density of beetles per host area, ρ  = 59.4 m −2 [29], and the dispersal kernel spread parameter, α  = 56 m, giving a mean dispersal distance of 50 m [30]. We considered a single generation of dispersal (a single redistribution event) where we summed the total number of beetles arriving at each host area from every other host area in the landscape; those redistributed to non-host areas were lost from the system.…”

Geographically variable response of Dendroctonus ponderosae to winter warming in the western United States

“…Some modifications to the ecoregion boundaries were made so that their boundaries closely approximated the geographic extent of interbreeding populations of D. ponderosae. Relatively large ecoregions (e.g., Coast Range, Middle Rockies, North Rockies, and Southern Rockies) were subdivided into separate regions based upon the underlying pine forest distribution and topographic features (e.g., river canyons, deserts, and mountains) known to affect movement of D. ponderosae populations (Mock et al 2007;Chen and Walton 2011;Gayathri Samarasekera et al 2012). For example, we created five subregions from the Ecoregion Level III classification of ''Middle Rockies'' to correspond to geographically distinct, forested areas (i.e., Black Hills, Big Horn mountains, Central mountains, Yellowstone Ecosystem, and the western Montana mountains) (Fig.…”

Dispersal Patterns of Pine Wilt Disease in the Early Stage of Its Invasion in South Korea

“…Generally, invertebrates display a stratified dispersal based on the combination of long distance dispersal (LDD) and short distance dispersal (SDD) [5]. There are many examples of stratified dispersal including gypsy moth (L. dispar) [6], Argentine ant (Linepithema humile) [7], and mountain pine beetle (Dendroctonus ponderosae) [8].…”