Mountain Pine Beetle

ESSA, in cooperation with scientists and others of the USFS, spent several years developing the Westwide Pine Beetle Model (WWPBM), which simulates the impact of mountain pine beetle (Dendroctonus ponderosae Hopkins), western pine beetle (Dendroctonus brevicomis LeConte), and Ips spp. on western pine tree species. The model is a multi-stand, landscape-level model and operates as an extension of the FVS/Prognosis stand projection model coupled with the multi-stand FVS Parallel Processing Extension (PPE).

Simulation of MPB spread on the Chilcotin plateau
Map summaries of three 60 year simulation scenarios of an MPB outbreak on a 149,000 ha landscape around Tatla Lake, BC. The simulation of over 6,900 stands was made with PrognosisBC linked to the WWPBM and PPE extensions. The upper map shows the period of maximum volume loss under a base scenario. The outbreak spreads fairly evenly over the homogeneous landscape, beginning with the initial outbreak in 1976. The middle map shows a scenario in which the modeled landscape is embedded in an “outside world” that is an additional source and sink of MPB. In this case the epidemic shows a less orderly spread. The bottom map shows a scenario in which a severe winter kill in 1985 (and inclusion of an “outside world”) drives down the MPB until a much later time in the simulation. See Beukema and Robinson (2004) for more details.

The WWPBM simulates the contagion of beetles in a landscape, moving beetles between stands based on the current location of the beetles, the relative attractiveness of the stands in the landscape, and the assumed state of the unsimulated "outside world." Once beetles have been allocated to a stand, the model simulates the attack of trees within the stand based on the size, species, and vigor of the trees. Beetle levels in a stand in the following year are related to the amount of beetle-related mortality that occurred in the stand.

Under the assumption that stressed trees are often preferred by beetles, the WWPBM has rudimentary models to simulate the effects of root disease, stem rust, dwarf mistletoe, lightning, fire, windthrow, and climate. The primary effect of these other agents it to help attract beetles to a stand during dispersion.

The model has recently undergone some updates by the USFS, and is being made available in some western FVS variants.

Additional Information at Related Sites:
USDA Forest Service Westwide Pine Beetle Model site
Incorporating MPB impacts at the stand and landscape level

Mountain Pine Beetle Reports and Publications