This study is part of a series of research papers that explore the biological, social, and economic aspects of British Columbia's mountain pine beetle epidemic. The objective of this study is to compare two different approaches for calculating beetle pressure, and to assess the impact these approaches have on the subsequent calculation of risk ratings. To meet this objective, beetle pressure was calculated using the traditional distance-based model, as well as using an alternative density-based model, implemented with a Voronoi tessellation generated from helicopter-GPS point survey data of known beetle infestation locations.--Includes text from document.

Two empirical methods for rating susceptibility of mountain pine beetle attack in ponderosa pine were evaluated. The methods were compared to stand data modeled to objectively rate each sampled stand for susceptibly to bark-beetle attack. Data on bark-beetle attacks, from a survey of 45 sites throughout the Colorado Plateau, were modeled using logistic regression to estimate the probability of attack on individual trees from tree and stand variables. The logistic model allowed flexibility to easily scale results up to a stand level for comparison to the empirical methods. The empirical method, developed by Munson and Anhold, most closely correlated to the logistic regression results. However, the Munson/Anhold method rated all 45 study sites as either moderately or highly susceptible to bark-beetle attack, which raises concern about its lack of sensitivity. Future work on evaluating risk of bark-beetle impact should consider more than stand characteristics.

In western Canada, the operational risk rating system for mountain pine beetle is based on biological knowledge gained from a rich legacy of stand-scale field studies. Owing to the large spatial and temporal extents of the current epidemic, new research into large-area mountain pine beetle processes has revealed further insights into the landscape-scale characteristics of beetle infested forests. This research evaluates the potential for this new knowledge to augment an established system for rating the short-term risk of tree mortality in a stand due to mountain pine beetle.--Publisher's website.