Probability of ponderosa pine infestation by mountain pine beetle in the Colorado Front Range

• Published in: Forest ecology and management 2004-04, Vol.191 (1), p.17-27
• Main Authors: Negrón, José F, Popp, John B
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Bark beetles; basal area; Biological and medical sciences; Dendroctonus ponderosae; forest pests; forest trees; Forestry; Fundamental and applied biological sciences. Psychology; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; host plants; infestation; insect pests; montane forests; Mountain pine beetle; pest outbreaks; Pinus ponderosa; Ponderosa pine; simulation models; stand density; Synecology; Terrestrial ecosystems; tree and stand measurements; tree classes
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2003.10.026

Insect-caused tree mortality, fires, and pathogens are primary disturbance agents in forest ecosystems. The mountain pine beetle, Dendroctonus ponderosae Hopkins, is a bark beetle that can cause extensive mortality in ponderosa pine, Pinus ponderosa Lawson, along the Colorado Front Range. Despite the history of outbreaks of this insect in Colorado, no models have been developed to estimate the probability of infestation. Thirty-five clusters of one infested and three baseline plots were established from 1998 to 2000 in the Arapaho-Roosevelt National Forest in north-central Colorado to develop empirical models of probability of infestation based on forest conditions. Mountain pine beetle-infested plots exhibited higher basal area and stand density index (SDI) for ponderosa pine and for all tree species combined, and higher number of ponderosa pine trees per hectare. Within infested plots, infested trees were larger in diameter at breast height and in the dominant and co-dominant crown positions. A classification tree model indicated that the likelihood of infestation by mountain pine beetle is 0.71 when ponderosa pine basal area is >17.1 m 2/ha at the stand level. A second plot-level model indicated that the probability of infestation increased with increasing ponderosa pine SDI, ponderosa pine quadratic mean diameter, and total basal area. For individual trees within infested plots the likelihood of infestation was 0.77 for dominant or co-dominant trees >18.2 cm in diameter at breast height. Results are consistent with other studies that have documented increased likelihood of infestation or enhanced mortality levels or both as a result of higher host type stocking. The simple models developed should help to guide silvicultural treatments and restoration efforts by establishing stocking levels below which mountain pine beetle-caused mortality is less likely, particularly in the dry sites and poor growing conditions characteristic of the Colorado Front Range.