Impact of a mountain pine beetle outbreak on young lodgepole pine stands in Central British Columbia

Abstract

The current mountain pine beetle (MPB) (Dendroctonous ponderosae Hopkins) epidemic has severely affected pine forests of Western Canada and killed millions of hectares of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forest. Generally, MPB attack larger and older (diameter > 20 cm or > 60 years of age) trees, but the current epidemic extends this limit with attacks on even younger and smaller trees. The study's aim was to investigate the extent of MPB attack in young pine stands and its possible impact on stand dynamics. Although MPB attacks were observed in trees as small as 7.5 cm diameter at breast height (DBH) and as young as 13 years old, the degree of MPB attack (percent stems ha-1) increased with increasing tree diameter and age class (13-20, 21-40, 41-60, and 61-80 years old) (6.4%, 49.4%, 62.6%, and 69.5% attack, respectively, by age class) which is greater than that reported from previous epidemics for stands of this age. The mean density of surviving residual structure varied widely among age classes and ecological subzones. Depending on age class, 65% to 77% of the attacked stands could contribute to mid-term timber supply. The surviving residual structure of young stands offers an opportunity to mitigate the effects of MPB-attack on future timber supply, increase age class diversity, and enhance ecological resilience in younger stands.