Impacts and Susceptibility of Young Pine Stands to the Mountain Pine Beetle, Dendroctonus Ponderosae in British Columbia

Abstract

The impact of mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytinae), is the most significant source of mortality of mature pine forests in western North America; however, in 2003-2004, high levels of mortality were observed in young pine stands in central British Columbia. This study investigagtes the impact of mountain pine beetle in these young pine stands. In 2005 and 2006, 24 plots were established throughout the mountain pine beetle-affected area of British Columbia. Cumulative mortality reached 83% in some plots. Secondary bark beetles and other pests contributed to overall stand mortality and decline but to a far lesser degree than mountain pine beetle. Stem deterioration and falldown was very rapid and severe in young stands following attack. Over 70% of attacked trees in the Sub-Boreal Spruce ecosystem were severely deteriorated, or had fallen less than 5 years after attack. The largest pines in young stands were attacked first, and brood production and emergence in these trees was more successful than in smaller, younger cohorts. Many attached stands had received silvicultural treatments. Once the outbreak in adjacent mature stands had subsided, very little new attack occurred in these young stands. Brood production was successful, albeit lower in young trees than in mature trees.