Evidence against planting lodgepole pine monocultures in the cedar-hemlock forests of southeastern British Columbia

Abstract

Single-species planting of lodgepole pine (Pinus contorta var. latifolia) following clear-cut logging or wildfire has been common throughout interior British Columbia, Canada, but health problems with the species have been documented as it grows beyond the juvenile stage. We examined damage and stocking in twenty-seven 15to 30-yearold lodgepole pine plantations that were previously declared free growing in the highly productive cedar–hemlock forests in southeastern British Columbia, where lodgepole pine is absent from many primary forests. In order to be free growing, stands must meet minimum tree density, height, damage and brush competition criteria as legislated by the Provincial government. Overall, 44 per cent of lodgepole pine trees had unacceptable damage (causing them to be rejected as crop trees), and as a direct result, one-third of the plantations were no longer defined as free growing because there were insufficient crop trees remaining. Natural regeneration of other tree species partially compensated for the unhealthy pine. Logistic regression and odds ratio analysis associated increasing risk of damage from western gall rust with increasing soil moisture, more northerly aspects and mechanical site preparation, and decreasing risk with pre-commercial thinning treatment. Risk of damage from snow and ice was associated with increasing mean annual precipitation, decreasing longitude and broadcast burning. Risk of bear damage was associated with increasing soil moisture, pre-commercial thinning treatment and broadcast burning. Based on our results, we recommend that single-species planting of lodgepole pine be curtailed in the Interior Cedar–Hemlock zone in southeastern British Columbia.