Site preparation can improve lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) survival and growth; however, we lack information regarding possible interactions between treatment effects and the impacts of western gall rust (Endocronartium harknessii (J.P. Moore) Y. Hirats.) and comandra blister rust (Cronartium comandrae Peck). Mechanical and burning techniques examined over 24 years at a sub-boreal British Columbia site did not significantly increase rust infection rates or characteristics relative to an untreated control. Most infection occurred before age 10 years and at heights <2 m. By age 24 years, 22% and 10% of pine had sustained at least one western gall rust or comandra blister rust stem infection, respectively, but only 4% of western gall rust infected trees were dead, compared with 60% of comandra blister rust infected trees. Exploratory regression analysis of the relationship between tree volume and percent stem encirclement and infection height suggested that volume of 24-year-old pine infected with western gall rust averaged 8% less than the corresponding volume of uninfected trees. Over 24 years, estimated stand-level, rust-related volume loss was 8.4%, with the majority due to mortality from comandra blister rust. One-fifth of estimated volume loss was provisionally attributed to growth reductions among live western gall rust infected pine.Résumé : La préparation de terrain peut améliorer la survie et la croissance du pin tordu latifolié (Pinus contorta var. latifolia Engelm. ex S. Watson) mais nous manquons d'information concernant les interactions potentielles entre les effets des traitements et les impacts de la rouille-tumeur autonome (Endocronartium harknessii (J.P. Moore) Y. Hirats.) et de la rouille-tumeur oblongue (Cronartium comandrae Peck). Les méthodes mécaniques et les techniques de brûlage étudiées depuis 24 ans dans une station subboréale de la Colombie-Britannique n'ont pas significativement augmenté les taux d'infection de la rouille ni les caractéristiques relatives au témoin non traité. La plupart des infections sont survenues avant l'âge de 10 ans à des hauteurs <2 m. À l'âge de 24 ans, respectivement 22 % et 10 % des pins avaient été infectés au moins une fois sur le tronc par la rouille-tumeur autonome ou la rouille-tumeur oblongue mais seulement 4 % des arbres infectés par la rouille-tumeur autonome étaient morts comparativement à 60 % des arbres infectés par la rouille-tumeur oblongue. Une analyse de régression exploratoire de la relation entre le volume des arbres, le pourcentage d'encerclement et la hauteur de l'infection a indiqué que le volume des pins âgés de 24 ans et infectés par la rouille-tumeur autonome était en moyenne 8 % plus faible que le volume correspondant des arbres sains. Sur une période de 24 ans, la perte de volume due à la rouille à l'échelle du peuplement a atteint 8,4 %, principalement à cause de la mortalité causée par la rouille-tumeur oblongue. Un cinquième de la perte de volume estimée a été provisoirement attribué aux réductio...

Lodgepole pine (Pinus contorta var. latifolia Engelm.) ecosystems of central British Columbia face cumulative stresses, and management practices are increasingly scrutinized. We addressed trade-offs between “light-on-the-land” versus more aggressive silvicultural approaches by examining plant communities and indicator species (non-natives, berry producers, epiphytes, mycotrophs, pine rust alternate hosts) across a gradient of five or six site preparation treatments at the Bednesti trial (established 1987). We tested whether more severe site preparation (i) caused plant community composition to diverge from a 35- to 46-year-old reference forest, (ii) accelerated succession by hastening crown closure, or (iii) delayed succession by promoting seral species. Nonmetric multidimensional scaling (NMDS) ordination showed all treatments converging toward the reference forest composition. At 10 years, succession was incrementally delayed by more severe treatments; at 25 years, only burned windrows were still delayed. Mixed-effects models based on site preparation severity were better than crown closure models for 11 of 13 variables tested, suggesting that mostly belowground processes drive succession in these infertile ecosystems. Invasive hawkweeds persisted on all treatments at 25 years. Limited, contradictory data did not support using mechanical or fire treatments to reduce alternate hosts of pine stem rusts. Long-term trials such as Bednesti highlight the need for ecosystem-specific strategies and diverse approaches to accommodate conflicting benefits and risks of disturbance in forests.