Lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) has been extensively planted throughout interior British Columbia, and as a result may be particularly susceptible to climate-induced changes in the range and severity of common damaging agents. We quantified the presence of 14 damaging agents in sixty-six 15- to 30-year-old pine stands. Hard pine stem rusts, primarily western gall rust, were present on every site. We used logistic regression to predict individual agent presence from climatic, location, site, and treatment factors and calculated odds ratios to evaluate whether risk to lodgepole pine increases or decreases as these factors change. Risk of damage from serious agents (stem disease, root disease, and mountain pine beetle) increased with increasing latitude; however, in several of these models, risk also increased as temperature of the coldest month got warmer. We also found evidence that increasing risk of damage from agents that are currently less serious (sequoia pitch moth, pine needle cast, and pine terminal weevil) was associated with warming and (or) increasingly dry climatic conditions. Given the predominance of lodgepole pine in northerly ecosystems and the prediction that climate change effects will increase with latitude, our results suggest the need to consider potential increases in damage from diseases and insects during silviculture planning and timber supply prediction.

Broadleaf trees are routinely removed from conifer plantations during vegetation management treatments, but whether the removal increases tree productivity or affects root disease and plant diversity is unknown. The effects of manual and chemical reduction of paper birch (Betula papyrifera Marsh.) and trembling aspen (Populus tremuloides Michx.) on conifer survival, growth, root disease incidence, and plant community diversity were investigated for 5 years in Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) plantations in southern interior British Columbia. Broadleaves were reduced by manual, girdling, and cut-stump glyphosate treatments for 5 years but most severely following cut-stump glyphosate and with a delay due to slow death following girdling. Conifer survival was reduced for 3–5 years following manual cutting or girdling of birch because of a 1.5- to 4-fold increase in mortality due to Armillaria ostoyae (Romagn.) Herink, but this did not occur following cut-stump glyphosate treatment of birch or manual cutting of aspen. Conifer diameter increased with treatment intensity and productivity of the vegetation complex. Competition thresholds were identified for diameter but not survival, although Armillaria-caused mortality tended to increase near the minimum growth threshold. Structural diversity increased following manual cutting and cut-stump glyphosate because birch dominants were removed and understory layers increased, but species richness and diversity were unaffected. Forest managers can expect increased conifer growth with birch removal but also small increases in mortality due to Armillaria ostoyae root disease following manual treatments and loss of large birch trees in all treatments.

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Manual cutting treatments are routinely applied to release lodgepole pine (Pinus contorta var. latifolia Engelm.) from trembling aspen (Populus tremuloides Michx.) competition in southern interior British Columbia. We studied the effects of this treatment on pine and an aspen-dominated community on three sites in the Interior Douglas-Fir and Montane Spruce biogeoclimatic zones. After 10 years, when stands were 17–20 years old, treated aspen was significantly shorter than control aspen, and treated pine had significantly (21%) larger diameter than control pine. There were few other differences between brushed and unbrushed pine, and survival was excellent (≥97%), regardless of treatment. Brushing nearly doubled the average density of conifer stems that were free-growing according to legislated standards, but results were variable, and the free-growing status of the stand was changed on only one site. Regression analysis was used to examine the correlation between aspen abundance and pine size. The density of aspen at least as tall as the pine (tall aspen) predicted 36.2% of the variation in pine diameter, and total aspen density predicted 35.9% of the variation in pine height. An average density threshold of 1,867 tall aspen stems/ha, above which pine stem diameter declined, was identified in the three stands.

Lodgepole pine is extensively planted across western Canada but little is known about development of these stands beyond the juvenile stage. We quantified stocking status and damage incidence in sixty-six 15-to 30-year-old lodgepole pine plantations that had previously been declared free-growing in the southern interior of British Columbia. The stands were located in six biogeoclimatic zones: Engelmann Spruce-Subalpine Fir (ESSF), Montane Spruce (MS), Interior Cedar-Hemlock (ICH), Interior Douglas-fir (IDF), Sub-Boreal Spruce (SBS), and Sub-Boreal Pine-Spruce (SBPS). Freegrowing standards were no longer met on 27% of plantations, with the worst performance (70% no longer free-growing) in the Interior Cedar-Hemlock forests. Natural regeneration was common but it was half the size of lodgepole pine. Biotic damage, especially hard pine stem rusts, was the dominant factor reducing free-growing densities. Stands were at greater risk of reduced stocking where summer precipitation was higher or soil moisture regimes were wetter and where stands had been broadcast-burned prior to planting or received secondary treatments of brushing or pruning. Reforestation policies that encourage widespread planting of lodgepole pine, particularly in areas where lodgepole pine has limited natural occurrence such as in the ICH zone, should be reconsidered given that health problems are extensive and are expected to increase with climate change.Key words: Pinus contorta, lodgepole pine, free-growing, stocking, forest health, damage, disease résumé Le pin lodgepole est planté à grande échelle partout dans l'Ouest canadien, mais on sait peu de chose sur le développe-ment de ces peuplements au-delà du stage juvénile. Nous avons quantifié la densité relative et l'incidence des dégâts de 66 plantations de pin lodgepole âgées de 15 à 30 ans qui avaient été déclarées comme étant établies et retrouvées dans la zone intérieure sud de la Colombie-Britannique. Les peuplements étaient répartis entre six zones biogéoclimatiques : épinette d'Engelmann -sapin subalpin (ESSF), épinette alpestre (MS), pruche-cèdre -intérieur (ICH), Douglas taxifolié -intérieur (IDF), épinette des forêts boréales moyennes (SBS) et épinette et pin des forêts boréales moyennes (SBSP). Les normes utilisées pour fin d' établissement de la plantation n' étaient plus respectées dans 27 % des plantations, la pire performance (70 % d' échec) se retrouvant dans les forêts de pruche-cèdre. La régénération naturelle était fréquente mais atteignait seulement la moitié du niveau du pin lodgepole. Les dégâts biotiques, notamment les rouilles du tronc des pins durs, ont été le facteur dominant de réduction des densités relatives permettant de déclarer les plantations comme étant établies. La densité relative était plus à risque d' être réduite dans le cas des peuplements où les précipitations au cours de l' été étaient élevées ou que le régime hydrique du sol était plus humide et lorsque les peuplements avaient été soumis à un brûlage contrôlé avant plantation ou à des traiteme...