-In British Columbia, vegetation management treatments are widely used to ensure successful establishment of young stands and achievement of free-growing requirements. A study was established in 1991 to examine the effectiveness of vegetation control treatments for release of Engelmann spruce (Picea engelmannii Parry) seedlings from a mixed-shrub community. The study consisted of eight treatments replicated three times in a completely randomized design. The treatments comprised six combinations of spring, summer and annual repeated manual cutting, a single application of glyphosate, and an untreated control. Controlling the mixed-shrub community one-year after planting using glyphosate and manual cutting treatments significantly improved spruce survival. Repeated manual cutting significantly improved survival over that achieved with only a single treatment. Consequently, the density of well-spaced trees was significantly increased in the repeated manual cutting and glyphosate treatments. In 2001, the untreated control only has 27% of well-spaced spruce trees that are free growing compared to more than 50%, 75% and 83% in single cutting, repeated manual cutting and glyphosate treatment, respectively. Treatments significantly increased height and groundline diameter from the third through the seventh year but not in year ten. Continued mortality of suppressed seedlings after year seven is a probable cause of lack of treatment differences in the tenth year. However, height-to-diameter ratio was significantly reduced in year ten for all treatments over the control and for repeated versus single cutting treatments. Ten-years after treatment, significant differences in vegetation community percent cover, richness, and diversity were not detected among treatments.Engelmann spruce / vegetation management / repeated manual cutting / glyphosate / free growing Résumé -Effets à long terme de traitements de contrôle de la végétation effectués pour dégager des épicéas d'Engelmann concurrencés par divers arbustes, en Colombie Britannique méridionale. En Colombie Britannique, on fait largement appel à des traitements de gestion de la végétation pour faciliter l'installation des jeunes peuplements et leur permettre de se développer librement. Une étude a été engagée en 1991 pour juger l'efficacité de traitements de contrôle de la végétation visant à dégager des épicéas d'Engelmann (Picea engelmanii Parry) concurrencés par divers arbustes. Cette étude comportait huit traitements, répétés trois fois selon un dispositif en blocs complets. Pour les traitements, il s'agissait de six combinaisons de dégagements par coupe effectués au printemps ou en été pendant une ou plusieurs années, d'une seule application de glyphosate, et enfin d'un témoin sans intervention. Le contrôle de la végétation arbustive par application de glyphosate un an après plantation, ou par les traitements dégagement par coupe, se traduit par une amélioration significative de la survie des épicéas. Des dégagements répétés pendant plusieurs années se révèl...

This study, initiated in 1992, examined the effectiveness of repeated cutting for controlling vegetation in a mixed-shrub-herb community to release planted Engelmann spruce (Picea engelmannii) seedlings. Eight treatments were compared: (a) cut once in spring of 1992, (b) cut once in summer of 1992, (c) 3 yr of cutting once annually in the spring (mid to late June) starting in 1992, (d) 3 yr of cutting once annually in the summer (late July) starting in 1992, (e) 3 yr of cutting twice annually, in the spring and in the summer starting in 1992, (f) 2 yr of cutting twice annually, in the spring and in the summer starting in 1993, (g) application of glyphosate herbicide at 2.1 kg ai/ha during late August, 1992, and (h) an untreated control. Treatments were replicated 3 times in 30 × 30 m plots. Glyphosate treatment (g) and spring cutting treatments (c, e, and J) significantly reduced vegetation (vascular plant) cover and height compared to the control in 1993 and 1994. There were no significant differences in vegetation cover among treatments in year 5 (1996), but vegetation height was significantly lower in the glyphosate treatment (g) and repeated cutting treatments (c, d, e, and f) compared to the control. After 5 yr, spruce survival was high for both control (86%) and treated (> 91%) plots, with no significant (P ≤ 0.05) differences detected among treatments. Repeated cutting treatments (c, d, e, and f) and glyphosate treatment (g) significantly increased root collar diameter (rcd) over that of untreated (h) seedlings, and repeated summer cutting (d) significantly increased seedling height. Three years of repeated cutting (c, d, and e) increased rcd by 54%, and glyphosate (g) increased rcd by 46% compared to the control (h). At the end of year 5, seedlings receiving 3 yr of cutting (e) were not significantly larger than seedlings receiving only 2 yr of cutting (J). West. J. Appl. For. 15(3):154-162.