-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...

Application . Results of this study show that boxed white spruce seedlings, removed from cold storage (-2 ° C) and thawed (+5 'Q, can tolerate warm (i .e . < 20 ° C) temperatures for up to 4 days without affecting field growth performance . However, exposure to temperatures above 5 °C for any duration during transport and field storage, is not recommended . Exposure to temperatures greater than 30 °C for longer than 48 h results in severe physiological deterioration of the seedlings and must be avoided . Physiological damage due to heat stress may be detected using electrolyte leakage or root growth potential tests prior to planting of seedlings . These tests could be used to decide whether to plant white spruce seedlings that may have been heat stressed after removal from cold storage.Abstract . This study investigated the effects of holding 1+0 PSB313a white spruce (Picea glauca (Moench.) Voss) seedlings in storage boxes at air temperatures of 5, 10, 20, 30 and 40 ° C for 12, 24,48, 72 and 96 h before planting . The ability to detect physiological damage to seedlings as a result of such treatment, before planting, was also examined . After one growing season, no needle damage or mortality >8% was found for temperature treatments up to 20 ° C for 4 days . At 30 ° C and above, seedling damage and mortality increased, while bud flush, shoot height, stem diameter and shoot dry weight decreased with increasing temperature and duration of treatment. Seedling mortality in the field was 100% after the 40 °C treatment exposure for 72 h or longer. Pre-planting needle electrolyte leakage was indicative of visible needle damage 14 days after planting, whereas stem electrolyte leakage and root growth potential were more closely related to end of season plantation mortality . Despite the lack of damage observed at 20 °C or below, preplanting exposure of white spruce seedlings to temperatures above 5 °C, during transportation and field storage, is not recommended .

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Respiration rates of shoot tips of 1st year (1-0) Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings of one interior and one coastal seed lot were measured using a polarographic Clark-type oxygen probe. Total respiration of shoot tips was high in August and early September (32 nmol O2•mg−1•h−1), the period of most rapid bud development, decreased to between 8 and 16 nmol O2•mg−1•h−1 in the later stage of bud development, and was between 8 and 12 nmol O2•mg−1•h−1 when bud development was complete. Bud development in the interior seed lot was in advance of that in the coastal seed lot, so the basal rate of respiration was reached earlier. However, differences in shoot-tip respiration between seed lots became smaller towards the later stages of bud development. Oxygen consumption increased gradually from February through March in the coastal seed lot but not in the interior seed lot. The capacity of the alternative pathway was determined by the addition of inhibitors of respiration, potassium cyanide (2 mM) and salicylhydroxamic acid (3 mM). The capacity of the alternative pathway did not vary throughout the dormant period and was always less than 10% of total respiration. Respiration rate during bud development is discussed, and it is concluded that this technique may be useful as a test to assess bud dormancy status.