The physiological and ecological characteristics of red spruce (Picea rubens Sarg.) are reviewed and integrated into ecosystem management options. Red spruce is a shade-tolerant, late-successional conifer species found in the temperate forests of northeastern North America. Its wood, being of excellent quality, is prized by the forest industry. Unfortunately, this high-value species has been in decline throughout its entire range for the past 50 years. At high elevations, in northeastern United States, crown dieback caused by the combined effect of atmospheric pollution and climate is largely responsible of this decline. In other areas, such as Québec (Canada), the scarcity of red spruce is mainly caused by forest management practices that are poorly adapted to the species' ecophysiology. Many physiological studies have shown that the species is sensitive to full sunlight (at juvenile and advance growth stages), high temperatures and frost. It also has particular microsite requirements for seed germination and early seedling establishment, such as the presence of large decaying woody debris. Hence, a management strategy adapted for red spruce should favour the use of partial cutting, maintaining some overstory and dead wood. This will emulate the natural dynamics of small canopy gaps and minimize the physiological stresses to regeneration. The ecophysiological aspects of natural and artificial regeneration of red spruce should be examined with respect to the increased use of partial cutting techniques.Keys words: advance regeneration, balsam fir (Abies balsamea L.), ecophysiology, ecosystem management, frost susceptibility, light response, microenvironment, red spruce (Picea rubens Sarg.), seedling establishment, shade tolerance, silvicultural systems, thermosensitivity RÉSUMÉ Les caractéristiques physiologiques et écologiques de l'épinette rouge (Picea rubens Sarg.) sont révisées et intégrées dans des options d'aménagement écosystémique. L'épinette rouge est un conifère tolérant à l'ombre et de fin de succession que l'on retrouve dans les forêts tempérées du nord-est de l'Amérique du Nord. Son bois, d'excellente qualité, est recherché par l'industrie forestière. Depuis 50 ans, cette essence de grande valeur a malheureusement connu un déclin sur l'ensemble de son aire de répartition. En haute altitude, dans le nord-est des États-Unis, le dépérissement de la cime causé par l'effet combiné de la pollution atmosphérique et du climat est en grande partie responsable de ce déclin. En d'autres endroits, comme au Québec (Canada), la raréfaction de l'épinette rouge est surtout attribuable à des pratiques d'aménagement forestier peu adaptées à son écophysiologie. Plusieurs études physiologiques ont montré que cette espèce est sensible à la pleine lumière (aux stades juvénile et de régénération préétablie), aux températures élevées et au gel. Elle requiert aussi des microsites particuliers, comme les gros débris ligneux en décomposition, pour la germination des graines et l'établissement initial des semis. Ainsi, ...
La coupe avec protection de la régénération et des sols (CPRS) et la plantation à la suite d'une préparation de terrain ou non (regarni) sont largement appliquées pour régénérer les peuplements d'épinette noire (Picea mariana (Mill.) BSP) de la forêt boréale du Québec, Canada. Toutefois, peu d'études à moyen terme ont comparé ces différents modes de régénération. Dans cette étude, nous avons suivi pendant 10 ans la croissance en hauteur et le statut nutritif de marcottes, de semis naturels et de semis plantés d'épinette noire, dans un dispositif expérimental combinant la CPRS, l'ensemencement naturel, la plantation et deux types de scarifiage (cônes et disques). En l'absence de scarifiage, la croissance des semis plantés (5,8 cm·an -1 ) a été légèrement supérieure à celle des marcottes (4,4 cm·an -1 ) et des semis naturels (4,1 cm·an -1 ). Le scarifiage a amélioré la croissance des trois types de régénération, mais le traitement a été plus profitable aux semis plantés (+7,1 cm·an -1 ) qu'aux semis naturels (+1,6 cm·an -1 ) et aux marcottes (+1,0 cm·an -1 ). Cinq ans après le traitement, le scarifiage avait augmenté la concentration en N des aiguilles de l'année courante chez les trois types de régénération, mais cet effet bénéfique n'était plus détectable que chez les marcottes après 10 ans. L'effet du traitement a été variable pour les teneurs en P et K, pour lesquelles la régénération naturelle semble avoir plus profité que les plants. Nos résultats indiquent que le scarifiage est un moyen d'améliorer la croissance initiale et le statut nutritif de la régénération naturelle et artificielle d'épinette noire, afin d'accélérer la remise en production des stations de la forêt boréale soumises à la coupe. De plus, le regarni effectué sans préparation de terrain est apparu nettement moins efficace que la plantation combinée au scarifiage.Abstract: Careful logging around advance growth (CLAAG) and tree planting following site preparation or not (fill planting) are widely used to regenerate black spruce (Picea mariana (Mill.) BSP) stands in the boreal forest of Quebec, Canada. However, few mid-term studies have compared these different regeneration modes. In this study, we examined height growth and nutrient status of black spruce layers, natural seedlings, and planted seedlings over a 10-year period, in an experimental design combining CLAAG, natural seeding, planting, and two types of scarification (cones and disks). Without scarification, growth of planted seedlings (5.8 cm·year -1 ) was slightly greater than that of layers (4.4 cm·year -1 ) and natural seedlings (4.1 cm·year -1 ). Scarification improved growth of the three types of regeneration, but the treatment was more beneficial for planted seedlings (+7.1 cm·year -1 ) than for natural seedlings (+1.6 cm·year -1 ) and layers (+1,0 cm·year -1 ). Five years after treatment, scarification had increased the current-year needle N concentration of the three types of regeneration, but this beneficial effect on N was still detectable only in foliage of layers after 10 ...
We examined the ecophysiology and growth of 0.3-1.3 m tall advance red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea [L.] Mill.) regeneration during a 5-year period following the application of different harvest types producing three sizes of canopy openings: (i) small gaps (<100 m(2) in area; SMA) created by partial uniform single-tree harvest; (ii) irregular gaps of intermediate size (100-300 m(2); INT) created by group-selection harvest (removal of groups of trees, mainly balsam fir, with uniform partial removal between groups); and (iii) large circular gaps (700 m(2); LAR) created by patch-selection harvest (removal of trees in 30-m diameter circular areas with uniform partial removal between gaps). An unharvested control (CON) was monitored for comparison. At the ecophysiological level, we mainly found differences in light-saturated photosynthesis of red spruce and specific leaf area of balsam fir among treatments. Consequently, we observed good height growth of both species in CON and INT, but fir surpassed spruce in SMA and LAR. Results suggest that intermediate 100-300 m(2) irregular openings create microenvironmental conditions that may promote short-term ecophysiology and growth of red spruce, allowing the species to compete with balsam fir advance regeneration. Finally, results observed for spruce in large 700-m(2) openings confirm its inability to grow as rapidly as fir in comparable open conditions.
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