Early growth of white spruce underplanted beneath spaced and unspaced aspen stands in northeastern British Columbia

Abstract

We examined the growth of white spruce planted underneath a 33-year-old stand of trembling aspen following thinning and fertilization. Thinning the stand to 2000 stems·ha -1 resulted in increased light reaching spruce seedlings and significant increases in height and diameter growth of seedlings over that observed in either the unspaced or 3000 stems·ha -1 treatments. Fertilization (applied 3 years prior to planting) stimulated development of understory vegetation and did not benefit the planted spruce. While growth was improved by thinning, the benefits of the thinning treatment to establishment of white spruce appeared to be small, and amounted to increasing seedling height from 62 cm (unthinned) to 73 cm (thinned to 1000 or 2000 stems·ha -1 ) at the end of 5 years. Results indicated that when stands are thinned for the purpose of accelerating growth rates of underplanted spruce, residual basal areas above 25 m 2 ·ha -1 should be retained to suppress growth of understory vegetation. Comparison of height at age 5 for seedlings planted under untended stands at Fort Nelson with three sites near Dawson Creek indicated no differences between locations, when height at the time of planting was included as a covariate.Résumé : Nous avons étudié la croissance des épinettes blanches plantées sous un peuplement de peuplier faux-tremble âgé de 33 ans à la suite d'une éclaircie et d'une fertilisation. Le fait d'éclaircir le peuplement à 2000 tiges·ha -1 a procuré plus de lumière aux semis d'épinette et a significativement augmenté leur croissance en hauteur et en diamètre comparativement à ce qui a été observé dans le traitement témoin ou l'éclaircie à 3000 tiges·ha -1 . La fertilisation (appliquée 3 ans avant la plantation) a stimulé le développement de la végétation de sous-bois mais n'a pas bénéficié aux semis d'épinette. Bien que l'éclaircie ait amélioré la croissance, les effets bénéfiques de ce traitement sur l'établissement de l'épinette semblent peu importants et se traduisent par une augmentation de la hauteur des semis de 62 cm (sans éclaircie) à 73 cm (éclaircie à 1000 ou 2000 tiges·ha -1 ) après 5 ans. Les résultats indiquent que lorsque les peuplements sont éclaircis dans le but d'accélérer le taux de croissance des épinettes plantées en sous-étage, la surface terrière résiduelle devrait être maintenue au-dessus de 25 m 2 ·ha -1 pour supprimer la croissance de la végétation de sous-bois. La comparaison de la hauteur à 5 ans de semis plantés sous des peuplements non traités à Fort Nelson avec les données provenant de trois sites près de Dawson Creek indique qu'il n'y a pas de différence entre ces endroits lorsque la hauteur au moment de la plantation est incluse comme covariable.[Traduit par la Rédaction] Comeau et al. 2283

Long-term response of planted conifers, natural regeneration, and vegetation to harvesting, scalping, and weeding on a boreal mixedwood site

“…Besides potentially increased productivity (Man and Lieffers, 1999b) and reduced costs of site preparation and tending Greene et al, 2002;MacDonald et al, 2004), planted white spruce may also benefit from improved nutrient status and reduced seedling damage from root rot (Tanner et al, 1996), frost (Groot and Carlson, 1996;Man and Lieffers, 1999a), and overwintering injuries (Krasowski, 1996). In these forests, white spruce can be established 10-20 years prior to harvesting Comeau et al, 2004), taking advantage of high light transmission in mature aspen stands and ensuring seedlings are well established to minimize damage during aspen harvesting (Greene et al, 2002). However, in eastern Canada understory light in mature aspen stands is low, ranging from 2 to 27% of full sunlight (Messier et al, 1998;Groot, 1999) compared to 20-50% in the west (Ross et al, 1986;Constabel and Lieffers, 1996), possibly due to the greater annual precipitation in eastern forests (Messier et al, 1998) that supports higher leaf area, particularly from the vigorous growth of shade-tolerant understory shrubs such as mountain maple and beaked hazel (Bell, 1991).…”

Early vegetation control for the regeneration of a single-cohort, intimate mixture of white spruce and aspen on upland boreal sites – 10thyear update

“…Acknowledging the need to produce both aspen and conifer for commercial demand, while maintaining the ecological goods and services provided by mixedwoods, a number of research efforts have been directed towards creating spatial mixtures, through various arrangements of pure groupings of spruce and aspen (Groot et al 1996, Groot 1999, Comeau et al 2005, Man et al 2013, or intimate mixtures (with species separation on the scale of a few metres or less) by using mature or semimature aspen as a shelterwood for the regeneration of a younger age class of spruce (Lieffers and Beck 1994, Lieffers et al 1996, Comeau et al 2004, 2009). These approaches serve various ecological objectives, but share potentially serious operational shortcomings in the spatial and structural complexity of the stands that they create.…”

Corrigendum to: Growth of white spruce underplanted beneath spaced and unspaced aspen stands in northeastern B.C.—10 year results

“…In stands over 40 years old, light levels above 20% are commonly observed (Groot et al, 1997;Lieffers et al, 2002;Comeau et al, 2006). In addition, overstory aspen cover reduces the vigor of shrubs, herbs and grasses, which can negatively affect the growth of small white spruce (Lieffers and Stadt, 1994;Comeau et al, 2004). , stands has substantial potential as a technique for regenerating boreal mixedwood stands.…”