Implications of selected approaches for regenerating and managing western boreal mixedwoods

Abstract

We describe a range of approaches for managing boreal mixedwood stands composed of trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) in British Columbia and Alberta. Successful management of these complex forests requires a combination of well-defined objectives at the landscape level and flexible planning at the stand level. A variety of management strategies must be applied concurrently across the landscape to ensure that the natural mix of forest types and structural diversity is maintained. Selected approaches are discussed with regard to their suitability to particular stand conditions and sets of objectives, the types of tending and harvesting activities required, expected outcomes, and costs. The three approaches discussed are: 1) creation and management of two-storied intimate mixtures; 2) creation of a single-storied mixture of aspen and white spruce; and, 3) creation of a mosaic of discrete patches of each species.Key words: boreal mixedwood management, mixedwood silvicultural systems, aspen, white spruce, planning Mots clés : aménagement des peuplements mélangés de la forêt boréale, régimes sylvicoles des peuplements mélangés, tremble, épinette blanche, planification

Effects of aerial strip spraying on mixedwood stand structure and tree growth

“…However, these approaches are costly when compared to options available for growing either aspen or spruce monocultures. An alternative approach for enhancing the growth of spruce in a mixedwood setting is to grow spruce in small patches or strips that can be tended at less cost using aerial application of herbicides (Comeau et al 2005). This has also been termed striping (OMNR 2003).…”

Managed Mixtures of Aspen and White Spruce 21 to 25 Years after Establishment

“…Yield from boreal mixedwoods may be higher than from single-species stands because of the physical, phenological, and successional differences in growth strategy that exist between aspen and white spruce [11,25,41,42]. Shade tolerance differences between aspen and white spruce provide the ecological niche separation which creates the potential for greater productivity of mixed stands [43].…”

“…White spruce can be expensive and difficult to establish in pure stands following disturbance [5,38], whereas mixedwoods may be easier to establish and may also produce higher quality spruce stems than those resulting from more open growing conditions [39,40]. Finally, overall yield from mixedwood stands may be higher than from single-species stands because of the physical, phenological, and successional differences in growth strategy that exist between aspen and white spruce [11,25,41,42]. Achievement of the potential for superior productivity and resilience to risk of mixed species stands requires a close spatial association of the species [43].…”

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.…”