Unformatted text preview: xtures” program would comprise three main pathways, to be applied in different proportions following harvesting across the landscape (Table 1). The first and most
common pathway would involve enrichment of the naturally
regenerated species mix with conifer species of current high
commercial value, much as is done now, but at lower densities and thus lower establishment cost. Similar approaches Can. J. For. Res. Vol. 36, 2006 are used in German forests according to Kenk (1992).
Stumping for root-disease abatement would be reduced and
applied only in areas designated for high-yield management,
with the remaining areas managed with resilient species
mixtures that include broadleaf trees. Brushing costs would
be reduced by removing the restrictions governing freegrowing on the density and proximity of broadleaf species
and allowing individual forest managers to apply selective
treatments where crop-tree survival is threatened. Chemical
brushing treatments would be applied on a limited basis to
root disease infested sites as a way to reduce the risk of disease accentuation. Thus, managers might prescribe brushing
to release western larch, which is very shade-intolerant, but
not other species that are more tolerant of shade. The resulting stands would be managed as stratified mixtures following the precepts of Smith et al. (1997). Stand-improvement
practices to control species composition or stem quality
would be chosen on the basis of individual perceptions of
species and stem value, market prices, and nonmarket values
at the time, rather than making an irrevocable decision about
future markets and values at the time of establishment. In
the longer term, we forecast that such stands would be managed on a continuous-cover basis, with frequent entries, natural regeneration, and low additional management costs.
Methods for projecting the yield of mixed-species stands
remain to be developed, even though vertical stratification of
mixed ICH stands, and the respective height-growth patterns
of species in mixtures, have been described (Cameron 1996).
German experience with mixtures of beech and spruce suggests that results can be positive or negative depending upon
the site (Kenk 1992). In Finland, experience with mixed
stands of birch and pine or spruce suggests that total stand
yield will be maximized with a birch component between
25% and 50% (Mielikainen 1996).
A second pathway would not involve enrichment planting
with conifers, but instead rely upon natural regeneration. In
the southern interior ICH forests, natural regeneration is
abundant adjacent to retained forest patches within large
patch cuts in most forest types, as well as in small harvested
patches in the younger mixed forest types that originated
from large wildfires 80–120 years ago (Vyse and DeLong
1994; Heineman et al. 2002). This pathway would be best
suited to less productive sites and more remote locations, in
keeping with the “semi-natural” approach recommended by
Lieffers et al. (1996). These forests would receive minimal
intervention, allowing natural stratification of the complex
mixtures to occur.
The third pathway would apply to a much more limited
portion of the landscape, where site productivity is highest.
It would focus on achieving high productivity of individual
species, or designed mixtures, over relatively short rotations.
Conifer production would follow the standard prescription
described earlier, but with more careful site selection, focusing on the most productive, mesic to subhygric portions of
harvested sites. Emphasis would be placed on eliminating
stand gaps and creating a sufficiently high density to permit
future choices of high-quality crop trees. Plantations of birch
are also a feasible option, and are common in Finland
(Puttonen 1996), where production of genetically improved
silver birch (Betula pendula Roth) reached 25 million seedlings annually in the 1990s. Birch should be established on
© 2006 NRC Canada Simard and Vyse mesic to subhygric sites, where the species performs best
(Simard and Vyse 1992; Simard et al. 2004a). Since genetically improved stock is not available at present, it should be
established at high densities to allow stem selection in subsequent stand entries. Managers would be free to invest
heavily in conifers and broadleaf species depending upon
their perception of market and pest risks. This intensivemanagement element would have to be encouraged by government, since most forest lands in British Columbia are
owned by the province. Private companies undertake forest
regeneration as a condition of their harvesting tenure and not
as an investment.
The management program we propose would be less
costly in total, provide a greater range of forest products,
provide a hedge against uncertainty in future wood-product
markets, and provide opportunities for the development of
nontraditional forest products, particularly those associated
with broadleaf species, which are either limited or not available under the current management approach. It uses an ecological approach to management that integrates facilitat...
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- Fall '13
- The Land, Forest, Temperate broadleaf and mixed forests, Suzanne Simard, paper birch