FRDA Report: Black Cottonwood and Balsam Poplar Managers ...

Information Sources:
McAuliffe 1989;
McLennan and Mamias
1992; Silviculture
Interpretations Working
Group 1993; Canadian
Forest Service 1994;
Robinson 1994;
Robinson and Eriksen
1994; B.C. Ministry of
Forests and B.C.
Ministry␣ of␣ Environment,
Lands and Parks 1995a.
A current guideline for extensive management of hybrid poplars is 370 stems per
hectare if sawlogs are desired and 730 stems per hectare if a mix of sawlogs and pulp
logs is desired. If there are fewer than 300 well-spaced cottonwood stems per hectare,
natural regeneration can be enhanced by harvesting early in the year after the frost is
out of the ground but while the soil is still moist and before spring growth begins. At
that time of year, movement of equipment over the ground can help stimulate vegetative
reproduction from broken branch and stem fragments.
For all the standards presented in Tables 17–22 we emphasize that it is not always
clear what variables are meant to be covered by the term “stocking standards.” In
British Columbia, progress to date to define stocking standards for broadleaf species
has centred on refinements of the Correlated Guidelines for Tree Species Selection (First
Approximation) and Stocking Standards (Second Approximation) for the Ecosystems of
British Columbia, prepared by the Silviculture Interpretations Working Group (1993).
Therefore, stocking standards include the following subjects: species acceptability;
definition of a free-growing tree or stand; minimum target stems per hectare at the
free-growing stage; minimum height; minimum inter-tree distance; target leader growth;
acceptable regeneration delay, earliest and latest acceptable free-growing dates; and
percentage by which tree height exceeds competing vegetation. Experience to date
indicates that the most important goal is to keep broadleaf stocking standards flexible
so as to meet a variety of timber and integrated resource management objectives.
Broadleaf stocking standards could differ for pulp, plywood, lumber, or oriented
strandboard end products. This suggests that managers should work backwards from
the anticipated product end use, desired piece size, crown width, and quality of stemwood
as criteria to define different stocking standards for the different desired raw materials.
In the Cariboo and Kamloops forest regions, the stocking standards proposed for
black cottonwood are the same as those for paper birch and aspen. On site series where
target conifer stocking is 400, 600, 1000, or 1200 stems per hectare, the corresponding
target cottonwood stocking is 600, 1000, 1600, or 2000 stems per hectare, respectively.
Other broadleaf stocking criteria corresponding to the four target conifer stocking
levels are listed in Table 19. These interim standards were developed jointly by the
Cariboo and Kamloops forest regions mainly for oriented strandboard end product.
They are considered to be applicable to the Prince Rupert and Nelson forest regions
and the Sub-boreal Spruce and Interior Cedar–Hemlock biogeoclimatic zones in the
Prince George Forest Region. These broadleaf stocking standards are for single-species
stands. Mixedwood stocking standards are planned as a future task.
The current Ministry of Forests stocking standards for broadleaf species in British
Columbia seem to be adequate and should continue to be used. Important provisos are
that these standards:
• apply only to timber resource end products;
• are restricted to broadleaf stands of a single species;
• have not been well tested with respect to free-growing criteria;
• have no specified maximum broadleaf densities (maximum number of stems per
hectare) under the latest version of the Silviculture Practices Regulation as there
are for conifers; and
• do not yet have specific criteria to define a “healthy” potential broadleaf crop tree.
The last condition is important because it is a basic assumption for all conifers
and broadleaves that a tree classified as free-growing be healthy.
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