Using Spot Treatments to Regenerate an Intimate Mixture of Trembling Aspen and White Spruce in Alberta: Results at Age 15

Mixedwood stands, dominated by trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss), are an important fibre source in Canada\u27s boreal forest and provide a range of ecological services. We present results from a study established in 2002 to test a strategy for growing intimate, single cohort mixtures of these two species involving controlling woody and herbaceous vegetation within 2-m radius spots centered on the spruce planted at 5-m spacing. After 15 growing season spruce survival was high (74-90%) in the radial treatments with spruce DBH and height being intermediate between untreated spruce growing under a dense aspen canopy and spruce growing without aspen in the broadcast complete control treatment. Repeated browsing by snowshoe hare, associated with reduced height of spruce, lead to severe reductions in spruce survival and size in the untreated stand, which had an average of 24 500 stems/hectare of aspen at age 15. While spot treatment alone did not significantly affect aspen height or diameter at age 15, thinning of the aspen matrix at age 10 in spot treated stands resulted in increases in diameter growth of both aspen and spruce. Results indicate that radial spot herbicide treatments can effectively improve early survival and growth of white spruce through control of aspen, shrubs, herbs, and grasses and that adding precommercial thinning leads to additional increases in growth of both trembling aspen and white spruce

Managing plantation density through initial spacing and commercial thinning: yield results from a 60-year-old red pine spacing trial experiment

We report on a 60-year-old red pine (Pinus resinosa Aiton) spacing trial experiment located in Ontario, Canada, that included the combinations between six initial spacings (from 1.2 to 3.0 m) and the presence or absence of a commercial thinning (CT) regime, as well as their impacts on quadratic mean diameter (QMD) and stand volume yield. The CT regime, initiated at age 30, targeted a residual basal area (BA) of 38 m2·ha−1 after each of four entries. Without thinning, as initial spacing increased, QMD increased; gross and net volume production peaked in the 2.1–2.4 m spacings. With thinning, similar trends with spacing were evident for QMD, although piece sizes were larger and differences between spacings were lower. The immediate increase of mean tree size caused by tree selection explained most of the differences in QMD between thinned and unthinned plots. Thinning to a common target BA resulted in similar standing volume across spacings. Cumulative gross yield was similar between spacings of <2.1 m for both thinned and unthinned stands and decreased for thinned plots for wider spacings. Greater net volume production in thinned stands with the narrower spacings confirmed that mortality was captured. Lower gross and net production for wider spacings suggested that thinning resulted in underutilized growing space.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Optimum Vegetation Conditions for Successful Establishment of Planted Eastern White Pine (Pinus strobus L.)

The 10th-growing season performance of planted eastern white pine (Pinus strobus L.) seedlings was evaluated in response to herbaceous and woody vegetation control treatments within a clearcut and two variants of the uniform shelterwood regeneration system (single vs. multiple future removal cuts). Herbaceous vegetation control involved the suppression of grasses, forbs, ferns and low shrubs for the first 2 or 4 growing seasons after planting. Deciduous woody vegetation control treatments, conducted in combination with the herbaceous treatments within a response-surface design, involved the permanent removal of all tall shrubs and deciduous trees at the time of planting, at the end of the 2nd or 5th growing seasons, or not at all. In general, the average size of planted pine was related positively to the duration of herbaceous vegetation control and negatively to delays in woody control. White pine weevil (Pissodes strobi Peck) altered these trends, reducing the height of pine on plots with little or no overtopping deciduous woody vegetation or mature tree cover. Where natural pine regeneration occurred on these plots, growth was similar but subordinate to the planted pine. Data from the three sites indicate that at least 60% of planted pine may be expected to reach an age-10 height target of 2.5 m when overtopping cover (residual overstory + regenerating deciduous) is managed at approximately 65% ± 10%, and total herbaceous cover is suppressed to levels not exceeding 50% in the first five years. On productive sites, this combination may be difficult to achieve in a clearcut, and requires fairly rigorous vegetation management in shelterwood regeneration systems. Currently, synthetic herbicides offer the only affordable and effective means of achieving such vegetation control