Juvenile response to conifer release alternatives on aspen-white spruce boreal mixedwood sites.Part II: Quality of aspen regeneration

Abstract

This study, a component of the Fallingsnow Ecosystem Project, was designed to investigate the effects of conifer release alternatives on the quality of regenerating trembling aspen (Populus tremuloides Michx.). A randomized block design was used to compare untreated aspen with aspen growing in areas treated with two broadcast cutting treatments (brushsaw and Silvana Selective) and two broadcast herbicide treatments (glyphosate and triclopyr). The glyphosate treatment virtually eliminated aspen, whereas triclopyr tended to top-kill aspen, resulting in lateral dominance. Both fall cutting treatments generated prolific aspen root suckering and stump sprouting. Stain was common in aspen across the study site in damaged, untreated, and post-treatment stems, indicating that stain develops rapidly in young aspen suckers. Stems damaged by the treatments had higher incidences of decay (33% of cut stems and 10% of herbicide-damaged stems) than untreated aspen (8% of stems); however, decay volume was low for all treatments (1–4% of total stem volume affected). The location of decay (e.g., near ground level in cut stems) and presence of stem crooks in herbicide-treated aspen are important effects of the treatments on aspen quality. Armillaria root disease, which was found throughout the study site, was more prevalent in roots of treatment-damaged and untreated aspen than in suckers that originated post-treatment. These differences can be attributed to proximity to parent stumps, prevalence of root wounds, and older age of damaged and untreated stems. Key words: aspen quality, decay, conifer release, vegetation management, fibre production

Juvenile response to conifer release alternatives on aspen-white spruce boreal mixedwood sites.Part I: Stand structure and composition

“…The result was the highest observed spruce height growth, with stem volumes and basal areas equivalent to trees that were more thoroughly released by the glyphosate treatment. Although top-killed aspen contained stem crooks seven years after treatment, relatively low levels of stem decay suggest that future volume production may not be significantly compromised (Greifenhagen et al 2005). As such, this treatment appears to temporarily reduce aspen height growth, allowing planted white spruce to maintain near-optimum growth, without jeopardizing the potential for the stand to pass through a productive mixedwood phase.…”

“…Without further treatment to reduce competition with the spruce, a single release cutting will likely produce deciduous-dominated mixedwoods as these stands mature. However, since approximately half of the aspen stems situated in the cut plots originated from cut stumps, concern for the future quality and merchantability of these stems is warranted (Greifenhagen et al 2005). Cutting aspen during peak growing season, when root reserves are low, and/or cutting with a higher stump has been shown to reduce root suckering and promote the development of low-vigour stump sprouts (Bell et al 1999), potentially allowing a mixedwood of more equal proportions to be established.…”

“…Our specific objective was to quantify the juvenile stand structures that have evolved as a consequence of five different conifer release options tested on the three Ontario boreal mixedwood sites comprising Fallingsnow. A companion paper (Greifenhagen et al 2005) reports the stem quality and health of the aspen portion of these young stands. Together, these data are necessary for fine-tuning forest regeneration and composition maintenance strategies, as well as predicting future forest conditions and stand growth and yield responses to different conifer release options on boreal mixedwood sites.…”

Cutting versus herbicides: Tenth-year volume and release cost-effectiveness of sub-boreal conifer plantations

“…in the Release treatment during field data collection showed that some individuals were not killed (Greifenhagen et al 2005). These individuals possess telltale "crooks" in their stems indicating Release induced rapid cell growth but not death.…”

Modelling Landscape-level Effects of Reduced Herbicide Use in Two Forests in Northern Ontario

“…For poplar, a cull factor of 30% for stems five to 75 years of age and 40% for stems older than 75 years was applied because poplar that re-sprouts after brush saw treatment is reported to be of lower quality (Greifenhagen et al 2005). White birch (Betula papyrifera Marsh.)…”