Regeneration and precommercial thinning silviculture of boreal mixed stands

收获的白杨/云杉混合林分经常导致种植或预先建立的针叶树幼苗很快被密集而有力的白杨吸盘覆盖。然后需要大量的造林努力来释放针叶林部分并保持这些林分的混合结构。本研究的第一个目标是评估与白杨密切生长的云杉对两种常用的商业前间伐处理（系统或作物-树木释放）的响应，包括两种物种的树木和林分生产力、动物栖息地质量以及土壤和地上和地下植被的碳封存动态。其次，我们想要评估杨树公共根系在混合林分预商业间伐和保留收获中的作用。事实上，之前的研究已经表明，白杨树的相互连接的根系在树木对环境变化的生理反应中起着重要作用，我们希望利用这一知识来设计适应混交林环境的造林方案。商业前间伐选择只保留最大的茎，无论其空间分布如何，应产生具有更粗壮的大茎的林分，以及随机分布的开口，以丰富云杉幼苗。此外，保留采伐选择保留分散的杨树茎，通过在公共根系中保持顶端优势，应该减少采伐后产生的杨树吸盘的数量，为云杉幼苗提供更好的生长条件，需要较少的未来造林干预。这项研究的结果将很容易转让给森林工业和forêts、森林和公园部（MFFP）的管理人员，方法是提供缺失的信息，指导根据管理目标选择造林，无论这些目标是主要侧重于针叶树或硬木生产力还是两者兼而有之，还是侧重于碳汇或维持最大限度的高质量野生动物栖息地，或两者兼而有之。因此，我们将利用这项研究的结果，为北方森林的白杨/云杉混交林推荐适当的管理措施。****

Harvested mixed aspen/spruce stands often result in planted or pre-established conifer seedlings quickly being overtopped by dense vigorous aspen suckers. Significant silvicultural efforts are then required to release the conifer portion and maintain the mixed structure of these stands. The first goal of this study is to assess the response of spruce growing intimately with aspen to two frequently used precommercial thinning treatments (systematic or crop-tree release) in terms of tree and stand productivity for both species, fauna habitat quality and dynamics of carbon sequestration in soils and above- and belowground vegetation. Second, we want to evaluate the role of aspen's communal root system in the response to precommercial thinning and retention harvesting in mixed stands. Indeed, previous research has shown that interconnected root systems of aspen trees play a role in trees' physiological response to environmental changes, and we want to use this knowledge in order to design adapted silvicultural scenarios in a mixedwood forest context. Precommercial thinning choosing to exclusively keep the largest stems, regardless of their spatial distribution, should produce stands with more vigorous larger individual stems, as well as randomly distributed openings to be enriched with spruce seedlings. Also, retention harvesting selecting to keep interspersed aspen stems, by maintaining apical dominance into the communal root system, should reduce the number of aspen suckers produced post-harvest, offering better growing conditions for spruce seedlings requiring less future silvicultural intervention. Results of this research will be easily transferred to forest industry and managers of the Ministère des forêts, de la faune et des Parcs (MFFP), by offering missing information guiding silvicultural choices according to management objectives, whether they mostly focus on conifer or hardwood productivity or both, or on carbon sequestration or the maintenance of a maximum of quality wildlife habitats, or a mix of these. Accordingly we will use results of this research to recommend appropriate management practices for mixed aspen/spruce stands of the boreal forest.****