Biomass harvests in boreal forests: minimizing environmental impacts and maximizing benefits

用于生物燃料的生物质收获已成为加拿大林业经济的重要活动。然而，生物质采伐和森林更新如何在保持立地生产力和促进林分更新的同时最好地维持和支持生物多样性和生态系统功能仍不确定。此外，缺乏可用于衡量不同管理战略对生物多样性和生态系统功能影响的环境成本和效益的工具。以中部寒带森林为重点，我们将讨论与传统的纯茎采伐和野火相比，生物质采伐如何影响场地生产力、生物质生产、碳储量、土壤温室气体通量、林分反照率和生物多样性；并将研究经济和生态目标之间的权衡。我们将测试以下假设：(i)与替代方案相比，生物质收获可能会损害场地生产力、林分更新、生物质生产、碳储存、土壤温室气体通量和生物多样性；（ii）森林更新促进干扰后的植被恢复可以减轻生物量采伐的潜在负面影响，或者，如果不进行森林更新，负面影响可能会加剧；（iii）生态系统可能对土地利用集约化表现出非线性响应，因此可以在业务层面确定生态损失有限或没有生态损失但仍能满足经济收益的管理方案。我们将重点研究两种主要的森林类型：中部地区粗、中沙质土壤上的杰克松生态系统和中沙质土壤上的颤杨与云杉混交林。对资源利用和造林处理与林分发展之间相互作用的机制理解，以及经济效益、生态功能和生物多样性之间的权衡，将使我们能够为林业部门就如何设计管理制度提出建议，以最大限度地减少负面生态影响，同时保持立地生产力和促进林分更新。

Biomass harvesting for biofuels has become an important activity for Canada's forestry economy. However, it remains uncertain how biomass harvesting and forest renewal can best maintain and support biodiversity and ecosystem functions while maintaining site productivity and promoting stand regeneration. In addition, there is lack of tools that can be used to measure the environmental costs and benefits of different management strategies in terms of their impacts on biodiversity and ecosystem functions. Focusing on central boreal forests, we will address how biomass harvesting, compared with conventional stem-only harvesting and wildfire, affect site productivity, biomass production, and carbon storage, soil greenhouse gas fluxes, stand albedo, and biodiversity,; and will examine tradeoffs among economic and ecological objectives. We will test the hypotheses that: (i) biomass harvesting may compromise site productivity, stand regeneration, biomass production, carbon storage, soil GHG fluxes, and biodiversity in comparison with alternatives; (ii) forest renewal that promote revegetation after disturbance can mitigate the potentially negative effects of biomass harvesting, and alternatively, negative impacts may be compounded without forest renewal; (iii) ecosystems may show nonlinear responses to land-use intensification, and thus management options with limited or no ecological losses that still satisfy economic gains may be identified at the operational level. We will focus our efforts on two dominant forest types: jack pine ecosystems on coarse and medium sandy soils and mixedwoods of trembling aspen and spruce on mesic soils in the central region. A mechanistic understanding of the interactions between resource use and silvicultural treatments with stand development and the tradeoffs between economic benefits, ecological functions, and biodiversity in boreal forests will allow us to make recommendations for the forest sector on how to design management regimes that minimize negative ecological impacts while maintaining site productivity and promoting stand regeneration.