Examining the offsetting potential of vegetation changes on wildfires in managed forests of boreal Canada

20世纪是北纬高纬度地区的关键时期，因为它标志着与全球大气成分的重大人为变化有关的快速气候变暖的开始。大气变化造成的显著影响包括20世纪中期至21世纪初加拿大北部北方地区野火活动增加。随着大气温室气体达到前所未有的水平，预计野火活动加剧的现象将持续整个本世纪，并将波及加拿大更大的地区。为了抵消人工林日益增加的野火风险，建议在茂密针叶林景观中进行植被控制处理。引入阔叶成分作为战略屏障可以降低野火的强度和蔓延速度，提高扑灭效果，减少野火的影响。我们在加拿大东部北方森林的工作清楚地表明，阔叶植被在减少温暖气候下野火活动水平方面的重要作用。然而，与实现野火管理目标所需的植被组成变化幅度（例如物种的相对丰度/生物量和管理区域的大小）以及物种建立成功的潜在限制（例如营养限制；不利的气候条件等）有关的重要问题仍然存在。此外，只有当生物反馈足够强大，能够调节未来气候变化对野火的影响时，这种管理选择才会起作用：在过度干旱的情况下，植被的相对重要性会降低，因为林分可以达到允许大规模野火发展所需的阈值。**本研究的目的是探索允许野火频率轨迹调节的区域林分属性设置（物种和林分统计）。这将通过动态全球植被模型（DGVM）与古生态数据（花粉、植物宏观遗骸、木炭颗粒）的创新配对来完成。古生态学数据的使用旨在为模型假设提供基于地面的验证。待验证的假设是，气候变暖导致北部森林地区容易受到高野火活动的影响，而这种脆弱性取决于景观中针叶林物种的优势。具体来说，这项工作将追求参数化和验证DGVM在加拿大管理的北方森林中的应用，确定这些森林在不同时空尺度的气候变化下对火灾的影响、暴露和敏感性。描述改变植被组成和结构对未来火灾活动的潜在影响，并评估各种植被改变方案的利弊。**过去十年，加拿大每年的灭火费用约为5亿至10亿美元，而2002年至2011年期间的财产损失平均为每年350万美元。减少火灾干扰的影响所带来的经济效益是显而易见的。该项目将提供基于科学的信息和技术，加拿大的司法管辖区（如省、地区）将能够利用这些信息和技术制定有关野火的明智决策和政策。将更好地评估火灾活动的变化和火灾对经济、环境和社会因素的影响，以及为保护人类社区和其他面临风险的价值而采取的减轻风险备选办法。

The 20th century was a pivotal period at high northern latitudes as it marked the onset of a rapid climatic warming associated with major anthropogenic changes in global atmospheric composition. Prominent effects resulting from the atmospheric changes include more wildfire activity in northern Canadian boreal regions from the mid-20th to the early 21st centuries. The phenomenon of enhanced wildfire activity is projected to continue throughout this century, and this across much larger areas of Canada, as atmospheric greenhouse gases attain unprecedented levels. To offset the increasing wildfire risks in managed forests, it was suggested that manipulative vegetation treatments be applied in dense coniferous landscapes. The introduction of a broadleaf component as strategic barriers could decrease the intensity and rate of spread of wildfires, improve suppression effectiveness, and reduce wildfire impacts. Our work in the eastern Canadian boreal forest clearly shows the important function for broadleaf vegetation in reducing levels of wildfire activity in a warmer climate. Nevertheless, important questions remain relative to the magnitude of vegetation composition changes needed to attain the wildfire management objectives (e.g. relative abundance/biomass of species and size of the managed areas), and the existence of potential constraints on the success of species establishment (e.g. nutrient limitations; unfavourable climate conditions, etc). Additionally, this management option will only work if the biotic feedback is strong enough for modulating the influence of future climate change on wildfire: under excessive droughts, the relative importance of vegetation diminishes since stands can achieve the threshold required to permit large wildfire development. ** The objectives of this research are to explore the regional stand attribute settings (species and stand demographics) that allow a modulation of wildfire frequency trajectories. This will be done by innovative paring of a dynamic global vegetation model (DGVM) with paleoecological data (pollen, plant macro-remains, charcoal particles). The use of paleoecological data is intended to provide a ground- based validation of model assumptions. The hypothesis to be tested is that northern forest areas are vulnerable to high wildfire activity brought about with climate warming, and this vulnerability is dependant upon the dominance of coniferous species in landscapes. Specifically, the work will pursue the parameterization and validation of a DGVM for application in managed boreal forests of Canada, determine the impact, exposure and sensitivity of these forests to fires under a changing climate at different temporal and spatial scales, and 3. Describe the potential impacts resulting from modifications of vegetation composition and structure, on future fire activity and evaluate the pro and cons of various vegetation modification scenarios. ** Fire suppression costs over the last decade in Canada have ranged from about $500 million to $1 billion a year, while property losses during 2002-2011 averaged $3.5 million annually. The economic benefits derived from minimizing the impacts of fire disturbances are evident. This project will provide science based information and technology that Canadian jurisdictions (e.g. provinces, territories) will be able to use for making informed decisions and policies concerning wildfires. Changes in fire activity and the impacts of fire on economic, environmental and social considerations, as well as risk mitigation options to protect human communities and other values at risk, will be better assessed.