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

20世纪是北方高纬度地区的关键时期，因为它标志着全球大气组成的重大人为变化导致气候迅速变暖。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部地区更多的野火活动。随着大气温室气体达到前所未有的水平，野火活动加剧的现象预计将在整个本世纪持续下去，而且在加拿大更大的地区也是如此。为了抵消森林管理中不断增加的野火风险，有人建议在茂密的针叶林景观中应用人工植被处理。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，并减少野火的影响。我们在加拿大东部北方针叶林的研究清楚地表明，在气候变暖的情况下，阔叶植被在减少野火活动方面具有重要作用。然而，与实现野火管理目标(例如物种的相对丰度/生物量和管理区域的大小)所需的植被组成变化的幅度有关的重要问题仍然存在，以及物种建立成功的潜在制约因素(例如营养限制；不利的气候条件等)。此外，只有当生物反馈足够强大，足以调节未来气候变化对野火的影响时，这种管理方案才会奏效：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。 这项研究的目的是探索允许调节野火频率轨迹的区域林分属性设置(物种和林分人口统计)。这将通过创新的动态全球植被模型(DGVM)与古生态数据(花粉、植物宏观遗骸、木炭颗粒)进行配对来实现。使用古生态数据的目的是为模型假设提供一个基于地面的验证。需要检验的假设是，北部林区容易受到气候变暖带来的高度野火活动的影响，这种脆弱性取决于针叶树种在景观中的优势。具体地说，这项工作将对DGVM进行参数化和验证，以应用于加拿大北方受管理的森林，确定这些森林在不同时间和空间尺度上变化的气候下对火灾的影响、暴露和敏感性，以及3.描述植被组成和结构改变对未来火灾活动的潜在影响，并评估各种植被修改方案的利弊。 过去十年，加拿大的灭火成本从每年约5亿美元到10亿美元不等，而2002-2011年期间的财产损失平均为每年350万美元。将火灾扰乱的影响降至最低所带来的经济利益是显而易见的。该项目将提供以科学为基础的信息和技术，加拿大司法机构(如省、地区)将能够利用这些信息和技术作出有关野火的知情决定和政策。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，以及保护人类社区和其他风险价值的风险缓解备选方案。

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.