RAPID: Increasing fire severity and the loss of legacy carbon from boreal ecosystems

气候变暖可能改变高北方纬度针叶林和泥炭地碳平衡的最快方式之一是通过更激烈的野火。大多数可以燃烧的碳发生在厚土层中，通常有数百至数千年的历史，这是过去野火的遗产，这些土层的燃烧是火灾期间释放的最大碳源。2014年夏天，野火烧毁了加拿大西北地区340万公顷的林地，是平均年烧毁面积的8倍，是当年美国野火烧毁面积的两倍。该项目将研究这些火灾对遗留碳燃烧的影响。研究人员还将加入一个快速反应的加拿大小组，以极大地促进通过水上飞机和直升机的访问，并获得地理空间数据。研究结果将与西北地区林业部门和阿拉斯加火灾科学研讨会合作，并通过冬季网络研讨会与土地和火灾管理人员分享。该项目还将为PI，博士后研究员和本科生提供新的国际研究经验。该项目的目标是开发控制这些生态系统中遗留碳损失的火灾特性的机械理解。更强烈的火灾导致更深的燃烧，并最终决定更强烈的火灾是否会通过碳循环加速气候变暖。它们还可以迅速改变生态系统，使其跨越一个阈值，从多个火灾周期的大气碳净积累到净损失。在大型和不同的景观和多个，空间上独立的火痕高火灾强度将使研究设计与复制自然火灾严重度梯度在关键景观位置。放射性碳测年的一个新应用将与广泛使用的和可扩展的有机物燃烧指标相结合，以量化特定地点遗留碳损失的程度。将建立永久性地块，用于长期监测永久冻土和植被，这是该生物群落碳循环的关键控制因素。早期活动将能够最好地估计特定地点的碳排放量、遗留损失、永久冻土的初始沉降和随后的场地排水变化以及半干旱种子的传播。这项研究将有助于新兴的生态系统理论的跨时间尺度的联系和相互作用，这些可能发挥的作用，在生态系统过程的弹性或脆弱性不断变化的干扰制度。

One of the most rapid ways climate warming could alter the carbon balance of high northern latitude conifer forests and peatlands is through more intense wildfires. Most of the carbon that can burn occurs in thick soil layers often hundreds to thousands of years old that are a legacy of past wildfires, and combustion of these layers accounts for the largest source of carbon released during fires. In the summer of 2014, wildfires burned 3.4 million hectares of forested lands of the Northwest Territories (NWT), Canada, eight times greater than the average annual area burned, and twice as much area as burned in United States wildfires that year. This project will study the impacts of these fires on the combustion of legacy carbon. Researchers will also join a rapid-response Canadian team to greatly facilitate access via floatplane and helicopter, and to gain access to geospatial data. Results will be shared with land and fire managers in collaboration with the NWT Division of Forestry and the Alaska Fire Science Symposium and through a winter webinar. The project will also provide new international research experience for a PI, postdoctoral researcher and undergraduate student.The objective of this project is to develop a mechanistic understanding of fire characteristics that control legacy carbon loss in these ecosystems. More intense fires result in deeper burning and ultimately determine whether more intense fires will accelerate climate warming via the carbon cycle, as has been proposed. They also could rapidly shift ecosystems across a threshold from net accumulation of carbon from the atmosphere over multiple fire cycles to net loss. High fire intensity across large and varied landscapes and multiple, spatially independent fire scars will enable a study design with replicate natural fire severity gradients across key landscape positions. A novel application of radiocarbon dating will be combined with widely used and scalable metrics of organic matter combustion to quantify the magnitude of legacy carbon loss on a site-specific basis. Permanent plots will be established for long-term monitoring of permafrost and vegetation, key controls over the carbon cycle in this biome. An early campaign will enable the best estimates of site-specific carbon emissions, legacy losses, initial subsidence of permafrost and ensuing changes in site drainage, and dispersal of semi-serotinous seeds. This research will contribute to emerging ecosystem theory on cross-time scale linkages and interactions and the role these may play in the resilience or vulnerability of ecosystem processes to shifting disturbance regimes.