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

气候变暖可能改变北纬高纬度针叶林和泥炭地碳平衡的最快方式之一是通过更强烈的野火。大多数可以燃烧的碳出现在厚厚的土层中，这些土层往往有数百到数千年的历史，是过去野火的遗留问题，这些土层的燃烧是火灾期间释放的碳的最大来源。2014年夏天，野火烧毁了加拿大西北地区(NWT)340万公顷的林地，是年均烧毁面积的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加拿大团队，以极大地方便通过浮式飞机和直升机进行访问，并获得对地理空间数据的访问。将与西北地区林业司和阿拉斯加火灾科学讨论会合作，并通过冬季网络研讨会，与土地和消防管理人员分享成果。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。该项目的目标是从机制上理解控制这些生态系统中遗留碳损失的火灾特征。更强烈的火灾会导致更深的燃烧，并最终决定更强烈的火灾是否会像所提出的那样，通过碳循环加速气候变暖。它们还可以迅速将生态系统从多个火灾周期中从大气中净积累的碳转变为净损失。在大而多样的景观和多个空间上独立的火灾伤疤上的高火灾强度将使研究设计能够在关键景观位置复制自然火灾严重程度梯度。放射性碳测年的一种新应用将与广泛使用和可扩展的有机物燃烧指标相结合，以特定地点为基础量化遗留碳损失的大小。将建立永久地块，对永久冻土和植被进行长期监测，这是对该生物群碳循环的关键控制。早期的活动将使人们能够对特定地点的碳排放、遗留损失、永久冻土的初始下沉和随之而来的地点排水变化以及半粘性种子的传播做出最佳估计。这项研究将有助于关于跨时间尺度的联系和相互作用的新兴生态系统理论，以及这些联系和相互作用在生态系统过程对变化的干扰制度的复原力或脆弱性中可能发挥的作用。

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.