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

RAPID：火灾严重性增加以及北方生态系统遗留碳的损失

• 批准号: 1542150
• 负责人: Michelle Mack
• 金额: $ 5万
• 依托单位: Northern Arizona University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1542150&HistoricalAwards=false
• 关键词: RAPID; Increasing; fire; severity; loss

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.

气候变暖改变北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。大多数可燃烧的碳发生在厚厚的土壤层中，这些土壤层通常有数百年至数千年的历史，是过去野火的遗留物，这些层的燃烧是火灾期间释放碳的最大来源。 2014年夏天，加拿大西北地区（NWT）的山火烧毁了340万公顷林地，是年平均烧毁面积的八倍，是当年美国山火烧毁面积的两倍。该项目将研究这些火灾对遗留碳燃烧的影响。研究人员还将加入加拿大的快速反应小组，以极大地方便通过水上飞机和直升机进行访问，并获取地理空间数据。结果将与西北地区林业部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者分享。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。该项目的目标是建立对控制这些生态系统中遗留碳损失的火灾特征的机械理解。正如人们所提出的那样，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通过碳循环加速气候变暖。它们还可以迅速使生态系统跨越一个阈值，从多个火灾周期中大气中碳的净积累到净损失。大型且多样化的景观中的高火灾强度以及多个空间上独立的火痕将使研究设计能够在关键景观位置上复制自然火灾严重程度梯度。放射性碳测年的新颖应用将与广泛使用且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措施。早期活动将能够对特定地点的碳排放、遗留损失、永久冻土的初始沉降和随后的地点排水变化以及半浆液种子的传播进行最佳估计。这项研究将有助于新兴生态系统理论的跨时间尺度联系和相互作用，以及它们在生态系统过程对不断变化的扰动机制的恢复力或脆弱性中可能发挥的作用。