Collaborative Research: Fire regime influences on carbon dynamics of Siberian boreal forests

合作研究：火灾状况对西伯利亚北方森林碳动态的影响

• 批准号: 1545558
• 负责人: Michelle Mack
• 金额: $ 8.18万
• 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: 2015-05-01 至 2018-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1545558&HistoricalAwards=false
• 关键词: Collaborative; Research; Fire; regime; influences

Boreal forests cover 40% of the vegetated land area above the Arctic Circle and are a critical component of arctic ecosystems. Global change models predict boreal forests will become increasingly susceptible to fire activity with climate warming. Because these forests contain a large proportion of global terrestrial carbon (C) stocks, changes in the fire regime are likely to alter global C cycling. Increased fire activity will increase C emissions to the atmosphere, with a potential positive feedback to climate warming. However, an altered fire regime may also initiate cascading effects on forest regrowth and permafrost degradation that could magnify or offset this feedback. Fire effects on these ecological mechanisms remain uncertain but will ultimately determine whether arctic ecosystems act as a C source or sink under future climate change scenarios. The primary objective of this research is to increase our understanding of post-fire C dynamics in boreal forests of the Siberian arctic by elucidating the ecological mechanisms by which increased fire severity could influence C accumulation and storage over the successional interval. The overarching hypothesis is that post-fire soil organic layer (SOL) depth regulates net ecosystem carbon balance (NECB) through indirect impacts on forest regrowth and permafrost stability because of its role as a barrier to seed germination and thermal regulator. The team will: 1) link near term fire effects on SOL depth to changes in larch recruitment and permafrost characteristics in experimental burn plots created in 2012, 2) determine the relationship between post-fire stand structure and above- and belowground C pools at the local and landscape level across stands of varying age and topographic positions, and 3) test via experimental manipulations and field observations the mechanisms by which fire-driven changes in stand density indirectly affect moss growth, SOL development, and susceptibility of deeper C pools to warming, decomposition, and release into the atmosphere. This research will offer novel insights into the importance of both vegetation and soil processes within arctic ecosystems in determining the net feedback of an intensified fire regime to the climate system.Intellectual Merit: Larch forests of the Siberian arctic comprise 20% of all boreal forest ecosystems and are distinct from other boreal forests in that they consist of a single tree genus (Larix spp.) with a deciduous growth habit and often grow on continuous, C-rich ?yedoma? permafrost. Thus, their response to warming climate and an altered fire regime is likely to differ from boreal forests in other regions. Uncertainties regarding current C pools in Siberian boreal forests remain a significant factor affecting our ability to predict climate-induced changes to the global C cycle. The proposed study will contribute to our understanding of how arctic forest fires impact global C cycling and provide essential data necessary for scaling-up arctic C pools, estimating C emissions from arctic fires, and calibrating predictive models of future global C cycling.Broader Impacts: This project will result in the training of undergraduate and graduate students from two predominantly undergraduate institutions and one Hispanic-Serving Institution. The PI and her students will develop outreach activities with local K-12 schools in south Texas to help teachers create lesson plans involving arctic science, boreal ecology, and climate change and involve researcher presentations to science classrooms to provide real-life examples of arctic research and expose K-12 students to different career and educational paths in the sciences.

北方森林覆盖了北极圈以上植被面积的40%，是北极生态系统的重要组成部分。全球变化模型预测，随着气候变暖，北方森林将变得越来越容易受到火灾活动的影响。由于这些森林含有全球陆地碳 (C) 储量的很大一部分，因此火灾状况的变化可能会改变全球碳循环。火灾活动的增加将增加向大气中的碳排放，对气候变暖有潜在的积极反馈。然而，火势的改变也可能对森林再生和永久冻土退化产生连锁效应，从而放大或抵消这种反馈。火灾对这些生态机制的影响仍然不确定，但最终将决定北极生态系统在未来气候变化情景下是否充当碳源或碳汇。本研究的主要目的是通过阐明火灾严重程度增加可能影响演替期间碳积累和储存的生态机制，增加我们对西伯利亚北极北方森林火灾后碳动态的了解。总体假设是，火后土壤有机层（SOL）深度通过对森林再生和永久冻土稳定性的间接影响来调节净生态系统碳平衡（NECB），因为它作为种子发芽和温度调节的障碍。该团队将：1）将近期火灾对 SOL 深度的影响与 2012 年创建的实验燃烧地块中落叶松补充和永久冻土特征的变化联系起来，2）确定火灾后的林地结构与地上和地下碳池之间的关系不同年龄和地形位置的林分的局部和景观水平，以及 3) 通过实验操作和现场观察测试火灾驱动的林分密度变化间接影响苔藓生长、SOL 发展和敏感性的机制更深的碳库变暖、分解并释放到大气中。这项研究将为北极生态系统中植被和土壤过程的重要性提供新的见解，以确定强化火灾对气候系统的净反馈。智力价值：西伯利亚北极的落叶松森林占所有北方森林生态系统的 20%与其他北方森林的不同之处在于，它们由具有落叶生长习性的单一树属（落叶松属）组成，并且通常生长在连续的、富含碳的土地上？耶多玛？永久冻土。因此，它们对气候变暖和火势变化的反应可能与其他地区的北方森林不同。西伯利亚北方森林当前碳库的不确定性仍然是影响我们预测气候引起的全球碳循环变化能力的一个重要因素。拟议的研究将有助于我们了解北极森林火灾如何影响全球碳循环，并为扩大北极碳库、估算北极火灾的碳排放以及校准未来全球碳循环的预测模型提供必要的基本数据。 更广泛的影响：该项目将对来自两所本科院校和一所西班牙裔服务机构的本科生和研究生进行培训。 PI 和她的学生将与德克萨斯州南部当地的 K-12 学校开展外展活动，帮助教师制定涉及北极科学、北方生态学和气候变化的课程计划，并让研究人员在科学课堂上进行演示，以提供北极研究的现实例子让 K-12 学生接触不同的科学职业和教育路径。