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

RUI：合作研究：火情对西伯利亚北方森林碳动态的影响

• 批准号: 1623764
• 负责人: Michael Loranty
• 金额: $ 18.92万
• 依托单位: Colgate 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: 2015-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1623764&HistoricalAwards=false
• 关键词: RUI; Collaborative; Research; Fire; regime

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.

北方森林覆盖北极圈上方的植被土地面积的40％，是北极生态系统的关键组成部分。全球变化模型预测，北方森林将越来越容易受到气候变暖的火灾活动。由于这些森林包含大部分全球陆地碳（C）股票，因此火灾状况的变化可能会改变全球C骑行。增加的火灾活动将增加对大气的c排放，并可能对气候变暖产生积极的反馈。但是，改变的火势也可能对森林再生和多年冻土降解产生级联影响，从而可以放大或抵消此反馈。对这些生态机制的火灾影响仍然不确定，但最终将确定北极生态系统在未来的气候变化情景下是否起到C来源或下沉。这项研究的主要目的是通过阐明火灾严重程度增加可能会影响c的累积和存储在继任时间间隔内，通过阐明西伯利亚北极北极北极森林中的火灾C动态的理解。总体假设是，后射击土壤有机层（SOL）深度通过间接影响净生态系统碳平衡（NECB）对森林再生和永久冻土稳定性的影响，因为它作为种子发芽和热调节剂的障碍。团队将：1）在2012年创建的实验性烧伤图中，链接对溶胶深度的近期火力对溶液深度的影响与落叶藻募集和多年冻土特征的变化； 2）确定火后燃烧图和地下C池之间的关系跨不同年龄和地形位置跨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的测试，该机制的机制是，架子密度的火力变化间接影响了苔藓的生长，SOL的发展，SOL的发育，以及更深的C池对变暖的敏感性，分解并释放到大气中。这项研究将为北极生态系统内植被和土壤过程的重要性提供新的见解并且与其他北方森林不同，因为它们由一个具有落叶生长习惯的单个树属（Larix spp。）组成，并且经常在连续的，富含C的Yedoma上生长？多年冻土。因此，它们对温暖气候和火灾状况改变的反应可能与其他地区的北方森林有所不同。关于西伯利亚北方森林中当前C池的不确定性仍然是一个重要因素，影响了我们预测气候引起的全球C周期变化的能力。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C循环，并提供扩大北极C池，估算北极火灾的C排放以及对未来全球C循环的预测模型的必要数据。该项目将导致对两个主要是本科机构和一家西班牙裔服务机构的本科生和研究生的培训。 PI和她的学生将与德克萨斯州南部的本地K-12学校开展外展活动，以帮助教师制定涉及北极科学，北方生态和气候变化的课程计划，并参与研究人员向科学课堂进行研究，以提供北极研究的实例并将K-12学生暴露于科学中的不同职业和教育道路上。

项目成果

Increasing tree density accelerates stand‐level nitrogen cycling at the taiga–tundra ecotone in northeastern Siberia

• DOI: 10.1002/ecs2.4175
• 发表时间: 2022-07
• 期刊: Ecosphere
• 影响因子: 2.7
• 作者: R. Hewitt;H. Alexander;Brian Izbicki;M. Loranty;S. Natali;X. Walker;M. Mack