Collaborative Research: Fire Influences on Forest Recovery and Associated Ecosystem Feedbacks in Arctic Larch Forests.

合作研究：火灾对北极落叶松森林恢复和相关生态系统反馈的影响。

• 批准号: 1708344
• 负责人: Michelle Mack
• 金额: $ 25.57万
• 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: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1708344&HistoricalAwards=false
• 关键词: Collaborative; Research; Fire; Influences; Forest

Larch forests overlie extensive areas of Arctic permafrost and contain half the carbon (C) in some boreal forests. Although larch is a fire-dependent tree species, previous research and that of others suggests that increased fire activity may limit larch forest recovery and potentially trigger forest loss and a shift to alternative vegetation dominated by shrubs or grasses. Forest loss could have large consequences for climate because of changes in C storage and reflection of heat and light (albedo). Larch forests occur across much of the Arctic latitudinal treeline, and future larch recruitment dynamics will be a primary determinant of whether boreal forests respond to climate warming via treeline migration. Despite the global importance of these forests and the potential for an altered fire regime to modify recruitment patterns and future forest cover, larch forests remain largely understudied compared to the boreal forests of North America. The many mechanisms governing post-fire larch recruitment and the consequences for system-level feedbacks to regional and global climate remain untested. This research will link constraints on larch forest recruitment after fire to system-wide observations of larch recruitment failure and associated feedbacks to climate.
Boreal forests cover a large portion of the vegetated land area above the Arctic Circle and are a critical component of the Arctic System. In larch forests, increased fire activity associated with climate warming and drying can lead to larch recruitment failure, which in turn can limit forest recovery and trigger forest loss. A transition from forests to successional trajectories dominated by shrubs or grasses could have important consequences for climate feedbacks. The primary objective of this research is to delineate the causes of varying larch recruitment after fire and to quantify the consequences of larch recruitment failure for climate feedbacks via changes in C storage and albedo using a combination of field-based measurements, dendrochronological analysis, remotely-sensed data, and statistical modeling. The project hypothesizes that post-fire larch recruitment will be most constrained by seed sources (i.e., biological legacies) but that environmental conditions (e.g., soil organic layer depth) and biotic interactions (e.g., degree of mycorrhizal colonization and community structure) will impose secondary limitations on recruitment when seed sources are available. Larch recruitment failure will shift successional trajectories to those dominated by shrubs and grasses, resulting in reduced C storage, higher albedo, and cooling of regional climate. We will test hypotheses via field observations and experimental manipulations, combine field- derived data and statistical modeling to determine the factors that most influence larch recruitment, use high-resolution satellite imagery to determine the recent extent of regional larch recruitment failure after fire, and estimate C pools and albedo across gradients of larch recruitment and stand succession to determine the relative system-level consequences of changes in these parameters for regional climate forcing. By focusing on the mechanistic connections between fire and larch recruitment, the research will provide critical information on the net feedback of an intensified fire regime in arctic ecosystems to regional and global climate.
This project will train about 16 undergraduate students, one MS student, three PhD students, and two post-doctoral scholars. It will provide support for four female scientists, two of whom are early-career. It will share results with researchers in Amsterdam for inclusion in a circumpolar map of fire activity and forest recruitment, further improving international collaborations. Research findings will be widely disseminated to the scientific community through publications in scientific journals, presentations at national conference, and professional seminars. PIs will develop and lead a workshop aimed at improving middle school teachers' understanding of climate change science and their ability to effectively teach climate science to students.

落叶松林覆盖在北极永久冻土的广阔区域上，含有一些北方森林一半的碳（C）。虽然落叶松是一种依赖于火的树种，但以前的研究和其他研究表明，火灾活动的增加可能会限制落叶松森林的恢复，并可能引发森林损失，并转向以灌木或草为主的替代植被。森林损失可能会对气候产生重大影响，因为碳储存和反射的热量和光（CO2）的变化。落叶松林发生在北极纬度树线的大部分地区，未来落叶松的招聘动态将是北方森林是否通过树线迁移应对气候变暖的主要决定因素。尽管这些森林的全球重要性和潜在的改变火灾制度，以改变招聘模式和未来的森林覆盖，落叶松林仍然在很大程度上研究相比，北美的北方森林。许多机制管理火灾后落叶松招聘和系统层面的反馈，区域和全球气候的后果仍然未经测试。这项研究将火灾后落叶松森林补充的限制因素与落叶松补充失败的全系统观察和相关的气候反馈联系起来。北方森林覆盖了北极圈以上大部分植被覆盖的陆地面积，是北极系统的重要组成部分。在落叶松林中，与气候变暖和干燥相关的火灾活动增加可能导致落叶松补充失败，这反过来又会限制森林恢复并引发森林损失。从森林过渡到以灌木或草为主的演替轨迹可能对气候反馈产生重要影响。本研究的主要目的是描绘不同的落叶松招聘火灾后的原因和量化的后果落叶松招聘失败的气候反馈，通过C存储的变化，并使用基于现场的测量相结合，年轮分析，遥感数据，统计建模。该项目假设，火灾后落叶松的补充将受到种子来源的最大限制（即，生物遗产），但环境条件（例如，土壤有机层深度）和生物相互作用（例如，菌根定殖的程度和群落结构）将在种子来源可用时对补充施加次级限制。落叶松补充失败将改变演替轨迹，以灌木和草为主，导致减少碳储量，更高的可吸收性，和冷却的区域气候。我们将通过实地观察和实验操作来检验假设，联合收割机结合实地数据和统计建模来确定最影响落叶松补充的因素，使用高分辨率卫星图像来确定火灾后区域落叶松补充失败的近期程度，估算落叶松更新和林分演替梯度上的碳库和碳量，以确定相关系统-这些参数的变化对区域气候强迫的影响。通过关注火灾和落叶松补充之间的机械联系，该研究将提供有关北极生态系统中强化火灾制度对区域和全球气候的净反馈的关键信息。本项目将培养16名本科生、1名硕士生、3名博士生和2名博士后。它将为四名女科学家提供支持，其中两人处于职业生涯初期。它将与阿姆斯特丹的研究人员分享结果，以纳入绕极火灾活动和森林补充的地图，进一步改善国际合作。研究结果将通过在科学期刊上发表、在国家会议上介绍和专业研讨会上向科学界广泛传播。PI将开发和领导一个研讨会，旨在提高中学教师对气候变化科学的理解和他们有效地向学生教授气候科学的能力。

项目成果

Direct and longer-term carbon emissions from arctic-boreal fires: A short review of recent advances

• DOI: 10.1016/j.coesh.2021.100277
• 发表时间: 2021-10
• 期刊: Current Opinion in Environmental Science & Health
• 作者: S. Veraverbeke;C. Delcourt;E. Kukavskaya;M. Mack;X. Walker;Thomas D. Hessilt;B. Rogers;R. Scholten-R.-Sc

Shrubs Compensate for Tree Leaf Area Variation and Influence Vegetation Indices in Post‐Fire Siberian Larch Forests

• DOI: 10.1029/2022jg007107
• 发表时间: 2023-02
• 期刊: Journal of Geophysical Research: Biogeosciences
• 作者: Nadav S. Bendavid;H. Alexander;S. Davydov;Heather Kropp;M. Mack;S. Natali;Seth A. Spawn‐Lee

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

Root‐associated fungi not tree density influences stand nitrogen dynamics at the larch forest–tundra ecotone

• DOI: 10.1111/1365-2745.13882
• 发表时间: 2022-03
• 期刊: Journal of Ecology
• 影响因子: 5.5
• 作者: R. Hewitt;H. Alexander;S. Miller;M. Mack

Range shifts in a foundation sedge potentially induce large Arctic ecosystem carbon losses and gains

• DOI: 10.1088/1748-9326/ac6005
• 发表时间: 2022-03
• 期刊: Environmental Research Letters
• 影响因子: 6.7
• 作者: S. Curasi;N. Fetcher;R. Hewitt;P. Lafleur;M. Loranty;M. Mack;J. May;I. Myers-Smith;S. Natali;S. Oberbauer;Thomas C. Parker;O. Sonnentag;Sergio A Vargas Zesati;S. Wullschleger;A. Rocha