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

落叶松森林覆盖在北极的大片永久冻土层上，含有的碳(C)是一些北方森林的一半。虽然落叶松是一种依赖火灾的树种，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和向以灌木或草为主的替代植被的转变。由于碳储量和热、光反射（反照率）的变化，森林损失可能对气候产生重大影响。落叶松森林分布在北极纬向树线的大部分地区，未来落叶松的补充动态将是北方森林是否通过树线迁移对气候变暖做出反应的主要决定因素。尽管这些森林在全球具有重要意义，而且火灾制度的改变有可能改变森林的补充模式和未来的森林覆盖，但与北美的北方针叶林相比，落叶松森林在很大程度上仍未得到充分研究。控制火灾后落叶松补充的许多机制以及对区域和全球气候的系统级反馈的后果仍未经检验。这项研究将把火灾后对落叶松森林补充的限制与落叶松补充失败的全系统观测和相关的气候反馈联系起来。北方森林覆盖了北极圈以上植被覆盖面积的很大一部分，是北极系统的一个重要组成部分。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，这反过来又可能限制森林恢复并引发森林损失。从森林到以灌木或草为主的演替轨迹的转变可能对气候反馈产生重要影响。本研究的主要目的是利用野外测量、树木年代学分析、遥感数据和统计建模相结合的方法，描述火灾后落叶松补充变化的原因，并通过碳储量和反照率的变化来量化落叶松补充失败对气候反馈的影响。该项目假设火灾后落叶松的补充将受到种子来源（即生物遗产）的最大限制，但当种子来源可用时，环境条件（如土壤有机层深度）和生物相互作用（如菌根定植程度和群落结构）将对补充施加次要限制。落叶松补充失败将使演替轨迹转向以灌木和禾草为主的演替轨迹，导致碳储量减少、反照率升高和区域气候变冷。我们将通过实地观测和实验操作来检验假设，结合实地数据和统计建模来确定最影响落叶松招募的因素，使用高分辨率卫星图像来确定火灾后区域落叶松招募失败的近期程度。估算落叶松增收和林分演替梯度上的碳库和反照率，以确定这些参数变化对区域气候强迫的相对系统水平影响。通过关注火灾与落叶松增收之间的机制联系，该研究将提供关于北极生态系统中火灾加剧对区域和全球气候的净反馈的关键信息。本项目将培养约16名本科生，1名硕士研究生，3名博士研究生，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早期。它将与阿姆斯特丹的研究人员分享结果，以纳入火灾活动和森林招募的环极地图，进一步改善国际合作。研究成果将通过在科学期刊上的出版物、在国家会议上的报告和专业研讨会向科学界广泛传播。pi将开发并领导一个研讨会，旨在提高中学教师对气候变化科学的理解，以及他们向学生有效教授气候科学的能力。

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.