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大片永久冻土之上，并含有一些北方森林中一半的碳(C)。虽然落叶松是一种依赖火的树种，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和转向以灌木或草为主的替代植被。由于碳储存和热光反射(反照率)的变化，森林损失可能会对气候产生重大影响。落叶松森林分布在北极大部分纬度林线上，未来的落叶松吸收动态将是决定北方森林是否通过树线迁移来应对气候变暖的主要决定因素。尽管这些森林具有全球重要性，并有可能改变火灾制度以改变招募模式和未来的森林覆盖率，但与北美的北方森林相比，落叶松森林在很大程度上仍未得到充分的研究。管理火灾后落叶松复垦的许多机制以及系统一级对区域和全球气候的反馈的后果仍未得到检验。这项研究将把火灾后对落叶松森林吸收的限制与系统范围内对落叶松吸收失败的观察以及相关的气候反馈联系起来。北方森林覆盖了北极圈上方大部分植被覆盖的陆地区域，是北极系统的关键组成部分。在落叶松森林中，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。从森林过渡到以灌木或草为主的演替轨迹可能会对气候反馈产生重要影响。本研究的主要目的是通过结合野外测量、树种年代学分析、遥感数据和统计模型，描述火灾后落叶松不同补给量的原因，并通过碳储量和反照率的变化来量化落叶松补充量失败对气候反馈的影响。该项目假设，火烧后的落叶松更新将受到种子来源(即生物遗产)的最大限制，但当种子来源可用时，环境条件(例如土壤有机层深度)和生物相互作用(例如菌根定殖度和群落结构)将对更新施加次要限制。落叶松更新失败将使演替轨迹转向以灌木和草本植物为主的演替轨迹，导致碳贮量减少，反照率升高，区域气候降温。我们将通过野外观测和实验操作检验假设，结合野外数据和统计模型来确定最大程度影响落叶松吸收的因素，使用高分辨率卫星图像来确定火灾后区域落叶松吸收失败的近期程度，并估计落叶松吸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后果。通过重点研究火灾和落叶松补给之间的机械联系，这项研究将提供关于北极生态系统强化的火灾制度对区域和全球气候的净反馈的关键信息。该项目将培训大约16名本科生、1名理科硕士学生、3名博士生和2名博士后学者。它将为四名女科学家提供支持，其中两名是职业生涯早期的科学家。它将与阿姆斯特丹的研究人员分享结果，将其纳入环极火灾活动和森林招募地图，进一步改善国际合作。研究成果将通过在科学期刊上发表文章、在全国会议上发表演讲和专业研讨会向科学界广泛传播。PIS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，并提高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.