Collaborative Research: Integrating paleoecological analysis and ecological modeling to elucidate the responses of tundra fire regimes to climate change

最近的气候变暖导致北极的环境发生了深刻的变化，包括灌木覆盖的扩大、永久冻土的融化和海冰的收缩。这些变化预示着，如果变暖趋势继续下去，将会发生更戏剧性的影响。预测这些影响的主要挑战包括？惊喜？在观测记录中保持相对稳定的系统组件(在北极地区通常是过去几十年)。冻土带燃烧可能就是这样的一个组成部分。现有证据表明，持续的气候和植被变化可能会显著增加冻土带的燃烧。例如，初步的发现揭示了温度和水分的阈值，这两个阈值可能会超过这两个阈值，从而导致燃烧速度远远超过观测记录中看到的速度。此外，灌木丰度的显著增加正在改变北极地区的地貌结构，以至于未来的冻土带火灾制度可能与现代截然不同。因此，在快速变化的北极，冻土带燃烧正在成为一个关键过程，了解冻土带火灾对气候变化的响应对于预测地球系统动力学、制定生态系统管理战略和为北极居民准备应对未来变化至关重要。观测火灾记录的持续时间短，火灾历史研究的匮乏，以及未来新颖气候和植被的可能性极大地阻碍了我们评估冻土带火灾对未来气候和植被变化的响应能力。古生态分析和生态建模绕过了这些限制，提供了获取此类信息的唯一途径。这项研究利用古生态和模拟方法的互补性，(1)量化北美北极冻土带生态系统中历史上的气候-植被-火关系，(2)对湖泊沉积物进行多代理分析，以利用气候和植被的新组合重建冰川晚期和全新世时期的冻土带火灾状况，(3)重建室外景观生态系统模型，最初开发的景观生态系统模型是为了研究亚北极植被对气候和火灾状况变化的响应，用于预测21世纪IPCC气候情景下的苔原火灾状况，(4)修正ED，一种最先进的基于生理学的冻土带生态系统研究模型，以及(5)将ED与露天相结合，以模拟与21世纪冻土带火区变化相关的碳动态。这些元素中的每一个都处于各自领域正在进行的研究的前沿，它们共同承诺极大地促进我们对过去、现在和未来冻土带生态系统气候-植被-火相互作用的了解。科学界很少考虑冻土带生态系统火制度变化的后果，主要是因为现代地形上冻土带火灾很少发生。北极地区的消防管理人员缺乏关于冻土带生态系统火情的最基本知识(例如，火势回归间隔)，无法设计和实施景观级的火情和燃料管理计划。这项研究直接解决了这个问题。对21世纪火灾状况的预测模拟将提供与阿拉斯加火灾管理规划和政策直接相关的信息。研究人员将通过这个项目与联邦管理机构的科学家合作。这一伙伴关系促进了联邦和州自然资源管理者对过去、现在和未来气候-火灾关系的更好理解。

Recent climate warming has resulted in profound environmental changes in the Arctic, including shrub-cover expansion, permafrost thawing, and sea-ice shrinkage. These changes foreshadow more dramatic impacts that will occur if the warming trend continues. Among the major challenges in anticipating these impacts are ?surprises? in system components that have remained relatively stable in the observational record (typically past few decades in arctic regions). Tundra burning is potentially one such component. Available evidence suggests that ongoing climate and vegetation change could significantly increase tundra burning. For example, preliminary findings reveal temperature and moisture thresholds, which may be crossed to result in burning rates that far exceed those witnessed in the observational record. In addition, a marked increase in shrub abundance is changing the physiognomic structure of arctic regions such that future tundra fire regimes may differ vastly from modern. Thus tundra burning is emerging as a key process in the rapidly changing Arctic, and knowledge of tundra fire-regime responses to climate change is essential for projecting Earth system dynamics, developing ecosystem management strategies, and preparing arctic residents for future change.The short duration of observational fire records, paucity of fire-history studies, and possibility of novel future climate and vegetation greatly hinder our ability to evaluate how tundra fire regimes may respond to future climate and vegetation change. Paleoecological analysis and ecological modeling circumvent these limitations and offer the only ways to acquire such information. This research takes advantage of the complementary properties of paleoecological and modeling approaches to (1) quantify historic climate-vegetation-fire relationships in the tundra ecosystems of the North American Arctic, (2) conduct multi-proxy analyses of lake sediments to reconstruct tundra fire regimes during periods of the late Glacial and Holocene with novel combinations of climate and vegetation, (3) reparameterize ALFRESCO, a landscape ecosystem model initially developed to study the response of subarctic vegetation to changes in climate and fire regimes, for predicting tundra fire regimes under the suite of IPCC climate scenarios for the 21st century, (4) modify ED, a state-of-the-art physiologically-based model for tundra ecosystem studies, and (5) couple ED with ALFRESCO to simulate carbon dynamics related to 21st-century shifts in tundra fire regimes. Each of these elements is at the forefront of ongoing research in the respective areas, and together they promise to substantially advance our knowledge of climate-vegetation-fire interactions of tundra ecosystems for the past, present, and future.The consequences of altered fire regimes in tundra ecosystems are rarely considered by the scientific community, largely because tundra fires occur infrequently on the modern landscape. Fire managers in the Arctic lack the most fundamental knowledge about the fire regimes of tundra ecosystems (e.g., fire return intervals) for the design and implementation of landscape-level fire and fuels management plans. This research addresses this issue directly. The prognostic simulations of the 21st century fire regime will provide information directly relevant to fire management planning and policy in Alaska. The researchers will collaborate with scientists from federal management agencies through this project. This partnership promotes an improved understanding of the range of past, present, and future climate-fire relationships by federal and state natural resource managers.