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了北极地区深刻的环境变化，包括灌木覆盖面积扩大、永久冻土融化和海冰萎缩。这些变化预示着，如果变暖趋势继续下去，将会发生更剧烈的影响。预测这些影响的主要挑战之一是“意外”。在观测记录中保持相对稳定的系统组成部分（通常在北极地区过去几十年）。苔原燃烧可能就是其中之一。现有证据表明，持续的气候和植被变化可能显著增加冻土带的燃烧。例如，初步调查结果揭示了温度和湿度阈值，这些阈值可能会被越过，从而导致燃烧速度远远超过观测记录中所看到的速度。此外，灌木丰富度的显著增加正在改变北极地区的地貌结构，使未来的冻土带火灾制度可能与现代有很大不同。因此，冻土带燃烧正在成为快速变化的北极地区的一个关键过程，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、制定生态系统管理策略以及为北极居民做好应对未来变化的准备至关重要。观测火灾记录的持续时间短，火灾史研究的缺乏，以及未来新的气候和植被的可能性，极大地阻碍了我们评估冻土带火灾制度如何响应未来气候和植被变化的能力。古生态分析和生态建模绕过了这些限制，提供了获取这些信息的唯一途径。本研究利用古生态学和建模方法的互补特性：(1)量化北美北极冻土带生态系统中历史气候-植被-火灾的关系；(2)通过湖泊沉积物的多代理分析，以新的气候和植被组合重建晚冰期和全新世冻土带火灾状况；(3)重新参数化ALFRESCO，(4)对目前最先进的基于生理的冻土带生态系统研究模型ED进行修正；(5)将ED与ALFRESCO结合，模拟与21世纪冻土带火情变化相关的碳动态。这些要素中的每一个都处于各自领域正在进行的研究的前沿，它们共同承诺大大提高我们对过去、现在和未来冻土带生态系统气候-植被-火灾相互作用的认识。科学界很少考虑冻土带生态系统中火灾制度改变的后果，主要是因为冻土带火灾在现代景观中很少发生。北极地区的火灾管理人员缺乏有关冻土带生态系统火灾状况（例如，火灾回火间隔）的最基本知识，无法设计和实施景观级火灾和燃料管理计划。这项研究直接解决了这个问题。21世纪火情的预测模拟将为阿拉斯加的火灾管理规划和政策提供直接相关的信息。研究人员将通过该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各州自然资源管理者对过去、现在和未来气候-火灾关系范围的更好理解。

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.