Siberian fire regime shifts during interglacials of the last 3.6 Myrs inferred from sedimentary records of Lake El’gygytgyn (NE Asia)

根据 Elâgygytgyn 湖（东北亚）的沉积记录推断，西伯利亚火势在过去 3.6 Myrs 的间冰期期间发生了变化

• 批准号: 419058007
• 负责人: Professorin Dr. Elisabeth Dietze
• 金额: --
• 依托单位: Desert Research Institute (DRI)
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/419058007?language=en
• 关键词: Siberian; fire; regime; shifts; during

Predicting and adapting to the impacts of ongoing and future climate change for society requires a deep understanding of internal natural feedbacks at the Earth surface beyond the influence that humans exert on natural ecosystems. The high-northern boreal and tundra biomes are especially sensitive to climate change and play a fundamental role in global biophysical and biogeochemical cycles, for example via their fire regime. However, the long-term feedbacks between fire, vegetation and climate are largely unknown, especially from Eastern Siberia, although long-term natural variability strongly influences short-term variability. Highly uncertain is, if and how currently increasing temperatures over the Arctic and increasing fire activity are already an indication for shifts in fire regimes and if they will be accompanied by biome shifts. The project studies northeastern Siberian fire regime shifts during multiple Plio-Pleistocene interglacials using the only continuous sedimentary record covering the last 3.6 Myrs, i.e., from Lake El’gygytgyn (ICDP Site 5011-1). Focusing on interglacials of different strengths (maximum temperature), biome configurations (tundra, summergreen boreal or evergreen boreal forest) and global land-ocean-atmosphere boundary conditions, I aim to answer the timely questions on what drove long-term shifts in fire regimes in higher latitudes – climate or vegetation, and which internal fire-permafrost erosion feedbacks stabilized or destabilized vegetation types. Regional fire regimes will be reconstructed using (i) sedimentary charcoal composition and influxes as proxies for high-intensity, stand-replacing fires and associated fuels, common in modern evergreen boreal forest, and, from the same samples, (ii) new sedimentary proxies for low-temperature fires – the molecular markers levoglucosan and its isomers, representing the surface fire regime in modern summergreen boreal larch forests.The project renewal aims to shift the focus in the reconstruction of fire histories to warmer-than-present interglacials and determine source-area specific fire regime shifts for the Early Pleistocene in comparison to the Late Pleistocene. To assess the drivers of fire regime shifts, fire records will be statistically compared with quantitative land cover reconstructions from pollen records and independent climate reconstructions from the same site and global compilations. To assess if frequent fires affected permafrost degradation and sediment erosion, the fire records will be statistically compared with regional and local erosional proxies derived from a re-evaluation of existing grain size data sets using end-member modelling analysis. This will allow to conceptualize time-scale dependent fire-climate-vegetation-permafrost relationships under warmer-than-Holocene climates – suitable for the parametrization of fire-vegetation models required for future predictions of high-northern environmental change.

预测和适应当前和未来气候变化对社会的影响，需要深入了解人类对自然生态系统的影响之外地球表面的内部自然反馈。北纬高纬度地区和苔原地区的生物群落对气候变化特别敏感，在全球生物物理和生物地球化学循环中发挥着重要作用，例如通过它们的火灾制度。然而，火灾、植被和气候之间的长期反馈在很大程度上是未知的，特别是在东西伯利亚，尽管长期自然变率强烈影响短期变率。高度不确定的是，目前北极地区不断升高的温度和不断增加的火灾活动是否以及如何已经表明了火灾制度的变化，以及它们是否会伴随着生物群落的变化。该项目利用El 'gygytgyn湖（ICDP Site 5011-1）的唯一连续沉积记录，研究了西伯利亚东北部多个上新世-更新世间冰期的火种变化。关注不同强度的间冰期（最高温度），生物群落配置（苔原，夏季绿色北方森林或常绿北方森林）和全球陆地-海洋-大气边界条件，我的目标是回答关于什么驱动了高纬度地区火灾制度的长期变化的及时问题-气候或植被，以及内部火-永久冻土侵蚀反馈稳定或破坏植被类型。将利用(i)沉积木炭组成和流量作为现代常绿北方森林中常见的高强度、替代林分的火灾和相关燃料的代用物，并从相同的样品中，（ii）低温火灾的新沉积代用物——分子标记物左旋葡萄糖聚糖及其异构体，代表现代夏季绿色北方落叶松森林的地表火灾。该项目的更新旨在将火灾历史重建的重点转移到比现在更温暖的间冰期，并确定与晚更新世相比，早更新世的源区域特定火灾状态的变化。为了评估火情变化的驱动因素，将火灾记录与来自花粉记录的定量土地覆盖重建和来自同一地点和全球汇编的独立气候重建进行统计比较。为了评估频繁的火灾是否会影响永久冻土退化和沉积物侵蚀，将火灾记录与区域和当地的侵蚀代用物进行统计比较，这些代用物来自使用末端成员模型分析对现有粒度数据集的重新评估。这将允许概念化在比全新世更温暖的气候下依赖于时间尺度的火-气候-植被-永久冻土关系，这适用于未来预测高北部环境变化所需的火-植被模型的参数化。