Collaborative Research: Development of High-Resolution Biomass Burning Records for Tropical South America from Andean Ice Cores

在卫星监测出现之前，南美洲热带地区发生森林火灾的记录很少。因此，对过去火灾活动、气候变化和人类社会之间的关系的基本理解是有限的。亚马逊森林火灾可以通过在大气、生物圈和土壤之间重新分配大量有机碳来显著影响全球碳循环。火灾还会影响森林健康、生物量丰度和生物多样性。这一研究项目将利用保存在高海拔安第斯冰原中的分子有机碳特征提供第一个年度分辨的南美洲热带古火灾记录，从而将过去的森林火灾活动及其与气候多变性和人类活动的联系联系起来。将利用奎尔卡亚(秘鲁)冰芯产生跨越过去1000年的晚全新世生物质燃烧记录，从而包括中世纪暖期和小冰期，该冰芯位于从亚马逊盆地和安第斯山脉接收有机碳输入的良好位置，并提供显著的时间限制。研究人员将使用新开发的分析技术来识别和量化少量冰中的大量痕量有机化合物，提供高分辨率的多分子记录，描述火灾发生和燃烧的材料类型，以及新鲜植被的直接排放。该项目将通过分析沿安第斯山脉和横跨安第斯山脉的其他几个冰芯中的植被有机碳，提供有关高海拔碳循环动力学的信息，这将限制燃烧过程中产生的气溶胶的沉积命运。通过表征与冰芯矿物粉尘和黑碳颗粒相关的较高的植物来源有机碳，研究通过不完全燃烧实现的有机碳固定，并通过放射性碳分析确定其持久性。在以前使用这种方法开发的20世纪火灾记录中观察到的变异性是明显的准周期性的，不同于奎尔卡亚冰芯的氧同位素和尘埃记录，这表明冰芯有机地球化学数据编码了独特的气候和人类信号。通过将这些记录追溯到大约公元1000年，该项目将提供有关南美洲热带森林在主要气候变化和社会发展中的健康状况的有价值的信息，为确定这一重要资源和有机碳库在未来气候变化中的作用提供基础。该项目将提供关于生物质燃烧可变性、热带植被火灾对碳循环的影响以及过去1000年亚马逊人口扩张和随后下降、全球气候显著变化和工业化发生的火灾、气候和人类活动之间的关系的有价值的新信息和见解。该项目产生的生物质燃烧信息将有助于推断亚马逊森林健康状况的变化，亚马逊森林是一种重要的自然和经济资源，受到自然和人类相关过程的影响。亚马逊盆地的植被代表着大气中二氧化碳的巨大汇或源。了解亚马逊盆地植被过去的变化与全球气候变异性之间的关系，对于确定热带森林在未来气候变化中的作用非常重要。

Records of forest fire occurrence in tropical South America are sparse prior to the advent of satellite monitoring. As a result, basic understanding of the relationships between past fire activity, climate variability, and human societies is limited. Amazonian forest fires can significantly affect the global carbon cycle through redistributing large amounts of organic carbon between the atmosphere, biosphere, and soils. Fires also impact forest health, biomass abundance, and biodiversity. This research project will relate past forest fire activity and its connections to climate variability and human activities by providing the first annually resolved tropical South American paleofire records using molecular organic carbon signatures preserved in high-altitude Andean ice fields. A late Holocene biomass burning record spanning the last 1,000 years, thereby including both the medieval warm period and little ice age, will be generated using the Quelccaya (Peru) ice core, which is well situated to receive organic carbon inputs from the Amazon Basin and Andes and affords remarkable temporal constraints. The investigators will use newly developed analytical techniques to identify and quantify numerous trace-level organic compounds in small volumes of ice, providing high-resolution, multi-molecular records that will describe fire occurrence and the type of material that burned as well as direct emissions from fresh vegetation. The project will provide information about high-altitude carbon cycle dynamics through analysis of vegetation-derived organic carbon in several other ice cores along and straddling the Andean range, which will constrain the depositional fate of aerosols generated during burning. Organic carbon sequestration achieved through incomplete burning will be investigated by characterizing higher plant-derived organic carbon associated with ice core mineral dust and black carbon particles, with its persistence determined through radiocarbon analysis. The variability observed in 20th-century fire records previously developed using this approach is pronounced and quasi-periodic and differs from that of Quelccaya ice core oxygen isotopic and dust records, suggesting that ice core organic geochemical data encodes unique climatic and anthropogenic signals. By extending these records back to roughly 1,000 AD, this project will provide valuable information about tropical South American forest health across major climate shifts and societal developments, providing a basis for determining the role of this important resource and organic carbon pool in future climate change.This project will provide valuable new information and insights regarding biomass burning variability, tropical vegetation fire impacts on the carbon cycle, and the relationships between fire occurrence, climate, and human activity over the last 1,000 years, during which time Amazonian populations expanded and subsequently declined, global climate changed significantly, and industrialization occurred. The biomass burning information generated by this project will help infer changes in the health of Amazonian forests, which are a vital natural and economic resource subject to change from both natural and human-related processes. Amazon Basin vegetation represents a vast sink or source of atmospheric carbon dioxide. Understanding how past changes in Amazon Basin vegetation were connected to global climate variability is important in determining the role of tropical forests in future climate change.