EAGER: Development of a High-Resolution, Multi-Century Paleo-Fire Reconstruction from Tropical Australian Stalagmites

火在生态学中扮演着关键的角色，特别是在干燥的热带地区，如澳大利亚西北部的大草原。一个区域内植被和凋落物(生物量)焚烧的速度和程度既反映了人类活动，也反映了降雨和闪电的数量和时间。很少有连续的记录、年度分辨率的火灾记录以及跨越多个世纪的记录，阻碍了理解生物质燃烧历史速率的尝试。该项目探索了一种记录历史火灾发生的新方法，方法是测量洞穴石笋中捕获的火灾产生的有机化学物质的痕迹。该项目将重点放在澳大利亚西北部一个研究充分的洞穴中的石笋上，以建立一个长达数百年的火灾活动记录。此外，这些石笋还为构建3000年的夏季风降雨史提供了详细的记录。通过结合石笋中的记录，研究人员将提供千禧年来人类活动和季风雨在塑造干燥热带景观和生态方面所起的作用的记录。这一新的方法是描述火灾发生的一种潜在的变革性方法，对于理解火灾在地球其他地区的历史作用将具有普遍价值。这些资料对土地管理人员非常有用。该项目还将为美国一个主要是本科生的机构的学生提供研究培训。多环芳烃(PAHs)，包括荧蒽、芘、苯并(A)芘和吲哚(1，2，3-c，d)芘，是通过燃烧生物质产生的，具有在环境中高度持久性的特点。已经从跨越数千年的湖泊沉积物中发现了多环芳烃，以前的研究已经使用它们来重建周围分水岭的火灾历史。研究人员开发了一种从石笋中提取多环芳烃的新方法，并使用高分辨率230Th-234U对石笋碳酸盐进行了初步的多环芳烃分析，结果表明，石笋碳酸盐的测年方法与卫星地图上的烧伤伤疤一致，表明2004年是唯一经历过洞穴烧伤的年份。因此，这些石笋中的多环芳烃可能代表了西澳大利亚等热带喀斯特地区史前火灾活动的一个重要的高分辨率新记录，并可以补充从相同样本提取的季风降雨重建。这项急切的奖项将把对这些石笋中与火有关的有机化合物的分析扩展到17世纪，以捕捉与以下相关的燃烧活动变化：(1)19世纪80年代与欧洲殖民地有关的土地利用变化；(2)与从小冰河时代向现代过渡相关的季风活动变化。

Fire plays a critical role in ecology, especially in the dry tropics such as the savannas of northwestern Australia. The pace and extent of the burning of vegetation and litter (biomass) in a region reflects both human activities and the amount and timing of rain and lightning. Attempts to understand historic rates of biomass burning are hampered by few continuous records, records of fire at annual resolution, and records that span multiple centuries. This project explores a new method of recording the occurrence of historic fires by measuring traces of organic chemicals produced by fires that are captured within cave stalagmites. The project focuses on stalagmites in a well-studied cave in northwest Australian to develop a multi-century-long record of fire activity. In addition, these stalagmites provide a detailed record for constructing a 3000-year history of summer monsoon rainfall. By combining the records contained in the stalagmites, researchers will provide the first millennial record of the role of human activity and monsoonal rains in shaping the landscape and ecology of the dry tropics. This new methodology is a potentially transformative approach to characterize fire occurrence, and would be of general value in understanding the historic role of fire in other regions of the planet. Such information is extremely useful to land managers. This project will also provide research training for students at a primarily undergraduate US institution.Polycyclic aromatic hydrocarbons (PAHs), including fluoranthene, pyrene, benzo(a)pyrene and indeno(1,2,3-c,d)pyrene, are produced by burning of biomass and are characterized by high persistence in the environment. PAHs have been recovered from lake sediments spanning several millennia and prior studies have used them to reconstruct fire histories of the surrounding watershed. The investigators have developed a novel method for the extraction of PAHs from stalagmites and preliminary PAH analyses using high resolution 230Th-234U dating methods of the stalagmite carbonate were consistent with satellite maps of burn scars in revealing that 2004 was the only year to experience a burn over the cave. PAHs in these stalagmites may thus represent an important new high-resolution record of prehistoric fire activity in tropical karst regions such as Western Australia and can complement the monsoon rainfall reconstructions extracted from the same samples. This EAGER award will extend the analysis of fire-related organic compounds in these stalagmites through the 17th century to capture changes in burn activity associated with (1) changes in land use associated with European settlement in the 1880s, and(2 changes in monsoon activity associated with the transition from the Little Ice Age to the Modern Era.