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

火在生态学中起着至关重要的作用，特别是在干燥的热带地区，如澳大利亚西北部的热带稀树草原。一个地区燃烧植被和垃圾（生物量）的速度和程度反映了人类活动以及降雨和闪电的数量和时间。试图了解生物质燃烧的历史速率受到很少连续记录，每年分辨率的火灾记录以及跨越多个世纪的记录的阻碍。该项目探索了一种记录历史火灾发生的新方法，通过测量洞穴石笋中捕获的火灾产生的有机化学物质的痕迹。该项目的重点是澳大利亚西北部一个经过充分研究的洞穴中的石笋，以建立一个长达数个世纪的火灾活动记录。此外，这些石笋为构建3000年的夏季季风降雨历史提供了详细的记录。通过结合石笋中所包含的记录，研究人员将提供人类活动和季风降雨在塑造干燥热带地区景观和生态方面所起作用的第一个千年记录。这种新的方法是一种潜在的变革性方法来描述火灾的发生，并将在了解火灾在地球其他地区的历史作用的一般价值。这些信息对土地管理者非常有用。该项目还将为美国一所以本科为主的大学的学生提供研究培训。多环芳烃（PAHs），包括荧蒽、芘、苯并（a）芘和茚并（1，2，3-c，d）芘，由生物质燃烧产生，在环境中具有高持久性。多环芳烃已经从湖泊沉积物中恢复了数千年，以前的研究已经用它们来重建周围流域的火灾历史。研究人员开发了一种从石笋中提取多环芳烃的新方法，并使用石笋碳酸盐的高分辨率230 Th-234 U测年方法进行了初步的多环芳烃分析，结果与烧伤疤痕的卫星地图一致，揭示了2004年是唯一一年经历过洞穴烧伤。因此，这些石笋中的多环芳烃可能代表了一个重要的新的高分辨率记录的史前火灾活动在热带喀斯特地区，如西澳大利亚州，可以补充季风降雨重建提取相同的样品。这个EAGER奖将延长这些石笋中与火有关的有机化合物的分析，通过17世纪世纪，以捕捉燃烧活动的变化与（1）土地利用的变化与欧洲定居在19世纪80年代，（2）季风活动的变化与过渡小冰河时代到现代。

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.