Doctoral Dissertation Research: Holocene Precipitation Variability and its Relationship to Prehistoric Agriculture and Fires

这项博士论文研究项目将使用保存在三个湖泊沉积物岩芯中的树叶蜡的氢同位素分析来重建整个全新世降水的变化。将降水数据与相同沉积物岩心中的古生态证据以及当地和区域考古进行比较，将使研究人员能够检查过去干旱对人类的影响，以及干旱和人类活动对植被和火灾的双重影响。这项研究将有助于更好地理解全新世环境变化，并为史前文明如何应对干旱提供洞察。这项研究的结果将作为案例研究在调查人员提供的课程中分享，包括本科课程、高中生暑期课程，以及为初中和高中教师提供的关于环境变化的研讨会。作为博士论文研究改进奖，该奖项将提供支持，使一名有前途的学生，一名退伍军人，建立一个强大的独立研究生涯。重建过去环境变化的原因，以及这些变化与地球系统中的自然变化而不是人类影响相关的程度，需要一个不受人为景观修改影响的信号。在受史前人类严重影响的地区，混合的环境信号可能会使建立过去干旱的准确记录变得复杂。湖泊沉积物中氢同位素的变化反映了降水的变化，不受人类活动的影响，这项技术可以用于缺乏生物碳酸盐的湖泊沉积物。研究人员将研究哥斯达黎加手头岩心中的氢同位素，以回答三个问题：1)不同生态区和人类干扰梯度的环境历史有何不同？(2)过去降水的变化能否解释考古记录中明显的人口转移？(3)无论人类影响如何，降雨量减少是否都会在高地和低地引发火灾？该项目开发的数据将有助于考古研究和改进火灾管理。

This doctoral dissertation research project will use hydrogen isotope analyses of leaf waxes preserved in sediment cores from three lakes to reconstruct variations in precipitation across the Holocene. Comparing the precipitation data to paleo-ecological evidence in the same sediment cores and to local and regional archaeology will allow the researchers to examine the effects of past droughts on people, and the coupled effects of droughts and human activity on vegetation and fire. The research will contribute to a greater understanding of Holocene environmental change, and provide insight into how prehistoric civilizations responded to drought. The results of this research will be shared as case studies in classes offered by the investigators, including undergraduate courses, summer courses for high school students, and workshops on environmental change offered to middle and high school teachers. As a Doctoral Dissertation Research Improvement award, this award will provide support to enable a promising student, an Army veteran, to establish a strong independent research career.Reconstructing the causes of past environmental changes and the degree to which those changes are related to natural variations in the Earth system rather than human impacts requires a signal that is unaffected by anthropogenic landscape modification. Building accurate records of past droughts can be complicated by mixed environmental signals in areas that were heavily influenced by prehistoric people. Variations in hydrogen isotopes in lake sediments reflect changes in precipitation that are unaffected by human activity, and the technique can be used on sediments from lakes that lack biogenic carbonates. The researchers will study hydrogen isotopes in cores in hand from Costa Rica to answer three questions: 1) How do environmental histories differ across ecological zones and gradients of human disturbance?;(2) Can past variations in precipitation explain population shifts apparent in the archaeological record?; and (3) Does reduced precipitation drive fire at both upland and lowland sites, irrespective of human impact? The data developed in this project will contribute to archaeological research and improved fire management.