Doctoral Dissertation Research: Assessing the Characteristics and Consequences of Prehistoric Land Use in the Cahokia Region

这项博士论文研究项目将调查气候变化和土地利用在卡霍基亚复杂农业社会出现和衰落中的作用。卡霍基亚是格兰德河以北最大的史前美洲原住民聚居地。卡霍基亚位于伊利诺伊州西南部密西西比河流域，靠近今天的圣路易斯。大约4,000年前，北美东部开始发展农业，到公元1050年，密西西比河流域中部出现了卡霍基亚，那里有大约10,000名居民，巨大的土方工程和广阔的贸易网络。尽管卡霍基亚是一个文化和政治中心，但由于尚不清楚的原因，它几乎完全被公元1350年抛弃。一种假设是，长期的干旱或严重的洪水导致了卡霍基亚的衰落。其他史前农业社会似乎极易受到缺水时期的影响，因为缺水导致作物减产并引发社会不稳定。农业集约化造成的环境退化可能加剧了气候变化的影响，并进一步导致了卡霍基亚的衰落。为了评估气候变化和资源过度开发在卡霍基亚出现和衰落中的潜在作用，这名博士生将从密西西比河泛滥平原的四个牛弓湖中收集湖泊沉积物岩心，沿着从卡霍基亚开始向南移动的横断面，向南移动到史前晚期人口较少的地区。从所有的沉积物岩芯中，学生将开发跨越过去两千年的农业扩张和收缩(使用化石花粉、木炭和碳同位素)和水文气候变化(使用沉积物矿物含量和颗粒大小)的长期记录。这些关于不断变化的土地利用、土地覆盖、火灾制度和水文气候条件的高质量记录，使我们能够测试有关环境变化在卡霍基亚荒废中的作用的假设。该项目将有助于更广泛地了解农业社会对土地利用集约化和气候变异性的复原力和脆弱性。通过加深对过去农业社会崩溃原因的理解，该项目将提供关于如何管理当代农业系统以提高其面对环境扰动的复原力的见解。该项目位于地球科学、生态学、地理学和人类学的交汇点，研究人员将在全国会议上向社会科学家和自然科学家展示他们的工作。这项研究的结果将通过在卡霍基亚的解释中心的陈述与公众分享。所有数据将通过新托玛古生态数据库公开，这是一个来自湖泊沉积物岩心数据的在线储存库。作为博士论文研究改进奖，该项目将为有前途的学生建立独立的研究生涯提供支持。

This doctoral dissertation research project will investigate the role of climate change and land use in the emergence and decline of the complex agricultural society at Cahokia, the largest prehistoric Native American settlement north of the Rio Grande. Cahokia was located in southwestern Illinois in the Mississippi River valley near present-day St. Louis. Agriculture began to develop in eastern North America around 4,000 years ago, and by 1050 CE, Cahokia had emerged in the central Mississippi River valley with a population of approximately 10,000 inhabitants, monumental earthworks, and an expansive trade network. Despite its role as a cultural and political center, Cahokia was almost completely abandoned by 1350 CE for reasons that remain unclear. One hypothesis is that prolonged drought or severe flooding caused Cahokia's decline. Other prehistoric agricultural societies appear to have been highly vulnerable to periods of water scarcity that reduced crop yields and triggered social instability. Environmental degradation caused by agricultural intensification may have exacerbated the effects of climatic change and further contributed to Cahokia's decline. To assess the potential role of climate change and resource overexploitation in the emergence and decline of Cahokia, the doctoral student will collect lake sediment cores from four oxbow lakes in in the Mississippi River floodplain along a transect beginning at Cahokia and moving southward towards areas that were less populated during the late prehistoric period. From all sediment cores, the student will develop long-term records of agricultural expansion and contraction (using fossil pollen, charcoal, and carbon isotopes) and hydroclimatic variability (using sediment mineral content and particle-size) that span the last two millennia. These high-quality records of changing land use, land cover, fire regimes, and hydroclimatic conditions that permit tests of hypotheses concerning the role of environmental change in Cahokia's abandonment.This project will contribute to a broader understanding of the resilience and vulnerability of agricultural societies to land-use intensification and climate variability. By developing an understanding of why past agricultural societies collapsed, this project will provide insights into how to manage contemporary agricultural systems in order to increase their resilience in the face of environmental perturbations. This project lies at the intersection of the earth sciences, ecology, geography, and anthropology, and the researchers will present their work at national conferences to both social and natural scientists. The results of this research will be shared with the public through presentations at the interpretive center at Cahokia. All data will be made publicly available through the Neotoma Paleoecology Database, an online repository for data from lake sediment cores. As a Doctoral Dissertation Research Improvement award, this project will provide support to enable a promising student to establish an independent research career.