Doctoral Dissertation Research: Holocene Climatic and Ecologic History of the Northern Great Basin

博士论文研究：北部大盆地全新世气候与生态史

• 批准号: 0220966
• 负责人: Cathy Whitlock
• 金额: $ 0.55万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-15 至 2003-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0220966&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Holocene; Climatic

The objectives of this doctoral dissertation research project are to reconstruct the climate, vegetation, and fire history in the northern Great Basin from an examination of fossil pollen and charcoal records contained in lake-sediment cores. The Great Basin is a region of diverse topography, vegetation, and climate, and as such it provides an excellent opportunity to study the response of ecosystems to a wide array of environmental changes in the past. By focusing on three lake sites at different elevations, this study will (1) elucidate the response of vegetation and fire regimes to changes in effective moisture, temperature, and other bioclimatic variables; (2) reconstruct the biogeographic history of important conifer species growing at different elevations; and (3) apply modern pollen-climate relations in western North America to identify the magnitude of past climate and vegetation changes. Past changes in vegetation will be determined by changes in the relative and absolute abundances of pollen types in stratigraphic records. The presence of plant macrofossils in the cores will help confirm species identifications in cases where the pollen cannot. Variations in past fire activity will be inferred from changes in the rates of macroscopic charcoal accumulation in contiguous samples. Interpretation of the fossil pollen data in terms of past climate and vegetation will be based on the quantitative relationship between modern pollen data and present-day climate information. The chronology of environmental changes will be developed from a series of radiocarbon dates and lead-210 dates, as well as the age of known tephra layers. The products of this study will be a better understanding of Holocene forest development at different elevations in the northern Great Basin, and information on the role of fire and climate in the ecological history.The results of this research will contribute to a better understanding of (1) the effects of global climate change, past and present, on regional vegetation patterns and fire regimes in the Great Basin; (2) modern pollen-climate relations and their use in the reconstruction of past climates; and (3) the environmental controls on human activities in the northern Great Basin during the Holocene. Since 1988, the western U.S. has experienced a number of large, stand-replacing fires. In the year 2000 over 8 million acres burned in the U.S., and in the first six months of 2002 there have been ~2.5 million acres consumed by wildland fires. Many of these fires may be attributable to anomalously dry conditions throughout the west. Heightened fire activity is predicted in models of future climate change, and the best analogue for these conditions may be past periods when the climate was warmer- and drier-than-present. By understanding the linkages between climate, vegetation, and fire in the past, recent fire events can be placed within a context of natural variations occurring on decadal-to-millennial time scales. Information on the natural range of variability will help land-use managers in the United States develop strategies that consider forest sensitivity to climate change and disturbance regimes. The use of modern pollen and climate analogues will improve our ability to reconstruct past climate conditions from fossil pollen records. Pollen data are the primary terrestrial database used to reconstruct past climate, so this refinement is an important contribution to paleoclimatology and geography. Finally, this study will contribute to archeology by providing an environmental backdrop for cultural changes in the Great Basin. Periods of drought, for example, seem to be associated with changes in subsistence patterns in this region. This research will help to clarify these relationships. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

该博士学位论文研究项目的目的是通过检查湖泊核心中包含的化石花粉和木炭记录来重建北部大盆地的气候，植被和火灾历史。 大盆地是一个各种地形，植被和气候的地区，因此为研究生态系统对过去的各种环境变化的反应提供了绝佳的机会。 通过关注不同海拔的三个湖泊地点，这项研究将（1）阐明植被和火灾对有效水分，温度和其他生物气候变量变化的反应； （2）重建在不同海拔的重要针叶树种类的生物地理历史； （3）在北美西部应用现代花粉气候关系来确定过去气候和植被变化的幅度。 植被的过去变化将取决于地层记录中花粉类型的相对和绝对丰富性的变化。 岩心中植物大化石的存在将有助于在花粉不能的情况下确认物种鉴定。 过去的火灾活动的变化将从连续样品中宏观木炭积累速率的变化推断出来。 在过去的气候和植被方面，对化石花粉数据的解释将基于现代花粉数据与当今气候信息之间的定量关系。 环境变化的年表将从一系列放射性碳日期和铅-210日期以及已知的tephra层的年龄开发。 这项研究的产品将更好地了解北部大盆地不同海拔的全新世森林发展，以及有关火和气候在生态史上作用的信息。这项研究的结果将有助于更好地理解（1）全球气候变化，过去和现在对大盆地区域植被模式和火灾制度的影响； （2）现代花粉气候关系及其在过去气候的重建中的使用； （3）全新世期间对北部大盆地人类活动的环境控制。 自1988年以来，美国西部经历了许多大型，替代的大火。 在2000年，在美国燃烧了超过800万英亩的土地，在2002年的前六个月中，荒地大火消耗了约250万英亩的土地。 这些大火中的许多可能归因于整个西方的异常干燥条件。 未来气候变化的模型预测了火灾活动的增强，并且对于这些条件的最佳类似物可能是气候温暖和更干燥的时期。 通过了解过去的气候，植被和火之间的联系，最近可以在十年到千禧年的时间尺度上发生自然变化的情况下，将最近的火灾事件放置。 关于自然变异性范围的信息将帮助美国制定策略，以考虑森林对气候变化和干扰制度的敏感性。 现代花粉和气候类似物的使用将提高我们从化石花粉记录中重建过去气候条件的能力。 花粉数据是用于重建过去气候的主要陆地数据库，因此这种完善是对古气候和地理学的重要贡献。 最后，这项研究将通过为大盆地的文化变化提供环境背景来促进考古学。 例如，干旱时期似乎与该地区的生存模式的变化有关。 这项研究将有助于阐明这些关系。 作为博士学位论文研究改进奖，该奖项还将提供支持，使有前途的学生能够建立强大的独立研究职业。