Doctoral Dissertation Research: Century-Scale Forest Dynamics From 20,000-10,000 Yr B.P. in the Western Klamath Mountains, California

博士论文研究：距今 20,000-10,000 年的世纪尺度森林动力学

• 批准号: 0221043
• 负责人: Roger Byrne
• 金额: $ 0.8万
• 依托单位: University of California-Berkeley
• 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: 2002-08-01 至 2004-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0221043&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Century; Scale

Long pollen records of terrestrial vegetation change are used to quantify past climatic conditions, to identify mechanisms of past climatic variability, to verify model simulations of past climate, and to reconstruct past biogeographic patterns. A gap currently exists in such records regarding glacial to recent conditions near the coast from central Oregon to central California. The goal of this doctoral dissertation research project is to develop a high-resolution pollen record to reconstruct changes in vegetation in northwestern California over the past 45,000 years, with particular emphasis on the period between 20,000 and 10,000 years ago. A pollen record from Twin Lake, California, near the Oregon border, will partially fill this gap and provide an analysis of forest history and climate dynamics in the Klamath Mountains. Lake sediments collected from Twin Lake indicate that the site contains a continuous record of local vegetation since at least 45,000 radiocarbon years ago. This study will focus on high-resolution pollen analysis of sediments deposited between 20,000 and 10,000 radiocarbon years ago, a period of rapid global and regional climate changes. Sedimentary characteristics such as magnetic susceptibility, organic content, and pollen influx rates will also be measured to identify changes in productivity and erosion rates in the Twin Lake watershed. Accurate chronological control will be ensured through 20 accelerator mass spectrometer radiocarbon dates on sedimentary charcoal and identifiable plant remains. This century-resolution study will complement a 500-year resolution analysis already completed for the entire length of the record, from 45,000 years ago to the present. Pollen data will be will be compared with modern pollen composition from 83 lake sites in the Klamath Region to attempt to quantify past climatic conditions at Twin Lake.The results of this study will serve to fill spatial and temporal gaps in our understanding of the regional variation of past climate change as well as provide insight into mechanisms of climate variability. In addition, the results will provide insight into the effects of rapid climate change on the forest systems of the west coast of North America. The Klamath Mountains region is known for having an unusually high diversity of coniferous tree species (including several endemic species of limited range), and has been recognized as an ecosystem of global significance. Rapid climate change at the end of the last glacial period may provide a reasonable analogue for projected carbon dioxide-induced climate change during the next century. Understanding past forest dynamics may help to predict potential future threats to regional biodiversity due to climate change, and perhaps aid in mitigating their effects. 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.

陆地植被变化的长期花粉记录被用来量化过去的气候条件，以确定过去的气候变率的机制，以验证过去的气候模式模拟，并重建过去的地理模式。 目前，从俄勒冈州中部到加州中部海岸附近的冰川到近代条件的记录中存在一个空白。 这个博士论文研究项目的目标是开发一个高分辨率的花粉记录，以重建在过去的45,000年，特别是在20,000年和10,000年前之间的时期，在西北部加州的植被变化。 来自俄勒冈州边界附近的加州双子湖的花粉记录将部分填补这一空白，并提供对克拉马斯山脉森林历史和气候动态的分析。 从双子湖收集的湖泊沉积物表明，该网站包含了至少45,000年前放射性碳的当地植被的连续记录。 这项研究将侧重于对20，000至10，000年前沉积的沉积物进行高分辨率花粉分析，这一时期是全球和区域气候迅速变化的时期。 还将测量磁化率、有机物含量和花粉流入率等沉积特征，以确定双子湖流域生产力和侵蚀率的变化。 将通过20台加速器质谱仪对沉积木炭和可识别的植物遗骸进行放射性碳年代测定，确保准确的年代控制。 这项世纪分辨率研究将补充已经完成的从45，000年前到现在的整个记录长度的500年分辨率分析。 花粉数据将与现代花粉成分从83个湖泊网站在克拉马斯地区试图量化过去的气候条件在Twin Lake.The研究结果将有助于填补空间和时间的差距，在我们的理解过去的气候变化的区域变化，以及提供深入了解气候变率的机制。 此外，研究结果还将深入了解快速气候变化对北美西海岸森林系统的影响。 克拉马斯山区以针叶树种的高度多样性（包括几种分布范围有限的特有树种）而闻名，并被公认为具有全球意义的生态系统。 末次冰期结束时的快速气候变化可能为预计的下一个世纪二氧化碳引起的气候变化提供合理的类比。 了解过去的森林动态可能有助于预测未来气候变化对区域生物多样性的潜在威胁，并可能有助于减轻其影响。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。