Doctoral Dissertation Research: Drought Sensitivity of Limber Pine in the Central Rocky Mountains Determined From C Isotopes and Ring Widths

博士论文研究：根据 C 同位素和环宽测定落基山脉中部阔叶松的干旱敏感性

• 批准号: 0503160
• 负责人: Elise Pendall
• 金额: $ 1.2万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-15 至 2007-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0503160&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Drought; Sensitivity

Global climate change models predict higher temperatures and increased variability in precipitation in the coming century, which could affect drought frequency and intensity. A relatively long-term drought has persisted throughout the central Rocky Mountain region of North America with negative impacts on the environment and the livelihood of local communities. Increasing the accuracy of future drought projections requires a glimpse into the past to look at long-term variability in precipitation and other factors associated with drought. Droughts are well documented in instrumental climate records from 1895 to present, while tree-ring widths have been used successfully to extend these climate records back in time for hundreds of years. This research project will characterize the climatology underlying recent droughts, and will reconstruct temporal and spatial patterns of drought in the central Rocky Mountains. Tree cores have already been collected and preliminary results suggest that climate and tree growth relationships are becoming more complacent at the mid to high elevation sites starting around 1955. This increasing complacency over time complicates the climate-tree growth relationship and subsequent drought reconstruction. Previous research suggests that combining stable carbon isotopes with tree-ring widths may strengthen the climatic signal necessary for reconstructions, and carbon isotopes have been found to correlate strongly with drought cycles in semi-arid regions. Thus, research objectives will be to use instrumental climate records (temperature, precipitation, and the Palmer Drought Severity Index), a multi-proxy approach (tree-ring widths and stable carbon isotopes), an elevation gradient sampling scheme, and dendroclimatic time series analysis to develop drought reconstructions for the central Rocky Mountains. It is the multi-proxy design of this project which will address a knowledge gap as to whether carbon isotopes will actually strengthen the predictive ability of tree-ring widths over time and space. Results of this project will provide new insights into the complex ecological responses of tree-ring widths and carbon isotope composition to climate. Inferences from these proxy records of annual and seasonal climate across an elevation gradient will improve the ability to identify spatiotemporal patterns of drought in the central Rocky Mountain region. This project will also benefit local communities by identifying the historical context of drought occurrence which can be incorporated into land use planning and water conservation strategies currently being reviewed at both the local and regional level.

全球气候变化模型预测，未来一个世纪气温升高，降水变化加大，这可能会影响干旱频率和强度。北美落基山脉中部地区持续较长时间的干旱，给当地环境和民生带来了负面影响。提高未来干旱预测的准确性需要回顾过去，以了解降水量和与干旱相关的其他因素的长期变化。从 1895 年至今，仪器气候记录中详细记录了干旱，而树木年轮宽度已成功地用于将这些气候记录追溯到数百年前。该研究项目将描述近期干旱的气候特征，并将重建落基山脉中部干旱的时间和空间模式。树芯已经收集完毕，初步结果表明，从 1955 年左右开始，中高海拔地区的气候和树木生长关系变得更加自满。随着时间的推移，这种自满程度的增加使气候与树木生长的关系和随后的干旱重建变得更加复杂。先前的研究表明，将稳定碳同位素与树木年轮宽度相结合可能会增强重建所需的气候信号，并且已发现碳同位素与半干旱地区的干旱周期密切相关。因此，研究目标将是使用仪器气候记录（温度、降水和帕尔默干旱严重指数）、多代理方法（树木年轮宽度和稳定碳同位素）、海拔梯度采样方案和树木气候时间序列分析以制定落基山脉中部的干旱重建计划。该项目的多代理设计将解决碳同位素是否会真正增强树木年轮宽度随时间和空间变化的预测能力的知识差距。该项目的结果将为树木年轮宽度和碳同位素组成对气候的复杂生态反应提供新的见解。根据这些海拔梯度上的年度和季节性气候代理记录进行的推论将提高识别落基山脉中部地区干旱时空模式的能力。该项目还将通过确定干旱发生的历史背景使当地社区受益，并将其纳入目前正在地方和区域层面审查的土地利用规划和节水战略中。