Refinement of Historical Variability and the Baseline for Hydroclimatic Conditions within the Walker Basin: A Multi-Elevational Dendrochronological and Ecohydrological Approach

在美国和世界的干旱和半干旱地区，水文气候变异性是供水规划的一个日益重要的方面。我们对相关时间尺度(即十年到百年)的过去过程的理解通常来自于高分辨率的古记录，如树木年轮。这项研究项目将使用树木年轮记录来量化内华达州西部/加利福尼亚州东部沃克河流域内的潮湿和干旱时段。随着从现在到1000多年前的树木年轮年表的收集，该项目将在多个研究地点建立气候和生态方面的基线条件。为了捕捉树木年轮对个别水文气候变量的响应，如夏季温度和冬季降雨量，研究人员将针对不同海拔范围和多个地形方面的四个树种。将在每个研究地点进行基线生态调查，以便比较整个大盆地地区其他调查地点的情况。研究人员将使用现场的自由空气温度传感器来更好地解释与建模和区域气候数据相关的微站点条件。一个气候监测站将安装在高海拔的分水岭的孤立部分，不仅可以捕捉温度和降水，还可以捕捉太阳辐射、风型和土壤条件。生态和感官数据都将有助于解释古气候记录，因为流域中大多数针叶林地带的现有数据仅限于模拟产品。该项目的一个主要目标是重建季节性气候变量，这些变量将作为过去1200年水平衡建模的输入，根据之前的树木年轮和湖泊沉积物研究，这一时间段具有巨大的变异性。评估过去时间段的分水岭行为超出了我们现代观察的范围，这将在我们进入不确定的未来时帮助水资源管理者和用户进行决策和规划。过去过程的记录显示了景观如何对气候和能源投入的变化做出反应，无论未来条件变化的原因是什么，了解干旱和半干旱环境中的流域动态是至关重要的。这一研究方法将加强树木年轮科学的知识，增加我们对分水岭尺度气候变异性的理解，并澄清树木年轮记录与水收支之间的关系。该项目的重建成果将立即用于沃克盆地和邻近流域的科学家、水资源管理人员和用水者。由于该项目的调查和安装而获得的气候和生态数据将提供给广泛的公众用户，并实时提供传感器数据。通过将联邦、大学和社区学院的研究人员聚集在一起，该项目为跨不同层次的合作和拓展提供了一个独特的机会。将为研究生、本科生和社区学院的学生提供教育机会，他们将能够参与实地和实验室工作以及科学会议。

Hydroclimatic variability is an increasingly important aspect of water supply planning in arid and semi-arid regions of the United States and the world. Our understanding of past processes at relevant timescales (i.e. decadal to centennial) is often derived from high resolution palaeorecords such as tree rings. This research project will use tree-ring records to quantify wet and dry episodes within the Walker River watershed in western Nevada/eastern California. Along with the collection of long tree-ring chronologies that will stretch from the present back over 1000 years, this project will establish baseline conditions at multiple study sites with respect to climate and ecology. To capture tree-ring responses to individual hydroclimatic variables, such as summertime temperatures and wintertime precipitation, the researchers will target four tree species across a range of elevations as well as multiple topographic aspects. Baseline ecological surveys will be conducted at each study site to allow for comparison of conditions among a wide range of other surveyed locations across the Great Basin region. The researchers will use in-situ, free-air temperature sensors to better interpret microsite conditions relative to modeled and regional climate data. A climate monitoring station will be installed at high elevation in an isolated portion of the watershed, which will capture not only temperature and precipitation, but also solar radiation, wind patterns, and soil conditions. Both the ecological and sensory data will aid interpretation of palaeoclimate records, as existing data for most of the conifer zones in the watershed are limited to modeling products. A primary goal of this project is to reconstruct seasonal climate variables which would serve as inputs to water balance modeling over the last 1200 years, a time period which has seen tremendous variability based on previous tree-ring and lake sediment studies. Evaluation of watershed behavior during past time periods that exceed the envelope of our modern observations will aid water managers and users in decision making and planning as we move into an uncertain future. Records of past processes show how landscapes respond to variations in climatic and energy input, and regardless of the cause of future changes in conditions, it is critical to understand watershed dynamics in arid and semi-arid environments. This research approach will bolster knowledge in tree-ring science, increase our understanding of climatic variability at the watershed scale, and clarify relationships between tree-ring records and water budgets. Reconstruction results from the project will be of immediate use to scientists, water managers, and water users within the Walker Basin and adjacent watersheds. Climatic and ecological data acquired as a result of the project's surveys and installations will be available to a wide range of public users, with sensor data provided in real-time. By bringing together Federal, University, and Community College researchers, this project provides a unique opportunity for collaboration and outreach across diverse levels. Educational opportunities will be provided to graduate, undergraduate, and Community College students, who will be able to participate in field and laboratory work as well as scientific conferences.