Linking Basin-Scale, Stand-Level, and Individual Tree Water Stress Indicators for Groundwater-Dependent Riparian Forests in Multiple-Use River Basins

这个研究项目将在几个尺度上制定一套水资源压力指标，以评估河岸生态系统的健康状况，以应对地下水的持续下降。该项目将讨论一个具有科学和社会重要性的主题，即如何评估和帮助防止干旱和人为引起的水资源短缺对脆弱的高价值河岸生态系统的负面影响。它将整合两个快速发展的领域的先进方法，高光谱遥感和同位素树木生态学，以在多分辨率尺度上发展对水分胁迫的更全面的理解。该项目将比较不同时间、强度和变化速率的水分胁迫指标，并将有助于评估生理水分胁迫、单株树木生长减少和枯死以及整个河流走廊明显的天气性森林退化之间的警告信号和时间滞后。这个项目有可能影响整个加利福尼亚州和其他地方水资源有限的多用途盆地的地下水管理做法。在与大自然保护协会和其他项目合作者的合作下，调查人员将把项目发现与加州最近实施的《地下水可持续管理法案》规定的全州保护地下水依赖的河岸生态系统的指导方针结合起来。调查人员将通过为管理人员和利益相关者举办的讲习班，与河流流域的地下水保护和管理工作进行互动。他们将指导早期职业环境科学家，包括STEM领域的女性，他们将为中小学生开展外展活动，以提高研究区域的区域环境意识。河岸森林和林地是生物多样性的热点，它们支持河流廊道内的关键功能和栖息地，但它们对供水的巨大变化特别敏感。该项目将在南加州的圣克拉拉河进行，在严重干旱期间持续抽取地下水进行灌溉，产生了负面影响，并允许研究河岸林地对短期和长期变化的环境条件的反应。研究人员将利用高分辨率航空图像和树木年轮来评估过去十年水压力的信号和阈值，以开发长期损害和崩溃的预测指标。他们将利用广泛的地下水井记录，将地下水位动态与植物水分状况的变化联系起来，在两个不同的尺度上检测到，通过使用全流域的高分辨率航空图像，在干旱期间季节性地拍摄，以及从同期树木年轮中获得的年度生长和碳同位素数据。

This research project will develop a suite of water-stress indicators at several scales to assess the health of riparian ecosystems in response to sustained groundwater decline. This project will address a topic of scientific and societal importance, namely how to evaluate and help prevent negative impacts of drought and human-induced water shortages on vulnerable, high-value riparian ecosystems. It will integrate advanced methods in two rapidly emerging fields, hyperspectral remote sensing and isotope dendroecology, to develop a more holistic understanding of water stress at multiple scales of resolution. The project will compare water stress indicators that vary in their timing, strength, and rates of change, and it will facilitate the evaluation of warning signs and time lags among physiological water stress, reduced growth, and dieback in individual trees as well as synoptic forest decline evident throughout a river corridor. This project has the potential to influence groundwater management practices throughout California and in water-limited, multiple-use basins elsewhere. In partnership with The Nature Conservancy and other project collaborators, the investigators will integrate project findings with statewide guidelines for protecting groundwater-dependent riparian ecosystems mandated under California's recently implemented Groundwater Sustainability Management Act. The investigators will interact with groundwater conservation and management efforts in river basins through workshops for managers and stakeholders. They will mentor early-career environmental scientists, including women in STEM fields, and they will conduct outreach activities for elementary and secondary school students to increase regional environmental awareness in the study region.Riparian forests and woodlands are hotspots of biodiversity, and they support key functions and habitats within river corridors, but they are particularly sensitive to large changes in water supply. This project will take place in the Santa Clara River in southern California, where sustained groundwater pumping for irrigation during a severe drought has had negative impacts and allows for study of riparian woodland response to changing environmental conditions over both short and longer terms. The investigators will assess the signals and thresholds of water stress over the last decade using high-resolution aerial imagery and tree-rings to develop predictors of long-term impairment and collapse. They will capitalize on extensive groundwater well records to link water-table dynamics with changes in plant water status detected at two different scales through the use of basin-wide, high-resolution aerial imagery taken seasonally during the drought and annual growth and carbon isotope data from tree rings covering the same period.