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

这一研究项目将在几个尺度上开发一套水压力指标，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。该项目将探讨一个具有科学和社会重要性的专题，即如何评估和帮助防止干旱和人为缺水对脆弱、高价值的河岸生态系统造成的负面影响。它将整合高光谱遥感和同位素树枝生态学这两个迅速崛起的领域的先进方法，以在多个分辨率尺度上更全面地了解水分胁迫。该项目将比较不同时间、强度和变化率的水分胁迫指标，并将有助于评估生理水分胁迫、个别树木生长减慢和枯萎以及整个河流走廊明显的天气林衰退之间的警告信号和时间滞后。该项目有可能影响整个加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。调查人员将与自然保护协会和其他项目合作者合作，将项目结果与加州最近实施的地下水可持续管理法案规定的全州范围内保护依赖地下水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攸关方举办讲习班，与河流流域的地下水保护和管理工作互动。他们将指导职业生涯早期的环境科学家，包括STEM领域的妇女，并将为中小学生开展外联活动，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，它们支持河流走廊内的关键功能和栖息地，但它们对供水的重大变化特别敏感。该项目将在加利福尼亚州南部的圣克拉拉河进行，在那里，在严重干旱期间持续抽水灌溉已经产生了负面影响，并允许研究河岸林地对短期和长期环境条件变化的反应。研究人员将使用高分辨率的航空图像和树木年轮来评估过去十年的水分胁迫信号和阈值，以开发长期损害和坍塌的预测指标。他们将利用广泛的地下水井记录，通过使用干旱期间季节性拍摄的全流域高分辨率航空图像和同一时期树木年轮的生长和碳同位素数据，将地下水位动态与在两个不同尺度上检测到的植物水分状况的变化联系起来。

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.