Collaborative Research: Impacts of Dynamic, Climate-Driven Water Availability on Tree Water Use and Health in Mediterranean Riparian Forests

沿着的森林正受到威胁，因为气候变化导致树木可用水量的变化。当生根区的水分有限时，树木会发生影响其整体生长和健康的生理变化。这个问题在夏季温暖干燥的地区（例如，美国的大部分地区）。这些森林提供了一系列生态系统服务，但它们的面积和物种多样性有限，在气候变化的情况下难以管理。该项目旨在建立新的理解？生态水文学通过采用一套跨学科的研究方法，研究水的供应与森林健康之间的联系。它涉及从洪泛区树木中提取树芯，以调查年生长情况，并将进一步调查？同位素特征树木在每个年轮中所使用的水源水的记录。通过监测气候变化和从各种水源收集水，该项目将深入了解森林树木潜在水源沃茨的变化。为了推广这项研究，这项研究将采用一个数值模型来评估气候如何控制在区域气候变化的合理情景下森林的水资源。该项目将产生：为森林/水/流域管理从业人员提供新的工具和信息，为水文科学领域代表性不足的群体提供国际教育机会，为大学生提供新的生态水文学课程。 该研究项目结合了：1）基于实地的气候和水文测量和实验室分析的氧同位素从所有潜在的树木水源;（2）在每年的树木年轮的氧和碳同位素的当代和回顾性分析，以调查最近的气候驱动的波动，树木用水和用水效率;（3）季节性（年内）分析氧同位素通过高分辨率？显微切片每年的树木年轮，以评估树木水源使用的季节性波动;和4）改进和应用气候驱动的数值生态水文学模型，包括动态水通量到河漫滩，同位素分馏/混合，和树吸水。它将比较生态水文响应气候的水供应在森林网站沿着一个强大的气候梯度。目前将树木/森林的反应与十年气候变化联系起来的能力有限。目前缺乏将区域气候与水资源供应和河岸树木跨森林的用水联系起来的普遍理解，这限制了森林对十年时间尺度上干旱胁迫反应的预测能力。这项研究将使：i）识别河岸森林内的水分胁迫特征; ii）森林对气候变化反应的预测能力; iii）更清楚地了解洪泛平原水资源可用性内气候表达的区域变化; iv）通过提供不同气候强迫条件下水资源可用性和使用的更好限制，改善树木-古气候重建。这一研究项目将为管理人员提供新的视角和工具，以预测和减轻气候变化对温带和地中海气候区域主要河流沿着脆弱河岸森林资源的风险。该项目将举办为期两天的研讨会，向研究区域的从业人员和利益相关者传播我们的研究结果。它还包括本科生研究经验（REU）补充，使两名女性和/或少数民族学生前往法国，作为他们的第一次国际旅行参加第一次实地活动。REU将为这些学生提供令人兴奋的国际研究经验，世界一流的学习机会，以及对环境/水文科学潜在职业的介绍。此外，这项研究的数据和模型将被纳入UCSB关于旱地生态水文学的新的高级课程。

Forests along rivers are under threat due to climate-driven changes in water availability to trees. When water in the rooting zone is limited, trees undergo physiological changes that affect their overall growth and health. This problem is particularly acute within forests in river floodplains in regions with warm, dry summers (e.g., large areas of the USA). Such forests provide a range of ecosystem services, but they are limited in area, species diversity, and are challenging to manage under a changing climate. This project aims to build new understanding of the ?ecohydrological? links between water availability and forest health by employing an interdisciplinary set of research methods. It involves extracting tree cores from floodplain trees to investigate annual growth and will further investigate the ?isotopic signatures? of source water used by trees as recorded within each annual ring. By also monitoring climate variations and collecting water from various contributing sources, the project will provide insight into variations in potential source waters to forest trees. To generalize this research, the research will employ a numerical model to assess how climate controls water access to forests under plausible scenarios of regional climate change. The project will generate: new tools and information for practitioners of forest/water/basin management, international educational opportunities for underrepresented groups in the hydrologic sciences, and a new ecohydrology course for undergraduates. This research project combines: 1) field-based measurements of climate and hydrology and laboratory analysis of oxygen isotopes from all potential tree water sources; (2) contemporary and retrospective analysis of oxygen and carbon isotopes in annual tree-rings to investigate recent climate-driven fluctuations in tree water use and water use efficiency; (3) seasonal (intra-annual) analysis of oxygen isotopes via high-resolution ?micro-slicing? of annual tree rings to assess seasonal fluctuations in tree water source use; and 4) improvement and application of a climate-driven numerical ecohydrology model that includes dynamic water fluxes into the floodplain, isotopic fractionation/mixing, and tree water uptake. It will compare the ecohydrologic responses to climate in water availability at forest sites along a strong climatic gradient. There is currently limited ability to link tree/forest response to decadal climate shifts. Generalizable understanding linking regional climate to water availability to water use by riparian trees across forests stands is currently lacking, which limits predictive capability of forest response to drought stress over decadal timescales. This research will enable: i) identification of signatures of water stress within riparian forests; ii) predictive capability of forest response to climate change; iii) a clearer picture of regional variations in the expression of climate within floodplain water availability; and iv) improvement of dendro-paleoclimate reconstructions by providing better constraints on water availability and use under different conditions of climatic forcing. This research project will provide managers with a new perspective and tools for anticipating and mitigating the risks of climate change on vulnerable riparian forest resources along major rivers in temperate and Mediterranean climatic regions. The project will host a 2-day workshop to disseminate our findings to practitioners and stakeholders in in the study region. It also includes a Research Experiences for Undergraduates (REU) supplement to enable two female and/or minority students to travel to France as their first international trip to participate on the first field campaign. The REU will provide these students will an exciting international research experience, a world-class learning opportunity, and an introduction to a potential career in environmental/hydrologic sciences. Additionally, data and models from this research will be integrated into a new upper division course on dryland ecohydrology at UCSB.