DISSERTATION RESEARCH: Riparian Tree Dynamics: Learning How to Restore Non-equilibrium Communities

加州中央山谷的河流治理改变了水文条件，损害了河岸树木种群的繁殖，这些种群随着定居前洪水和夏季干旱的周期而演变。这项研究的目的是发展对主导河岸群落发展的关键初始阶段的棉杨和柳树物种的招募和生存的预测性理解。将进行有针对性的实地研究和对照实验，以参数化和验证驱动加州托洛梅河下游杨树和柳树补充的水文地貌、物候和生态生理因素的概念模型。该模型综合了种子释放和存活期的长短、地下水位动态和土壤水分的田间条件以及幼苗对地下水位衰退的存活阈值。这些研究将为资源管理人员提供必要的量化信息，以模拟具有成本效益的战略，以恢复中央山谷河岸林地的自然招募进程。这个项目具有重要的科学意义，因为它测试了一个综合了水文学、生态学和生态生理学的概念性模型，该模型在基于实地的资源管理背景下，在一个非平衡系统中进行。该项目的更广泛影响包括优化整个河流的径流恢复方案，评估当前的洪泛区恢复项目，向各机构传播恢复规划的结果，以及指导本科生的研究方法。

River regulation in California's Central Valley has altered hydrologic conditions and impaired reproduction of riparian tree populations that evolved with pre-settlement cycles of flooding and summer drought. The goal of this research is to develop a predictive understanding of recruitment and survival of the cottonwoods and willow species that dominate the crucial initial phase of riparian community development. Targeted field studies and controlled experiments will be conducted to parameterize and validate a conceptual model of hydrogeomorphic, phenologic, and ecophysiological factors driving cottonwood and willow recruitment on the lower Tuolumne River, CA. The model integrates length of seed release and viability periods, field conditions of water table dynamics and soil moisture, and seedling survival thresholds in response to water table recession. The studies will provide quantitative information necessary for resource managers to model cost-effective strategies to restore natural recruitment processes to Central Valley riparian woodlands. This project is important scientifically because it tests a general conceptual model integrating hydrology, ecology, and ecophysiology in a non-equilibrium system within a field-based resource management context. Broader impacts of this project include optimizing reach-wide flow restoration scenarios, evaluating current floodplain restoration projects, disseminating results to agencies for restoration planning, and mentoring undergraduates in research methods.