Doctoral Dissertation Research: Streamwood Flux from Forested Mountain Watersheds Into Reservoirs in the Sierra Nevada, California

森林覆盖的山地流域占了流入和流经河道的流木的很大比例，流木的定义是长度大于1米，直径大于10厘米的活木或死木。最近有人提出了追踪流木流动和进出河道的“预算”，但由于除了最小的流域外，所有流域的实地工作都很复杂，因此很少有人完成。一个很少被衡量的预算组成部分是出口变量。然而，大坝阻碍了上游流域的流木运动，从而形成了可以进行表征的沉积带。该博士论文研究项目将利用遥感图像分析、视频监控和实地研究，在多个时空尺度上确定流木与水文、地貌和陆地机制之间的潜在联系。这位博士生将分析与加州内华达山脉两个水库相关的流木聚集：北福克尤巴河上的布拉德酒吧和图奥勒米河上的唐佩德罗。遥感软件方法将用于分析1982年至今的30米分辨率多光谱Landsat图像。验证将使用存档的1米分辨率数字正射影像四边形（DOQ）和国家农业图像计划（NAIP）图像，并通过近年来的实地观测进行。数字视频监控将安装在研究水库的顶部，以记录季节性水文的流木运输量和速度，包括基流、冬季降水、融雪以及雨雪洪水（如果发生）。现场工作将用于描述水库流木和上游流域的储存和分解过程，这将大致解释简化流木预算（输入=出口+储存+分解）的输入（吸收）部分。GIS分析将用于了解流木产量与物理过程之间的关系，预期结果包括每日、季节、年度和年代际尺度的平均流木出口；放电-流木产量等级曲线；流木的招募和储存潜力；以及流材流量-坝出流量、输运距离-流材属、腐烂分类-流材密度之间的回归关系。该项目将填补在基本了解森林碳循环中重要的颗粒有机成分——流木出口的区域变化方面的时空空白。了解流木出口将有助于了解驱动流木生产和通过流域运输的物理机制。新的方法可能会促使对流木输出到其他地方水库的量化，这将使人们更深入地了解这一重要的生态和地貌河流组成部分。水库管理者将提高基于流量和已知流域特征预测流木出口的能力。在坝下生态系统恢复项目中增加基于科学的流木量建议，可以从根本上改变水库和河流的管理做法。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

Forested mountain watersheds account for a large percentage of streamwood movements into and through river channels, with streamwood defined as live or dead wood greater than 1 m in length and greater than 10 cm in diameter. Streamwood "budgets" recently have been proposed to trace the movement of streamwood and in out of river channels, but few have been completed because of the complexity of field work in all but the smallest watersheds. One budget component that rarely has been measured is the export variable. Dams impede streamwood movement from upper watersheds, however, resulting in depositional zones where characterization can occur. This doctoral dissertation research project will use remotely sensed imagery analysis, video monitoring, and field studies to identify underlying linkages between streamwood and hydrologic, geomorphic, and terrestrial mechanisms at multiple spatial-temporal scales. The doctoral student will analyze streamwood aggregations associated with two California reservoirs in the Sierra Nevada: Bullard's Bar on the North Fork Yuba River and Don Pedro on the Tuolumne River. Remote sensing software methods will be used to analyze multispectral 30-m resolution Landsat images from 1982 to the present. Validations will be performed with archival 1-m resolution digital orthophoto quadrangle (DOQ) and National Agriculture Imagery Program (NAIP) images, and via field observations for current years. Digital video monitoring will be installed at the top of the study reservoirs to document streamwood transport volume and velocity across seasonal hydrographs, including baseflow, winter precipitation, and snow melt as well as rain-on-snow floods if they occur. Fieldwork will be used to characterize reservoir streamwood and upper watershed storage and decomposition processes, which will broadly explain the input (recruitment) component of a simplified streamwood budget (Inputs = Exports + Storage + Decomposition). GIS analyses will be used to understand the relationship between streamwood yield and physical processes, with expected results to include average streamwood export at daily, seasonal, yearly, and decadal scales; discharge-streamwood yield rating curves; streamwood recruitment and storage potentials; and regression relationships between streamwood discharge-dam outflow, transport distance-streamwood genera and decay classification-streamwood density.This project will fill spatial and temporal gaps in basic understanding regional variation of an important particulate organic component of the forest carbon cycle, streamwood export. Understanding streamwood export will provide insight into physical mechanisms that drive streamwood production and transport through a watershed. New methods may prompt quantification of streamwood export into reservoirs in other locales, which would lead to a deeper understanding of this important ecological and geomorphic river component. Reservoir mangers will have increased ability to predict streamwood export based on discharge and known watershed characteristics. Scientifically based recommendations of streamwood volume to be added to ecosystem rehabilitation projects below-dam could fundamentally alter reservoir and river management practices. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.