Doctoral Dissertation Research: Biogeomorphic Effects of Ligustrum Sinense (Chinese Privet) Invasion on the Oconee River Floodplain in North Georgia

入侵物种是人类引起的全球变化的重要组成部分。入侵植物既能改变本地植物群落的结构和组成，也能改变被入侵生态系统的干扰状态。虽然已经研究了一些外来植物入侵河岸带的生态效应，但对河岸带河流扰动机制与外来植物入侵这些栖息地之间的反馈关系了解甚少。本博士论文研究项目将研究入侵女贞（Ligustrum sinense）对乔治亚山前奥科尼河流域洪泛区森林结构和组成以及洪泛区沉积速率的影响。这项研究将包括一个景观尺度上的分析，对白羊草的传播和随后的地貌变化进行分析，并对当地尺度上的森林组成和结构的变化、河流地貌以及与白羊草入侵相关的沉积速率变化进行调查。景观尺度分析将采用航拍解译来确定柽柳的入侵时间和传播速度。此外，本文还将关注与水蛭入侵有关的河道形态变化。局地尺度分析将使用两个严重入侵地区和一个L - sinense密度稀疏地区的采样样带来收集植被数据、土壤样本、深度到地下水位的测量数据以及计算平均沉积物年增长率所需的数据。将对不同地点的植被和环境数据进行比较，以确定与白羊草成功入侵有关的河流地貌和条件，并确定白羊草入侵是否与洪泛区森林组成和结构的变化以及洪泛区沉积速率的变化有关。该项目将提高对洪水状况与入侵植物引起的植被变化之间可能的反馈关系的普遍理解；它将在未来几十年里为山前漫滩森林的命运提供洞见。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。

Invasive species are an important component of human-induced global change. Invasive plants can alter both the structure and composition of native plant communities and the disturbance regimes of invaded ecosystems. Although some of the ecological effects of nonindigenous plants invading riparian zones have been studied, feedbacks between fluvial disturbance regimes in riparian zones and nonindigenous plants invading these habitats are poorly understood. This doctoral dissertation research project will investigate the effects of invasive Ligustrum sinense (Chinese privet) on floodplain forest structure and composition as well as on rates of floodplain sedimentation in the Oconee River watershed of the Georgia Piedmont. The study will include both a landscape-scale analysis of L. sinense spread and subsequent geomorphic changes and a local-scale investigation of altered forest composition and structure, fluvial landforms, and changes in sedimentation rates associated with invasive L. sinense. The landscape-scale analysis will use aerial photograph interpretation to determine the timing of L. sinense invasion and its rate of spread. Attention also will be given to any changes in stream channel morphology associated with L. sinense invasion. The local-scale analyses will use sampling transects in two heavily invaded areas and an area with sparse density of L sinense to collect vegetation data, soil samples, and depth-to-water-table measurements as well as needed data to calculate average annual rates of sediment accretion. Comparisons will be made of vegetation and environmental data among sites to identify fluvial landforms and conditions associated with successful L. sinense invasion and to determine whether L. sinense invasion has been associated with changes in the composition and structure of floodplain forests and changes in rates of floodplain sedimentation. This project will improve general understandings of possible feedback relationships between flood regimes and vegetation changes caused by invasive plants; and it will provide insights into the fate of Piedmont floodplain forests invaded by L. sinense in the coming decades. 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.