Doctoral Dissertation Research: Vegetation Dynamics and Biogeomorphic Influences in a Highly Eroded Landscape

尽管人们已经广泛研究了植被覆盖对侵蚀过程的影响，但对加速土壤侵蚀对植被结构和组成的影响的关注却少得多。 在相对稳定的干旱荒地的研究表明，河流侵蚀造成的陡峭的环境梯度创建相应的分级植被群落，但很少有研究探讨植被的反应频繁的地貌干扰，发生在积极侵蚀景观以及地貌过程之间的关系，地形变量，土壤（土壤相关的）特性，在潮湿环境中的植被格局。 这篇博士论文的研究将通过在格鲁吉亚州的普罗维登斯的一个案例研究来调查这些关系，在过去的150年里，由于粗心的棉花种植实践，这个景观经历了严重的土壤侵蚀和深沟切割。 将利用航空摄影分析来描述过去60年来在景观尺度上发生的植被和地貌变化的时空特征。 作为对这一更大范围分析的补充，将重点审查对植被格局有主要影响的地貌、地形和土壤变量，包括作为景观特定部分特征的地貌扰动的性质和频率;坡度、形态和陡度;坡度;谷底以上的海拔;山谷宽度;土壤质地;土壤养分水平。 博士生将测量植物和土壤特性在广泛的网站表现出不同的地貌干扰制度和地形位置，并将相关的变量使用典型对应分析，分类分析和判别函数分析。 在应用层面上，这项研究将有助于景观管理人员在严重侵蚀的景观恢复。 更广泛地说，由于这些景观中存在的地貌和地形变量的独特组合，这项研究将增加我们对这些变量对植被组成，结构和动态的影响的理解。 这项研究将加强地貌学家和植被学家之间的现有联系，并将使地貌学家能够用更具体的植被变量改进侵蚀模型。 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的研究生涯。

Although the impact of vegetation cover on erosional processes has been studied extensively, far less attention has been given to the effects of accelerated soil erosion on vegetation structure and composition. Research in relatively stable, arid badlands suggests that the steep environmental gradients caused by fluvial erosion create correspondingly graded vegetation communities, but few studies have examined vegetation responses to the frequent geomorphic disturbance that occurs in actively eroding landscapes as well as relationships among geomorphic processes, topographic variables, and edaphic (soil-related) characteristics, and vegetation patterns in humid environments. This doctoral dissertation research study will investigate those relationships through a case study in Providence Canyons, Georgia, a landscape that has experienced severe soil erosion and deep gully incision over the last 150 years because of careless cotton-farming practices. Aerial photographic analysis will be used to characterize vegetation and geomorphic change occurring both spatially and temporally on a landscape scale over the past 60 years. Complementing this broader-scale analysis will be focused examinations of geomorphic, topographic, and edaphic variables that have primary influences on vegetation patterns, including the nature and frequency of geomorphic disturbance that characterize a particular portion of the landscape; slope aspect, configuration and steepness; gradient; elevation above the valley floor; valley width; soil texture; and soil nutrient levels. The doctoral candidate will measure vegetative and soil characteristics in a broad range of sites exhibiting differing geomorphic disturbance regimes and topographic position and will relate the variables using canonical correspondence analysis, classification analysis, and discriminant function analysis. On an applied level, this study will assist landscape managers in the restoration of severely eroded landscapes. More broadly, because of the unique blend of geomorphic and topographic variables present in these landscapes, this study will increase our understanding of the influence of those variables on vegetation composition, structure, and dynamics. This study will strengthen existing links between geomorphologists and biogeographers and will enable geomorphologists to refine erosion models with more specific vegetation variables. 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.