Doctoral Dissertation Research: Characterizing Land-Management Impacts on Ecosystem Structure in the Botswana Central Kalahari

干旱和半干旱稀树草原生态系统具有全球意义，是地球系统的重要组成部分，因为它们在陆地-大气能量平衡以及碳和养分循环中发挥重要作用。它们是生产力和生物多样性的重要贡献者，特别是在南部非洲，它们支持经济上至关重要的大量家畜、一些最大的受保护野生动物栖息地以及以野生动物为基础的旅游业。近年来，土地利用压力的变化、火势的改变和气候的变化导致了旱生系统植被结构和功能属性的大规模变化，这对生物地球化学过程和与生境有关的关键结构资源的可用性都具有重要影响，如独巢树木、觅食场、繁殖区、藏身之处和安全的迁徙路线。这项博士论文研究项目将集中在博茨瓦纳卡拉哈里中部的半干旱稀树草原系统，以考察三种主要的土地管理战略(保护区、狩猎牧场和开放获取/养牛牧场)对生态系统结构和功能的不同影响。这名博士生将在实地收集数据和随后对中卡拉哈里野生动物保护区(CKGR)内区域进行分析的基础上，将采样扩展到保护区外的邻近和类似系统。他将使用一种自下而上的分层方法，将野外植被测量与来自高分辨率和中等分辨率卫星图像的时空重合数据相结合，以量化植被和土壤特征。对高分辨率图像进行分析得出的估计数将用于验证对中部喀拉哈里地区的中分辨率图像进行光谱混合分析得出的估计数。为了更好地了解稀树草原系统的空间异质性，分数估计将与代表坡度、坡向、海拔、土壤湿度和植被生产力的其他地形和光谱变量相结合，以绘制地形-地貌景观单元。这一项目的结果将有助于填补稀树草原生态系统在学术文献中的空白，这些文献中的结构评估通常是在远程或实地进行的，但很少被纳入一个连贯的多尺度抽样战略中。该项目将产生实地和卫星衍生的生态系统变量，并在一个功能类似于全球稀树草原系统的未得到充分研究的偏远地区测试新的研究方法。项目成果将提供给野生动物、公园和农业政府当局、当地研究人员、牧场协会和农村行政区域官员，从而促进将在该地区学到的经验教训整合到牧场生态和保护管理的实践中。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。

Arid and semi-arid savanna ecosystems are globally significant and are an important element of the Earth system due to their major role in land-atmosphere energy balance as well as carbon and nutrient cycles. They are essential contributors to both productivity and biodiversity, especially in southern Africa, where they support high populations of economically critical domesticated livestock, some of the largest expanses of protected wildlife habitats, and wildlife-based tourism. Recent changes in land-use pressure, altered fire regimes, and climatic shifts have led to large-scale changes in the vegetation structural and functional attributes of xeric systems, which have important implications for both biogeochemical processes and the availability of habitat-related key structural resources, such as solitary nesting trees, foraging grounds, breeding zones, hiding places, and safe migration routes. This doctoral dissertation research project will focus on the semi-arid savanna system in the central Kalahari, Botswana, in order to examine the differential impacts of three dominant land-management strategies (protected areas, game ranching, and open access/cattle ranching) on ecosystem structure and function. The doctoral student will build on field-based data collection and subsequent analysis of areas within the Central Kalahari Game Reserve (CKGR) to extend sampling to neighboring and similar systems outside the reserve. He will use a bottom-up hierarchical approach to integrate field-derived vegetation measurements with spatio-temporally coincident data from high- and medium-resolution satellite imagery to quantify the vegetation and soil characteristics. Estimates derived from analysis of high-resolution imagery will be used to validate the estimates derived from spectral mixture analysis of medium-resolution imagery across the central Kalahari. To better understand the spatial heterogeneity of savanna systems, fractional estimates will be combined with other topographic and spectral variables representing slope, aspect, elevation, soil moisture and vegetative productivity) to map physiographic-physiognomic landscape units. Fractional cover and landscape units will be integrated and then parsed into the three land management designations to comparatively assess their impacts on savanna ecosystem structure in the central Kalahari.The results of this project will help to fill a void in the scholarly literature of savanna ecology, where structure assessments typically are conducted either remotely or in the field but rarely are integrated into a cohesive multi-scale sampling strategy. The project will generate both field- and satellite-derived ecosystem variables and test new research methodologies in an understudied and remote area that is functionally similar to savanna systems globally. Project results will be provided to wildlife, park, and agriculture government authorities, local researchers, ranching associations, and rural administrative district officers, thus facilitating the integration of lessons learned at this locale into the practice of rangeland ecology and conservation management. 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.