Spatiotemporal Dynamics of Woody Cover in a Savanna Landscape

稀树草原生态系统覆盖地球陆地表面的广大区域，通过为野生动物提供栖息地和为农村社区提供资源，在地球化学循环中发挥着关键作用。经验证据和建模工作表明，随着时间的推移，这些以草为主的生态系统中的许多生态系统正在变得更加茂密，这些变化将对其区域的广泛生态和社会生态过程产生深远影响。 本研究计画将分析过去二十年来草地与稀树草原系统中林木覆盖变化过程的生态机制与空间互动。 该项目将提供有关这些生态系统的变化将改变其功能的影响的新视角，包括土壤水分动态，辐射，土壤温度和养分，以及碳循环和储存。 该项目的见解将促进对在广泛的环境设置中驱动木本覆盖变化的基本力量的基本理解。 项目结果将有助于指导决策者、政府机构和资源管理者评估适当的行动方针。 该项目还将加强美国和非洲科学家和机构之间的国际研究合作。草原生态系统中草原和木本植被之间的相互作用取决于空间背景，即使是微小尺度的微小变化也可能产生改变整个植被分布格局的大规模生态层面的影响。 利用遥感方法，实地调查和空间建模，调查人员将寻求三个核心问题的答案：（1）空间过程在确定邻里尺度的树木覆盖动态中发挥什么作用？ (2)这些空间过程是由资源还是干扰驱动的，它们是否会在气候梯度上发生变化？ (3)随着时间的推移，木本覆盖的变化表现出渐进或突然的过渡（政权转移），这些动态如何与精细尺度的空间结构和资源和干扰梯度？ 项目调查结果将使人们更好地了解树木覆盖的广泛增加对野生动物栖息地结构、生态系统功能和经济活动的影响。

Savanna ecosystems cover vast areas of the earth's land surface and play a key role in biogeochemical cycling by providing habitat for wildlife and resources for rural communities. Empirical evidence and modeling efforts suggest that many of these grass-dominated ecosystems are becoming woodier over time and that these changes will have profound effects on a wide range of ecological and socio-ecological processes of their regions. This research project will analyze the ecological mechanisms and spatial interactions that underpin the process of woody cover change in grassland and savanna systems over the past two decades. The project will provide new perspectives about the impacts that changes in these ecosystems will have in altering their functions including soil moisture dynamics, radiation, soil temperature and nutrients, and carbon cycling and storage. The insights from this project will advance basic understanding about the fundamental forces driving woody cover change across a wide range of environmental settings. Project results will help guide policy makers, governmental agencies, and resource administrators in assessing appropriate courses of action. This project also will strengthen international research collaborations among U.S. and African scientists and institutions.Interactions between grassland and woody vegetation in a savanna ecosystem depend on the spatial context where even a small change at a fine-scale may have large-scale landscape-level ramifications of modifying entire vegetation distribution patterns. Using remote sensing methods, fieldwork, and spatial modeling, the investigators will seek answers to three core sets of questions: (1) What role do spatial processes play in determining woody cover dynamics at neighborhood scales? (2) Are these spatial processes resource- or disturbance-driven, and do they shift across climate gradients? (3) Do woody cover changes exhibit gradual or abrupt transitions (regime shifts) over time, and how are these dynamics related to fine-scale spatial structure and resource and disturbance gradients? Project findings will lead to a better understanding of the impacts that widespread increases in woody cover are having on habitat structure for wildlife, ecosystem function, and economic activity.