Creating Woodlands: Integrating Land-Use Practices and New Savanna Models

这一研究项目将侧重于确定日常土地管理做法通过哪些机制创造有利于在大草原环境中建立和生长高价值树木的条件。该项目还将寻求提高预测管理做法的转变将如何影响未来环境的能力。稀树草原长期以来一直是科学家们面临的一个难题，树木和草如何在同一片公园景观中共存，以及是什么因素阻止一种植被形式主宰另一种植被，仍然存在不确定性。该项目将解决热带草原科学的基本问题，这些问题与热带草原不同生命周期阶段的草和树之间的竞争有关。它将整合新的不平衡生态学理论和人类土地利用实践，以确定人类活动对公园内树木建立和生长的长期影响，并将提供有关公园如何随着时间的推移形成的宝贵历史数据。该项目将加强对稀树草原公园是如何通过人-环境互动创造的理解，从而为寻求改善公园管理和扭转公园衰落趋势的林农和土地管理者提供关键信息。该项目将为碳固存模型的开发提供信息，并将为那些依赖大草原环境，特别是高价值树木的产品谋福利的人提供改善经济生计的信息。该项目还将帮助评估无人驾驶飞行器(无人机，通常被称为无人机)作为在研究区域和世界其他地区收集局部规模数据的廉价手段的使用。长期以来，地理学家、生态学家和其他对地球生态系统的基本功能和分布感兴趣的人一直对解释决定景观中树木与草的比例的机制感兴趣。最近的科学发展增加了这项任务的重要性，因为在降雨量中等的中原地区，森林和稀树草原都存在，这表明稀树大草原与热带森林不同。这些替代国家覆盖了广大地区，包括非洲的大部分地区以及美洲的部分地区。现在的树木覆盖率被认为在很大程度上是由火灾和其他干扰制度决定的，包括人类土地管理。该项目将包括一个重点案例研究，研究人类做法在确定热带草原干扰制度方面的作用，在那里，人们几乎放火焚烧，并负责轮作农业和畜牧业。调查人员将在西非国家马里工作。研究人员将测试这样一种假设，即在稀树草原上，对木质环境的操纵既是有意识的，也是无意识的，而且它是选择特定有价值的树种的一个因素，例如乳木果树(Vitellaria Paroxa)，它的果实由营养丰富的果肉和富含油脂的种子组成，可以用来加工乳木果油。调查人员将开展三组相互关联的活动。他们将进行实地实验，以检验这一假设，即特定的人类行为在树木生命的不同时间对特定树种产生不同的影响。他们将分析一项自然实验，将野外和遥感方法结合起来，以检验干扰历史比生物物理条件更大程度上决定当前植被覆盖的假设，他们将进行人种学研究，以了解占据稀树草原的人如何理解人类与植物的互动和动态。

This research project will focus on determining the mechanisms through which everyday land-management practices create conditions conducive to the establishment and growth of highly valued trees in savannah environments. The project also will seek to improve capabilities for predicting how shifts in management practices will impact future environments. Savannas long have posed a conundrum for scientists, with uncertainty remaining regarding how trees and grasses coexist in the same parkland landscapes and what factors prevent one vegetation form from dominating the other. This project will address fundamental questions of savanna science pertaining to competition between grasses and trees at different life-cycle phases in a mesic savanna. It will integrate new theories of disequilibrium ecology and human land-use practices to determine the long-term impacts of human actions on tree establishment and growth in parklands, and it will provide valuable historical data about how parklands form over time. The project will enhance understanding of how savanna parklands are created through human-environment interactions, thereby providing critical information for foresters and land managers seeking to improve parkland management and to reverse trends that have seen the parklands decline. The project will inform the development of models of carbon sequestration, and it will provide information to improve economic livelihoods for those who rely on savannah environments, especially the products of highly valued trees, for their well-being. The project also will help assess the use of unmanned aerial vehicles (UAVs, often known as drones) as an inexpensive means for gathering data at local scales in the study area and in other parts of the world. Explaining the mechanisms that determine the ratio of trees to grasses within landscapes has long been of interest to geographers, ecologists, and others interested in the basic functioning and distribution of the Earth's ecosystems. Recent scientific developments have increased the importance of this task, because in mesic areas that receive intermediate amounts of rainfall, both forests and savannas persist, which indicates that savanna is a different stated from a tropical forest. These alternative states cover vast areas, including large parts of Africa as well as parts of the Americas. Tree cover now is thought to be largely determined by fire and other disturbance regimes, including human land management. This project will consist of a focused case study of the role of human practices in determining disturbance regimes in savannas where people set nearly all fires and are responsible for rotational agriculture and animal grazing. The investigators will work in the western African nation of Mali. The investigators will test hypotheses that manipulation of woody environments has been both conscious and unconscious in savanna and that it has been a factor in the selection of specific valued tree species, such as shea trees (Vitellaria paradoxa), which yield a fruit that consists of a nutritious pulp and an oil-rich seed from which shea butter can be processed. The investigators will pursue three interconnected sets of activities. They will conduct field experiments to test the hypothesis that specific human practices differentially affect specific tree species at different times in the lives of the trees. They will analyze a natural experiment, combining field and remote sensing methods to test the hypothesis that disturbance history determines current vegetation cover more so than biophysical conditions, and they will conduct ethnographic research to learn how people occupying savannas understand human-plant interactions and dynamics.