COLLABORATIVE RESEARCH: Mechanisms of tree recruitment limitation across a savanna soil moisture availability gradient

热带草原，或称稀树草原，覆盖了地球上20%以上的土地，供养着世界上大部分的牲畜和野生食草动物，从而养活了世界上很大一部分人口。 在其边缘，稀树草原通常逐渐变成森林，它们可以缩小或扩大，这取决于森林的前进或后退。 三个主要因素似乎可以解释稀树草原和森林之间的边界：杀死树木的火灾，维持它们的降雨，以及草食动物对树苗和草的放牧。 该项目将在世界上最多产的热带稀树草原之一，坦桑尼亚的塞伦盖蒂进行一个非常大的实地实验，以测试火，水和放牧的最佳组合。来自美国和坦桑尼亚的研究人员将把优势树种的种子和幼苗种植到不同地点的围栏或未围栏、烧毁或未烧毁的地区，这些地区的降雨量从低到高不等，然后在三年内测量树木的成功率。除了让我们对稀树草原为什么会出现在它们所在的地方以及它们的边界在未来可能如何变化有新的理解，这些知识对我们管理牲畜和提供粮食的能力至关重要，这项研究将培养新的科学家，促进国际合作，并建立发展中国家的科学能力。 该项目将帮助培训两名坦桑尼亚研究人员和一名密苏里州大学的坦桑尼亚研究生以及一名北卡罗来纳州的维克森林大学的博士后学者。 为了建设非洲的科学能力，该项目将为坦桑尼亚Sokoine农业大学的学生举办关于数据收集和统计的年度讲习班。

Tropical grasslands, or savannas, cover over 20 percent of the land on Earth, support most of the world's livestock and wild herbivores, and thus feed a large fraction of the world's population. At their edges, savannas often grade into forest, and they can shrink or expand depending on whether the forests advance or retreat. Three major factors seem likely to account for the boundary between savanna and forest: fire that kills trees, rainfall that sustains them, and the grazing of the herbivores on tree seedlings and grass. This project will mount a very large field experiment in one of the most productive savannas in the world, the Serengeti of Tanzania, to test which combinations of fire, water, and grazing best maintain savanna. Researchers from the U.S. and Tanzania will plant seeds and seedlings of dominant trees into fenced or unfenced, and burned or unburned areas within different sites that range from low to high rainfall, and then measure the success of the trees over three years.Besides giving us new understanding of why savannas occur where they do and how their boundaries may change in the future, knowledge important to our ability to manage livestock and provide food, this research will train new scientists, promote international collaboration, and build the capacity for science in the developing world. The project will help train two Tanzanian researchers plus a Tanzanian graduate student at the University of Missouri and a postdoctoral scholar at Wake Forest University in North Carolina. To build scientific capacity in Africa, the project will offer annual workshops on data collection and statistics for students at Tanzania's Sokoine University of Agriculture.