DISSERTATION RESEARCH: Nutrient cycling and distribution over multiple scales in a Kenyan savanna as mediated by an acacia-ant mutualism

在肯尼亚，一棵普通的相思树实际上雇佣了一支蚂蚁大军来保护自己的叶子不被长颈鹿、大象和其他大型食草动物吃掉。作为这种保护的交换，树木为蚂蚁提供筑巢空间和食物花蜜。然而，相思树和蚂蚁之间的这种互利互动可能不仅仅是保护：初步数据表明，至少有一些蚂蚁可能还会让它们生活的树木受精。这项研究的目的是研究蚂蚁和树木之间的养分交换，确定这种相互作用如何影响土壤养分的有效性，并调查大型哺乳动物的消失对这些过程的影响。为了解决这些问题，这项研究将结合氮素示踪实验和土壤采样来追踪蚂蚁衍生的营养物质，并使用长期的哺乳动物排斥地块来调查哺乳动物的影响。这项研究结合了直接适用于东非土地管理的工作：原生昆虫的丧失是非洲大部分地区的一个重大问题，可能会改变蚂蚁和植物之间的互利互动，进而影响土壤肥力和饲料的数量和质量。这项研究将雇用一名肯尼亚研究助理，并邀请斯坦福大学的本科生参与。研究的应用方面的结果将通过当地出版物、讲座和对话传达给当地土地所有者和管理者。

In Kenya, a common Acacia tree in effect employs an army of ants to defend its leaves from being eaten by giraffes, elephants, and other large herbivores. In exchange for this protection, the trees provide the ants with nesting space and nectar for food. This mutually beneficial interaction between Acacia trees and ants may involve more than just protection, though: preliminary data suggest that at least some of the ants may also fertilize the trees in which they live. The objective of this research is to examine how nutrients are exchanged between ants and trees, to determine how this interaction might affect soil nutrient availability, and to investigate the effect of the disappearance of large mammals on these processes. To address these questions, this study will combine a nitrogen-tracing experiment with soil sampling to track ant-derived nutrients, in addition to using long-term mammal-exclusion plots to investigate the influence of mammals.This study incorporates work directly applicable to land management in eastern Africa: loss of native browsers, a significant problem across much of Africa, could alter the mutually beneficial interaction between ants and plants, in turn affecting soil fertility and forage quantity and quality. This research will employ a Kenyan research assistant as well as involve undergraduates from Stanford University. Results of applied aspects of the research will be communicated to local land owners and managers through local publications, talks, and conversations.