Dissertation Research: Controls Over Nitrogen Fixation in a Tropical Rain Forest

特定物种在控制生态系统过程中的作用是我们对生物多样性如何影响生态系统功能的认识的核心。然而，对热带生态系统中物种和功能之间的联系的理解仍然很差，对任何生态系统中微生物物种-功能关系的理解也是如此。这笔拨款用于研究哥斯达黎加热带雨林低地的树种、树上和树下的自由生活固氮微生物群落和自由生活固氮率之间的联系。初步数据表明，不同树种的邻近树木支持不同的游离固氮速率。利用一套互补的遗传技术，本研究将研究微生物群落动态的作用，以及它们与特定冠层树木的联系，在调节观察到的固氮率差异中的作用。热带森林与大气交换的碳、水和能量比其他任何生物群落都多，因此在调节全球范围内的环境变化方面发挥着关键作用。随着人类活动不断改变这些森林的物种组成，了解热带系统中高度本地生物多样性的重要性变得越来越迫切。负责这项研究的学生有广泛的外展和培训记录，她将继续与当地高中生和初中女生一起工作，将她的研究经验融入以学生为中心的研讨会。

The role of particular species in controlling ecosystem processes is central to our perceptions of how biodiversity may influence ecosystem function. Yet, the understanding of links between species and function in tropical ecosystems remains poor, as does the understanding of microbial species-function relationships in any ecosystem. This grant supports experiments that examine the connections between tree species, free-living nitrogen-fixing microbial communities living on and beneath trees, and rates of free-living nitrogen fixation in a lowland tropical rain forest in Costa Rica. Preliminary data show that neighboring trees of different species support distinct rates of free-living nitrogen fixation. Using a suite of complementary genetic techniques, this research will examine the role of microbial community dynamics, and their links to specific canopy trees, in regulating the observed differences in nitrogen fixation rates. Tropical forests exchange more carbon, water, and energy with the atmosphere than any other biome and thus play a critical role in regulating environmental change on a global scale. As human activities continue to alter the species composition of these forests, the need for understanding the importance of high native biodiversity in tropical systems becomes increasingly urgent. The student responsible for this research has an extensive record of outreach and training, and will continue her work with local high-school students and middle-school girls by integrating her research experiences into student-focused workshops.