Evolutionary and Ecological Feedbacks as Determinants of Savanna-Forest Dynamics

就面积、生物多样性、总碳储量和人类利用而言，稀树草原和常绿森林是地球上最重要的两种热带植被类型。了解控制稀树草原-森林边界动态的过程对于预测热带植被对气候、火灾和人类活动变化的长期反应至关重要。本研究的主要假设是，正反馈在热带稀树草原与森林边界的动态中起着重要作用，并且这些反馈被热带稀树草原与森林树木的结构、生理和生态特征的差异所强化。还有一种假设认为，稀树草原和森林物种之间的生物学差异是通过一种进化反馈产生的，在这种反馈中，物种的特征直接或间接地影响当地环境，这反过来又决定了驱动物种特征进化的选择压力。为了了解植物与其自然环境之间的反馈，本项目将整合生理测量、实验操作、植被动态研究和生态建模。这项研究加强了巴西利亚大学和三家美国机构的研究人员之间的现有合作。该项目将为拉丁美洲学生提供与研究人员以及美国学生互动和合作的机会，并将为美国本科生提供研究经验。这将产生对热带生态学的兴趣和专业知识，同时促进可能发展为长期合作的互动。该项目将资助一名美国高中生物教师参加由凯南研究所管理的为期两年的职业发展计划，该计划旨在提高教师的领导能力，留住教师，并推进K-12科学。

Savannas and evergreen forests are the two most important tropical vegetation types on Earth, in terms of area, biodiversity, total carbon stocks, and use by humans. Understanding the processes that control the dynamics of savanna-forest boundaries is essential to predicting the long-term responses of tropical vegetation to changes in climate, fire, and human activity. The primary hypothesis of this study is that positive feedbacks have an overriding role in the dynamics of savanna-forest boundaries, and that these feedbacks are reinforced by the contrasting structural, physiological and ecological characteristics of savanna and forest trees. It is also hypothesized that the biological differences between savanna and forest species arose through an evolutionary feedback in which species' traits directly and indirectly influence the local environment, which in turn determines the selective pressures that drive the evolution of species' traits. To understand the feedbacks between plants and their physical environment, this project will integrate physiological measurements, experimental manipulations, studies of vegetation dynamics, and ecological modeling. This research reinforces existing collaborations between researchers at the University of Brasilia and three US institutions. The project will provide Latin-American students with an opportunity to interact and collaborate with the investigators of this grant as well as with students from the US, and will provide research experiences for US undergraduate students. This will generate interest and expertise in tropical ecology while fostering interactions likely to grow into long-term collaborations. The project will sponsor a US high school biology teacher through a two-year career development program administered by the Kenan Institute designed to promote teacher leadership, teacher retention, and advance K-12 science.