CAREER: Composition, Internal Cycling and Losses of Dissolved Organic Nitrogen Along a Temperate Forest Fertility Gradient

氮(N)是温带地区最限制植物生长和森林生产力的营养元素。直到最近，科学家们才认识到植物有可能从土壤中获得有机形式的氮，而溶解的有机氮（DON）的淋滤对森林生态系统中氮的损失起着重要的作用。该研究项目将确定一系列温带森林生态系统中DON对树木营养的贡献，将表征森林DON淋滤的化学成分，并将努力更好地了解森林中DON生产、内部循环和损失的环境控制。为了实现这些目标，我们将在密歇根州的一系列森林生态系统中比较植物吸收、DON组成、内部循环和DON损失，这些生态系统在肥力、树种组成和生产力方面存在系统差异。这些森林实验点也将作为一系列教学活动的基础，旨在向本科生和少数民族高中生介绍生态系统科学和可持续林业的概念。更好地了解氮的循环形式（有机与矿物）对于管理森林生产力、理解森林生态系统对人为氮沉积的响应以及理解氮淋滤对周围湿地、河流和地下水的影响具有重要意义。这个项目的教学部分将向下一代土地管理者传达生态系统科学和可持续管理的基本原则。

Nitrogen (N) is the nutrient element most limiting to plant growth and forest productivity in temperate regions. Only recently, scientists have recognized that plants have the potential to acquire organic forms of N from the soil, and that leaching of dissolved organic N (DON) contributes significantly to the loss of N from forest ecosystems. This research project will determine the contribution of DON to tree nutrition across a range of temperate forest ecosystems, will characterize the chemical composition of DON leaching from forests, and will strive to better understand the environmental controls over the production, internal cycling, and loss of DON in forests. To accomplish these goals plant uptake, DON composition, internal cycling, and losses of DON will be compared across a series of forest ecosystems in Michigan that vary systematically in fertility, tree species composition, and productivity. These forested experimental sites also will serve as the foundation for a series of teaching activities designed to introduce concepts of ecosystem science and sustainable forestry to undergraduate students and minority high school students.A better understanding of the form in which N is cycled (organic vs. mineral) has important implications for managing forest productivity, understanding the response of forest ecosystems to anthropogenic N deposition, and understanding the impacts of N leaching on surrounding wetlands, rivers and groundwater. The teaching component of this project will convey fundamental principles of ecosystem science and sustainable management to the next generation of land managers.