Nitrogen Saturation: Mechanisms and Consequences of Altered Ecosystem Metabolism

陆地生态系统氮(N)饱和是当代最重要的生态问题之一。密歇根理工大学和密歇根大学的研究人员正在北部阔叶林中进行一项长期的田间实验，以了解森林碳(C)和N循环对长期N沉积的响应。自1994年实验开始以来，模拟的大气氮沉降已经导致这个非常常见的五大湖生态系统中出现了氮饱和的高级阶段。在接下来的三年里，来自国家科学基金会的资金将使研究团队能够确定这些反应背后的机制及其潜在的长期后果。假设氮饱和将减少土壤有机质的分解，增加土壤中碳的储存，硝酸盐、溶解有机碳和溶解有机氮将继续从这些森林中淋失。这项研究是世界范围内为数不多的长期实验之一，在这些实验中，关于对氮沉积的反应及其控制机制的预测可以在现场进行测试。

Nitrogen (N) saturation of terrestrial ecosystems is one of the most important contemporary ecological issues. Researchers at Michigan Technological University and the University of Michigan are conducting a long-term, field experiment in northern hardwood forests in order to understand the responses of forest carbon (C) and N cycling to chronic N deposition. Since the experiment began in 1994, simulated atmospheric N deposition has caused advanced stages of N saturation to occur in this very common Great Lakes ecosystem. Over the next three years, funds from the National Science Foundation will allow the research team to determine the mechanisms behind these responses and their potential long-term consequences. It is hypothesized that N saturation will decrease decomposition of soil organic matter, enhancing C storage in the soil, and that nitrate, dissolved organic C and dissolved organic N will continue to leach from these forests. The study is one of few long-term experiments world-wide where predictions regarding responses to N deposition, and the mechanisms controlling them, can be tested in the field.