Biogeochemical Controls on Altered Nitrogen Cycling in the Third Decade of Whole - Watershed N Deposition

全流域氮沉积的第三个十年中改变氮循环的生物地球化学控制

• 批准号: 1056692
• 负责人: Ivan Fernandez
• 金额: $ 119.97万
• 依托单位: University of Maine
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-01 至 2016-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1056692&HistoricalAwards=false
• 关键词: Biogeochemical; Controls; Altered; Nitrogen; Cycling

This research will study nitrogen cycling in two paired, forested watersheds of the northeastern U.S. Scientists will experimentally increase the abundance of the rare, naturally occurring, stable isotope of nitrogen (15N) to track the movement of nitrogen from precipitation through trees, microbes, soils, soil solutions and finally into streams. This research will be carried out in two adjacent forested watersheds at the Bear Brook Watershed in Maine. One watershed has been treated with nitrogen fertilizer for 22 years to mimic air-pollution effects on forests and streams - one of the longest studies of its kind in the world. Nitrogen dynamics in forested watersheds are of intense scientific interest because nitrogen is typically the most limiting plant nutrient in land-based ecosystems. And yet, during the last half of the 20th century, emissions of nitrogen and sulfur from fossil-fuel combustion and other sources created "acid rain," causing the leaching of soil calcium and aluminum. These emissions also resulted in excess nitrogen inputs to forested watersheds, a condition referred to as nitrogen saturation, which yields increased amounts of nitrogen in streams draining forests. In the 21st century, nitrogen dynamics altered by climatic change will also influence forest health and downstream ecosystems.

这项研究将研究美国东北部两个成对的森林流域的氮循环。科学家将通过实验增加稀有的、自然存在的稳定氮同位素(15N)的丰度，以跟踪氮从降水中通过树木、微生物、土壤和土壤溶液的移动，最终进入溪流。这项研究将在缅因州熊溪流域的两个相邻的森林流域进行。一个流域已经用氮肥处理了22年，以模拟空气污染对森林和溪流的影响--这是世界上时间最长的同类研究之一。森林流域的氮素动态具有强烈的科学意义，因为在陆地生态系统中，氮素通常是最具限制性的植物养分。然而，在20世纪后半叶，化石燃料燃烧和其他来源排放的氮和硫制造了“酸雨”，导致土壤钙和铝的淋失。这些排放还导致对森林流域的过量氮输入，这种情况被称为氮饱和，在排干森林的溪流中产生更多的氮。在21世纪，气候变化改变的氮素动态也将影响森林健康和下游生态系统。