TECO: Collaborative Research: Immobilization of Nitrate in Temperature Forest Soils

9727057哈奇人类导致的全球变化最微妙和最普遍的方面之一是美国东北部森林中大气氮的长期沉积。无机氮的输入转化为有机氮并保留在森林凋落物层和矿物土壤中的机制是了解大气沉积氮的去向及其对森林碳储存的影响的关键。目前，大气沉积中的无机氮固定在土壤中的过程尚不清楚。土壤中产生的有机氮随后是否可用于植物生长，或者是否储存在土壤-腐殖质基质中，目前尚不清楚。在传统的湿化学分析中，“未知氮”组分通常是土壤总氮中最大的单一组分。这项研究将使用15N-核磁共振技术来解决这些问题。对这两个基本问题的回答是充分理解土壤N循环和预测长期N沉积对森林生态系统的最终影响所必需的。该项目将利用马萨诸塞州哈佛森林LTER地点、缅因州熊溪流域和西弗吉尼亚州费诺实验森林现有的长期森林氮素添加实验来解决这两个基本问题。

9727057 Hatcher One of the most subtle and pervasive aspects of human-induced global change is the chronic deposition of atmospheric nitrogen in the forests of the northeastern United States. The mechanisms by which inputs of inorganic nitrogen are converted to organic nitrogen and retained within the forest litter layer and mineral soil are key to understanding the fate of nitrogen from atmospheric deposition and its effects on carbon storage in forests. Currently, the processes by which inorganic nitrogen from atmospheric deposition is immobilized in soil are not understood. Whether or not organic nitrogen produced in soil is subsequently made available for plant growth or if it is stored in the soil-humus matrix are unknown. The "unknown nitrogen" fraction commonly comprises the largest single fraction of total soil nitrogen in conventional wet chemical analyses. This research will use 15N-nuclear magnetic resonance (NMR) technology to address these questions. Answers to these two fundamental questions are needed to fully comprehend the soil N cycle, and to predict the ultimate impact of chronic N deposition in forest ecosystems. This project will address these two fundamental questions by using existing long-term forest nitrogen addition experiments at Harvard Forest LTER site in Massachusetts, the Bear Brook Watershed in Maine, and the Fernow Experimental Forest in West Virginia.