TECO: Collaborative Research: Immobilizaiton of Nitrate in Temperate Forest Soils

人类引起的全球变化中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。研究输入的无机氮转化为有机氮并保留在森林凋落物层和矿质土壤中的机制是了解大气沉降氮的命运及其对森林碳储量影响的关键。目前，大气沉降中的无机氮在土壤中固定化的过程尚不清楚。土壤中产生的有机氮是否随后可用于植物生长或是否储存在土壤-腐殖质基质中尚不清楚。在传统的湿化学分析中，“未知氮”组分通常占土壤总氮的最大单一组分。本研究将使用15n核磁共振（NMR）技术来解决这些问题。要全面理解土壤氮循环，预测森林生态系统慢性氮沉降的最终影响，需要回答这两个基本问题。该项目将通过在马萨诸塞州的哈佛森林LTER站点、缅因州的贝尔布鲁克流域和西弗吉尼亚州的费尔诺实验森林进行现有的长期森林氮添加实验来解决这两个基本问题。

9727056 Davidson 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.