Collaborative Research: Landscape and regional scale studies of nitrogen gas flux

了解景观、区域和全球尺度上的氮循环是当前环境科学面临的一个巨大挑战。大量所谓的“缺失氮”支配着所有尺度上的氮平衡，并使解决过量氮污染对对流层臭氧水平、沿海富营养化和饮用水质量的影响以及确定大气氮沉积到流域的临界负荷的努力复杂化。氮平衡的不确定性增加了人们对氮气通量作为过量氮的潜在命运的兴趣。然而，由于测量技术存在问题，空间和时间变异性高，以及缺乏将点测量扩展到更大区域的方法，这些通量难以量化。一个特别的挑战是，小区域（热点）和短时间（热时刻）占氮气通量活动的很大比例。最近在测量氮气通量的方法以及在景观和区域尺度上对氮循环过程的水文和生物地球化学控制进行标度和建模的前景方面有了改进。因此，重新评估氮气通量对生态系统氮平衡的重要性的时机已经成熟。这项研究将产生与一个紧迫和全球重要的环境问题（氮污染）有关的资料，将涉及研究生和代表性不足的群体，并将与大学、管理和政策领域的教育和推广工作相结合。

Understanding the nitrogen cycle at landscape, regional and global scales is a great current challenge in environmental science. Large amounts of so-called missing nitrogen dominate nitrogen balances at all scales and have complicated efforts to address the effects of excess nitrogen pollution on tropospheric ozone levels, coastal eutrophication and drinking water quality, and to determine critical loads for atmospheric nitrogen deposition to watersheds. Uncertainty about nitrogen balances has led to increased interest in nitrogen gas fluxes as a potential fate of excess nitrogen. However, these fluxes are difficult to quantify because of problematic measurement techniques, high spatial and temporal variability, and a lack of methods for scaling point measurements to larger areas. A particular challenge is that small areas (hotspots) and brief periods (hot moments) account for a high percentage of nitrogen gas flux activity. There have been recent improvements in the methods for measuring nitrogen gas fluxes and in prospects for scaling and modeling the hydrologic and biogeochemical controls on nitrogen cycle processes at landscape and regional scales. Thus, the time is ripe for a critical re-assessment of the importance of nitrogen gas fluxes to ecosystem nitrogen balances. This research will produce information relevant to a pressing and globally important environmental problem (nitrogen pollution), will involve graduate students and underrepresented groups, and will be coupled to education and outreach efforts in University, management and policy arenas.