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.
