Nitrogen Cycling and Dynamics in Terrestrial Ecosystems

Nitrogen (N), the fifth most abundant element in the earth, is the most abundant element in the atmosphere, comprising 78% by volume as N 2 (Nitrous oxide) gas. However, it is unavailable to most organisms because of the strength of the triple bond that binds the two N atoms together. Nitrogen is an important element in biogeochemical cycles and plays a pivotal role in regulating species composition, diversity, dynamics, and function. Atmospheric N 2 is transformed by Nitrogen fixation and imported into aquatic and terrestrial ecosystems. The Nitrogen cycling is driven by a combination of assimilatory and dissimilatory biological transformations. Overall, the anthropogenic alteration of the global Nitrogen cycle has multiple consequences in the atmosphere, terrestrial, and marine ecosystems as well as human health. The significant consequences of anthropogenic acceleration of the Nitrogen cycle is the eutrophication of estuaries and coastal waters, leading to hypoxic zones in many areas, as well as increased global inventories of N 2 O.