The nitrogen cycle. A perspective for the terrestrial ecologist

Abstract

García-Velázquez, L., Gallardo, A. 2017. The global nitrogen cycle. A perspective for the terrestrial ecologist. Ecosistemas 26(1): 4-6. Doi.: 10.7818/ECOS.2017.26-1.02

The nitrogen (N) availability in the biosphere, the alteration of the global cycle, and its impact on the ecosystem are given by three key functional characteristics of the N cycle. First, the atmospheric N abundance allows both the biological and industrial fixation through the Haber-Bosch process, doubling the atmospheric N total inputs. Thus, the atmospheric N reservoir is the main source of the N cycle alteration, being the easiness to return to its original compartment the principal difference with the carbon (C) and phosphorus (P) cycles. Second, low concentrations of N in rock and soil minerals determines that in the long-term N limitation is mainly regulated by the biological fixation rate, being also dependent on the soil development and the presence of organic sedimentary rocks. Finally, an essential property of the N cycle in the biosphere is the high mobility of N across ecosystem boundaries through N-fixation, nitrification, denitrification and ammonification processes. All these properties cause that the fixed N molecule have multiples effects along its movement across different ecosystems, leading to  acidification, eutrophication, alteration of albedo among other processes, and contributing substantially to climate change.