title: Nitrogen and nature.
abstract: Anthropogenic changes to the global N cycle are important in part because added N alters the composition, productivity, and other properties of many natural ecosystems substantially. Why does added N have such a large impact? Why is N in short supply in so many natural ecosystems? Processes that slow the cycling of N relative to other elements and processes that control ecosystem-level inputs and outputs of N could cause N supply to limit the dynamics of ecosystems. We discuss stoichiometric differences between terrestrial plants and other organisms, the abundance of protein-precipitating plant defenses, and the nature of the C-N bond in soil organic matter as factors that can slow N cycling. For inputs, the energetic costs of N fixation and their consequences, the supply of nutrients other than N, and preferential grazing on N-fixers all could constrain the abundance and/or activity of biological N-fixers. Together these processes drive and sustain N limitation in many natural terrestrial ecosystems.
authors.affiliation: Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA. vitousek@stanford.edu
authors.forename: Peter M
authors.initials: PM
authors.lastname: Vitousek
authors.forename: Stephan
authors.initials: S
authors.lastname: Hättenschwiler
authors.forename: Lydia
authors.initials: L
authors.lastname: Olander
authors.forename: Steven
authors.initials: S
authors.lastname: Allison
mesh_terms: D000818:Animals; D002244:Carbon / Q000737:chemistry; D011232:Chemical Precipitation; D017753:Ecosystem; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism*; D009586:Nitrogen Fixation; D009930:Organic Chemicals; D010944:Plants; D011506:Proteins / Q000378:metabolism; D012987:Soil
chemical_list: D009930:Organic Chemicals; D011506:Proteins; D012987:Soil; D002244:Carbon; D009584:Nitrogen