title: Soil carbon sequestration in prairie grasslands increased by chronic nitrogen addition.
abstract: Human-induced increases in nitrogen (N) deposition are common across many terrestrial ecosystems worldwide. Greater N availability not only reduces biological diversity, but also affects the biogeochemical coupling of carbon (C) and N cycles in soil ecosystems. Soils are the largest active terrestrial C pool and N deposition effects on soil C sequestration or release could have global importance. Here, we show that 27 years of chronic N additions to prairie grasslands increased C sequestration in mineral soils and that a potential mechanism responsible for this C accrual was an N-induced increase in root mass. Greater soil C sequestration followed a dramatic shift in plant community composition from native-species-rich C4 grasslands to naturalized-species-rich C3 grasslands, which, despite lower soil C gains per unit of N added, still acted as soil C sinks. Since both high plant diversity and elevated N deposition may increase soil C sequestration, but N deposition also decreases plant diversity, more research is needed to address the long-term implications for soil C storage of these two factors. Finally, because exotic C3 grasses often come to dominate N-enriched grasslands, it is important to determine if such N-dependent soil C sequestration occurs across C3 grasslands in other regions worldwide.
authors.affiliation: Environmental Sciences Research Institute, University of Ulster, Coleraine BT52 1SA, United Kingdom. d.fornara@ulster.ac.uk
authors.forename: Dario A
authors.initials: DA
authors.lastname: Fornara
authors.forename: David
authors.initials: D
authors.lastname: Tilman
mesh_terms: D002244:Carbon / Q000737:chemistry*; D017753:Ecosystem; D005390:Fires; D009584:Nitrogen / Q000737:chemistry* / Q000378:metabolism*; D018517:Plant Roots; D006109:Poaceae / Q000502:physiology*; D012987:Soil / Q000737:chemistry*; D013997:Time Factors
chemical_list: D012987:Soil; D002244:Carbon; D009584:Nitrogen