review of nitrogen enrichment effects on three biogenic GHGs: the CO₂ sink may be largely offset by stimulated N₂O and CH₄ emission

• Published in: Ecology letters 2009-10, Vol.12 (10), p.1103-1117
• Main Authors: Liu, Lingli, Greaver, Tara L
• Format: Article
• Language: English
• Subjects: Agricultural system; Air Pollutants - analysis; Air Pollutants - chemistry; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; carbon dioxide; Carbon Dioxide - analysis; Carbon Dioxide - chemistry; Carbon sequestration; Ecosystem; Ecosystems; emission/uptake factor; Environmental Monitoring; forest; Forestry; forests; Fundamental and applied biological sciences. Psychology; General aspects; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; global GHG budget; Greenhouse Effect; Greenhouse gases; Human influences; Meta-analysis; methane; Methane - analysis; Methane - chemistry; N deposition; N saturation; Nitrogen; Nitrogen - chemistry; Nitrogen Dioxide - analysis; Nitrogen Dioxide - chemistry; nitrous oxide; wetland
• ISSN: 1461-023X; 1461-0248
• DOI: 10.1111/j.1461-0248.2009.01351.x

Anthropogenic nitrogen (N) enrichment of ecosystems, mainly from fuel combustion and fertilizer application, alters biogeochemical cycling of ecosystems in a way that leads to altered flux of biogenic greenhouse gases (GHGs). Our meta-analysis of 313 observations across 109 studies evaluated the effect of N addition on the flux of three major GHGs: CO₂, CH₄ and N₂O. The objective was to quantitatively synthesize data from agricultural and non-agricultural terrestrial ecosystems across the globe and examine whether factors, such as ecosystem type, N addition level and chemical form of N addition influence the direction and magnitude of GHG fluxes. Results indicate that N addition increased ecosystem carbon content of forests by 6%, marginally increased soil organic carbon of agricultural systems by 2%, but had no significant effect on net ecosystem CO₂ exchange for non-forest natural ecosystems. Across all ecosystems, N addition increased CH₄ emission by 97%, reduced CH₄ uptake by 38% and increased N₂O emission by 216%. The net effect of N on the global GHG budget is calculated and this topic is reviewed. Most often N addition is considered to increase forest C sequestration without consideration of N stimulation of GHG production in other ecosystems. However, our study indicated that although N addition increased the global terrestrial C sink, the CO₂ reduction could be largely offset (53-76%) by N stimulation of global CH₄ and N₂O emission from multiple ecosystems.