A review of nitrogen enrichment effects on three biogenic GHGs: the CO 2 sink may be largely offset by stimulated N 2 O and CH 4 emission

• Published in: Ecology letters Vol. 12; no. 10; pp. 1103 - 1117
• Main Authors: Liu, Lingli, Greaver, Tara L.
• Format: Journal Article
• Language: English
• Published: 01-10-2009
• ISSN: 1461-023X; 1461-0248
• DOI: 10.1111/j.1461-0248.2009.01351.x

Abstract
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: CO
2
, CH
4
and N
2
O. 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 CO
2
exchange for non‐forest natural ecosystems. Across all ecosystems, N addition increased CH
4
emission by 97%, reduced CH
4
uptake by 38% and increased N
2
O 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 CO
2
reduction could be largely offset (53–76%) by N stimulation of global CH
4
and N
2
O emission from multiple ecosystems.