Nitrogen limitation constrains sustainability of ecosystem response to CO sub(2)

• Published in: Nature Vol. 440; no. 7086; pp. 922 - 925
• Main Authors: Reich, Peter B, Hobbie, Sarah E, Lee, Tali, Ellsworth, David S, West, Jason B, Tilman, David, Knops, Johannes MH, Naeem, Shahid, Trost, Jared
• Format: Journal Article
• Language: English
• Published: 14.04.2006
• ISSN: 0028-0836; 1476-4679

Enhanced plant biomass accumulation in response to elevated atmospheric CO sub(2) concentration could dampen the future rate of increase in CO sub(2) levels and associated climate warming. However, it is unknown whether CO sub(2)-induced stimulation of plant growth and biomass accumulation will be sustained or whether limited nitrogen (N) availability constrains greater plant growth in a CO sub(2)-enriched world. Here we show, after a six-year field study of perennial grassland species grown under ambient and elevated levels of CO sub(2) and N, that low availability of N progressively suppresses the positive response of plant biomass to elevated CO sub(2). Initially, the stimulation of total plant biomass by elevated CO sub(2) was no greater at enriched than at ambient N supply. After four to six years, however, elevated CO sub(2) stimulated plant biomass much less under ambient than enriched N supply. This response was consistent with the temporally divergent effects of elevated CO sub(2) on soil and plant N dynamics at differing levels of N supply. Our results indicate that variability in availability of soil N and deposition of atmospheric N are both likely to influence the response of plant biomass accumulation to elevated atmospheric CO sub(2). Given that limitations to productivity resulting from the insufficient availability of N are widespread in both unmanaged and managed vegetation, soil N supply is probably an important constraint on global terrestrial responses to elevated CO sub(2).