Yield response of Lolium perenne swards to free air CO2 enrichment increased over six years in a high N input system on fertile soil
Article first published online: 9 OCT 2008
Global Change Biology
Volume 6, Issue 7, pages 805–816, October 2000
How to Cite
Daepp, M., Suter, D., Almeida, J. P. F., Isopp, H., Hartwig, U. A., Frehner, M., Blum, H., Nösberger, J. and Lüscher, A. (2000), Yield response of Lolium perenne swards to free air CO2 enrichment increased over six years in a high N input system on fertile soil. Global Change Biology, 6: 805–816. doi: 10.1046/j.1365-2486.2000.00359.x
- Issue published online: 9 OCT 2008
- Article first published online: 9 OCT 2008
- Received 1 October 1999; revised version received and accepted 22 February 2000
- Cited By
- elevated CO2;
- increased CO2;
- Lolium perenne;
- N availability;
After a step increase in the atmospheric partial pressure of CO2 (pCO2), the availability of mineral N may be insufficient to meet the plant's increased demand for N. Over time, however, the ecosystem may adapt to the new conditions, and a new equilibrium may be established in the fluxes of C and N. This would result in a higher dry mass (DM) yield response of the plants to elevated pCO2.
The effect of elevated atmospheric pCO2 (60 Pa pCO2) was studied in Lolium perenne L. swards with two N fertilization treatments (14 and 56 g m−2 y−1) in a six-year FACE (Free Air Carbon dioxide Enrichment) experiment. In the high N treatment, the input of N with fertilizer considerably exceeded the export of N with the harvested plant material in both CO2 treatments leading to an apparent net input of N into the ecosystem. Accordingly, the proportion of harvested N derived from 15N labelled fertilizer N, applied throughout the experiment (< 6 years), increased over the years. Under these high N conditions, the annual DM yield response of the Lolium perenne sward to elevated pCO2 increased (from 7% in 1993 to 25% in 1998). In parallel, the response of N yield to elevated pCO2 increased, and the initially negative effect of elevated pCO2 on specific leaf area (SLA) disappeared. The high N input system seemed to overcome in part an initially limiting effect of N on the yield response to elevated pCO2 within a few years. In contrast, there was no apparent net input of N into the ecosystem in the low N treatment, because N fertilization just compensated the export of N with the harvested plant material. Accordingly, the proportion of harvested N yield, derived from fertilizer N, which was applied throughout the experiment, remained low. At low N, the availability of mineral N strongly limited plant growth and yield production in both CO2 treatments; the low yields of DM and N, the low concentration of N in the plant material, and the low SLA reflected this. Although the plants grew under the same environmental conditions and the same management treatment as plants in the high N treatment, the response of DM yields to elevated pCO2 in the low N treatment remained weak throughout the experiment (5% in 1993 and 9% in 1998). The results are discussed in the context of the sizes of the different N pools in the soil, the allocation of N within the plant and the possible effects on temporal immobilization, and the availability of mineral N for yield production as affected by elevated pCO2 and N fertilization.