Einflüsse des CO2-Anstieges auf die C-Flüsse in Wiesenökosystemen

• Forschungsstelle: COST
• Projektnummer: C95.0035

Schlüsselwörter (Englisch)

CO2 CLIMATE CHANGE; GRASSLAND; CARBON FLUXES; CARBON SEQUESTRATION; LONG TERM; NITROGEN FIXATION

Forschungsprogramme (Englisch)

COST-Action 619 - Effects of an atmospheric CO2 increase on carbon fluxes in grassland ecosystems

Kurzbeschreibung (Englisch)

See abstract

Partner und Internationale Organisationen (Englisch)

A, B, CH, D, DK, E, F, FIN, H, I, IRL, N, NL, S, UK

Abstract (Englisch)

Since the beginning of the Industrial Revolution the atmospheric CO2, concentration has risen by 30% to 365 ppm. Current predictions suggest that this rise will continue at an annual rate of 1.5 ppm. Grassland with its great C storage capacity and its slow C turnover in the soil may impose strong regulating effects on the global carbon cycle, and thus presumably slow down the predicted atmospheric CO2 increase. The initiative for COST 619 was based on the need for field-scale experiments designed to test the effect of elevated CO2 on complex grassland systems. COST 619 facilitated the collaboration between experimenters and modellers in order to advance the development of predictive ecosystem-level models. The Swiss FACE (Free Air Carbon Dioxide Enrichment) experiment at Eschikon (Zürich) was the core-experiment of this COST action and attracted collaborating scientists from Switzerland, EU, CN and USA. The project leader (J. Nösberger) acted also as chair of the Management Committee of COST 619 in which 17 countries were formally participating. In the course of COST 619 from 19 short-term scientific missions, the Swiss FACE acted for 15 of these missions as host institution. Average midday leaf photosynthetic rates in L. perenne were increased by 35% under elevated pCO2 as compared to ambient pCO2. However, annual yield of T. repens in monoculture increased, as the mean over all management treatments, in average by 25% when grown at elevated pCO2. In contrast, yield of L. perenne monoculture increased by only 10% on average over the first six years under elevated pCO2. The yield response of L. perenne to pCO2 changed according to the nitrogen fertilisation. At high nitrogen fertilisation, the yield response to pCO2 of L. perenne started at 7% (1993) and increased steadily to 24% in 2000. At low nitrogen was the yield response to pCO2 of L. perenne after eight years of fumigation still negative. These slow changes in the response to pCO2 indicate an adaptation of the ecosystem to growth under elevated pCO2, and a new equilibrium may be established between C and N flows There was a fundamental difference in the yield response to pCO2 of the various model ecosystems depending on the presence of T. repens. Irrespective of nitrogen fertilisation, grassland swards containing L. perenne monoculture showed marked nitrogen deficiency symptoms. In contrast, L. perenne growing in association with T. repens and T. repens growing in monoculture or mixture showed no nitrogen deficiency symptoms. An evaluation of the N-sources revealed that all the nitrogen that was additionally assimilated in T. repens under elevated pCO2, both in mixture and in monoculture, derived from symbiotic N2 fixation. Analysis of the population of soil bacteria also showed that elevated CO2 induced a genetic shift in the population of soil microbes.

Datenbankreferenzen (Englisch)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C95.0035