Effects of elevated CO2 concentrations on carbon turnover in crop rotations studied in a Chinese and a German free air carbon dioxide enrichment (FACE) approach
Final Report Abstract
Using FACE (free air CO2 enrichment) facilities in Germany and China information should be gained about the direction and the extent of effects of future elevated atmospheric CO2 concentrations on CO2 fluxes and on processes of soil carbon (C) turnover. In addition this project was intended to identify how this potential CO2 effect is modified by different soil properties, nitrogen (N) fertilization levels and climatic conditions at two FACE study sites in Germany and China. The elevated atmospheric CO2 concentration in Braunschweig applied during a crop rotation generally resulted in a stimulation of the growth of C3 crops (Waigel et al. 2005) and therewith in additional C input into the soil due to enhanced rhizodeposition and higher plant residues. In the long term, this could result in rising content of organic C in the soil. The microbial biomass C is considered to be a sensitive early indicator for changes of Corg (Weigel et. al 2006). In the present FACE experiments, where soil C tumover is also strongly affected by repeated soil management measures throughout the year, there was no evidence after 2 years (China and Germany) of an effect of CO2 enrichment at the level of soil microbial biomass. In addition, rates of soil CO2 evolution were measured in situ, as it was assumed that a change in soil respiration rates is another suitable indicator for different C turnover in the soil. Considering previous FACE experiments, Pendali et al. (2001) for instance found an increase of soil respiration of wheat between 40-70 % under elevated CO2 conditions. In the present study there was neither an effect of the different N levels nor of elevated CO2 on soil respiration rates of sugar beet in Germany. This might be due to the fact that sugar beet responded to the CO2 Treatment with a decrease of leaf area index and chlorophyll content of the leaves during the season and that the biomass increase was much less than expected (Manderscheid et al., 2005). Winter wheat soil respiration rates showed significantly higher values for the plots with elevated CO2 concentration compared lo ambient air conditions at seven out of 14 measurement dates. This effect was increasingly significant in the course of the vegetation period, probably due to a more pronounced effect of elevated CO2 on plant activity with increasing temperature. Reductions in N supply increased dry matter of rools (Pacholski et al. 2006) probably accompanied by higher rhizodeposition and rool respiration. In the Chinese FACE study, however, opposite tendencies were observed. In the winter wheat season 2006 soil respiration was significantly lower under elevated CO2 concentration at some of the measurement dates and the plots of the full N treatment (N100) showed higher soil respiration rates than at reduced N treatment (N50) for both, FACE and ambient air conditions. It can be hypothesized that the stimulalion of plant growth by elevated CO2 was similar in both study sites (about 10 %), however, higher Corg content in the Chinese bulk soil in combination with the warm humid weather conditions might have resulted in higher soil microbial activity and C mineralization rales, which would have masked the slimulalion of root respiration and rhizodeposition. The differences between Germany (accelerated C turnover processes) and China (retarded C turnover processes) could be explained by the different amounts of organic matter and related microbial biomass in the soils studied. Soil processes regarding CO2 fluxes in China seem to be mainly driven by the higher microbial activity, while the short term stimulation of CO2 efflux in Germany under FACE conditions was probably due to a more pronounced effect on plant aclivity compared to the lower bulk soil C turnover. The chosen model approach (FASSET) proved to be applicable to simulate above ground plant growth as well as C lurnover as indicaied by CO2 efflux and microbial biomass at the Braunschweig FACE site. The FASSET model could thus be used for scenario calculations for an analysis of the probable long-term impacts of the changes in C turnover observed in the experimental studies on C sequestration at the German study site.
Publications
- "Effects of elevated CO2 concentrations on soil respiration under crop rotations and fallow soil in Eastern China and Germany" CARBOEUROP/COST Workshop "Partitioning soil CO2 efflux", Capri, Italien, 02.-04.10.2004
Heiduk K., Pacholski A., Waloszczyk K. Weigel H.J.
- "Effects of Elevated CO2 Concentrations (FACE) on Carbon Turnover in a Chinese and a German Crop Rotation - Experimental Outline and First Results". Sino-German workshop on "Effect of Land Use and Management System on Soil and Environment" September 29th to October 4th 2005
Heiduk K., Pacholski A., Zhu J.G., Siemens J., Martens R., Weigel H.J.
- 2005. Bilanzierung der CO2-Freisetzung aus Böden unter erhöhtem atmosphärischem CO2-Gehalt (FACE) - Verwendung zweier statischer Kammerverfahren mit unterschiedlicher räumlichzeitlicher Auflösung. Mittlgn. Dtsch. Bodenkundl. Gesellsch. 107(1) 235-236
Heiduk K., Heinemeyer O., Pacholski A., Weigel H.J.
- 2005. Gelöster Kohlenstoff und Stickstoff in einem Ackerboden unter erhöhter atmosphärischer CO2 Konzentration (FACE). Mittlgn. Dtsch. Bodenkundl. Gesellsch. 107(1), 277-278
Siemens J., Heiduk K., Pacholski A., Giesemann A., Kaupenjohann M., Weigel H.J.
- 2005. Modellierung und experimentelle Messung des Kohlenstoffumsatzes in einem Agrarökosystem unter erhöhten CO2-Konzentrationen (FACE). Mittlgn. Dtsch. Bodenkundl. Gesellsch. 107(1) 265-266
Pacholski A., Manderscheid R., Giesemann A., Heinemeyer O., Heiduk K., Weigel H.J.
- 2005. Soil respiration and soil biological dynamics under elevated CO2 (FACE) in a German and in a Chinese agro-ecosystem. Proceedings Ecol Soc Germany Austria Switzerl 35:291
Pacholski A., Heiduk K., Heinemeyer O., Anderson T.-H., Manderscheid R., Burkart S., Zhu J.G., Weigel H.J.
- "Effects of elevated atmospheric CO2 concentrations on carbon turnover processes in an agro-ecosystem" 36th Annual Conference of the Ecological Society of Germany, Switzerland and Austria (GfÖ) 11-15 September 2006, Bremen, Germany
Heiduk K., Pacholski A., Martens R., Weigel H.J.
- 2006. Effects of elevated atmospheric CO2 concentrations on carbon turnover processes in an agro-ecosystem. Proceedings Ecol Soc Germany Austria Switzerl 36:12
Heiduk K., Pacholski A., Martens R., Weigel H.J.
- „Einfluss erhöhter atmosphärischer CO2 Konzentration auf den Kohlenstoffumsatz im Boden in Agrar-Ökosystemen„ Doktorandenseminar Bodenkunde, Hannover, 13.07.2006
Heiduk K.
- 2007. Comparing responses of carbon dynamics to elevated atmospheric CO2 concentrations in arable crop rolations in Germany and China. Conference proceedings: International Symposium on Organic Matter Dynamics in Agro-Ecosystems. 16.-19. July 2007, Poitiers, pp 42-43
Heiduk K., Pacholski A., Marrtens R., Weigel H.J., Zhu J.G.
