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Biogeosciences Discuss., 5, 4071-4105, 2008
www.biogeosciences-discuss.net/5/4071/2008/
doi:10.5194/bgd-5-4071-2008
© Author(s) 2008. This work is distributed
under the Creative Commons Attribution 3.0 License.

Precipitation as driver of carbon fluxes in 11 African ecosystems

L. Merbold1, J. Ardö2, A. Arneth2, R. J. Scholes3, Y. Nouvellon4,14, A. de Grandcourt4,5, S. Archibald3, J. M. Bonnefond6, N. Boulain7, C. Bruemmer8, N. Brueggemann8, B. Cappelaere7, E. Ceschia9, H. A. M. El-Khidir10, B. A. El-Tahir10, U. Falk11, J. Lloyd15, L. Kergoat9, V. Le Dantec9, E. Mougin9, M. Muchinda12, M. M. Mukelabai12, D. Ramier7, O. Roupsard4, F. Timouk9, E. M. Veenendaal13, and W. L. Kutsch1
1MPI for Biogeochemistry, Jena, Germany
2Department of Physical Geography and Ecosystems Analysis, Lund University Sölvegatan 12, 223 62 Lund, Sweden
3Natural Resources and the Environment, CSIR, P.O. Box 395, Pretoria, South Africa
4CIRAD, Persyst, UPR80, TA B-80/D, 34 398 Montpellier Cedex 5, France
5UR2PI, BP 1291, Pointe-Noire, The Republic of Congo
6INRA-EPHYSE, BP 81, 33 883 Villenave d'Ornon Cedex, France
7UMR Hydrosciences, IRD, BP 64 501, 34 394 Monpellier Cedex 5, France
8Atmospheric Environmental Research Division, Institute of Meteorology and Climate Research, Forschungszentrum Karlsruhe, Garmisch-Partenkirchen, Germany
9CESBIO, 18 Avenue Edouard Belin, 31 401 Toulouse Cedex 9, France
10Agricultural Research Cooperation, El Obeid Research Station, P.O. Box 429, 51 111 El Obeid, Sudan
11Department of Ecology and Resource Management, Center for Development Research, University of Bonn, Bonn, Germany
12Zambia Meteorological Department, Haile Sellasie Avenue, City Airport, P.O. Box 30 200, 10 101 Lusaka, Zambia
13Nature Conservation and Plant Ecology Group, Wageningen University, Droevendaalse Steeg 3a, 6708 PD Wageningen, The Netherlands
14Professor visitante USP (ESALQ e IAG), Departamento de Ciêncas de Atmosféricas/IAG/Universidade de Sao Paulo, Rua do Matao, 1226 - Cidade Universitária, Sao Paulo, Brasil
15Earth and Biosphere Institute, School of Geography, University of Leeds, LS2 9JT, UK

Abstract. This study reports carbon and water fluxes between the land surface and atmosphere in eleven different ecosystems types in Sub-Saharan Africa, as measured using eddy covariance (EC) technology in the first two years of the CarboAfrica network operation. The ecosystems for which data were available ranged in mean annual rainfall from 320 mm (Sudan) to 1150 mm (The Republic of Congo) and include a spectrum of vegetation types (or land cover) (open savannas, woodlands, croplands and grasslands). Given the shortness of the record, the EC data were analysed across the network rather than longitudinally at sites, in order to understand the driving factors for ecosystem respiration and carbon assimilation, and to reveal the different water use strategies in these highly seasonal environments.

Values for maximum net carbon assimilation rates (photosynthesis) ranged from 12 μmol CO2 m−2 s−1 in a dry, open Acacia savanna (C3-plants) up to 40 μmol CO2 m−2 s−1 for a tropical moist grassland. Maximum carbon assimilation rates were highly correlated with mean annual rainfall (R2=0.89). Maximum photosynthetic uptake rates were positively related to satellite-derived fAPAR. Ecosystem respiration was dependent on temperature at all sites, and was additionally dependent on soil water content at sites receiving less than 1000 mm of rain per year. All included ecosystems, except the Congolese grassland, showed a strong decrease in 30-min assimilation rates with increasing water vapour pressure deficit above 2.0 kPa.

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Citation: Merbold, L., Ardö, J., Arneth, A., Scholes, R. J., Nouvellon, Y., de Grandcourt, A., Archibald, S., Bonnefond, J. M., Boulain, N., Bruemmer, C., Brueggemann, N., Cappelaere, B., Ceschia, E., El-Khidir, H. A. M., El-Tahir, B. A., Falk, U., Lloyd, J., Kergoat, L., Le Dantec, V., Mougin, E., Muchinda, M., Mukelabai, M. M., Ramier, D., Roupsard, O., Timouk, F., Veenendaal, E. M., and Kutsch, W. L.: Precipitation as driver of carbon fluxes in 11 African ecosystems, Biogeosciences Discuss., 5, 4071-4105, doi:10.5194/bgd-5-4071-2008, 2008.   Bibtex   EndNote   Reference Manager    XML
 

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