Biosphere-atmosphere exchange of CO2, water and energy in natural savannah in Burkina Faso (W Africa)
Abstract
Tropical savannahs cover an area of 17 x 106 km2 worldwide. Their role in the global greenhouse gas budget still remains uncertain. In the past large parts of the former native African savannahs have been converted to agricultural land. To contribute to evaluating greenhouse gas exchange of tropical savannah ecosystems, especially in sub- Saharan Africa, biosphere-atmosphere exchange of N2O, CH4 and CO2 was quantified in natural savannah and in rainfed agricultural land in Burkina Faso by means of eddy covariance (EC) and chamber measurements. An EC tower was established in a nature reserve to determine the net ecosystem exchange of CO2 (NEEC) and energy fluxes from November 2004 to October 2006. A Soil-Vegetation-Atmosphere-Transport (SVAT) model MixFor-SVAT (Oltchev et al., 2002) was used to compute the heat exchange between canopy and atmosphere, to conduct a plausibility test to the measured fluxes, and to investigate the component fluxes. MixFor-SVAT is a multi- layer model that describes the vertical distribution of radiation, momentum, energy and matter fluxes within and above mono- or multi-specific tree stands at 30-min resolution. Water fluxes in the plants are computed using a non-steady-state approach (HUNT et al., 1991). The EC measurements revealed that the natural savannah acted as a small C source in the dry period, whereas large amounts of CO2-C were bound during the rainy seasons, particularly from June to September. The balance of the first year of our observations indicated a C uptake of 373 g m-2 of the ecosystem, which is comparable to deciduous forests in Europe. The CO2 fluxes showed clear diurnal patterns with the highest uptake rates at noon (up to 1 mg m-2 s-1 in July and August) and a permanent slight release to the atmosphere during night-time.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFM.B23C1502F
- Keywords:
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- 0428 Carbon cycling (4806);
- 0439 Ecosystems;
- structure and dynamics (4815)