title: Carbon dioxide fluxes from contrasting ecosystems in the Sudanian Savanna in West Africa.
abstract: BACKGROUND
  The terrestrial land surface in West Africa is made up of several types of savanna ecosystems differing in land use changes which modulate gas exchanges between their vegetation and the overlying atmosphere. This study compares diurnal and seasonal estimates of CO2fluxes from three contrasting ecosystems, a grassland, a mixture of fallow and cropland, and nature reserve in the Sudanian Savanna and relate them to water availability and land use characteristics.
  
  
  RESULTS
  Over the study period, and for the three study sites, low soil moisture availability, high vapour pressure deficit and low ecosystem respiration were prevalent during the dry season (November to March), but the contrary occurred during the rainy season (May to October). Carbon uptake predominantly took place in the rainy season, while net carbon efflux occurred in the dry season as well as the dry to wet and wet to dry transition periods (AM and ND) respectively. Carbon uptake decreased in the order of the nature reserve, a mixture of fallow and cropland, and grassland. Only the nature reserve ecosystem at the Nazinga Park served as a net sink of CO2, mostly by virtue of a several times larger carbon uptake and ecosystem water use efficiency during the rainy season than at the other sites. These differences were influenced by albedo, LAI, EWUE, PPFD and climatology during the period of study.
  
  
  CONCLUSIONS
  These results suggest that land use characteristics affect plant physiological processes that lead to flux exchanges over the Sudanian Savanna ecosystems. It affects the diurnal, seasonal and annual changes in NEE and its composite signals, GPP and RE. GPP and NEE were generally related as NEE scaled with photosynthesis with higher CO2assimilation leading to higher GPP. However, CO2effluxes over the study period suggest that besides biomass regrowth, other processes, most likely from the soil might have also contributed to the enhancement of ecosystem respiration.
authors: Federal University of Technology, Akure, Nigeria ; Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
authors: Emmanuel
authors: E
authors: Quansah
authors: Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany.
authors: Matthias
authors: M
authors: Mauder
authors: Federal University of Technology, Akure, Nigeria.
authors: Ahmed A
authors: AA
authors: Balogun
authors: Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
authors: Leonard K
authors: LK
authors: Amekudzi
authors: Chair for Regional Climate and Hydrology, University of Augsburg, Augsburg, Germany.
authors: Luitpold
authors: L
authors: Hingerl
authors: Chair for Regional Climate and Hydrology, University of Augsburg, Augsburg, Germany.
authors: Jan
authors: J
authors: Bliefernicht
authors: Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany ; Head of Chair for Regional Climate and Hydrology, University of Augsburg, Augsburg, Germany.
authors: Harald
authors: H
authors: Kunstmann
keywords: Carbon fluxes; Net ecosystem exchange; Sudanian Savanna; West Africa
references: Philos Trans A Math Phys Eng Sci. 2011 May 28;369(1943):2038-57
references: 21502175
references: Biogeosciences. 2010 Aug;7(8):2297-2309
references: 23293657
references: Science. 2003 Jun 6;300(5625):1538-42
references: 12764201
references: Carbon Balance Manag. 2008 Dec 01;3:7
references: 19046418
references: Ecol Appl. 2008 Sep;18(6):1351-67
references: 18767615