Carbon dioxide fluxes from contrasting ecosystems in the Sudanian Savanna in West Africa
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Date
2015-01
Journal Title
Journal ISSN
Volume Title
Publisher
Carbon Balance and Management
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 CO2 fluxes 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.
Conclusion: 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 CO2
assimilation leading to higher GPP. However, CO2 effluxes 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.
Description
An article published by Carbon Balance and Management and available at
DOI 10.1186/s13021-014-0011-4
Keywords
West Africa, Sudanian Savanna, Carbon fluxes, Net ecosystem exchange
Citation
Carbon Balance and Management (2015) 10:1 DOI 10.1186/s13021-014-0011-4