Browsing by Author "Amekudzi, Leonard"

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    Carbon dioxide fluxes from contrasting ecosystems in the Sudanian Savanna in West Africa
    (Carbon Balance and Management, 2015-01) Quansah, Emmanuel; Mauder, Matthias; Balogun, Ahmed; Amekudzi, Leonard
    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.
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    The ewiem Nimdie Summer School SerieS iN GhaNa Capacity Building in Meteorological Education and Research—Lessons Learned and Future Prospects
    (American Meteorological Society, 2012-05) Tompkins, Adrian M.; Parker, Douglas J.; Amekudzi, Leonard; et-al
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    The ewiem nimdie summer school series in Ghana Capacity Building in Meteorological Education and Research—Lessons Learned and Future Prospects
    (Bulletin of the American Meteorological Society, 2012-05) Tompkins, Adrian M.; Douglas J. Parker, Douglas J.; Danour, Sylvester; Amekudzi, Leonard; Bain, Caroline l.
    T H E E W I E M N I M D I E S U M M E R CONCEPT S C H O O L . The Ew iem Nimdie summer school is a biennial or triennial event that to date has been hosted in Ghana and focuses on the atmospheric sciences; “Ewiem Nimdie” means “atmospheric science” in the local Ashanti language. The first school was conducted in the summer of 2008, hosted by the Kwame Nkrumah University of Science and Technology (KNUST) located in Kumasi, with the second school taking place at the same institution two years later, in July 2010.
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    Land Use/Cover Response to Rainfall Variability: A Comparing Analysis between NDVI and EVI in the Southwest of Burkina Faso
    (Climate, 2014-12-24) Zoungrana, Benewinde Jean-Bosco; Conrad, Christopher; Amekudzi, Leonard; Thiel, Michael
    A comparative analysis of the sensitivity of NDVI and EVI to rainfall indicators has been carried out for different land use/covers in the Southwest of Burkina Faso. Three classified land use/covers maps for 1999, 2006 and 2011 were produced and change detection was applied to locate persistent areas. Thereafter monthly vegetation indices of plots of 750 × 750 m2 were extracted from 2001 to 2011 for persistent woodland, mixed vegetation, and agricultural area within 5 km radius around four rain gauges. Furthermore, correlation analysis to measure the relationship between vegetation indices and rainfall indicators was performed. The results indicate some similarities between NDVI and EVI. Both indices, for all land use/covers, showed significant and strong positive correlation with the rainfall indicators. In general, NDVI was more sensitive to rainfall than EVI in the study area, but the difference between the Pearson’s coefficient values of both vegetation indices was insignificant. The findings of this work agree with some previous studies,butcontrasting conclusions were also noted in literature. Hence wider spatial investigation will be necessary to confirm the results of this paper.