Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Woody aboveground biomass and its drivers in mosaic landscapes in West and East Africa

Auteur : Amara, Edward

Université de soutenance : University of Helsinki,

Grade : Doctoral dissertation (article-based) / Doctoral Programme in Atmospheric Sciences 2022

Résumé partiel
A heterogeneous landscape with different land uses or a cluster of several ecosystems is known as a mosaic landscape. In the African savannas, such landscapes comprise, for example, agricultural fields, patches of forest, fallow fields, and wooded and open grasslands. Woody plants play important role in ecosystem services in the African savanna biome. Woody aboveground biomass (AGB) is a critical Earth’s terrestrial carbon sink and exerts a strong control on the evolution of atmospheric CO2 concentration. Mapping and monitoring carbon stocks in the tropical African region has attracted a great deal of attention in recent years. Deforestation and land degradation account for large amounts of anthropogenic carbon emissions and are now included in climate change negotiations. Therefore, quantification of woody AGB and understanding its drivers are significant in the implementation of climate change mitigation strategies in tropical savanna regions. Also, considering the growing impact of climate change and anthropogenic consequences on savanna land cover, understanding of the AGB and land use and land cover (LULC) dynamics in this region is important. The main goal of this thesis was to examine woody AGB and its drivers in mosaic landscapes of West and East Africa, namely in Sierra Leone and Kenya. More specific objectives were to study 1) the relationships among aboveground carbon stock, soil organic carbon stock and tree species diversity, 2) the impact of conservation and fences on density and distribution of woody AGB, and 3) the effect of tree size and species composition on AGB across LULC types. To accomplish these objectives, field inventory data and remote sensing data were used. The field data were collected from northern Sierra Leone and southeastern Kenya. In Sierra Leone, field data were collected from 160 plots of 1000m2 while 224 plots of the same size and airborne laser scanning (ALS) data were used in Kenya. Acquiring field data is arduous, expensive, and sometimes challenging, especially in remote areas. Remote sensing data (e.g., ALS and Sentinel-2 satellite images) data complement field-based inventories to produce LULC and AGB maps.

Mots clés : Aboveground biomass ; carbon ; biodiversity ; land use land cover types ; wildlife conservation ; fence ; tree species composition ; diameter at breast height ; field inventory ; mosaic savanna biome

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