L´impact des aires protégées et des utilisations anthropogènes du sol sur la regeneration des terrains boisés à Acacia dans l´est du Burkina Faso

Regeneration success, persistence strategies (seedlings vs. coppicing), and population trend of Acacia spp. were tested under two land-use regimes in eastern Burkina Faso: (i) protected areas shielded to livestock grazing pressure, to logging, and using early annual fire as a management system; (ii) areas with high human impact (heavily and extensive livestock grazing, harvesting for wood and for medicinal plants). Generally, a good regeneration rate of Acacia species was observed in protected areas and a poor regeneration rate in areas with high human impact. Nevertheless, some species affiliated to the subgenus Aculeiferum as A. dudgeoni and A. polyacantha showed a good regeneration under both land use regimes. Juvenile plants less than 25 cm height of A. dudgeoni and A. gourmaensis increased by 116 to 50 % in areas with human impact as compared to their populations in protected areas. With SCD slopes varying from –0.40 to -0.70, the protected Acacia woodland displayed a stable population structure due to abundance of recruitment, and coppicing persistence (more common in the subgenus Aculeiferum) favoured by early annual fire. Consequently, the protected areas are favourable for Acacia woodland regeneration. Conversely, SCD slopes are positive or close to zero in areas of anthropogenic regime and showed a declining population, especially more marked with the subgenus Acacia due to permanent seed and seedling removal by livestock grazing. Nevertheless, the number of seedlings of some species was higher in areas under human pressure than in protected areas, especially for the subgenus Aculeiferum, improving the genetic variability and thus the long-term maintenance of the population. Key words: Acacia, early fire, land use, sudano-sahelien zoneLe statut de la régénération, les stratégies de persistance et la dynamique des Acacia spp. ont été évalués suivant deux modes d’utilisation dans la région est du Burkina Faso: (i) les zones protégées soustraites du pâturage extensif et de la coupe du bois, mais sont parcourues annuellement par des feux précoces ; (ii) les zones à forte impact anthropique (fort pâturage extensif, exploitations humaines diverses). En général, les zones protégées montrent un taux de régénération élevé des Acacia spp. alors que les zones anthropogéniques présentent une faible régénération. Néanmoins, certaines espèces affiliées au sous genre Aculeiferum comme A. dudgeoni et A. polyacantha montrent une bonne régénération dans les deux modes d’utilisation des terres. La population juvénile de moins de 25 cm de hauteur des espèces tel que A. dudgeoni et A. gourmaensis est 116 à 50 % plus élevée dans les zones anthropisées que dans les zones protégées. Avec des pentes de régression variant entre -0.40 à -0.70 dans les zones protégées, les populations présentent une structure stable due à l’abondance des plantules, et des rejets de souches maintenues par les feux précoces (plus fréquent dans le sous genre Aculeiferum). Par conséquent, les zones protégées sont plus favorables à la régénération des formations d’Acacia. A l’opposé, les pentes de régression sont positives ou proche de 0 dans les zones anthropisées montrant des populations peu stables particulièrement pour le sous genre Acacia à cause du prélèvement des semences et des plantules due au pâturage extensif. Néanmoins, les plantules issues de la germination de certaines espèces du sous Aculeiferum sont plus nombreuses dans les zones anthropisées que dans les zones protégées et pourraient améliorer la variabilité génétique pour la conservation à long termes des peuplements. Key words: Acacia, feux précoces, pâturage, utilisation des terres, zone soudano-sahélienn

Sustainable Choices for a Comprehensive Agricultural Sector in the Congo Basin of Central Africa

Agriculture in the Central African sub-region is still to fulfill its promise of creating decent employment and welfare. Climate change threatens to exacerbate this challenge. This paper specifies a model for sustainable comprehensive agricultural development in the Congo Basin and identifies options for improving livelihoods and achieving food security while addressing the global concerns of carbon sequestration and preserving biodiversity. It is suggested that the capacity of local and regional institutions be enhanced to communicate the model recommendations as part of a broad agenda in agricultural planning and decision making processes which address biodiversity management, climate change adaptation and national development priorities

Les aptitudes agricoles et pastorales des sols dans les pays du CILSS

projet Alerte Précoce et Prévision des Productions Agricoles (AP3A

Knowing the African Soils to Improve Fertilizer Recommendations

Africa is the continent with the lowest fertilizer use per hectare notwithstanding the fact it possesses geologically old, infertile and degraded soils. This chapter discusses the agro-ecological zones (AEZ) and main soil types in Africa followed by a section on the extent, effects and costs of land degradation including issues of soil productivity and profitability associated with fertilizer use in Africa. There are a variety of soil types in the five major agro-ecological zones of Africa. Ferralsols and the Acrisol are dominant in the humid zones. Ferralsols are dominant in the sub-humid zone and so are Lixisols while in the semi-arid zone Lixisols have the larger share. Sixty five percent of the agricultural land in Africa is degraded and soil fertility depletion, a manifestation of soil degradation, is currently a serious threat to food security among small-holder farmers. Because of this state of affairs there is a strong case for enhanced fertilizer use. Maize yield has reportedly increased over the control due to NPK fertilizer application from various AEZ and when soils are amended with lime and manure yield response has been even higher. Indeed, there is credible evidence of fertilizer response and profitability in Africa relative to other parts of the world, particularly, for maize and rice thus making fertilizer investment worthwhile. In conclusion, there is need for agricultural intensification through efficient use of soil nutrient and water resources. Technologies need to be adapted to the specific bio-physical and socio-economics circumstances of the small scale farmers in Africa. There is also need to focus more on increasing the fertilizers use efficiency and the development of the local fertilizer sector in order to make them more profitable

Towards a harmonisation of the soil map of Africa at the continental scale

In the context of major global environmental challenges such as food security, climate change, fresh water scarcity and biodiversity loss, the protection and the sustainable management of soil resources in Africa are of paramount importance. To raise the awareness of the general public, stakeholders, policy makers and the science community to the importance of soil in Africa, the Joint Research Centre of the European Commission has produced the Soil Atlas of Africa. To that end, a new harmonised soil map at the continental scale has been produced. The steps of the construction of the new area-class map are presented, the basic information being derived from the Harmonized World Soil Database (HWSD). We show how the original data were updated and modified according to the World Reference Base for Soil Resources classification system. The corrections concerned boundary issues, areas with no information, soil patterns, river and drainage networks, and dynamic features such as sand dunes, water bodies and coastlines. In comparison to the initial map derived from HWSD, the new map represents a correction of 13% of the soil data for the continent. The map is available for downloading

Soil Atlas of Africa

The sustainable management of natural resources in Africa is a formidable challenge yet crucial for the survival of over one billion people! Africa has the capacity to feed itself yet the continent has a history of land developments, often driven by a desire for a quick economic return, that completely ignore the capabilities of the soil to support it. Reliance on inappropriate cultivation practices, a lack of concern about how natural ecological cycles have maintained soil fertility in Africa over millennia and a high level of rural poverty has led to land degradation throughout Africa. Understanding the evolution of soils and associated vegetation patterns in relation to their use by society is fundamental if we wish to assess fully the impacts of processes driving change in Africa. This applies equally to climate change, population growth and food security. The evidence for soil degradation and environmental change is apparent in many parts of Africa. For this reason we are pleased to see that the Joint Research Centre (JRC) is taking responsibility to highlight these issues. By building on existing cooperation with researchers from Africa, EU Member States and international organisations, the JRC has used science to bring together people from diverse national and political backgrounds to address a common goal. Given its scientific understanding of the issues, the JRC is carrying out a crucial role in communicating science to the wider society. This innovative “Soil Atlas of Africa” is intended to be a step towards raising public awareness on the importance and the key role of soil in Africa. The atlas compiles existing information on different soil types in easily understandable maps that cover the entire African continent. While it is intended primarily for the general public, the educational sectors and policy makers, the atlas aims to bridge the gap between soil science and society at large. Recognising the importance of soil as a nonrenewable resource which provides many critical ecological functions that are crucial to human existence will support the development of protective measures that will safeguard soils for current and future generations.JRC.H.5-Land Resources Managemen