84 research outputs found
Dynamique de la matiÚre organique à l'échelle d'un terroir agro-pastoral de savane ouest-africaine (Sud-Sénégal)
Organic matter dynamics in mixed-farming systems of the West African savanna : a village case study from South Senegal
Ăvaluation du stock de carbone et de la productivitĂ© en bois d'un parc Ă karitĂ©s du Nord-Cameroun
In the sudanian zones of northern Cameroon, the steady influx of migrants is causing much land clearance in large swathes of savannah lands. Creating denser stands of relict tree populations would be of value at once for agronomic, economic and environmental reasons. A method for evaluating the carbon stored in aerial biomass is proposed here for a village area of shea trees (Vitellaria paradoxa). The aim is to introduce agroforestry projects that will be eligible for the Clean Development Mechanism (CDM) as from 2012. In addition, an evaluation of fuelwood productivity in the area, using pollarding methods, was conducted for about thirty trees over a three-year period. A series of allometric equations was developed (for six shea specimens and one specimen each of Anogeissus leiocarpus and Combretum nigricans), establishing a ratio between aerial biomass and the diameter of the trunk (at chest height or at the branch base) or the surface area of the crown. This provided an estimation of carbon stocks per tree, and then per plot. Given the human pressure exerted on the tree zone, it was established that an 8-year rotation between pollarding operations would offer a healthy trade-off between the various interests involved. These studies offer a preliminary approach that will need to be consolidated with hindsight. Keywords: Vitellaria paradoxa, Clean Development Mechanism (CDM), pollarding, fuelwood productivity, carbon, agroforestry, sudanian zone, Cameroon
Ramial wood amendments (Piliostigma reticulatum) mitigate degradation of tropical soils but do not replenish nutrient exports
Restoring degraded soils to support food production is a major challenge for West African smallholders who have developed local innovations to counter further degradation. The objective of this study was to evaluate a local farmer's technique that uses ramial wood (RW) as soil amendment (Piliostigma reticulatum shrub). Three treatments were applied in an experimental plot in Burkina Faso: control (no amendment), low RW (3 Mg fresh mass·haâ1·yrâ1), and high RW (12 Mg fresh mass·haâ1·yrâ1). RW was chipped to <5âcm pieces and either buried or mulched. Topsoil carbon (C), nitrogen (N), and phosphorus (P) in control and lowâRW treatments declined after 7 years of continuous sorghum cultivation. Use of highâRW amendment stabilized soil C content while N and P declined, thus not replenishing nutrient exports. Net contribution to soil C in the layer measuring 0â15 cm was 15% of the applied C in the highâRW
amendments. Although biomass and grain yields were higher in highâRW treatments, crop productivity declined throughout the experiment for all treatments. Termite casts on RW treatments evidenced the potential role of woodâforaging termites in diluting
the impact of RW on soil fertility buildâup and soil water content. We conclude that mitigating soil degradation under semiarid conditions in Burkina Faso would require large amounts of woody amendments, particularly if the level of termite activity is high.
Additional nutrient sources would be needed to compensate for removal in exported products so that biomass and grain production can be stabilized or increased.EstaciĂłn Experimental Agropecuaria BarilocheFil: FĂ©lix, Georges F. Wageningen University. Farming Systems Ecology; HolandaFil: Clermont-Dauphin, Cathy. Montpellier SupAgro- Centre de CoopĂ©ration Internationale en Recherche Agronomique pour le DĂ©veloppement-Institut National de la Recherche Agronomique. Eco&Sols; FranciaFil: Hien, Edmond. Laboratoire Mixte International. Intensification Ecologique des Sols CultivĂ©s en Afrique de l'Ouest; Burkina FasoFil: Groot, Jeroen C.J. Wageningen University. Farming Systems Ecology; HolandaFil: Penche, Aurelien. Laboratoire Mixte International. Intensification Ecologique des Sols CultivĂ©s en Afrique de l'Ouest; Burkina FasoFil: BarthĂšs, Bernard G. Universidad Montpellier; FranciaFil: Manlay, RaphaĂ«l J. AgroParisTech; FranciaFil: Tittonell, Pablo Adrian. Instituto Nacional de TecnologĂa Agropecuaria (INTA). EstaciĂłn Experimental Agropecuaria Bariloche; ArgentinaFil: Cournac, Laurent. Montpellier SupAgro- Centre de CoopĂ©ration Internationale en Recherche Agronomique pour le DĂ©veloppement-Institut National de la Recherche Agronomique. Eco&Sols; Franci
Chapitre 13. Séquestration du carbone et usage durable des savanes ouest-africaines : synergie ou antagonisme ?
Introduction Les Ă©cosystĂšmes de savane ouest-africaine couvrent de vastes superficies (5.106 km2), en grande majoritĂ© exploitĂ©es par lâagriculture et le pastoralisme (Mayaux et al., 2004). Ils associent des systĂšmes herbacĂ©s et arborĂ©s, les faciĂšs de vĂ©gĂ©tation Ă©tant fortement pilotĂ©s par la pluviositĂ© annuelle selon un gradient latitudinal. Dans ces Ă©cosystĂšmes, pour des raisons principalement dĂ©mographiques et techniques â et, demain, sans doute climatiques â les ressources carbonĂ©es se rar..
Carbone des sols en Afrique
Les sols sont une ressource essentielle Ă prĂ©server pour la production dâaliments, de fibres, de biomasse, pour la filtration de lâeau, la prĂ©servation de la biodiversitĂ© et le stockage du carbone. En tant que rĂ©servoirs de carbone, les sols sont par ailleurs appelĂ©s Ă jouer un rĂŽle primordial dans la lutte contre lâaugmentation de la concentration de gaz Ă effet de serre. Ils sont ainsi au centre des objectifs de dĂ©veloppement durable (ODD) des Nations unies, notamment les ODD 2 « Faim zĂ©ro », 13 « Lutte contre le changement climatique », 15 « Vie terrestre », 12 « Consommation et production responsables » ou encore 1 « Pas de pauvretĂ© ». Cet ouvrage prĂ©sente un Ă©tat des lieux des sols africains dans toute leur diversitĂ©, mais au-delĂ , il documente les capacitĂ©s de stockage de carbone selon les types de sols et leurs usages en Afrique. Il propose Ă©galement des recommandations autour de lâacquisition et de lâinterprĂ©tation des donnĂ©es, ainsi que des options pour prĂ©server, voire augmenter les stocks de carbone dans les sols. Tous les chercheurs et acteurs du dĂ©veloppement impliquĂ©s dans les recherches sur le rĂŽle du carbone des sols sont concernĂ©s par cette synthĂšse collective. Fruit dâune collaboration entre chercheurs africains et europĂ©ens, ce livre insiste sur la nĂ©cessitĂ© de prendre en compte la grande variĂ©tĂ© des contextes agricoles et forestiers africains pour amĂ©liorer nos connaissances sur les capacitĂ©s de stockage de carbone des sols et lutter contre le changement climatique
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