Chapitre 13. Séquestration du carbone et usage durable des savanes ouest-africaines : synergie ou antagonisme ?

Introduction Les écosystèmes de savane ouest-africaine couvrent de vastes superficies (5.106 km2), en grande majorité exploitées par l’agriculture et le pastoralisme (Mayaux et al., 2004). Ils associent des systèmes herbacés et arborés, les faciès de végétation étant fortement pilotés par la pluviosité annuelle selon un gradient latitudinal. Dans ces écosystèmes, pour des raisons principalement démographiques et techniques – et, demain, sans doute climatiques – les ressources carbonées se rar..

International Science Foresight Workshop: Global Challenges and Research Gaps. The Royaumont process.

How scientists might better contribute to SDGs in the land sector? At the invitation of INRAE, a group of high-level international experts delivers a comprehensive and systemic approach

Carbone des sols en Afrique

Les sols sont une ressource essentielle à préserver pour la production d’aliments, de fibres, de biomasse, pour la filtration de l’eau, la préservation de la biodiversité et le stockage du carbone. En tant que réservoirs de carbone, les sols sont par ailleurs appelés à jouer un rôle primordial dans la lutte contre l’augmentation de la concentration de gaz à effet de serre. Ils sont ainsi au centre des objectifs de développement durable (ODD) des Nations unies, notamment les ODD 2 « Faim zéro », 13 « Lutte contre le changement climatique », 15 « Vie terrestre », 12 « Consommation et production responsables » ou encore 1 « Pas de pauvreté ». Cet ouvrage présente un état des lieux des sols africains dans toute leur diversité, mais au-delà, il documente les capacités de stockage de carbone selon les types de sols et leurs usages en Afrique. Il propose également des recommandations autour de l’acquisition et de l’interprétation des données, ainsi que des options pour préserver, voire augmenter les stocks de carbone dans les sols. Tous les chercheurs et acteurs du développement impliqués dans les recherches sur le rôle du carbone des sols sont concernés par cette synthèse collective. Fruit d’une collaboration entre chercheurs africains et européens, ce livre insiste sur la nécessité de prendre en compte la grande variété des contextes agricoles et forestiers africains pour améliorer nos connaissances sur les capacités de stockage de carbone des sols et lutter contre le changement climatique

CaTMAS: a multi-agents model to simulate the dynamics of carbon resources of West African villages

International audienceCarbon is an important determinant of the sustainability of West African farming systems and of the atmospheric greenhouse effect. Given the complexity of C dynamics, various simulation models have been developed. Few include socioeconomic factors or handle system heterogeneity. This study pro- poses a generic, multi-agent model for the analysis of C dynamics at village level. It assumes that a better analysis of carbon dynamics at village level requires account to be taken of social, economic, physical and biological factors as well as of the actions of individuals and their interdependence. The Carbon of Territory Multi-Agent Simulator (CaTMAS) model is based on the Organization-Role-Entity-Aspect (OREA) meta-model and the Multi-Agent Systems (MAS) approach. OREA enables C dynamics to be studied from various points of view through the roles played by entities within organizations and also allows various entities to play the same role in various ways through the notion of aspects. The model was coupled with the Century model and a geographical information system to provide a realistic representation of C dynamics. CaTMAS provides not only a framework for the explicit description of the carbon dynamics of farming systems but can also be used to assess the viability of farming systems using various socioeconomic and biophysical scenarios. The model includes interactions between human activities and the environment. Simple simulations involving two cropping systems and focusing on the impact of population growth and different climate regimes on the C dynamics indicate that CaTMAS accounts realistically for the relationships between population, agriculture, climate and SOC dynamics. In simulation, population growth, which drives food demand, leads to agricultural expansion, land scarcity and decrease in fallow duration. These effects are accentuated by increasing temperature and decreasing rainfall which affect the SOC dynamics controlling soil fertility and thus crop production. Improvements to the model should make it possible to extend the scale of the simulation of C dynamics and include refinements such as the inclusion of the trading of carbon credits

Relationships between abiotic and biotic soil properties during fallow periods in the sudanian zone of Senegal

Relationships between soil characteristics, various forms of soil organic matter, microbial biomass and the structure of phytoparasitic nematode populations were investigated in six fallow fields aged from 1 to 26 years in the West African Savanna (WAS) belt in southern Senegal. Soil sampling was performed along two transects in each field. Herbaceous biomass and soil physical, chemical and biological characteristics were studied with principal component analysis (PCA) and the relationships between the parameters were extracted with co-inertia analysis. Soil properties (mainly calcium, magnesium and total carbon content, and cation exchange capacity) slightly improved in the upper soil layer (0-5 cm) during the succession of vegetation. In contrast, in the 0-10 cm soil layer, microbial biomass and total soil organic carbon content showed no clear pattern of change over time, while highest charcoal stocks were found in older fallows where bush fires are frequent. In the 0-40 cm layer, living root biomass increased and herbaceous biomass decreased through the chronosequence. Evidence is presented here for particular relationships between some of the carbon components and the structure of the nematode community. #Pratylenchus and #Ditylenchus species were associated with the grass vegetation of the youngest fallows. In contrast #Helicotylenchus and #Scutellonema were present in old fallows. The multiplication of the latter appeared closely related to the presence of woody fine roots, whereas, that of the former seemed to be favoured by the presence of the coarsest root of trees. #Xiphinema$ had a higher density in soils with higher bulk density. Microbial biomass was not affected by fallow duration and was not correlated with the abundance of non-parasitic nematodes... (D'après résumé d'auteur