122418 research outputs found
Sort by
Rapport de la mission réalisée du 8 au 20 octobre 2023. Évaluation des travaux de première année de deux thèses financées par le projet INNOVACC et confiées à : MM. Romain ROUSGOU et Faustin AMBOMO
No full textCette mission Cirad réalisée dans le cadre du projet INNOVACC (Innovation pour l'Adaptation au Changement Climatique) par Amah Akodewou et Régis Peltier (UR Forêts et Sociétés) et par Jean-Michel Harmand (UMR Eco&Sols & ICRAF) avait pour objectifs d'évaluer l'avancement des travaux de de thèse de doctorat des étudiants Faustin Ambomo Tsanga et Romain Rousgou qui portent respectivement sur la dynamique des parcs à Faidherbia dans les régions Nord et Extrême Nord et, sur l'effet des parcs à Faidherbia sur les cultures et les propriétés des sols. Le terrain, réalisé du 9 au 18/10/2023, a permis de rencontrer les deux doctorants, de leur faire exposer le bilan de leur première année de thèse, de clarifier leurs hypothèses, leurs questions de recherche, leurs méthodes et d'établir un calendrier de travail pour leur deuxième année. Un accompagnement a été apporté à Faustin pour une première analyse exploratoire de ses données d'émondage. Il a été également possible d'organiser des réunions avec les responsables du projet INNOVACC, avec ceux de l'IRAD (régions Nord & Extrême-Nord) et avec quelques agents de la Sodécoton, pour leur présenter les travaux de thèses et discuter des choix des terrains et des moyens à mettre en oeuvre. Une réunion du comité de première année de la thèse de Faustin Ambomo Tsanga a été réalisée pour évaluer la progression de l'étudiant et discuter de la suite des travaux. Afin de discuter des travaux en cours et à venir, quatre parcs agroforestiers à dominance de Faidherbia albida ont été visités. Par ailleurs, il a été demandé à Faustin Ambomo Tsanga de pousuivre et terminer ses relevés de phénologie des arbres des parcs à Faidherbia en février 2024. Les échanges entre les encadrants et les doctorants se poursuivront par courriels ou visio-conférences tout au long de l'année 2024. Il a été prévu de faire venir en mission à Montpellier Faustin Ambomo Tsanga, pour traiter ses données actuelles d'inventaire et d'émondage et préparer son programme d'enquêtes de 2024. Il est prévu que Vincent Freycon et J-M Harmand effectuent une mission de terrain en fin de saison sèche 2023-2024 pour effectuer des prélèvements de sol et programmer la campagne de mesure des récoltes de la saison des pluies 2024 pour Romain Rousgou
Achieving healthy and profitable production through collective action? The case of vegetable farmers in the French West Indies
No full textGiven the multiple challenges that agriculture faces, collective action is a potential pathway towards more sustainable agriculture. This article aims to contribute to the literature by assessing the extent to which collective action can meet the objective of both healthy and profitable production in the French West Indies. To do so, we call on the theory of collective action and emphasise the role of formal and informal collectives in achieving the objectives of improving income and implementing agroecological practices. We use original data collected in 2022 from 409 vegetable farmers in Martinique and Guadeloupe. We consider the interdependence between farmers' economic and environmental objectives through a simultaneous equations model. We characterise the diversity of collectives according to their degree of formalisation and to the adequacy between the objectives pursued by these collectives and the individual objectives of their members. Our results show that the achievement of an individual objective is fostered by its adequacy with the objective set by the collective and also, to a certain extent, by the degree of formalisation of this collective. It appears that achieving individual objectives is based on sharing common objectives as well as having collective rules. More particularly, we find that producer organisations – collectives considered to be the most formal – best meet the objectives of improving income and adopting agroecological practices. However, in the French West Indies, the instability of such collectives and the organisational deficiencies of the sector call into question their real long-term impact. These findings contribute to a better understanding of farmers' decision-making and provide relevant policy implications for supporting agricultural collectives in managing and federating producers towards achieving a more healthy and profitable production
Atelier de conception d'un chemin d'impact et d'une vision partagée avec la démarche ImpresS ex ante (SELMET, 7-9 juin 2022, Castelnau le Lez)
No full textAssessing pastoral reforms through the performance of agro-pastoral community-based organizations in South Tunisia
No full textPastoralism is one of the most important agricultural production systems in drylands worldwide. It plays an important role in both the economy and the cycle of ecosystem goods and services. However, it is vulnerable to climatic challenges such as prolonged drought and socioeconomic pressures such as administrative shortcomings and ineffective governance. Under neoliberal influence, political and economic reforms have been implemented over the last 30 years to address these threats. These reforms have promoted local institutions for rangeland management and agro-pastoral development. In this paper, we assess the impact of these reforms on pastoral devolvement and Community-based natural resource management (CBNRM) by analyzing the performance of agro-pastoral community-based organizations CBOs in the province of Médenine (south-eastern Tunisia). We use a two-step methodology, with the first step focusing on a quantitative typology analysis of the performance of 31 CBOs. In a subsequent qualitative step, data from semi-structured interviews with 21 CBO chairpersons were used to identify the drivers of CBO performance. Results show that only 10% of the CBOs studied are able to move towards autonomy and proper integration into local and regional institutional networks and development dynamics. About 42% of the CBOs need further support and are in a precarious situation as they are dependent on public support. The remaining 48% have a low growth potential and in the early stages of consolidation. The qualitative analysis suggests that these shortcomings are mainly related to the CBOs' lack of networking skills. In addition, CBOs should improve their reputation and gain more trust from pastoral communities. Our findings suggest that well-functioning institutions do contribute to rural development; however, the design of pastoralist policy and institutional reforms should include long-term complementary support for the institutions created and consideration of the pastoralist community and regional contexts in order to achieve long-lasting transformative outcomes
Quantifying impacts of biomass feedstock attributes in optimizing tropical biorefineries: Case of Peninsular Malaysia
No full textAmid growing global energy demands and climate concerns, sustainable biofuels offer a key alternative to fossil fuels. This study quantifies the impacts of spatial fragmentation, moisture content, resource yield density, and sourcing strategies on biofuel production costs and scalability in Peninsular Malaysia. Oil palm fronds with high moisture and fragmentation and reduced capacity by 36 % compared to rice straw. Single-feedstock systems like palm press fiber proved more cost-effective unless moisture in multi-feedstock combinations was reduced. For example, a PPF-EFB combination with 48.1 % moisture is 31 % cheaper than EFB alone at 60 % moisture. These results emphasize early-stage moisture management through mobile drying units or pre-treatment hubs are essential for economic viability. By benchmarking against crude oil prices, this study challenges assumptions about multi-feedstock cost savings and offers actionable insights for building scalable, cost-effective tropical biofuel supply chains
Of tropical forests and humans in the Americas: response trajectories of tree diversity and composition to anthropogenic disturbances
No full textTropical forests face more frequent and intense anthropogenic disturbances, such as selective logging, namely the felling and harvesting of a few commercially valuable trees in old-growth forests, while the remaining stand is left for natural regeneration. Many studies focused on this regeneration, particularly on the recovery of carbon and timber stocks, most likely due to a strong interest in climate change mitigation and logging profitability. However, despite the crucial role of biodiversity for ecosystem maintenance and functioning - and its intrinsic value - there have been few studies on the impact of selective logging on biodiversity. Therefore, this thesis - organised in three studies - aimed at characterising the response of tree diversity and composition to logging in tropical American forests.First, we drew upon the long-term forest inventories (1986-2021, trees with a diameter at breast height ≥ 10 cm) from Paracou experimental station to build a Bayesian modelling framework of tree diversity and composition trajectories after selective logging. Paracou is located in French Guiana and was disturbed by silvicultural treatments of different intensities in 1986-1987. We propagated in our Bayesian framework the uncertainty associated with botanical determination and functional trait measurements, and modelled Paracou trajectories of taxonomic, phylogenetic and functional tree diversity and composition at the species level, relatively to their pre-disturbance levels. Additionally, we assessed the effect of pre-disturbance tree community characteristics, biophysical conditions and disturbance properties on our forest attribute trajectories. Second, we used a simplified version of the aforementioned Bayesian modelling framework on long-term forest inventories from sample plots located in Costa Rica and three Amazonian countries (respectively belonging to the Observatorio de los Ecosistemas Forestales de Costa Rica and the Tropical managed Forest Observatory). We modelled their post-logging trajectories of taxonomic and functional tree diversity and composition at the genus level, from which we extracted indicators solely over the inventory timespan of each site. We then assessed the effect of pre-disturbance tree community structure and disturbance properties on such indicators. While more variable in the second study with a broader geographical scope than in the first one, we observed similar trends in both studies: diversity mostly increased after logging and tree communities mainly shifted from resource-conservative strategies to resource-acquisitive strategies. Such changes appeared to be driven by the abundant and transient recruitment of early-successional species with acquisitive trait values, which provided them with a competitive advantage as disturbance intensity - i.e., light and space availability - increased. Indeed, changes in diversity and composition increased in both studies with disturbance intensity whereas disturbance selectivity, pre-disturbance tree community characteristics and biophysical conditions had no significant effect. Third, building up on the paramount importance of disturbance intensity in the two previous studies, we developed an original Bayesian hierarchical model of recovery trajectories, considering disturbed forests in a common framework, through a disturbance intensity gradient. We tested our modelling approach on data from two long-term experiments in Costa Rica and French Guiana, set up after selective logging, agriculture, and clearcutting and fire.Overall, these results opened various perspectives on the methods used to evaluate forest response to disturbance, the forest response itself and the ecological processes underlying forest succession, and how disturbed forests could be considered in forest management and conservation plans
Surface albedo and thermal radiation dynamics under conservation and conventional agriculture in subhumid Zimbabwe
Get PDFWhile conservation agriculture (CA) has been widely evaluated for its biogeochemical effects (e.g soil organic carbon sequestration and greenhouse gas emissions) for climate mitigation, its biogeophysical impacts related to changes in surface albedo remain understudied. This study assessed the biogeophysical effects of CA cropping systems with maize (Zea mays L.) in Zimbabwe. Measurements were conducted continuously over two cropping years at two long-term experiments with contrasting soil characteristics, on an abruptic Lixisol and on a xanthic Ferralsol. The dynamics of surface albedo, longwave radiation, leaf area index, soil moisture and temperature were monitored under three different treatments: conventional tillage (CT, tilled to ~15 cm), no-tillage (NT) and no-tillage with mulch (NTM, 2.5 t DM ha⁻¹). Our results revealed that, on the Ferralsol, NT and NTM significantly (p < 0.05) increased mean annual albedo (0.17) relative to CT (0.16), resulting in a negative instantaneous radiative forcing (iRF) and indicating a net cooling effect. iRF was stronger in 2021/22 (NT: -0.83 ± 0.17 W m-2; NTM: -1.43 ± 0.7 W m-2) than in 2022/23 (NT: -0.43 ± 0.09 W m-2; NTM: -1.03 ± 0.21 W m-2). Conversely, on the Lixisol, while NT increased surface albedo (0.27 vs. CT: 0.24), NTM significantly reduced albedo (0.23), causing positive iRF (warming). iRF was -3.34 ± 0.69 W m-2 and -2.78 ± 0.77 W m-2 for NT in the first and second cropping year, respectively, and increased from 1.14 ± 0.21 W -2 (2021/22) to 2.77 ± 0.41 W m-2 (2022/ 23) under NTM. Overall, our results suggest that the soil background albedo is an important site characteristic that needs to be considered and demonstrates the importance of considering biogeophysical effects when promoting practices of CA for climate change mitigation
Trajectoires d'innovations sur les bioproduits à base de micro-organismes une contextualisation par l'agriculture tropicale
No full textL'utilisation des micro-organismes comme ressources constitutives de l'agriculture est historiquement ancrée dans les pratiques agricoles (compostage, lactofermentation.) des sociétés rurales depuis des siècles. La caractérisation de ces micro-organismes (virus, champignons, bactéries) par leur fonctionnalité pour restaurer la fertilité des sols, réduire l'usage de pesticides mobilise elle depuis une trentaine d'années les organisations de la société civile, entreprises, organisations professionnelles agricoles et la recherche agronomique principalement dans les pays du sud. L'augmentation, la multiplication des situations exploratoires de développement ou productives est cependant en croissance en liens par la science qui explore les conditions d'exploitation de ces ressources invisibles. Pour la recherche agronomique elles sont la promesse d'une révolution agronomique majeure qui permettra de s'affranchir des externalités négatives des intrants chimiques, mais aussi répondre à des enjeux économiques dont les couts reliés à ceux de l'énergie sont en croissance dans l'agriculture et l'alimentation. Le marché des bioproduits connaît ainsi depuis une dizaine d'année une croissance spectaculaire. Ces nouveaux intrants peuvent être différenciés en deux catégories : les produits de lutte biologique au sens large (y compris les biopesticides) et les biofertilisants (y compris les biostimulants). Ils peuvent être autoproduit par les agriculteurs et les petites entreprises à partir de ressources locales ou faire l'objet d'une production industrielle ce qui structure potentiellement deux trajectoires technologiques qui s'affirment à l'échelle mondiale. Cette communication référence l'historicité de ces trajectoires est documente par des recherches participatives situées en quoi l'autoproduction de biofertilisants est une opportunité d'intensification socio-écologique de l'agriculture ou une nouvelle "promesse" pour solidifier l'intensification industrielle et chimique mondialisée de l'agriculture
Evaluating DayCent and STICS in simulating the long-term impact of contrasting organic resource amendments on soil organic carbon and maize yields in sub-Saharan Africa
Get PDFProblem: Low crop yields in sub-Saharan Africa mainly result from low soil fertility and insufficient nutrient inputs. A key component of Integrated Soil Fertility Management (ISFM), namely combining inputs of mineral fertilizers and organic resources, presents an opportunity to boost yields and maintain soil organic carbon (SOC) stocks in the long run. Soil-crop models help to assess the performance of ISFM under contrasting soil, climate, and management combinations. Yet, to date, most soil-crop models have been calibrated and tested in temperate conditions. Objective: Our objective was to evaluate and compare the performance of two different soil-crop models, DayCent and STICS, to represent crop yields and SOC dynamics under contrasting organic resource amendments. Methods: We used a large dataset representing 3384 cropping situations (site x season x treatment) from four long-term experiments in Kenya. Each experiment included the same treatments with the addition of two quantities of low- to high-quality organic resource amendments (high vs low C/N ratio, respectively), with (+N) and without (-N) mineral nitrogen fertilizer. Each treatment included a cropped and uncropped subplot, allowing for a unique stepwise calibration of soil and crop parameters. Results: Both models represented SOC and yield dynamics with similar accuracy across sites and treatments. They reproduced SOC dynamics well (nRMSE below 30 %) in the two clayey soils sites but not in the two sandy soils. Yet, in most sites they reproduced well SOC differences between high (Farmyard manure, Thithonia and Calliandra) and low-quality (maize stover and sawdust) organic resources. Models reproduced the average yield across sites and treatments similarly. They reproduced the positive effects of high-quality organic resources and the addition of mineral N on maize yield well. Models had similar inaccuracy in reproducing yield and yield variability under poor-quality organic resources and -N treatments. Conclusion: The stepwise calibration approach used in this study enabled highlighting the models' strengths and weaknesses in soil and plant simulations. The results suggest that the two models have similar strengths and struggle with the same problems despite having different structures. Collecting detailed plant (leaf area index, plant N uptake) and soil (water, nitrogen dynamics) in-season data from long-term experiments will be critical to exploit the full model complexity and improve their accuracy for tropical conditions
Morphological variation and genetic diversity of breadfruit [Artocarpus altilis (Parkinson) Fosberg] in Vanuatu
No full textBreadfruit, Artocarpus altilis (Parkinson) Fosberg, is a versatile tree crop widely distributed in Oceania and tropical regions. It produces starchy fruits that contribute to food security in Pacific Island countries. In Vanuatu, where it is considered as a secondary food crop, a better understanding of the diversity of this species is a prerequisite for setting up a genetic improvement strategy. A diversity study of 123 accessions collected in 27 villages on eleven islands across Vanuatu and conserved in an ex-situ field gene bank was conducted in 2023–24. Eighteen morphological descriptors of fruits and leaves were utilized and genotyping was performed using 15 single sequence repeat (SSR) markers. The results showed that Vanuatu cultivars exhibit important morphological variation. Most of them (except two) are diploid and seeded. Analysis of SSR profiles revealed four genetic groups and 99 unique multilocus genotypes. Cultivars collected in the northern and north-central regions of Vanuatu appeared to be more genetically diverse than those collected further south. A total of 152 alleles were detected across the 15 loci, with an average number of 10.13 alleles per locus. For comparison, SSR analysis of triploid seedless cultivars from Eastern Polynesia and the Indian Ocean showed that these cultivars, although morphologically different, share a very narrow genetic base and are hardly distinguishable with the set of markers used in this study. These results confirm that Vanuatu is an important centre of breadfruit diversity and that this diversity is dynamic due to the diploid nature of cultivars with a high percentage of seed propagated trees