Mapping plant diversity in cocoa-based agroforestry systems to improve overall productivity

In cocoa-based agroforestry systems (CAFS), the cocoa trees are associated with other cultivated plant species at variable densities. There, the spatial distribution of the cultivated plants can be regular, random or aggregated, and their age may vary even in the same species. Variables of (i) density, (ii) spatial distribution and (iii) age can thus influence the overall productivity of CAFS and its distribution in space. We studied the relationships between these 3 variables and CAFS productivity based on data collected in 34 experimental yield tracking plots placed in agroforestry fields of producers in the Dominican Republic. A mapping of the cultivated plants was carried out on each plot at their installation and harvests of the ripe products of each individual plant were carried out every two weeks over a period of one year. The first results of this study indicate that optimal CAFS productivity can be maintained along a decreasing density gradient of crops, associated with cocoa tree ageing. In addition, regular and random spatial distribution of all plant species may increase overall productivity. The analysis of the variability of cocoa, fruit, tuber and timber yields allows us to provide recommendations on the most suitable species and the optimal distance between plants to improve overall productivity and therefore the producer's income

Sustainable cocoa production. Learning from agroforestry

In order to meet growing demand for chocolate products, numerous initiatives have been launched over the last 10 years with a view to increasing cocoa production. These initiatives continue to promote the input-intensive model advocated since the 1960s, even though this model has reached its agronomic, socio-economic, and environmental limits. Hence the proposal to learn from agroforestry in order to develop the current model: introducing fruit and forest tree species into cocoa plantations contributes to the agro-ecological intensification of cocoa production, while improving flexibility and resilience, which are essential to smallholder farmers, who grow 95% of the world's cocoa

Producción sostenible de cacao. Inspirarse de la Agroforestería

Para satisfacer el incremento en el consumo de productos con chocolate, se tomaron varias iniciativas en la última decena para aumentar la producción de cacao. Esas iniciativas siguen promoviendo el modelo intensivo en insumos recomendado desde los años 1960, aun si este modelo ha alcanzado sus límites agronómicos, socio-económicos y ambientales. A raíz de esto se elaboró la propuesta de inspirarse de la Agroforestería para influenciar la evolución del modelo actual: introducir árboles frutales y maderables en las plantaciones de cacao contribuye a la intensificación agroecológica del cultivo del cacao, aportando al mismo tiempo la flexibilidad y la resiliencia necesarias a los pequeños agricultores quienes producen el 95% del cacao en el mundo

How habitat heterogeneity affects pollinator's communities in cocoa-based agroforestry systems?

In the humid tropics, a significant amount of the agricultural landscape where cocoa (Theobroma cacao) is grown is managed as agroforestry systems. As pressure to intensify cocoa production is increasing, the current worldwide trend for the intensification of cocoa production aims at significant reductions of the shade canopy. However, this trend implies losing the potential to produce valuable ecosystem services. Among those services, pollination is a limiting factor of cocoa production that has been investigated in the 70's and 80's essentially by trapping methods. The genus Forcypomia sp. is acknowledged to be the main insect responsible for cocoa pollination, when other insects such as ants and Trips sp. would play a secondary role. Regulation and habitat provision for cocoa pollinating insect communities are poorly documented in the literature. Most pollinating species are known from trapping methods in the immediate surroundings of the tiny cocoa flowers and no study has succeeded so far in observing and describing the insects actually visiting the inside of the cocoa flowers. In this investigation, we characterized habitats for pollinating insects at plot scale, in a 3ha cocoa-based agroforestry system located in the Peruvian Amazon. Local climate, topography, leaf litter's biomass, composition and water content, cocoa trees and associated plant diversity and structure, were described, as well as farmer's practices. Based on habitats characterization, we compared the pollinating insects' communities of two contrasted habitats within the same plot. We used a digital video recording system that allowed us to monitor and record all insects visiting cocoa from 6:30 am to 05:30 pm during the main flowering season. Each habitat was sampled in 2 or 3 different locations when possible and 20 to 30 flowers were monitored in each repetition, resulting in a total amount of 180 monitored flowers. Our results showed that the diversity and the frequency of insects visiting cocoa flowers are influenced by habitat quality. The heterogeneity of habitat often found in cocoa-based agroforestry system is mostly due to farmer's practices relying on opportunistic shade management. Pollinating insects' communities do not always rely specifically on the Forcypomia genus but rather depend on habitat quality. These results open good perspectives for the ecological intensification of cocoa production in Agroforestry Systems. (Résumé d'auteur

Compromis entre productivité et biodiversité sur un gradient d'intensité de gestion de systèmes agroforestiers à base de cacaoyers de Talamanca, Costa Rica

Le cacaoyer (Theobroma cacao, L.) est cultivé dans les tropiques humides d'Amérique latine, d'Afrique et d'Asie. Principale source de revenus d'une agriculture essentiellement familiale, les systèmes agroforestiers à base de cacaoyers fournissent de nombreux services écologiques et contribuent à la conservation de la biodiversité. Ces systèmes associent plantes ligneuses et cultures de manière simultanée, dans une gamme importante et peu décrite de richesses et de structures botaniques. Les connaissances actuelles sur leur productivité se limitent à des essais en milieu contrôlé associant un petit nombre d'espèces. Nos travaux testent l'hypothèse d'une relation de compromis entre le niveau de productivité des cacaoyers et le niveau de biodiversité hébergée par les agroforêts à base de cacaoyers. Nous caractérisons ces compromis sur un gradient de situations de production paysannes, reposant sur la structure verticale, l'intensité de gestion de la composante végétale et le contexte bio"physique des agro"systèmes étudiés. Sur un dispositif de 36 cacaoyères paysannes situées dans la région de Talamanca, Costa Rica, nous montrons que des variations significatives de la structure végétale reflètent les modes de gestion de la parcelle et affectent le rendement par cacaoyer (295 à 667g/arbre/an) mais pas le rendement en cacao (136 kg/ha/an), ni le volume végétal global (400 m3/ha). Ces variations de la structure végétale affectent peu la diversité # des peuplements de plantes associées, d'épiphytes, d'amphibiens, de reptiles, de mammifères, d'invertébrés du sol et de la litière, mais leur diversité β répond de manière contrastée à ces variations d'habitat. Les relations de compromis que nous mettons finalement en évidence entre la productivité en cacao marchand à l'hectare ou à l'arbre et les niveaux de biodiversité atteints sont de nature (linéaire, cubique, quadratique) et de tendances (négative, positive) contrastées selon le taxon considéré et remettent en cause les résultats de certains travaux récents. Nos travaux dévoilent également des situations de compromis optimales, offrant des perspectives positives pour l'intensification écologique des systèmes agroforestiers tropicaux. (Résumé d'auteur

Comparison of the contribution of a participatory approach and a mathematical modeling in the design of complex agroforestry systems

Redesigning our agricultural systems has become a priority today in order to limit the negative impacts on the environment and global health caused by our farming systems. Two main types of approach to the design of innovative cropping systems exist: the top-down type, a linear approach where research produces knowledge that is disseminated by advisory agencies to farmers, and the bottom-up type, a participatory approach that includes a set of relevant actors to produce innovations. We tested these two approaches for the design of cocoa-based agroforestry systems in the Dominican Republic. On the one hand, agronomic monitoring of 34 agroforestry plots allowed us to produce different prototypes for optimizing the functioning of these systems using different algorithms. On the other hand, an original participatory design process was conducted to develop four prototypes of innovative cocoa agroforestry systems. The economic and environmental sustainability, through the biodiversity grown within the prototypes from these two types of approaches, are compared. The mathematical modelling approach resulted in prototypes that are less diverse than those from the participatory approach, with a crop biodiversity from 2 to 4 species and from 4 to 7 species respectively. From an economic point of view, the results are also weaker, with a turnover of between US$2500 and US$ 3500 ha-1 yr-1 for the modeling approach compared to US$6683 to US$ 8670 ha-1 yr-1 for the participatory approach. These systems have real potential for improvement because the complexity of interactions between different crop species, and in particular of facilitation processes, is still poorly explored. The strengths and weaknesses of the two methods are discussed and clearly indicate that hybrid approaches, giving a prominent place to both rural and research actors, would provide more disruptive and sustainable solutions