ECOSYSTEMIX - Mixing species to produce ecosystem services: co-design of an integration and knowledge sharing tool mobilizing the concepts of functional ecology

Malick Ouattara defended his doctoral thesis on 11/12/2023. 

Summary

In a transition to agroecological cropping systems, the diversification of agroecosystems through species mixtures has been identified as a central practice. Carefully-designed mixtures could provide ecosystem services to support sustainable, resilient agriculture and less dependence on synthetic inputs. However, it is not easy to choose the right species for a mixture, in order to deliver the ecosystem services sought and adapted locally. The trait-function-service approach of functional ecology has been identified as an interesting way to establish trait assembly rules, in order to guide the choice of species in a mixture according to the targeted service. Our aim is therefore to propose a generic method to design species mixtures based on a functional ecology approach, taking into account local conditions and the ecosystem services sought.In this PhD work, we (i) compiled and analyzed existing data, with the aim to assess the diversity of mixtures and the services provided, (ii) conducted a field experiment with the aim to study the behavior of species in sole crop vs. in mixture (iii) conducted knowledge sharing workshops in order to build assembly rules for the design of mixtures and (iv) modeled and developed a prototype tool to assist in the design of mixtures.Our results showed that (i) 60% of the mixtures made were between cereals and legumes, and that the most sought-after services were weed regulation and nitrogen recycling, (ii) the trait values of a sole crop and a mixed crop were different and depended not only on the trait considered, but also on the species present in the mixture, (iii) the realization of an ecosystem service depended on several traits, and that the same trait could be important for the realization of several ecosystem services. In addition, we showed that (iv) the expertise of different stakeholders was complementary and made it possible to fill knowledge gaps and decontextualize some knowledge to make it generic, and (v) the functional approach is a strong basis for the design of mixtures. We built a prototype tool to support the design of species mixtures based on this approach.Finally, the different methodological approaches used (experimentation, modelling, knowledge-sharing workshops, database analysis) proved to be highly complementary in the design of the EcosysteMIX prototype.