International Journal of Plant & Soil Science

In the fight against the global challenges of climate change, carbon storage in agroforestry systems is seen as a biological mitigation strategy. The floristic diversity of agroforestry systems acts as a driver of carbon sequestration by increasing total biomass, stabilising soil carbon and ensuring the system's resilience to disturbances. The richer, more diverse and more structured the agrosystem, the more effective and sustainable its role as a carbon sink. In Côte d'Ivoire, farmers are increasingly practising agroforestry, particularly in cocoa cultivation. However, the estimated carbon stock of cocoa-based agroforestry systems (AFS) has not been enough measured at the local level, particularly in main production areas such as Nawa and Indénié-Djuablin. This study aims to assess the estimate carbon stock in the Nawa and Indénié-Djuablin regions.

Then, this research was conducted on a sample size of 10 plantations and in each of them, a sampling scheme was etablished. In order to determine the floristic diversity of the AFs, we identified the species present using the forest survey method. We also determined the species richness of the inventoried species by calculating the Shannon, Simpson and Pielou biodiversity indices. The carbon stock of the AFS was estimated on the basis of above-ground, below-ground biomass and soil carbon stock. We first measured the DBH of trees at 1.3 meters and that of cocoa trees at 30 centimeters above the ground. The DBH measurements then enabled us to calculate the density, basal area, above-ground and below-ground biomass according to the allometric models. Finally, soil carbon stock was estimated based on the results of laboratory analysis of soil samples taken from the plantation and standard methodological guidelines.

Nawa contained the most diverse AFS (31 species) compared to 23 species in Indénié-Djuablin. The AFS in these two regions were mostly young (86%), and the carbon stock varied according to tree density, which in turn varies according to history, previous cultivation, and particularly associated species. The average density (cocoa trees and shade trees) was 805 trees.ha-1 (Nawa) and 686 trees.ha-1 (Indénié-Djuablin), and the average carbon stock was 66 tC.ha-1 (Nawa) and 36 tC.ha-1 (Indénié-Djuablin).

The AFS studied store more than monocultures but less than old-growth agroforests. The carbon storage data from this study could serve as a reference for generating carbon certification scenarios. This study was conducted on a limited sample size due to financial constraints. Furthermore, it would be interesting to continue the research by comparing the species of shade trees inventoried according to their ability to fix carbon, improve soil fertility or regulate the microclimate through shading.