Effect of Lighting in the Canopy of Hevea brasiliensis on the Establishment and Development of Thaumatococcus daniellii

This study aims to identify the optimal lighting conditions under rubber tree canopy to promote the establishment and growth of Thaumatococcus daniellii, a plant of high economic value. Five rubber tree stands, differentiated by their metabolism (slow, medium, fast) and age (IRCA 18 at 4 and 5 years, IRCA 41 at 5 years, and PB 217 at 2 and 4 years), were evaluated. T. daniellii was planted at a density of 3.17 plants/m2 (70 × 44 cm) in the inter-rows of the rubber trees. Establishment was monitored through emergence and tillering rates, while the light conditions in the understory were assessed by canopy closure and trunk circumference measured at 1 m above the ground. The results show that moderate shading supports the emergence of T. daniellii seedlings, whereas excessive shade limits their development. The germination rate, which ranged from 7 to 66%, was strongly correlated with the level of light available under the canopy. Thirty months after planting, T. daniellii produced between 50 and 70 leaves/m2, and the first fruits appeared in plots that successfully completed their establishment phase, particularly those with the IRCA 18 (4 years) and IRCA 41 (5 years) clones. The IRCA 18 clone recorded the highest production, with 73 fruits/m2, followed by the IRCA 41 clone with 68 fruits/m2, performances associated with favorable light conditions. This research highlights the positive interactions between rubber cultivation and biodiversity and suggests that integrating T. daniellii into rubber plantations could serve as a lever to enhance food security in Côte d’Ivoire.