18th Congress of the European Society for Agronomy

Maximizing tree diversity in cocoa agroforestry: taking advantage of planted, spontaneous, and remnant Trees

Aug 27, 2024, 5:10 PM

15m

Salle 13 (1st floor) (The Couvent des Jacobins)

Oral Synergies between researchers, society and farmers Cropping systems changes to support agro-ecological transitions

Speaker

Mr Kouamé Isaac Konan (University Felix Houphouet-Boigny)

Description

1. Introduction: Cocoa production is recognized as a main factor of forest loss and biodiversity declined in west Africa[3]. Thus, agroforestry is being promoted to restore a minimum forest cover, to conserve biodiversity, and to reinstate key ecosystem services in agricultural landscape. This introduced the Cocoa Forest Initiative in Ivory Coast and Ghana and several certifications for adequate forest cover in cocoa plantations while ensuring cocoa production[4]. Consequently, millions of trees are distributed in cocoa fields. However, it has largely failed, as very few trees have survived and developed properly[5]. Paradoxically, most forest tree species found in cocoa fields today are from natural regeneration, selected by farmers[5]. Three distinct cohorts of trees associated with cocoa plantations[5]: (1) trees spared during forest clearing (remnants), (2) transplanted or planted trees (planted), and (3) spontaneously recruited trees (spontaneous) after or during the creation of the cocoa plantation. The objective of this study is to understand the structure of tree diversity in Ivorian cocoa plantations and identify the main determinants.

2. Materials and Methods: Across 150 cocoa plots, we inventoried all trees with a diameter at breast height (DBH) ≥ 10 cm present on each plot. Twelve socio-environmental variables were measured/estimated for each plot.
   (1) We calculated the Shannon’s Alpha and Beta diversity for each cohort and each pair of cohorts respectively and then expressed them in Hill numbers. (2) We assessed the effects of twelve socio-environmental variables on the alpha diversity of each cohort with a log-normal likelihood model.

3. Results: Alpha diversity in these fields comes from spontaneous and remnant trees, while planted trees exhibit very low Alpha diversity. However, since planted trees show high complementarity (resulting in high Beta diversity) with spontaneous and remnant trees. Several socio-environmental factors explain these different levels of observed diversity. These factors exhibit different effects by cohort.
4. Discussion: Planted or transplanted trees are typically fruit trees[6], Occasionally, commercial timber species are found[5] explained the low diversity observe. The remnant trees which are spared to provide shade for young cocoa plants[4] reflect the level of diversity of the forest preceding the cocoa plantation, a level that is very high[7]. Spontaneous trees mainly come from propagules from remnant trees[1]. That explained the high diversity of remnants and spontaneous trees. Planted trees and remnant/spontaneous are very complementary and can be explained by the exotic or non-indigenous nature of many planted species, particularly fruit trees[6]. Planted, spontaneous and remnants trees have different ontogenetic development Consequently, it is expected that performance trajectories and the factors modulating these trajectories will be very different among cohorts[2].
5. References:

1.Amani, B. H. K., N’Guessan, A. E., Van der Meersch, V., Derroire, G., Piponiot, C., Elogne, A. G. M., Traoré, K., N’Dja, J. K., & Hérault, B. (2022). Lessons from a regional analysis of forest recovery trajectories in West Africa. Environmental Research Letters, 17(11). https://doi.org/10.1088/1748-9326/ac9b4f
2.Aubry-Kientz, M., Rossi, V., Boreux, J. J., & Hérault, B. (2015). A joint individual-based model coupling growth and mortality reveals that tree vigor is a key component of tropical forest dynamics. Ecology and Evolution, 5(12), 2457–2465. https://doi.org/10.1002/ece3.1532
3.Barima, Y. S. S., Kouakou, A. T. M., Bamba, I., Sangne, Y. C., Godron, M., Andrieu, J., & Bogaert, J. (2016). Cocoa crops are destroying the forest reserves of the classified forest of Haut-Sassandra (Ivory Coast). Global Ecology and Conservation, 8, 85–98. https://doi.org/10.1016/j.gecco.2016.08.009
4.Kemper, L., Sampson, G., Larrea, C., Schlatter, B., Luna, E., Dang, D., & Willer, H. (2023). The State of Sustainable Markets 2023: Statistics and Emerging Trends.
5.Kouassi, A. K., Zo-Bi, I. C., Aussenac, R., Kouamé, I. K., Dago, M. R., N’guessan, A. E., Jagoret, P., & Hérault, B. (2023). The great mistake of plantation programs in cocoa agroforests – Let’s bet on natural regeneration to sustainably provide timber wood. Trees, Forests and People, 12(February). https://doi.org/10.1016/j.tfp.2023.100386
6.Laird, S. A., Awung, G. L., & Lysinge, R. J. (2007). Cocoa farms in the Mount Cameroon region: Biological and cultural diversity in local livelihoods. Biodiversity and Conservation, 16(8), 2401–2427. https://doi.org/10.1007/s10531-007-9188-0
7.Maney, C., Sassen, M., & Hill, S. L. L. (2022). Modelling biodiversity responses to land use in areas of cocoa cultivation. Agriculture, Ecosystems and Environment, 324, 107712. https://doi.org/10.1016/j.agee.2021.107712