Farmers' assessment of the use value of agrobiodiversity in complex cocoa agroforestry systems in central Cameroon

摘要

Agroforestry systems in humid tropical areas are complex multispecies cropping systems whose value for farmers is often hard to assess. We present the findings of a participatory assessment that we applied to cocoa agroforestry systems. This assessment, adapted from the pebble distribution method, was used to quantify the value given by farmers to each species of their cocoa agroforestry system according to the attributed uses. A tree inventory in 50 cocoa agroforests was carried out in central Cameroon. Overall, 122 non-cocoa tree species were inventoried. The mean species richness was 23 species per plot and the mean Shannon index was 2.42, for a mean density of 180 non-cocoa trees ha(-1) and 1,511 cocoa trees ha(-1). Cocoa farmers defined seven different uses for tree species, including Theobroma cacao. 81 % of the species (including cocoa trees) had one to seven uses whereas the highest use value was given to T. cacao, with a mean score of 23.6 %. Then, in descending order, the 10 non-cocoa species with the highest use values were Dacryodes edulis, Persea americana, Elaeis guineensis, Citrus sinensis, Mangifera indica, Milicia excelsa, Cola nitida, Citrus sp., Ricinodendron heudelotii, and Terminalia superba. The frequency of non-cocoa species was significantly and positively correlated with their use value (R-2 = 0.914). Our results showed that technical innovations designed to improve cocoa agroforestry systems should take into account farmers' knowledge to propose them systems so as to be able to more effectively address their expectations.