Clément SEWADE (2017). Diversity, leaf biomass of fodder trees and carrying capacity of rangelands in the Guineo-Congolese / Sudanian transition zone of Benin. Doctoral School of Water and Agronomic Sciences, University of Abomey Calavi, Benin. 242 pages.
Thesis promotor: Prof. Dr Ir. Marcel Romuald Benjamin HOUINATO.
SUMMARY: Native plant species in general and fodder trees in particular contribute significantly to the daily needs of both human and animal especially in developing countries. During the dry season, fodder trees are an important source for the survival of ruminants because of herbaceous forage lack. They are multipurpose species exploited by various actors who are sometimes protagonists. In view of the pressure faced by these trees, and their consequent rarity noted in rangelands, a study was conducted in the Guineo-Congolese/Sudanian transition zone of Benin at the level of the local population surrounding the protected forests of Monts Kouffé, Wari-Maro and Ouémé Supérieur. This thesis contributes to the rational management of fodder trees’ resources. Specifically, it aims at (i) evaluate the diversity, the pastoral and conservation priority of fodder trees; (ii) assess the influence of age, sex and ethnicity on the perception of fodder species use values; (iii) describe the relationship between the availability and the use status of fodder species; (iv) develop models for estimating leaf biomass of three priority browse species; (v) contribute to the understanding of the socio-cultural dynamics of the study area in relation to the fodder trees’ exploitation and the associated conflicts. A total of 220 informants belonging to three sociolinguistic groups (Bariba, Nago and Peul) were interviewed through a semi-structured survey on the fodder trees that they use for different purposes. The citation rates of the fodder trees by the surveyed populations were used to establish pastoral priority, while their conservation priority was established using a combination of four methods and nine criteria. The use categories were defined in the study area and at an international level for the use rates calculation. The ethnoecological approaches were used to analyze the availability of fodder tree species in the study region. A total of 25 trees per species were sampled for biomass estimating. Carrying capacity was determined for the dry season in the study area. A total of 48 fodder trees belonging to 17 families dominated by Leguminosae (27.1%) and Moraceae (16.6%) were reported. These species were distributed among 37 genera, with the genus Ficus being the most represented (16.6%). Palatability, species availability and the impact of tree fodder on animal productivity were the criteria used by the surveyed sociolinguistic groups in their selection of fodder trees. The prioritization methods yielded ten top ranked species: Afzelia africana, Pterocarpus erinaceus, Khaya senegalensis, Vitellaria paradoxa, Mangifera indica, Ficus platyphylla, Balanites aegyptiaca, Annona senegalensis, Ficus umbellata and Daniellia oliveri. As a multipurpose species, the fodder trees are classified in six use categories: food, medicine, construction, fuel, veterinary and fodder. A. africana, K. senegalensis and P. erinaceus are the most widely used species by Peul and Bariba sociolingustic groups to feed animals, while the Nagos use M. indica comes first followed by F. umbellata, F. platyphylla and P. Erinaceus. Combining the different use categories, overharvested or underutilized species depend significantly on the sociolinguistic group. The forest inventory revealed 63 tree species of dbh ≥ 10 cm distributed in 24 families and 52 genera. The most represented families in genus and species are Leguminosae (28.57 %), Combretaceae (14.28 %). The Leguminosae family had the highest importance values (FIVI=83.42) followed at a distance by Combretaceae (21.68). The most important and ecologically dominant species are V paradoxa (SIVI = 42.76); I. doka (41,88); B. ferruginea (22.98); and D. oliveri (16,18). It is also noted that aerial fodder production significantly varied among species. The best models that estimated leaf biomass production of A. africana and P. erinaceus were obtained with diameter at breast height; a plant trait not directly affected by pruning as predictors. For D. oliveri the best model uses the crown height as estimator parameter. Globally, the carrying capacity of each species is about 0.05 to 0.09 TLU ha-1an-1 for A. africana; 0.03 to 0.08 TLU ha-1an-1 for P. erinaceus and 0.04 to 0.79 TLU ha-1an-1 for D. oliveri. The number of animal that can sustainably be fed in the study area was 38 497 TLU. Conflicts arise between sawyers and foresters, between foresters and Peul (herders), farmers and herders, farmers and sawyers, foresters and farmers. These conflicts are caused by the illegal exploitation of trees for their timber and fodder, and the breeders camp near the agricultural areas or sometimes in the forest reserves. Direct negotiations between those involved in conflicts or the arbitration of a local authority were the main strategies and ways of these conflicts managing. With the aim of establishing a sustainable management of pasture lands, we suggest that priority be given to the pastoral and conservation priority species witch are also overexploited species in the restoration, afforestation/reforestation and plantation activities. The introduction of these fodder tree species in afforestation/reforestation activities can improve the availability of leaf biomass to feed animals.
Keywords: Availability, Benin, Biodiversity, Conservation priority, Ethnoecology, Fodder trees, Leaf biomass, Pastoralism.