The daily increase in human activities due to population explosion is a great threat to biodiversity conservation. Man is using land, water and natural resources more than ever before. In view of this, the main objective of the present study is to evaluate the contribution of the traditional agroforestry systems to environmental and biodiversity conservation. In the Tandjile East, farmers generally associate exotic and native trees in their farming systems; studies on their floristic composition are scarce. The actual investigations were carried out in three main land use systems (home gardens, parklands, natural savannahs) and three ethno-linguistic groups (Gama, Goulaye and Gabri) were involved. Floristic surveys were carried out in plots measuring 50 x 50 m2. All the woody species were sampled; their diameter at breast height (dbh) and their height were also determined. For the 45 floristic records, a total of 8.644 stems with dbh equal or more than 10cm were registered, belonging to 33species, 26 genera and 17 families. The average number of trees density was 76.83 ± 8.70 stems ha-1. The contribution of the different traditional agroforestry systems in a decreasing order is 35.30 % for the natural savannahs, 32.52 for the home gardens and 32.20 for the parklands. Concerning the indigenous knowledge, the Goulaye people conserve the highest number of trees (906) in their systems than others. For the global survey, the diversity was evaluated using Shannon and Simpson indices. In all the agrosystems, socio-economic producing tree species tend to be more frequent. All the agroforestry trees were native savannah species and only mango and citrus were introduced. These species provide food, medicine, charcoal and other non timber forest products for consumption and for sale. The traditional agroforestry systems of Tandjile were found to be particularly rich in Fabaceae Mimosoideae, Fabaceae Caesalpinioideae. Topography, heterogeneity, moderate precipitations and community endogenous knowledge may all contribute to explaining the high tree diversity found. This study highlights the botanical importance of the Tandjile East region within the Chad Republic and the role of traditional agroforestry practices to support tree species richness and provides evidence of the farms’ role as biodiversity reservoirs.
