Characterization of Natural Regeneration of Three Local Multipurpose Tree Species in the Ouaddaï sahelian Zone of Chad

: In the Sahelian zone of Ouaddaï in Chad, Balanites aegyptiaca (L.) , Sclerocarya birrea (A. Rich.) and Ziziphus mauritiana Lam. are multipurpose woody species that are found in agroforestry land use systems and contribute to the nutrition, health and economy of local populations. The purpose of the study is to assess the natural regeneration and population structure of these species in view to contribute to their domestication. The study was carried out in three land use systems (farms, fallows and savannahs). Regeneration characterization consist in a carefull excavation of root system of mother - tree and of regenerations to distinguish suckers from seedlings. The origin of the plant (sucker or seedling) was determined by carefully checking of the root system to see if there was a connection between the root of the regenerations and that of the mother - tree. In addition to the prudent excavation of the root system of the regenerations, their dendrometric parameters as well as those of the mother - tree were determined. Results show that populations of these species are not uniformly distributed in land use systems of the area. The mean density of the trees varied significantly between species (0.000<0.001) as well as in land use systems (0.000<0.001). Trees of wide diameter are significantly more abundant in farms than in savannahs (0.000<0.001). Among the 10151 juvenile trees recorded in plots, 59.58% are reiterations; 33.62% seedlings while 6.79% are suckers. S. birrea presented the highest natural suckering percentage. S. birrea shows a highest suckering percentage in the three land use systems while the lowest was that of B. aegyptiaca . The highest natural root suckering percentage is registered in fallows (7.14% in B. aegyptiaca , 12.57% in Z. mauritiana and 14.77% in S. birrea ). The ecological conditions favourable to natural root suckering were those of farms whereas those of fallows were suitable for the growth and rooting of suckers. These results suggest the urgent needs to promote low coast vegetative propagation techniques like root suckering for the domestication of these important tree species.