A study was carried out in the Biaro forest to determine the vulnerability index of the species Alstonia congenis, Cynometra hankei, Cynometra sessiliflora and Milicia excelsa. Over an area of 50 hectares; 526 trunks of Alstonia congensis, 87 trunks of Cynometra hankei, 482 trunks of Cynometra sessiliflora and 482 trunks of Milicia excelsa were identified by the method of mesuring the diameters of these trees. At the end of the results, all these four species are declared vulnerable in this Biaro forest.

A study on the diametrical structure of the species Diospyros crassiflora was carried out in the Yoko Forest Reserve and in the Biaro Forest in two permanent devices of 400 ha each. This work pursued the objectives based on the distribution of the density by diameter class and the soil parameters in the two sites. All feet at dbh10 cm of the species studied were inventoried, measured across 40 strips of 10 ha each and soil samples were also taken at the two sites. 519 feet were counted, of which 325 were inventoried in the Yoko Forest Reserve. This one presents a good reconstruction of the stems of the species to have several individuals in the lower diameter classes. Soil analyzes were carried out and showed acidic soils at both sites.