Structure and Flora Tree Biodiversity in Congo Basin: Case of a Secondary Tropical Forest in Southwest of Congo-Brazzaville

Abstract

The Boubissi forest exploitation unit is one of the forest management units assigned to logging. Knowledge of the existing floristic resource through a management inventory is a preliminary operation allowing the planning of the logging activity. In the Boubissi forest exploitation unit, floristic diversity was studied from the floristic surveys made along the inventory tracks on 0.5 ha contiguous plots. Altogether 35 ha of forest were inventoried allowing to count 5158 trees of DBH ≥ 20 cm belonging to 160 species spread within 38 botanical families. In qualitative terms, this forest consists mainly of species from the Fabaceae family in general and Fabaceae-Caesalpinioideae specifically, Meliaceae, Annonaceae, Sapotaceae, Euphorbiaceae, Olacaceae, Burseraceae, Guttifereae, Sapindaceae, Moraceae, Fabaceae-Mimosoideae and Irvingiaceae. Measurement of the phytogeographic spectra showed that the flora of the study area is essentially Guineo-Congolese. Calculation of the Shannon-Weaver index yielded high values indicating a high floristic diversity. Results from the calculation of the Jaccard and Sorensen similarity indices do not show a large floristic heterogeneity between inventory plots. The distribution of tree numbers within diameter classes showed that the forest studied consists of 66% crop trees, 14 % trees that are exploitable in the first cut and 20% will be at the second cut. The floristic composition of the study area is a reflection of an old secondary forest of the central Mayombe. Its operation must be done with the pace of growth of trees to not compromise its regeneration.