Soils Typology and Floristic Diversity of the Forest of the “Cité Scientifique” of Brazzaville, Congo

摘要

A study of the typology of soils and floristic diversity was carried out in the forest of the “Cité Scientifique” of Brazzaville. The study aimed to assess the influence of soil cover on the distribution of taxa. The study covers 18 plots of 625 m style="font-family:Verdana;">2 style="font-family:Verdana;font-size:12px;"> each, distributed in different soil profiles. The floristic inventory concerns the measurement of diameter of trees with dbh ≥ 10 cm and the counting of herbaceous and shrubs of dbh < 10 cm. The floristic composition reveals a total of 129 plant species distributed in 48 families dominated by Fabaceae and a preponderance of pioneer taxa. The Jaccard coefficients of similarity reveal a low degree of homology of woody plots, whereas for the flora as a whole, the floristic composition is heterogeneous. The Shannon biological diversity index of ligneous varies from 0.6 to 2, against a maximum diversity of 0.69 to 3. The Pielou index of ligneous (0.5 to 0.9) does not reveal any dominance. Soil cover consists of ferrallitic and podzol soils. Their texture is sandy, weakly structured, fragmentary polyhedral throughout the profile, but lumpy and/or nuciform at the surface and sub angular in depth. The porosity decreases proportionally with the depth and thickness of the horizons. The floristic analysis presents an ecosystem with a low degree of diversification for a high floristic richness. The preponderance of anthropization markers is a proof of its very advanced state of disturbance. The study shows that soil cover does not influence the distribution of timber. Indeed, the establishment and development of pioneer species style="font-family:Verdana;">are style="font-family:Verdana;"> less prone to soil properties.