Woody flora and dynamic of Aucoumea klaineana forest in the Congolese littoral

Abstract

The floristic dynamics of the woody facies of the Aucoumea klaineana forest of the Congolese littoral has been done according to a gradient evolving of the pioneer front towards the interior of the ecosystem. This settlement integrates a dynamics going from the youthful stages towards the most stable of this formation. The objective of this study was focused on the dynamics of the woody formation, the monodominant installation of the Aucoumea klaineana facies with d^1.30 . 10 cm and highlights the evolution and the correlation between the density, the basal area and the floristic diversity. The phytoecological parameters count 1186 trees of d^1.30 . 10 cm (an average 395 arbres.ha^-1) for 71 species. The trees number by subplot oscillated between 70 and 159 trees (6 to 13% of listed trees). The species number by subplot varies from 8 to 28 (11 to 39% of inventoried species). Basal area by plot oscillates of 22 and 35 m².ha^-1 (27 m².ha^-1 an average). It varies from 4 to 10 m² per subplot (7 m² by . ha an average). The trees number by subplot and diameter classes vary from 3 to 636 trees (1 to 212 trees.ha^-1 an average). The trees of 10 < d^1.30 . 20 cm are dominating with 54% and this prevalence is regular in all the subplots. As for the indices of diversity, the Green index (GI) decrease from 0.9 to 0.1 as the ecosystem increases in age. This observation is also true for the skewness coefficient which regresses from pioneer front towards the interior of the forest. The values are respectively 2.10^-2 in the first plot, 7.10^-4 in the second and 4.10^-3 for the third. In this inventory where Aucoumea klaineana is dominating, its density by subplot varies from 42 to 384 trees.ha^-1 (183 trees.ha^-1 an average). Just like the density, basal area is decreasing to pioneer front towards the interior of the forest. The values oscillate from 87 to 32% of basal area of the subplot (19 m².ha^-1 an average). The report basal area by the density of Aucoumea klaineana is lower than 1 for an average of 0.1. The ecological parameters analysis which allowed seizing the floral dynamics of this forest is stressed by a numerical multivariate analysis (grouping and ordination). It highlights the weak resemblance degree between the twelve plots of the inventory and clearly marks the existence of variation characterizing the Congolese coastal forest, notably during the first stages of installation.

Keywords: Congo, Aucoumea klaineana, biological diversity indices, Coastal forest, floristic diversity, phytoecological parameters.