Diversité Et Structure Floristiques Sous Des Peuplements d’Acacias Australiens En Zone Forestière De La Côte d’Ivoire

Since thirty years, four Australian Acacias species are introduced and studied in Anguédédou Research station. The station research is located in evergreen forest in the south of Côte d'Ivoire. The objective of the introduction of these species, is to rehabilitate degraded grounds and fallow after growing. The study aims at appreciating the impact of Acacia species on floristic diversity and the regeneration of forest species. For collecting data, we use quadrat method (35 x 50 m and 6 x 6 m).This method permitted the inventory of 212 species on 1.05 ha. Among these species, 1.89 % are Ivorian endemic species and 11.32 % are endemic of West African flora. The flora under the different species of Acacia are relatively diversified and dense. The majority of plant inventoried under Acacia species have small diameters. The highest specific richness average per plots (36 m2) were noted in the 11 years old parcels of Acacia mangium (26.20±2.34) and 27 years old parcels of Acacia auriculaeformis (25.40±2.34) and Acacia crassicarpa (30.60±2.34). The mean values of diameters (dbh ≥ 2.5 cm) fluctuate from 2.94±0.56 cm for the 8 years old stands of Acacia mangium to 8.09±0.56 cm for the 27 years old settlements of Acacia crassicarpa. The results show that leguminous trees can be used for recolonization of the deforested areas in order to rebuild quickly their plant biodiversity

Dynamisme de la structure diamétrique du peuplement ligneux des différents biotopes de la forêt classée de Yapo-Abbé, sud de la Côte d’Ivoire.

Objectif : L’étude a été menée dans la forêt classée de Yapo-Abbé, pour évaluer la perturbation de la flore ligneuse, suite aux actions anthropiques, à travers la distribution spatiale des espèces ligneuses et le potentiel de la régénération naturelle dans les différents biotopes constitutifs de cette forêt (forêt naturelle, forêt aménagée, zone reboisée, jachères).Méthodologie et résultats : La méthodologie a porté sur l’inventaire de surface. Ainsi, 50 relevés de 100 m x 50 m ont été disposés et inventoriés à travers les différents biotopes. Les résultats obtenus ont montré que l’exploitation forestière et la pratique agricole clandestine dans cette forêt ont entraîné une variation importante du nombre des espèces ligneuses d’un biotope à l’autre : 195 espèces dans la forêt naturelle, 155 dans la forêt aménagée, 117 pour la zone reboisée et 86 dans les jachères. Le diamètre moyen élevé dans cette forêt classée est de 24,7 ± 0,2 cm. Il ne se rencontre que dans le biotope forêt naturelle. La perturbation de cette forêt a entrainé une forte régénération naturelle, plus 74,6% dans tous les biotopes. Elle n’a, toutefois, pas été observée avec les espèces à valeur commerciale. Les espèces les plus abondantes de la végétation adultes des biotopes forêt naturelle, forêt aménagée et jachères sont remplacées par d’autres espèces dans la végétation juvénile.Conclusion et application : L’étude a montré que l’exploitation non contrôlée de la flore ligneuse dans la forêt classée de Yapo-Abbé constitue, pour elle, une menace réelle pour la gestion durable de ses ressources naturelles et de sa biodiversité. Cette investigation mérite d’être effectuée dans d’autres forêts classées de la Côte d’Ivoire pour la gestion durable de leurs ressources naturelles.Mots clés : forêt classée de Yapo-Abbé, biotopes, dynamisme, peuplement ligneux, structure diamétrique. Dynamism of the diametric structure of ligneous of the different habitats of the reserved forest of Yapo-Abbe, Southern Côte d'IvoireDynamism of the diametric structure of ligneous of the different habitats of the reserved forest of Yapo-Abbe, Southern Côte d'IvoireABSTRACTObjective: The study was conducted in the reserved forest of Yapo Abbé, to assess the disturbance of woody flora, following human activities, through the spatial distribution of tree species and the potential for natural regeneration in different habitats constituent of this forest (natural forests, managed forest, reforested areas, fallow)Methodology and results : The methodology focused on surface inventory. Thus, 50 records of 100 m x 50 m were arranged and inventoried through the various biotopes. The results showed that illegal logging and agricultural practice in the forest led to a significant change in the number of woody species of a biotope to another: 195 species in the natural forest, 155 in the managed forest, 117 for the reforested area and 86 in fallow. The high average diameter in the reserved forests is 24.7 ± 0.2 cm. It is only found in the natural forest habitat. The disruption of this forest has led to a strong natural regeneration, 74.6% more than in all biotopes. It has, however, not observed with commercial species. The most abundant species of the adult vegetation of natural forest habitats, forest fallows fitted and are replaced by other species in juvenile vegetation.Conclusion and application of results : The study showed that the uncontrolled exploitation of the woody flora in the reserved forest of Yapo Abbé is, for her, a real threat to the sustainable management of its natural resources and its biodiversity. This investigation should be carried out in other reserved forests of Côte d'Ivoire for the sustainable management of their natural resources.Keywords: Reserved forest of Yapo Abbé, biotopes, dynamism, ligneous, diametric structure

Influence of Downward Tapping Delay on Agronomic Parameters of Upward Tapping Rubber Trees

The nine-year period of downward tapping prior to upward tapping is often considered too long and irrelevant. Thus, a study was carried out to determine the minimum time needed for downward tapping for which the agronomic parameters (rubber production, vegetative growth) of the rubber trees could best be expressed in upward tapping. Clones with slow (PB 217 and IRCA 41), moderate (GT 1) and fast (PB 260 and IRCA 18) metabolisms were used as plant material in the experiments carried out in Gagnoa, Bettié, Daoukro, San Pedro and Divo. The rubber trees were tapped in a half-spiral downward direction at different times followed by quarter-spiral upward or upward tapping. The experimental design was a Fisher block design with 9 treatments and 4 replications. The results showed that upward tapping preceded by downward tapping for 5 and/or 6 years was the best regardless of the metabolic activity class of the clone. Rubber production expressed in kg.ha-1. year-1 [Slow (5y-2675 ± 79) (6y-2488 ± 59) (T9y-2238 ± 45); Moderate ((5y-5417 ± 127) (6y-5094 ± 141) (T9y-3993 ± 58); Fast (5y-5210 ± 239) (6y-4733 ± 500) (T9y-3723 ± 245)] resulting from these upward tappings increased with an increasing gradient of clone metabolism without, however, detrimental to vegetative growth (cm. yr-1) [Slow (5 yr-3.90 ± 1.27) (6 yr-4.05 ± 1.48) (T9 yr-3.40 ± 1.13); Moderate ((5 yr-3.02 ± 0.25) (6 yr-2.80 ± 0.05) (T9 yr-2.39 ± 0.02); Fast (5 yr-4.27 ± 0.42) (6 yr-3.97 ± 0.28) (T9 yr-3.60 ± 0.05)]. These results show that upward tapping in year 6 is more advantageous than tapping in year 10