Sciage De Rebuts De Tectona Grandis L. F. (Teck)

Les rebuts de billons de teck abandonnés dans les parcelles après exploitation, sont taxés de faibles diamètres et de faible rendement au sciage. Le travail réalisé vise à montrer la similitude de ces valeurs entre les rebuts et les billons de premier choix. Sept cent (700) rebuts de billons de teck de 24 ans, sélectionnés en zone de forêt dense semi-décidue, ont été cubés et sciés en usine avec un plateau technique adapté aux bois de petits diamètres. Les résultats obtenus montrent que les diamètres moyens des rebuts de billons étudiés sont faibles et gravitent autour de la classe 15/19 cm à 37%, autour de la classe 20/24 cm à 44% (majoritaire), autour de la classe 25/29 cm à 15% et autour de la classe 30/34 cm à seulement 3%. Ces valeurs, bien que faibles, sont du même ordre de grandeur que celles des billons de premier choix de même âge ou d’âge proche. Le rendement brut sciage obtenu est de 38,12% qui est faible mais également similaire à celui des billons de teck de premier choix. Ce rendement chute de 4 à 7% en éliminant l’aubier pour améliorer la qualité des débités. Les rebuts de billons de teck présentent des diamètres et des rendements sciages faibles mais similaires à ceux des billons de premier choix. Les quantités abandonnées dans les parcelles prenant de plus en plus de l’ampleur, les rebuts offrent ainsi une bonne opportunité de valorisation de matière première à l’échelle industrielle par un plateau technique fixe ou mobile. Discarded teak logs in post-harvest plots are taxed with small diameters and low sawing yield. The work carried out aims to show the similarity of these values between the rejects and the logs of first choice. Seven hundred rejects of 24-year-old teak logs, selected in semi-deciduous dense forest zone, were cubed and sawed at the factory with a technical platform adapted to small diameter woods.The results obtained show that the average diameters of the discarded teak logs studied are low and revolve around the 15/19 cm class at 37%, around the 20/24 cm class at 44% (majority), around the 25/29 cm class at 15% and around the class 30/34 cm at only 3%. These values, although low, are of the same order of magnitude as those of firstgrade logs of the same age or near age.The gross sawing yield obtained is 38.12% which is low but also similar to that of the first choice teak logs. This yield drops by 4 to 7% by eliminating the sapwood to improve the quality of the sawn timber. Discarded teak logs have low lumber diameters and yields, but are similar to those of high grade logs. The quantities left in the plotstaking more and more scale, the rejects thus offer a good opportunity for raw material valorization on an industrial scale by a fixed or mobile technical platform

Fiche technique - Le Limettier, une espèce fruitière dédiée à l’amélioration des haies vives en zones sèches

No Abstrac

Le bois du frake issu de plantation exprime aussi de bonnes qualités technologiques

Objectif: Les qualités technologiques du bois mature de Fraké issu de plantation sont mal connues à la différence de celles du bois issu de forêt naturelle. Le travail réalisé vise à montrer la ressemblance entre les Frakés de plantation et ceux de forêt naturelle en ce qui concerne les qualités technologiques de leurs bois.Méthodologie et résultats: Six arbres, âgés de 32 ans, issus d’un peuplement de Fraké artificiellement planté, ont été sélectionnés, abattus et soumis aux tests technologiques de leurs bois. Les résultats montrent qu’à 32 ans, le Fraké de plantation produit des billes de bonne rectitude dont les dimensions sont relativement élevées en longueurs (13 à 21 m) et en diamètres (25 à 50 cm) par rapport aux Frakés de forêt naturelle. Certains arbres comme le Fraké3 dans le cas de notre étude, affichent des diamètres particulièrement intéressants pour une exploitation en bois d’oeuvre. Le sciage est facile et donne un bon rendement avec des débités de largeurs intéressantes pour les échanges commerciaux. Les qualités physiques et mécaniques montrent une tendance à la baisse avec la hauteur de l’arbre à partir de 6 m.Conclusion et applications: Les Frakés de plantation expriment des aptitudes technologiques similaires à celles de forêt naturelle. En conséquence, ils peuvent être utilisés sous forme de bois d’oeuvre au même titre que les Frakés de forêt naturelle.Mots-clés: Fraké de plantation, cubage, sciage, qualité physique et mécanique, Côte d’IvoireEnglish AbstractObjective: Technological qualities of the mature wood of Terminalia superba (Fraké) from plantation are badly known unlike those from wood from natural forest. Achieved work aimed to show the likeness between Frakés from plantation and those from natural forest regarding technological properties of their wood.Methodology and results: Six trees, aged thirty-two, from artificially planted Fraké standing forest, were selected, felled and subjected to technological test of their woods. Results showed that at 32 years old, Frakés from plantation yield logs expressing good straightness whose dimensions are relatively high in length (from 13 to 21 m) and in diameters (from 25 to 50 cm) compared to Frakés from natural forest. Some trees like Frake 3 in the case of our study showed interesting diameters for logs exploitation. The sawing is easy and gives good  yield with lumbers showing interesting width for commercial transactions. Physical and mechanic properties tend to decrease when height becomes greater than or equal to 6 m.Conclusion et applications: Plantation Frakés express the same technological properties than those from natural forest. Therefore, they can be used in the form of lumber in the same manner as the natural ones

Tree allometry and stand structure in dryland forests relics of northern Côte d’Ivoire

The contribution of dryland forests in West Africa to carbon stocks remains poorly documented due to the lack of appropriate allometric models and inventory data. In this study, we gathered such data for dryland forest relics of northern Côte d’Ivoire. Inventory data were used to determine and sample the dominant species, and to characterize the stand structure. Destructive biomass data were used to develop local mixed-species allometric models for estimating tree aboveground biomass (AGB) and test the validity of existing allometric models, and to characterize the stand structure (including carbon stock). A total of 118 tree species belonging to 102 genera and 36 families were inventoried in 41 plots of 25 × 25 m (625 m² each, totalling 2.56 ha) sampled in three sites in the Korhogo department. Among them, seven predominant species, including one exotic, were selected for destructive sampling in one site, the Lataha Forest Research Station. Destructive biomass data for 34 trees belonging to these dominant species and with diameter at breast height between 6 and 41 cm were used to fit allometric equations specific to this forest type and to test the predictions of existing equations earlier developed for the global tropics and for African dry forests. Six equations integrating three predictors, stem diameter (D), total tree height (H) and wood specific gravity (ρ) were developed and the models with the three predictors showed the best performance. Pantropical models significantly over-estimated tree AGB by 20 % while models developed for African dry forests provided reliable estimates, suggesting a specific allometry of trees in dryland forest relics that needs to be further explored.. With our best AGB model, a quantity of 141.26 ± 92.72 tDM.ha−1 was estimated confirming that these dryland forest relics are important carbon stocks for this region where open vegetation dominates. This study constitutes an important contribution for the carbon accounting programs related to the implementation of REDD+ initiatives in Côte d’Ivoire

The long-term performance of 35 tree species of sudanian West Africa in pure and mixed plantings

The rapidly growing human population in sudanian West Africa has generated increasing demand for agricultural land and forest products so that most of the original vegetation cover has disappeared and the remainder is highly degraded, meaning that it is urgent to draw up a long-term assessment of the potential of local species to be promoted in pure and mixed plantings as contribution to global forest restoration efforts. We inventoried the survival and growth of 5817 trees belonging to 35 species planted more than 25 years ago in pure and mixed plantings. For a subset of individuals, we estimated heights and volumes of standing timber. We found that (i) the long-term survival (from 50 to 99%.yr−1) and diameter growth (from 1 to 10 mm.yr−1) are highly diverse between species and not correlated to each other, (ii) the annual increase in biomass per tree averages 2.22 kg while the annual increase in stand biomass may be over 6 Mg. ha−1 for three highly-productive species (Khaya senegalensis, Pterocarpus erinaceus and Anogeissus leiocarpa) (iii) the effect of mixture on annual growth is significantly positive with an across-species gain of 0.7 mm.yr−1 while there is no effect on the survival probability. Considering a potential productivity of 10 m3 of timber wood per hectare at 30 years, 13 species have been retained in the list of woody species of interest for planting in the Sudanese zone of West Africa