The accuracy of ten methods of scaling (Smalian, Huber, Newton, Neloïd, paraboloid, cone, paracone, cylinder, truncated cone and truncated Neloïd) was evaluated on logs of 0.5, 1, 2 and 3 m cut to different heights of 27 teak trees. For this purpose, the volumes estimated by the ten formulas were compared with real volumes obtained by the technique of xylometer. The results obtained showed that the method of Huber was more efficient to calculate the volume of logs throughout the stem when the length was 0.5 m. For the other length logs, it was also the best formula when the logs came from the base of the stem. The formulas of Newton and Smalian gave in the center and top of the stem, in the case of 1 m and 2 m logs, relatively similar results and were better than other methods of scaling. As might be expected, the dendrometric method (cylinder, paraboloid, Neloïd, cone) gave worse results regardless of the length of logs considered. With logs of 0.5, 1, 2 and 3 m long, truncated forms of cone and Neloïd could also be used without significant errors in estimating the volume of teak logs. The model scaling obtained for the entire tree expresses the logarithm of the volume against the logarithm of the diameter and the logarithm of height.

Accurate and non-destructive methods to determine individual leaf areas and dry mass of plants are very important. Since they stand as key parameters linked to plant production and are used in functional–structural plant models to simulate plant growth. This paper describes an investigation of the variation in cashew leaf dimensions at different sites within a plantation with the aim of developing a model for calculating leaf area and dry mass. Five location (South, Central, North, East and West) were considered in an eight years old cashew plantation, with rectangular plot and with an area of 3.5 ha. Two trees were selected randomly by location. Their crown was divided vertically into three zones. Within each zone, 60 leaves were collected randomly on different categories of the tree axis. The length, width, area, and the dry mass of each leaf were measured. The longest leaves were obtained in the North, Center and South of the plantation (15.27 cm). The tree leaves located in the South of plantation were the largest (9.6 cm) and had the largest areas (109.1 cm²). The largest quantities of dry mass were obtained from the leaves of the trees located in the South and in the East of the plantation (1.35 g per leaf). The best models according to adjustment and prediction qualities were in all cases stated as follows: S^λ= aln(LW) + b for leaf area and m^λ= aln(LW) + b for dry mass. The results indicated an important variation in leaf size and dry mass according to a tree location in the plantation. Therefore, it is important to take into account this variability in the sample constitution when trying to estimate leaf area and dry mass.

Typologie des systemes d’elevage bovin de la commune de gogounou au nord-est du Benin

Caractérisation morphologique d’une collection de fruits d’anacardier provenant de la commune de Parakou (Bénin)

The aim of this study is to select “Plus Trees” based on dendrometric character- istics and wood properties in teak plan- tations in Benin and Togo. For this pur- pose, growth performance was assessed in 569 trees in 5 forests in Togo and 90 trees in 3 forests in Benin, based on diameter at breast height, total height and bole height measurements. Wood properties – density, percentage of heart- wood and colour – were also measured for the final selection of Plus trees. Heart- wood natural durability, fibre saturation point, modulus of elasticity and shrink- age were assessed against previous near infrared spectroscopy models. The results showed that in Togo, inter-tree variability in the forests was relatively high for Annual Height (0.81 ± 0.27 m) and Annual Circumference Increments (2.95 ± 1.02 cm) and for bole heights (10.64 ± 3.51m). In Benin, while the dendrometric performance of the trees did not vary significantly between the forests, the coefficient of variation val- ues were higher (40%) for bole heights (10.99 ± 3.80 m) in Koto forest. The final multi-criteria selection including wood properties showed that the Avetonou and Tchorogo tree populations in Togo make up a homogenous group with the highest values for wood density and heartwood percentage. The trees in Haho-Baloe and Eto forests had lower natural durability and modulus of elasticity, a lower per- centage of heartwood and lower wood density. In Benin, the Agrimey forest trees had a higher wood density but the 3 forests were similar in terms of fibre saturation point, natural durability and shrinkage. Based on the variability of dendrometric performance and wood quality of the candidate trees, we were able to select 33 Plus trees