Global Journal of Science Frontier Research, H: Environment & Earth Science, Volume 23 Issue 2

e) Density Determination Density tests were performed on these smaller fragments (pieces). The methodology used for these tests was water displacement, and it was based on the Archimedes principle by displacement water: the volume of a sample is estimated by the mass of the volume that is moved while the sample is immersed in deionized water, according to (Olesen 1971; Williamson & Wiemann 2010). This method is also called the hydrostatic method. To regain its green condition, the small piece of wood (that had naturally dried) was immersed or soaked in a container filled with demineralized water for a few minutes to the point of saturation of the fibers. This container was under a digital balance, SCLATECSPB53 (max. 610; 0.01 g precision), and was calibrated and tared before and after measurement in the digital balance (Fig.3. a, b.). And those samples were immediately weighed. Then the dry weight or mass was obtained by introducing the samples to a Memmert UN75 oven for 48 h (2 h at 60° C, 4 h at 80°C, and 42 h at 103°C) (Fig.3.b,c.). To achieve constant mass, the oven temperature is gradually increased. To avoid the risks of burst or cracked samples, the dry weights were immediately taken out of the oven. At ambient moisture within the wood laboratory in the RMCA-Tervuren, it was 8 percent. To avoid a constant dry weight, samples were measured on a digital balance KERN 572 (up to 2,100 g; 0.1 g) three times successively (Fig. 3.a.). a b c d Using the formula, wood-specific gravity was computed as the ratio of each wood's dry mass to its corrected dry volume (Williamson & Wiemann 2010a). WSG (8%) = (Md)/ (Vcd) 〖 W SG 〗 (8%) = (M d )/ (V cd ) Where Wsd is the wood-specific gravity in g/cm3, Md is the anhydrous weight in g, and Vcd is the corrected dry volume in cm3. III. R esults a) Wood Density Intra and Inter-Radial Variation ANOVA test results (P > 0.05) showed that there was radial variation in wood density (WD) for each tree species and between tree species. These inter- and intra-specific radial variations in WD were as follows: A. bipendensis range, 0.65-0.75 g.cm3; and the average were 0.70 ± 0.05 g.cm3; C. gabunensis range, 0.65- 0.93 g.cm3; and the average were 0.79 ± 0. 14 g.cm3; E. cylindricum range, 0.64-0.74 and the average were 0. 0.78-0.84 g.cm 3 and the average were 0.81 ± 0.03 g.cm 3 ; M. altissima range, 0.61-0.65 g.cm 3 and the average were 0.63 ± 0.08 g.cm 3 ; M. excelsa range, 0.45-0.73 g.cm 3 and the average were 0.65 ± 0.08 g.cm 3 ; P. soyauxii range, 0.59-0.69 g.cm 3 and the average were 0.64 ± 0.05 g.cm 3 and finally for T. scleroxylon range, 0.37 - 0.63 g.cm 3 and the average were 0.44 ± 0.07 g.cm 3 (Fig.2). The observation of variations in WD from bark- to-pith enabled three qualitative types of radial patterns to be distinguished (Fig. 2.). Type 1 was represented by a tree species in which WD increased from bark to pith: A. bipendensis . Type 2 corresponded to tree species in which WD decreased from the bark to the pith: C. gabunensis ; E. cylindricum ; E. utile ; E.suaveolens ; M. excelsa; and P. soyauxii . And type 3 was represented by tree species in which WD values were substantially equal from bark-to-pith: M. altissima and T. scleroxylon (Figure 3, Table 2). 69 ± 0.05 g.cm 3 ; E. utile range, 0.51-0.58 and the average were 0.55 ± 0.03 g.cm 3 ; E. suaveolens range, 1 Year 2023 69 © 2023 Global Journals Global Journal of Science Frontier Research Volume XXIII Issue ersion I VII ( H ) Wood Density Variations of Tropical Trees Differing in Shade-Tolerance and Leaf Phenology of the Congo Basin Fig. 3: Process of Density Tests a. Experimental Apparatus; b. Weighing Of Sub-Fragments To Obtain Fresh Mass; c. Removal of Fragments Dried in an Oven for Weighing of Dry Mass; and d. Drying of Wood Fragments in an Oven for 48 Hours