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

and those two timber tree species were not similar with WD of A. bipendensis (0.70 ± 0.05 g.cm 3 ) and with WD of P. soyauxii (0.64 ± 0.05 g.cm ), who is less dense wood species in this family. There was also a significant difference in the WD of Meliaceae: E. cylindricum with a WD of (0.69 ± 0.05 g.cm 3 ) which was not similar to the WD of E. utile (0.55 ± 0.03 g.cm 3 ). The WD of Moraceae was only for M. excelsa (0.65 ± 0.08 g.cm 3 ). And finally, there was also a significant difference between WD Malvaceae ( M. altissima with a WSG of 0.63 ± 0.02 g.cm 3 ) and WD T. scleroxylon (0.44 ± 0.07 g.cm 3 ) (Figure 3). b) Wood Density Shade Tolerance and Phenology These timber tree species were classified into three leaf phenological types: brevideciduous, deciduous, and evergreen for drought tolerance (Bénédet et al. 2019). All these nine timber tree species were deciduous and were classified as heavy for the lower WSG: E. suaveolens (0.81 ± 0.03 g.cm 3 ); C. gabunensis (0.79 ± 0.14 g.cm 3 ); A. bipendensis (0.70 ± 0.05 g.cm 3 ); E. cylindricum (0.69 ± 0.05); P. soyauxii (0.64 ± 0.05 g.cm 3 ); M. altissima (0.63 ± 0.02); M. exselsa (0.58 ± 0.06 g.cm 3 ); E . utile (0.55 ± 0.03 g.cm 3 ); and T. scleroxylon (0.44 ± 0.07 g.cm 3 ). Particularly A. bipendensis , C. gabunensis , E. cylindricum , E. utile , and E. suaveolens were all deciduous; meanwhile, C. gabunensis and P. soyauxii were brevideciduous (Table 1; Table 2). At the level of light requirement succession, these timber tree species were classified into three regeneration guilds: pioneer, non-pioneer light demander, and shade bearer (Hawthrone 1995; Bénédet et al. 2019). The pioneer species were: E. the WD of the GWDD base: A. bipendensis, 0. 70 ± 0. 05 / 0. 73 ± 0. 05 g.cm 3 ; P. soyauxii, 0. 64 ± 0. 05 / 0. 66 ± 0. 07 g.cm 3 . The calculated WD were greater than the WD value of the GWDD: E. utile, 0.55 ± 0. 03 / 0. 54 ± 0. 04 g.cm 3 . And the calculated WSG were equal to the WD of the GWDD: C. gabunensis, 0.79 ± 0. 14 / 0. 79 ± 0. 07 g.cm 3 . In contrast, the difference was very significant for the following species: E. cylindricum 0. 69 ± 0. 05 / 0. 57 ± 0. 04 g.cm 3 ; E. suaveolens 0. 81 ± 0. 03 / 0. 77 ± 0. 06 g.cm 3 ; M. altissima 0. 63 ± 0. 02 / 0. 56 ± 0. 03 g.cm 3 ; M. excelsa 0. 65 ± 0. 08 / 0. 58 ± 0. 06 g.cm 3 and T.scleroxylon 0.44 ± 0.o7 / 0.33 ± 0.03 g.cm 3 (Table 2). At the family species level, there was a significant difference between the WD of Fabaceae: E. suaveolens, with a WD of 0.81 ± 0.03 g.cm3, was less similar to the WD of C. gabunensis (0.79 ± 0.14 g.cm 3 ), suaveolens, with its highest wood density (0.81 ± 0.03 g.cm 3 ); M. excelsa, with its medium wood density (0.65 ± 0.08 g/cm3); and T. scleroxylon, with its weakest wood density (0.44 ± 0.07 g.cm 3 ). And non-pioneer light demander species were: C. gabunensis, with its very highest wood density (0.79 ± 0.14 g.cm 3 ); A. bipendensis, with its highest wood density (0.70 ± 0.05 g.cm 3 ); E. cylindricum, with its highest wood density (0.69 ± 0.05 g.cm 3 ); P. soyauxii , with its medium wood density (0. 64 ± 0. 05 g.cm 3 ); M. altissima, with its medium wood density (0.63 ± 0.02 g.cm 3 ) and E. utile, with its lowest wood density (0.55 ± 0.03 g.cm 3 ) (Table 1; Table 2) c) Comparison between Estimated Wood Density and Database Values The difference was not significant between the calculated and measured WD and those of the Global Wood Density Database (Zane et al. 2009), particularly for tree species who’s calculated WD were lower than © 2023 Global Journals 1 Year 2023 70 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