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

Wood Density Variations of Tropical Trees Differing in Shade-Tolerance and Leaf Phenology of the Congo Basin Yves Achille Amougou Ndi α , François Borgia Amougou Amougou σ , Ndongo Din ρ , Hans Beeckman Ѡ & Marie Marguerite Mbolo ¥ Abstract- Wood density (WD) is not only a key element in tropical forest ecology to estimate tree biomass but also an indicator of timber quality, and it integrates many aspects of tree mechanical properties and functioning. Notably, contrasting patterns of radial variation of WD have been demonstrated and are related to regeneration guilds (light- demanding vs. shade-bearing) but haven't been demonstrated to be related to leaf phenology (deciduous vs. evergreen). With the destructiv e method and the “archimed” principle, we investigated the WD radial variation of nine timber tree species harvested in the eastern region of Cameroon. The result sho wed that WD differed significantly among these nine species (P > 0.05). Their average WD was 0.70 ± 0.05; 0.79 ± 0. 14; 0. 69 ± 0.05; 0.55 ± 0.03; 0.81 ± 0.03; 0.63 ± 0.08; 0.65 ± 0.08; 0.64 ± 0.05; 0.44 ± 0.07 g.cm3 for Afzelia bipendensis ; Cylicodiscus gabunensis ; Entandrophragma cylindricum ; Entandrophragma utile ; Erythrophleum suaveolens ; Mansonia altissima ; Milicia excelsa ; Pterocarpus soyauxii and Triplochiton scleroxylon . Variation in WD from bark-to-pith enabled three distinct patterns: type 1 in which WD increases ( A. bipendensis ); type 2 in which WD decreases ( C. gabunensis ; E. cylindricum ; E. utile ; E. suaveolens ; M. excelsa and P. soyauxii ); and type 3 in which WD values are substantially equal ( M. altissima and T. scleroxylon ). All nine timber tree species were deciduous. At the level of light requirement succession, the pioneer species were E. suaveolens , M. excelsa , T. scleroxylon and the other one was non-pioneer light demander species: C. gabunensis , A. bipendensis , E. cylindricum , P. soyauxii, M. altissima and E. utile . In addition, we found that WD in this study compared to the DRYAD global repository may strongly differ depending on the species (up to 133% for T. scleroxylon and less than 96% for A. bipendensis ). Therefore, when estimating forest biomass in specific sites, we recommend that future studies on WD include the analysis of the effect of vertical variation with long- term phenological data and anatomical analysis in the same species and use a large sampling size, including individuals of both the same and different species. Keywords: wood density, radial variation, tropical forest, shade tolerance, leaf phenology, congo basin. I. I ntroduction eduction of tropical forest areas has a great impact on the amount of carbon dioxide stored in the atmosphere (Houghton 1985) because the forest is a great essential source of the world producing oxygen (O 2 ) and storing carbon dioxide (CO 2 ). Importantly, CO 2 is an influential gas leading to climate change. Estimating the aboveground biomass (AGB) content is necessary for considering the total carbon content stored in the forest ecosystem (Ketterings et al. 2001; Chave et al., 2004). This AGB is generally estimated by using allometric equations, the variables involved in such equations are the diameter at breast height, total height, and wood density (WD) or more conventionally the wood-specific gravity (WSG). Chave et al. (2005; 2014) showed that this calculation is used in the majority of studies involving allometric models. WD is one of the most important variables in forest and wood science as it is crucial for understanding tree structures and functions, and is relevant for timber properties and the energy content of the material. WD is calculated by dividing the oven-dry mass of a sample by the mass of a volume of water equal to the volume of the sample at a particular moisture content (ASTM 2011). According to Panshin & de Zeeuw 1980; Chave et al. 2009, it is a major predictor of wood's mechanical properties and is also a trait distinguished by chemical and anatomical traits (Lachenbruch & Mcculloh 2014). A key source of information on tree adaptation is the variety in wood anatomy (Beeckman 2016; Tarelkin et al. 2016). The anatomical structure of wood, which includes the features of the vessels and fibres, can be used to describe the density fluctuations inside a tree (Roque & Filho 2007). In hardwood species, the ratio or R 1 Year 2023 65 © 2023 Global Journals Global Journal of Science Frontier Research Volume XXIII Issue ersion I VII ( H ) Author: Forestry and Ecological Laboratory, Department of Plant Biology, Faculty of Science, University of Yaoundé I, P.O.Box: 812 Yaoundé, Cameroon (University of Yaoundé I). /Mbalmayo University Institute of Wood Technology, P.O.Box: 306 Mbalmayo-Cameroon (University of Yaoundé I). /Laboratory for Wood Biology and Xylarium, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren-Belgium e-mail: a.amougoundi@gmail.com Author: Institut de la Recherche Agronomique pour le Développement (IRAD) de Wakwa P.O.Box:67 Ngaoundéré-Cameroon. e-mail: jra_@yahoo.fr Author: Department of Plant Biology, Faculty of Science, University of Douala, P.O.Box: 8948 Douala-Cameroon. e-mail: ndongodin@yahoo.com Author: Laboratory for Wood Biology and Xylarium, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren-Belgium. e-mail: hansbeeckman@africamuseum.org Author: Forestry and Ecological Laboratory, Department of Plant Biology, Faculty of Science, University of Yaoundé I. P.O.Box: 812 Yaoundé- Cameroon. e-mail: mbolomarie831@yahoo.com