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

quantity of various cell types and their spatial patterns determine this WD variation. These cell types include axial parenchyma, vessels, fibres, and rays (Panshin & de Zeeuw 1970). De Mil et al. (2018) shown that whereas vessels and parenchyma are adversely connected to the WD of the tree growth rate during ontogeny, fibres with thicker walls and flattened lumina increase WD. DRYAD is a global repository from which the average WD values at the species or genus level have been derived (Zanne et al. 2009). Using these repositories (Zanne et al. 2009; Chave et al. 2009) could result in an overestimation of WD for the species community of roughly 16 %. (Ramananantoandro et al. 2015). Also according to these archives, tropical WD (for light- to heavy-wood) range from 0.1 to 1.5 g.cm -3 (Zanne et al. 2009; Chave et al. 2009). In the tropical regions of the planet, this variety has been well preserved (Détienne & Chanson, 1996; Turner, 2001). Nonetheless, the majority of species have values that are quite near to the mean (Détienne & Chanson 1996). It was demonstrated by Chave et al. (2006) and Maniatis et al. (2011) that species differences in WD were bigger than those between them. With differences between shade-tolerant and light-demanding species (Chave et al. 2009; King et al. 2005). Light-demanding species are thought to require investment in denser wood to survive in a mature forest when there is greater competition for light since they are so sensitive to light exposure (Nock et al. 2009; Wiemann & Williamson 1988). In general, the fast growth of light-demanding species in the early stages is often associated with the production of softwood with low density (Woodcock & Shier 2002; Nock et al. 2009), in contrast with shade-tolerant species produced denser wood and grow very slowly (Woodcock & Shier 2002). Thought to offer a competitive edge, this relationship between density and growth can actually shorten a tree's lifespan (Wiemann & Williamson 1988). Greater resistance to physical harm and dangerous infections is induced by high values of WD (Putz et al. 1983; King et al. 2006; Chao et al. 2008). Together with a tree's vertical profile (Henry et al. 2010; Wassenberg et al. 2014) and radial profile, WD can also reveal changes inside the tree (Henry et al. 2010; Plourde et al. 2015; Osazuwa-Peters et al. 2014; Lehnebach et al.2018). Within specific trees, WD can also vary radially from pith to bark (Wiemann & Williamson 1988; 1989; Henry et al. 2010; Hietz et al. 2013).These density variations across a pith-to-bark profile are thus a good indicator of the variations of the fibres' anatomy and the abruptness of the change in wood anatomical structure. The three goals of this study were to: (1) compare wood density (WD) between and within nine harvested tropical tree species; (2) find out how leaf phenology and shade tolerance may affect potential changes in WD; and (3) assess the discrepancy between estimated WD and database values. II. M aterials and M ethods a) Study Site The study was conducted around the city of Gari-Gombo in the eastern region of Cameroon. Stem discs were collected inside the 2013 cutting block in the Forest Management Unit (FMU) 10 025 of the "Sociéte Forestière Industrielle de la Lokoundjié (SFIL)" of the Decolvenaere Group Cameroon (DC). This FMU has been partially or fully exploited previously (1990–1997); its approximate boundaries are 3° 30' N and 3° 55' N latitudes and 14° 45' E and 15° 00' E longitudes. Its area is 49 595 ha, and the area of the 2013 cutting block (3- 3) is 1586 ha (SFIL 2009). Soils are mainly ferralitic type, reddish-brown to yellow (Jones et al. 2013), and rest on a geological base consisting of metamorphic rocks with a high content of clay oxides iron and aluminum, formed from materials such as mica schists and chlorous schists (Martin & Segalen 1966). The climate of the site is equatorial rainforest, fully humid (Köppen 1936), with a unimodal rainfall distribution and a dry season from December to February: monthly rainfall less than 60mm (Worbes 1995). Rainfall amounts vary between nearby weather stations. The Yokadouma (85 km to the southeast of the study area) has four seasons, including a long dry season (mid-November to mid-March). The average annual rainfall is 1471.78 mm, and the annual average temperature is about 24 °C (21.94–24.56 °C). The annual average air humidity is 80 percent, with ranges of elevation between 600 and 680 meters above sea level. (Fig. 1.) © 2023 Global Journals 1 Year 2023 66 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