16 © 2017 Conscientia Beam. All Rights Reserved. VARIATION OF WOOD DENSITY IN TROPICAL RAINFOREST TREES Adrien N. Djomo 1+ Guylene Ngoukwa 2 Louis Zapfack 3 Cédric D. Chimi 4 1 Department of Geography and Planning, Queen’s University, Kingston, ON, Canada 2,3,4 Laboratory of Plant Systematic and Ecology, Department of Plant Biology, Faculty of Science, University of Yaoundé I, Yaoundé, Cameroon (+ Corresponding author) ABSTRACT Article History Received: 4 October 2017 Revised: 14 November 2017 Accepted: 21 November 2017 Published: 30 November 2017 Keywords Drying temperature Vertical variation Wood density Measurement of wood density in Congo Basin forests are needed to reduce uncertainties on estimations of carbon stocks. The purpose of this study was to test vertical variation and temperature variation (80 °C, 105 °C) effects on wood density of species in a semi-deciduous forest of eastern Cameroon. Wood samples were collected on felled trees, at the base, middle of the trunk and on the branches in plots of 10 m x 10 m for trees <5 cm diameter, of 20 m x 10 m for trees with diameter between 5 and 10 cm and, of 20 m x 250 m for trees with diameter ≥ 10 cm. 162 trees with diameter between 1 cm and 146 cm were used. The highest wood density (0.912) was found in Ficus sp. and lowest (0.295) in Enantia chlorantha. Using 80 °C as temperature to estimate wood density increased the value of about 10% when compare to the reference temperature of 105 °C. A significant difference was observed between wood density of the base and the top of trees studied. 10 species did not have wood density reported in the Global Wood Density database. This study recommends further research on wood density to cover as many tree species as possible in the Congo Basin. 1. INTRODUCTION Tropical forests are particularly important because of the extent of anthropogenic transformations and the amount of carbon that they contain per unit area. Currently, almost all tropical regions are experiencing major changes that modify their structure either through shifting cultivation or through logging activities (Cuny, 2011). Uncertainties remain on the contribution of forests in the Congo Basin to the global carbon cycle due to its floristic diversity estimated at more than 500 species per hectare (dbh> 10 cm), its high variability in size and density of trees, the types of forests, the natural disturbances such as mortality, recruitment, etc. (Chave et al., 2005; GIEC, 2007; Lewis et al., 2009). Malhi et al. (1999) estimated that tropical forests contribute at about 32-36% of terrestrial net primary carbon production and for this purpose Picard et al. (2012) indicated that special emphasis should be placed on these forests. Therefore, Fearnside (1997) and Reyes et al. (1992) highlighted the need of developing wood density databases for the estimation of tropical biomass. Dry wood density can be defined as the ratio of the anhydrous mass of a sample to the mass of a volume of water corresponding to the volume of the anhydrous sample (Fearnside, 1997). Different ways of calculating wood density include apparent density or density at X% (the ratio of weight to volume at a given moisture level), green density (green weight / green volume), basic density obtained by the ratio between the dry weight and the volume of green wood (Fearnside, 1997; De Souza et al., 2002; ASTM, 2007). In addition of being an excellent indicator of the amount of wood present in a sample and its workability (Silva, 1984; Trugilho et al., 1990; Chimelo, 1992; ASTM, Journal of Forests 2017 Vol. 4, No. 2, pp. 16-26 ISSN(e): 2409-3807 ISSN(p): 2413-8398 DOI: 10.18488/journal.101.2017.42.16.26 © 2017 Conscientia Beam. All Rights Reserved.