Colour variation in teak (Tectona grandis) wood from plantations across the ecological zones of Ghana

The colour of teak wood from plantations in Ghana was characterized by the International Commission on Illumination (CIE) L* a* b* colour measurement system in order to study the variations of wood colour parameters (lightness-darkness, redness-greenness and yellowness-blueness), among the different ecological zones. Teak trees totaling 46 were felled from 8 different plantation stands in four different ecological zones of Ghana (moist semi-deciduous forest, MSDF; dry semi-deciduous forest, DSDF; transition savanna forest; and savanna forest). Colour measurements were made on strips obtained from logs cut from the felled trees. Chemical analyses were performed on soil samples obtained from the rooting zones of the teak trees. Both environmental and tree age effects on colour were observed. However, environmental factors had a stronger effect on the colour of teak heartwood than the stand age. Although there were no significant differences between teak wood colour in moist semi-deciduous forest and transition savanna forest on one hand, and dry semi-deciduous forest and savanna forest on the other hand, in general, environment seemed to be an important factor, with teak wood colour being relatively darker in wetter areas than drier ones. Wood colour parameters showed differing relationships with soil chemical properties ranging from no relation through weak to moderate relations. For instance, soil pH decreased moderately with decreasing L* values (increasing darkness), indicating some evidence that teak wood colour may be predicted from soil pH. However, there was very little evidence that teak wood colour could be predicted from soil exchangeable cations (Ca2+, Mg2+, Na+ and K+). The range of observed site quality was rather limited. Nevertheless, richer plantation sites showed a tendency toward darker and less red heartwood.