Timber Species

Enumerations of the Ghanaian forest reserves have generally shown between 200 and 250 species of hardwood within any individual forest reserve. Since many species are confined to particular vegetation (or climatic) regions, the total number of indigenous hardwood species within Ghana is in excess of 400. Although it would have been useful to test the whole of this range of species for their resistance against termite attack, several considerations acted to reduce the number included in the tests.

Firstly, many of the species are extremely rare, only occurring with a frequency of 1 or 2 in samples of 100,000 or more trees. Although the persistence of many rare species in tropical forest ecosystems has considerable ecological interest, these rare species are of relatively minor commercial importance because there are insufficient quantities of their timber for effective marketing, and since they are difficult to locate in the forest.

Secondly, there was a practical aspect of collecting timber samples. The authors are indebted to the many sawmills which provided timber, but only 15 species were regularly available from mills, and a further 13 species were obtained (these were infrequently milled, and in general samples from only one or two logs could be obtained). Hence, sawmills could only supply 28 species of hardwood during the year in which samples were being collected.

An attempt was made to list all the more frequent forest species of the major vegetation zones and, where these species were not available from sawmills, to liaise with the Forestry Department so that appropriate trees could be felled. In this manner a total of 85 species have been included in the experiments. Although this represents only about 20% of the hardwood species in Ghana, these species probably account for at least 85% of the trunks above 50 cm diameter in the majority of forest reserves south of 7º30' N.

The original aim was to test timber from at least three different trees of each species included in the tests. With the 15 species regularly available from sawmills this proved possible (the average number of trees per species tested was 6 3). An average of 4 7 trees/species was obtained for the 13 species infrequently obtained from sawmills. However, this level of replication could not be attained with the species felled by ourselves: of these 57 species there is an average of 1 -9 trees/species. Wood from a total of 266 trees has been included in the tests.

Full details of the 85 timber species are given in Table 4 at the end of this bulletin and an alphabetical list of trade and local names is given in Table 1. The scientific names of the species follow the Flora of West Tropical Africa by Hutchinson and Dalziel (1954- 1972), without later revisions, though synonyms in common usage by Taylor 11960), Irvine (1961) and Bolza and Keating (1972) are given in the text. The number of trees of each species included in the tests is shown in Table 4, where it will be seen that 32 of the species are unsatisfactorily represented since wood from only a single tree could be obtained. A further 17 species were represented by wood from only two trees, and the results here are also relatively unsatisfactory.