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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 132.211. INTRODUCTIONThe most recent attempts to classify the forest vegetation of Ghana are those of Taylor (1960) and Mooney (1961), who based their classifications on inventories of trees in forest reserves. Their work has two major shortcomings. Firstly, forest which had not been enumerated could not be included. Secondly, the failure of the authors to describe the methods by which their classifications were derived makes it impossible to identify a forest stand other than by its map position, thus greatly reducing their practical value (cf. Greig-Smith 1969a). We have attempted to produce a floristic classification with a defined empirical basis, applicable to all forests in Ghana, and readily permitting identification.The structural complexity and species-richness of tropical forest make difficult or impossible its study by the traditional phytosociological procedures, but numerical methods have proved successful (Greig-Smith 1969b), especially in demonstrating correlations between vegetation and environmental factors in fairly small areas (Austin, Ashton & Greig-Smith 1972; Greig-Smith, Austin & Whitmore 1967). There are relatively few published accounts of the use of numerical methods in a survey of a large area of tropical forest, mainly because of the problem of dealing with a data matrix of the size involved. Webb et al. (1970) analysed tropical and subtropical forests in Australia spanning 20? of latitude, but took only sixty-eight plots and used only eighty-two species in the final analysis. Recent improvements in methodology and computer capacity encouraged us to undertake sampling more intensive than this, using a much larger number of species. Conditions in Ghana are particularly suitable for a survey of tropical forest. Of a total forest zone covering 82 260 km2, the area under forest amounts to 20 530 km2 including 16 790 km2 within forest reserves distributed more or less throughout the forest zone (Anon. 1973). Most reserves can be reached by motor road. The forest flora of West Africa is relatively well known, and is less diverse than that of tropical Asia or America. All Ghanaian forest falls within the categories of Tropical Evergreen Seasonal forest and Tropical Semi-deciduous forest (UNESCO 1973). It has a more or less uneven tree canopy at 10 to 40 m above the ground (emergent trees may reach 60 m); woody climbers are always present. Vascular epiphytes are present except in the driest forests, but not abundant except in the most humid; some of the canopy trees are deciduous in the dry season, but the understorey trees and shrubs are evergreen. Gymnosperms and stem succulents are absent, and palms are generally uncommon; a herb...

Forest under low rainfall (averaging 745 mm yr-1) on the Shai Hills in S.E. Ghana has redeveloped following cessation of farming in the 1890s. Forest stature is low, with a canopy at about 11 m, principally of three species, Diospyros abyssinica, D. mespiliformis and Millettia thonningii. Drypetes parvifolia and Vepris heterophylla are common understorey trees. Twelve species of woody liane were recorded. Species of thicket vegetation in the area were also present at low density. Most species are evergreen.Tree mortality averaged 2.3~o yr ~ and exceeded recruitment (1.5~ yr-1). Differences between species in mortality and recruitment were pronounced: canopy species showed a small decline in density; understorey species increased markedly and the thicket species declined. Seed production was very variable, but seedling establishment was very poor for all species. Seedling mortality was high (11 ~o yr -1 ) especially for small seedlings. These population trends probably represent the latter stages of succession of forest regrowth after farming about 100 years ago.Compared with tropical rain forest, Shai Hills forest has similar relative tree diameter growth (1-3.5 ~o yr-1), mortality and recruitment rates, and small-litter fall (5.52 t ha-1 yr-1).Shai Hills forest differs from rain forest by its short stature, relatively few (evergreen) tree species, poor regeneration from seed, high soil nutrient status and low rainfall. Similar forests have been reported in east Africa and in parts of New Guinea.Abbreviations: dbh = diameter at breast height (1.3 m), gbh = girth at breast height.

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Changes in two 1-ha samples of Moist Semi-deciduous forest at Kade, Ghana are described for 14 years from 1968 to 1982. Density of trees ≥10 cm dbh was 552 ± 13 ha−1and the basal area was 30.85 ± 1.38 m2 ha−1, and showed little variation over the study period: diameter class distributions did not change significantly. There were 120 species of tree ≥10 cm dbh, including seven immigrants and seven emigrants.Mortality did not differ significantly between diameter classes, but was significantly greater amongst trees showing negative diameter increment. Total mortality for the 2 ha over the 12-year period 1970–1982 was 216 trees (1.77% yr−l) and was balanced by a recruitment of 212 trees to the measured population.Growth rates were highly variable within species populations. Overall, bigger trees tended to have higher growth rates. Successive diameter increments in individual trees were strongly correlated, and were still significant after 10 years. These results support the idea that the faster-growing individuals are the more likely to reach the canopy.Estimates of the age of trees by summing mean passage times for successive diameter classes is shown to be misleading because similar calculations using only the fastest-growing trees gives substantially lower estimated ages.Although overall forest composition showed little change, a few species showed small but significant imbalance between recruitment and mortality. Recruitment and mortality differed significantly from overall rates for some species, but only markedly for the megaphanerophyte Celtis mildbraedii which had lower than average rates for both mortality and recruitment.