Seedling performance of four sympatric Entandrophragma species (Meliaceae) under simulated fertility and moisture regimes of a Central African rain forest

Relative densities of mahogany species vary across tropical Africa and correspond with changes in soil fertility and moisture status. Seedling growth of four co-occurring African mahoganies (Entandrophragma spp.) was studied in relation to soil nutrient and moisture status in a shade-house experiment. On naturally occurring forest soils, E. cylindricum and E. utile exhibited increased relative growth rate (RGR) and decreased root mass ratio (RMR) with an increase in soil fertility while E. angolense and E. candollei did not. Changes in leaf morphology with fertility did not correspond to changes in species performance. On moist, fertile soils, E. angolense outperfonned congeners but E. candollei performed equally well on moist infertile soils. Entandrophragma cylindricum performed as well as E. angolense and E. candollei on two of three soil moisture stress treatments but E. utile consistently performed poorly. Comparative seedling performance fitted well with limited available data on the distribution of Entandrophragma spp. in relation to soil fertility and moisture gradients and suggests that within-forest microsite heterogeneity may help explain the distribution of Entandrophragma species within the Dzanga-Sangba Dense Forest Reserve, Central African Republic.