catena in tropical moist semi-deciduous forest near Kade, Ghana

Investigations have been made into the variation in structure and composition of vegetation along a catena in moist semi-deciduous forest near Kade, Ghana, and correlations with soil types and microclimate attempted. Microclimatic observations show that there is little difference in the diurnal ranges of air and soil temperatures, relative humidity and evaporation of the top, middle and bottom slopes of the catena under forest conditions, though much larger differences were found where the canopy had been removed. Transpiration measurements indicated little control of transpiration by the ground-layer herb Costus engleranus and the understorey tree Memecylon lateriflorum, but marked control by the liane Calycobolus africanus. In upper (Bekwai series) and middle (Nzima series) slope soils over 80% of the root mass occurs in the top 10 cm as against only about 50% in the alluvial soil in the valley bottom. Determinations of pH and water-holding capacities of these soils are given. Basal area measurements indicate that the standing crop of trees on the middle slope is somewhat greater than that of the upper slope. Celtis mildbraedii and Trichilia prieureana, especially the former, appear to be more prevalent on the upper slope. An association analysis of the ground flora clearly shows that the upper slope bears a distinct plant community, but that the vegetation of the middle slope is not very different from that of the lower slope.