Tree population dynamics at Kade, Ghana (1968-1982)

Abstract

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.