Forest Growth: A 35-Year Southern Cape Case Study

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Abstract
Tree growth, mortality and recruitment rates were determined on a 44 ha evergreen mixed forest stand in the southern Cape, South Africa, for the period 1972 to 1987. All trees with a DBH > 10 cm on the study area were marked and the DBHs measured in 1972, 1978 and 1987. Up to 1954 experimental thinnings were executed. Since then (i.e. more than 30 years) no timber has been extracted. Mean basal area for all species together changed from 32,7 m2/ha in 1972, to 34,1 m2/ha in 1978 and 35,3 m2/ha in 1987. Net growth rates since 1942 have declined from 1,63 % per annum for 1942 to 1953 to only 0,35 % per annum for the period 1978 to 1987. Mortality rates of most species increased, and for some species exceeded their recruitment rates. Gross volume growth rate for the stand since 1972 is very similar to that for unlogged tropical forests elsewhere in the world, i.e. about 2 m3/ha per annum. Recovery from disturbances was, nevertheless relatively fast. Many aspects of the observed growth and mortality rates could be explained in terms of the development phases of the forest. It was concluded that the forest could be close to its maximum timber carrying capacity.