GROWTH OF <em>ACACIA</em> <em>MANGIUM</em> DURING THREE YEARS FOLLOWING THINNING: PRELIMINARY RESULTS
Keywords:Crown thinning, increment, Acacia mangium
The growth response of Acacia mangium stands under two thinning intensities is discussed. A mean annual diameter increment of 3.0cm for the whole period could not be achieved even for the 300 biggest crop trees in the heavily thinned stands. The periodic annual increment was 2.0 cm. Similar was the periodic annual increment for the 300 selected crop trees (PCT) in the heavily thinned plots (1.9 cm). The total volume increment (volume over bark up to 10 cm top diameter limit) of three years was highest in the unthinned control (130.51 m3) and lowest in the heavily thinned plots (110.56 m3). Live crown ratio gained distinctly from the thinning interventions. At the beginning of the thinning trial live crown ratio ranged from 27.3% (control plots) to 33.1 % (heavily thinned plots). After three years, live crown ratio ranged from 22.9 % (control plots) to 38.3 % (heavily thinned plots). Highest live crown ratios were found in the heavily thinned plots and lowest in the unthinned control plots. Overall, the thinning trial gave pronouncedly stratified results. Acacia mangium reacts favourably to thinning interventions with improvement of the growth rates and crown size. However, it will be impossible to achieve an average diameter increment of 3 cm y-1 over the rotation time of 15 y . As a result, a reduction in the number of final crop trees and raising of the rotation age is advisable.