RESPONSE OF A CLONAL TEAK PLANTATION TO THINNING AND PRUNING IN JAVA']JAVA, INDONESIA

Over the last decade, there has been a shortage of teak (Tectona grandis) timber supply in Indonesia, which cannot be fulfilled by the current rate of production. Genetic improvement has produced two promising clones, but the performance of the clones in degraded lands, where most new plantations are established, is still to be tested. The study shows initial results from a pilot forest of the clones established on degraded limestone soil in Java Island, where various thinning (0, 25 and 50% of trees) and pruning (1/3, 1/2 and 2/3 of the crown) treatments were applied four years after planting. Light levels inside the stands increased with increasing levels of thinning and pruning. Diameter growth increased with thinning intensity, especially in the first year, whereas the effect of pruning was undetectable after three years. Although standing stock in the thinned stands did not recover to pre-thinning levels in three years, cumulative production ( standing stock plus harvested timber) was highest for the heaviest thinning treatment. Initial high growth rate after thinning could not be maintained due to poor soil condition. Fast growth may have induced canopy closure and crown competition among the residual trees. The results suggest that, in clonal teak plantations on degraded soils, short-rotation commercial thinning could maintain growth rates and provide income for the tree growers.