Growth Mechanism of Fast Grown Species in Tropical Forest

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The effort to recovery of tropical forest increases year by year and plantation of trees called fast grown species has been done flourishingly around Indonesia and Malaysia. But the grasp of their wood qualities as materials has not been investigated almost.It is required to know the quality and to establish the ways of species selection and silvicultural technology considering the performance as timber.On the other hand, to know the influence of growth rate to the level of tree growth stress is important to elucidate the mechanism of growth stress generation.In joint study of this time, studies aim of the above two agreed with Indonesian researcher of Bogor university, and came true.By the field measurement, Acacia mangium, Falcataria, Kapok and Sungkai were used for test tree.The released strain was measured 8-12 places for each standing tree, and the disks which contained the measuring points were gathered after felling and dispatched to Nagoya university to analyze the quality. On … More these samples, Young's moduli and Poison's ratios of longitudinal and tangential directions were measured and growth stresses were calculated.Other measured items were diametral distribution of specific gravity at air dry condition, microfibril angle and degree of crystalinity by means of X-ray deflaction method, alpha-cellulose content and Klason's lignin content by Wise's method. These values were compared with the growth stress. The distance of each measuring point from the pith was used for an index of growth rate.(a) As for level of growth stress of all tree measured, the correlation with the diameter wasn't found. This is same as a result provided about Sugi which have been studied up to now. In other words, it is shown that growth stress is not depend on growth rate of tree.This result suggests that the accelerate growth condition does not make tree growth stress large.(b) A negative correlation was found between growth stress and microfibril angle. And a positive correlation between growth stress and alpha-cellulose content was seen even it was not so clear as Sugi.These tendencies are same as the Temperate Zone species, and suggest that species has a particular value of growth stress so long as there is no condition to make a reaction wood during silviculture.(c) A difference between species was found on the distribution of specific gravity. For instance, specific gravity of Acacia mangium changed suddenly in a boundary of heart wood and sap wood.This fact leads the conclusion that Acacia mangium is an inferior materials as industrial point of view. Elucidation of the generation mechanism of specific gravity is more necessary.As mentioned above, even it was limited number of data, some important results were given about tropical fast grown species. Increasing the measurement object species and an individual number, we should identify reliability of this conclusion and suggest silvicultural conditions which make good quality of fast grown species furthermore. Less