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Conséquences des pratiques sylvicoles sur les contraintes de croissance et le bois de compression chez Pinus kesiya planté à Madagascar

Baillères H., Bouillet J.P., Rakotovao G.. 1997. In : IUFRO. Forest Products for Sustainable Forestry : final program and proceedings. Hambourg : IUFRO, p. 196-196. IUFRO All Division International Conference. 5, 1997-07-07/1997-07-12, Pullman (Etats-Unis).

The objective of this study is to assess the impact of the silviculture on the growth stresses and on the repartition and the proportion of the related compression wood of Pinus kesiya (Royle) planted in Madagascar. Moreover the influence of the prevailing wind is evaluated. All the plantations of the study were planted to 1 300 trees/Ha and were sixteen and twenty years old at the felling. Four silvicultural treatments are compared : - a control which has never had any treatment, - a stand which has been subject to two thinnings, - a stand which has been subject to two thinnings and pruning up to 6m at the first thinning, - a stand which has been subject to a late and heavy thinning. In Madagascar there are 10000 Ha of fast growing uncleared plantations of Pinus kesiya (Benguet pine) which are more than 12 years old and it is important to know the impact of such clearing intensity on wood properties. For all the thinned stands the final density is 300 trees/Ha. The sampling includes 8 dominant and codominant trees by treatments, 3 levels of height are taken into account (1.3m, 4m, 8m) . They concern the timber part of the stem. The general trends are : an increase in compression wood proportion with increasing height, After a thinning, the remaiing trees tend to grow more rapidly and become more prone to develop compression wood, especially if leaning, late thinning induces more compression wood than normal thinnings, There is a significant influence of prevailing wind.

Mots-clés : régime sylvicole; bois de réaction; pinus kesiya; croissance; madagascar; tension interne

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