Technological characterisation of Amazonian trees submerged by the Tucurui dam in Brazil

摘要

Amazonian trees -- angelim (Dinizia excelsa), castanheira (Bertholletia excelsa), macaranduba (Manilkara huberi) -- submerged for 14 years in the waters of the Tucurui dam in Para State, Brazil, are being extracted by divers working 30-50 metres down with water-proof, portable hydraulic chainsaws, and floated to the sawmill. Various innovative techniques were developed during the operation, such as the waterproof chainsaws, sonar to detect the trees, and extraction techniques using a crane installed on the boat. Daily yields with a team of three people (diver, technician and assistant) are approximately 20 commercial logs. The technological properties of the wood, i.e. density and tangential, radial and volumetric shrinkage and its mechanical strength (static flexural bending, perpendicular compression, shear and Janka hardness), were measured for each species using Copant standards. No significant differences were found between the values for their mechanical characteristics and those quoted inthe literature, apart from the slight darkening of both sapwood and heartwood, which has no incidence on their uses. Deep water is the best way of preserving whole tropical trees as well as the technological properties and appearance of the wood. The work involved in recovering the trees has proved to be both commercially and industrially viable, considering the value of the trees already used and the quantity of trees left to be exploited.