Crescimento e propriedades da madeira de árvores de Vismia cayennensis (Jacq.) Pers. em uma Floresta Secundária na Amazônia Central

Abstract

One option to produce timber and non-timber products in the Amazon is the management of regenerating forests or secondary forests. In this sense, the proposal of alternative species through knowledge of the quality of their products can contribute to the need to guarantee a continuous supply of timber goods in forest management. This study aimed to investigate the productive capacity and wood quality of Vismia cayennensis trees in a secondary forest in the Central Amazon. The study was carried out in a stand of secondary forest located at the UFAM Experimental Farm, Manaus, Amazonas. This stand is 36 years old and covers an area of 35 hectares. In 2020, five experimental blocks were installed, with two 1-hectare plots in each block. In the plots, the diameter at breast height (DAP) was measured and the botanical identification of all individuals with DAP ≥ 10 cm was carried out. Of the species inventoried, 24 V. cayennensis trees were selected, 10 for dendrochronological analysis and anatomical description and 14 for physical-mechanical testing. For the dendrochronological analyses, disks were taken from the base, DBH and heights of 50 and 100%. The X-ray image densitometry technique was used to identify the limits of the growth rings more precisely and to obtain the microdensity profiles of the wood. By measuring the width of the rings using WinDENDRO software, the trees' Average Annual Growth Rate (AGR) and Current Annual Growth Rate (CAGR) indicators were calculated. The regions of the microdensity profile showed bulk density values in the fibrous zones with peaks at their limits of (0.8 g cm-3). There was an increasing variation in microdensity values in the pith - bark direction of the trees. The pattern of increase in the cross-sectional area of the trees over the years showed an apparent stabilization in the last years of growth. The species' trees had an IMA of 0.0008 m2 year-1, with a maximum ICA of 0.0012 m2 at 18 years of age. As for the physical-mechanical tests, towers were removed in the field and then sectioned into planks from the base, middle and top of the tree stem, for later removal of the specimens. The apparent density was determined and

10 compression tests parallel to the fibers and tangential shear tests were carried out. Under these conditions, the wood had an average bulk density of 0.66 g cm3. The apparent density increased in the pith-to-bark direction. The resistance to compression parallel to the fibers was 50.3 MPa, placing it in resistance class C40 - dicotyledons according to NBR7190. The average value for shear strength was 15 MPa. The V. cayennensis species has medium mechanical strength and can be used in various applications, such as civil construction and furniture. However, the results of this study do not yet offer definitive conclusions about the possibilities for commercial use of the wood of this species. It is therefore essential to carry out further tests and specific evaluations to determine the suitability of the species for a particular application.