Efeito do espaçamento de plantio na biomassa do fuste de um clone híbrido interespecífico de Eucalyptus grandis e Eucalyptus urophylla

Abstract

The use of forests of Eucalyptus has become each time more expressive in Brazil, over all on account of the excellent production in volumetric terms for them reached and the good characteristics of the gotten wood. Some companies of the forest sector are in search of the increase of the wooden production for unit of area, trying to identify, in regimes of handling, the technique that strong adds more quality to the end item for them generated. In this context, the present work was developed to search the bests plantations spacing for clonal forests of a interspecific hybrid of Eucalyptus grandis and Eucalyptus urophylla, to maximize the production of the stem biomass per hectare, and as a complementary objective to analyze the influence of the plantation spacing in the annual increment in diameter, height, stem volume and volume per hectare, basal area throughout the age, beyond the percentage of bark of the trees and basic density of the wood in the last year. The data came from the Duraflora Company and are proceeding from a clonal test exploration that aims at the increase of the productivity and improvement of the quality of the substance cousin through the study of plantations spacing. The used statistical delineation was the systematic with continuous quantitative factor, 16 treatments and 40 repetitions, considering that the variation between the treatments was only the spacing between the trees and the space between lines was a constant of 3 meters. With this arrangement, the vital area for tree was about 1,50m2 (6,667 trees per hectare) until 15,75m2 (635 trees per hectare). The trees height and the diameter breast height - DBH had been measured to the age of 36, 48, 60 and 72 months, and only in the last year three trees of each treatment had been sampled to determinate the individual tree volume and the wood basic density, so the stem biomass was estimated per hectare. The analyzed data of growth of the plantation in diameter, basal area and height of the 36 to the 72 months allowed to conclude that the increase of the plantation spacing, increase too the diameter and height of the trees, presenting the same trend in the two variables, however, the height less intensely. The evolution of the basal area - BA of the forest along the years portraits that the accumulated plantation spacing had presented the greater results in BA, due to the biggest frequency of individuals per hectare. The density and stem volume was analyzed on the 72 months, and it was evidenced that in the ample plantations spacing it had greater volumetric production per tree in function of the biggest available vital area for its development; It was also evidenced that trees with the greater diameters had less bark that the accumulated plantations spacing, where exists a bigger frequency of lesser trees, as much in diameter how much in height. From these results, the choice of the best plantations spacing was established of form that the stem biomass production per hectare was maximized in an interval where the vital area for plant favored the growth in diameter and the wooden formation of the bigger basic density, thus varying of 3,30m 2 4,95m 2 per tree, that corresponds to the 3x1,10m, 3x1,35m and 3x1,65m plantations spacing.