Estrutura bioeconômica da produção no manejo da densidade de Pinus taeda L. na região do planalto catarinense, Brasil

Abstract

This work was developed with the aim of studying the efficiency of the models that express the relationship of density and diameter in evenaged stands of Pinus taeda L., managed in full density and highly stocked for a bioeconomic model of production. For this, were tested density and diameter models, using data derived from 50 permanent plots, measured annually until 18 age, allocated to settlements established in the spacing of 1.5x1.0 m, 2.5x 1.0 m, 1.5x2.0 m, 2.0x2.0 m, 1.5x3.0 m, 2.5x2.0 m, 2.0x3.0 m and 2.5x3.0 m, kept at full density, in Otacílio Costa, physiographic region of Santa Catarina State plateau.The results of the bioeconomic modeling of production, based on the density management diagram system for tall trees, we concluded that the models proposed by Reineke, Yoda, Zeide and Tang showed a good statistical precision, with a determination coefficient higher than 0,88 and coefficient of variation less than 1.25 % but the model of Tang was more accurate and efficient. The size of the diameter at the point where you start self-thinning in the population varies considerably with the density of trees established per hectare. For all plant spacings analyzed did not prove the value of the slope of -3/2 law of self-thinning proposed by Tang and is a result of the initial spacing. The limit of self-thinning in less dense populations, occurs with a diameter slightly less than in maximum density, which is directly proportional to the density of trees when the implementation of the forest. The model of self-thinning described the management zones of great individuals in the population, between 0.45 and 0.55 limits the maximum density of the forest. The annual increment in diameter between 6 and 7 years, when related to relative density (G/d0,5622) identified five areas of growth, defined by: excessive space - trees grow free of competition;free growth - where growth in diameter is maximum; increased competition- when the diameter increment begins to decrease; full density - when productivity of the stand is maximum; and imminent death - begins when individuals have died by excessive density and high competition. The Diagrams Density Management of the variables mean diameter, basal area, volume by the Population Density Index was efficient and to estimate thisis values with accuracy, showed an efficiency of 0.99. The lines demarcating the areas of competition allow us to project the trajectory of the diameter and density, with the definition of the clearcutting. The Normal, Lnnormal, Weibull and Gamma probability distributions, described accurately the variation of the density of the stands, but the Weibull function with two parameters was comparable to the adjustment by the simplicity and efficiency in the prognosis of frequencies for diameter in time. The shape of the trunk was adjusted by the polynomial of five degree, allowed the best estimates than other models. The net present value of R$ 15587.60 ha-1 was given to the management regime with three thinnings at 9, 13 and 18 years and cut at 22 years, higher than the other schemes simulated. A comparison of management regimes for the equivalence of planning horizons for 28 years, determined by the equivalent annual value, said the management regime with three thinned and cut at 22 years, such as greater economic efficiency, with a value of R$ 1380.10 ha-1. The internal rate of return in any simulated management regimes was highly attractive, with varying from 14.83 % per year in managed regimes stands with three thinning and cut to 22 years to 14.25 % per year in managed regimes stands with threethinning and cut to 18 years. The biggest benefit/costs ratio was 2.81, obtained in the management regime with three thinnings, at 9, 13 and 18 years and final cutting at 22 years.