Influência do espaçamento no crescimento de Pinus taeda L. na região Centro-Sul do Paraná

Abstract

This study evaluated the effect of nine initial densities on the growth of Pinus taeda L., using the complete stem analysis (ANATRO). The experiment was established in 2002 and it is located in the municipality of Irati, Central-Southern state of Paraná, Brazil. Nine treatments were implanted with vital spaces between 1.0 and 16.0 m² (1.0 x 1.0 m, 2.0 x 1.0 m, 2.0 x 2.0 m, 3.0 x 2.5 m, 3.0 x 3.0 m, 3.5 x 3.0 m, 4.0 x 3.0 m, 4.0 x 3.5 m and 4.0 x 4.0 m). Data were collected during June and July, 2012, at 9 years old, stratifying by the diameter distribution of each treatment in 9 classes of diameter at 1.3 m (DBH), being sampled one tree per class, totaling therefore, 81 trees to be applied the ANATRO. The effect of initial density on the growth of diameter (DBH), cross-sectional area, total height, individual volume, basal area and volume per hectare was evaluated by a randomized design. The variable production was represented by a Chapman-Richards biological model, as well as current and mean annual increments. It was also studied the stem taper evolution with the common form factor. The diameter (DBH), cross-sectional area, individual volume, basal area and volume per hectare were influenced by the initial densities from the fifth year of age and vital spaces of 14 and 4 m2 presented, respectively, the highest and lowest rates of individual increment. The vital space of 14 m2 had an average increment in diameter (DBH), 37% higher than the vital space of lower growth (4 m²) at the 9 years old. The average height up to 9 years of age showed no statistical difference, indicating that this variable is not affected by spacing, being that the greater total height, found in 14 m² vital space at the 9 years of age, is 11% higher than the vital space of lower growth for this variable (1 m²). The basal area (G) and volume per hectare were affected by spacing and showed different growth between treatments from the fifth years old, where the vital spaces of 1 and 2 m² had the highest growth for both variables at age 9. The form factor at age 9 years old indicated that higher initial densities result more cylindrical stems around 17% of that found for lower initial densities. The growth evaluated by ANATRO and permanent plots (PP) showed similar results to the individual average diameter, cross-sectional area and volume. The results indicated that the 7.5 m2 vital space could be divided into two major groups, namely, smaller vital spaces (1 to 7,5 m²) with short rotation which could be employed to produce biomass (pulpwood management regime) while the largest vital spaces (7,5 to 16 m2) would be more suitable to generate multiproduct on longer rotations. Vital spaces with about 7.5 m2 could be used when to the planting of the stand, the owner is still not sure of the final destination of the product, and can therefore opt for the pulpwood or utility management regime.