Índices de competição em árvores individuais de Tachigali vulgaris

Abstract

Competition in forest cultivation is a complex process, starting when its growth is affected by the dispute over resources that are fundamental to growth. One way of representing this is by competitive indices. These indices have been used in different species, but not yet for the “tachi-branco”. Thus, the objective of this study was to evaluate and select the best competition index to represent competition in “tachi-branco” cultivations. The data were sourced from an experiment on the initial planting spacing of “tachi-branco” (Tachigali vulgaris L. F. Gomes da Silva & H. C. Lima), in Monte Dourado, Para. The trial design was in randomized blocks, by using three blocks with six treatments each, represented by the following initial spacing: T1 (3.0 × 1.5 m); T2 (3.0 × 2.0 m); T3 (3.0 × 2.5 m); T4 (3.0 × 3.0 m); T5 (3.0 × 3.5 m); and T6 (3.0 × 4.0 m). Data were obtained at ages 3, 3,76, 4,77, 5,74, 7,63, 8,62, 9,72 and 10,78 years. A total of 147 trees were measured by treatment, divided into 3 blocks, 49 for each treatment. Eight competition rates were evaluated: IC1, IC2, IC3, IC4, IC5, IC6, IC7 and IC8. In each treatment, the diameter at breast height and the total height of each tree were measured. For resprouted trees, the equivalent diameter (DEQ) was calculated and, in these cases, the total height is considered as one of the tallest stems. For the selection of the competition index, the Spearman function was alternated between these indices and the variables diameter (d), total height (h), and cross-sectional area (g), for each treatment. The tendency of competition over time was also analyzed for each index and treatment. Based on the temporal trend, the indices were able to satisfactorily represent the competition, that is, they were able to demonstrate an increase in competition with advancing age and in the smallest spacing, except for IC4 and IC6. In IC4, the competition fluctuated irregularly over time. And in IC6, behavior contrary to the expected was verified. From the results of the successive analysis, the index that best represented the competition concerning diameter and cross-sectional area was IC5 and IC2 for the total height of the trees. Among the indices evaluated, IC5 and IC2 were the most appropriate to quantitatively represent the competition in experimental plantings of “tachi-branco”. The final choice of a single rate will depend on the purpose of its use.