Análise estrutural e corte seletivo baseado no método BDq em vegetação de caatinga.

Abstract

The Caatinga has been acting as a support for the demand of wood energy products, such as firewood and charcoal, such support occurs in the following ways, with illegal and legal logging, or by the application of forest management. This study aimed to determine three levels of selective logging on the vegetation of the savanna, based on the method BDq and analyze the composition of costs of such interventions. This work was carried out at Andreza farm, in the municipality of Diamante, Paraíba, Brazil. Forest inventory was carried out using the systematic method, measuring 28 permanent 20x20 m plots, and all standing individuals, dead or alive being sampled, measuring the circumference at the base, to 0.30 m soil (CNB0,30), the circumference, 1.30 m above the ground (CAP), and total height for each tree within the plots, at a minimum level of inclusion of CAP ≥ 6 cm, and analyzing the floristic and phytosociological composition,as well as the diametric structure. Meyer function was adjusted in order to obtain the constant "q" De Liocourt. It was proposed three alternatives of management method based on BDq, Treatment 1, with 40% reduction of basal area, Treatment 2, with 50% of basal area and Treatment 3, with 60% of basal area and the Witness, the alternatives were divided into two blocks, with three treatments and a witness in each. The cost analysis was based on expenses for marking trees, cutting and stacking. We sampled 2.836 individuals belonging to 16 families, 28 genera and 36 species. The three species which showed the highest average number of individuals per hectare were Croton blanchetianus, Poincianella pyramidalis and Combretum leprosum, the distribution of species densities shows that the first three diametric classes correspond to 96.79% of individual.ha-1, following the trend of “inverted J” distribution. The basal area was 14.651 m2.ha-1, the five species which showed higher basal area per hectare were Poincianella pyramidalis, Croton blanchetianus, Anadenanthera colubrina, the group of dead trees and Bauhinia cheilantha, representing 63.86% of the total basal area. The average estimated volume was 79.48 m3.ha-1, the value q = 2.61 was found, the remaining maximum diameter of 35 cm, the treatment 1, with 40% reduction in basal area, presents the remaining results in the post-harvest inventory of basal area (7.735 m2.ha-1), number of individuals (2543.26 individual.ha-1) and volume (37.754 m3.ha-1); for Treatment 2, with 50% reduction of total basal area, shows remaining values in the post-harvest inventory of basal area (7.481 m2.ha-1), number of individuals (2062.5 individual.ha-1) and volume (38.307 m3.ha-1) and Treatment for 3, with 60% reduction in basal area, shows remaining values in the post-harvest inventory of basal area (6.123 m2.ha-1), number of individuals (1,764,42 individual.ha-1) and volume (36.972 m3.ha-1). The average total cost per hectare for application of the BDq method was R$ 701.67. ha-1. The reduction of basal area at different intensities, used in treatments, was presented as an easy manipulation variable during the selection of trees which were meant to be felled, making it operationally feasible the application of the BDq method as a silvicultural treatment.