Avaliação dos tratamentos silviculturais aplicados em áreas de produção diversificada das unidades experimentais de manejo em florestas secundárias do município de Bragança, Pará.

Abstract

The increasing destruction of natural forests has caused the emergence of large areas of secondary vegetation, known regionally as capoeira. In the Brazilian Amazon, this type of vegetation has been used for traditional slash-and-burn agriculture. In order to study non-destructive methods of utilization of secondary forest, such as management for various uses, research has been developed in the northeast of Pará, of which the present study is a part. This work aims to study the effects of silvicultural treatments in relation to annual growth and to verify the resistance of the species eliminated in thinning operations. The study is being conducted in two stands of different ages in the municipality of Bragança - PA. The younger one, 20 years old, has 1.20 ha and the older one, 35 years old, has 4.80 ha. The stands were randomly divided into equal plots, being Ti (where thinning operations were carried out) and TO (witness without intervention). As criteria for species selection, the following characteristics were adopted: minimum diameter of 5 in, at 1.30 m from the ground; minimum height of 4 meters; straight stem without damage or rot; healthy crown and with good development. The silvicultural treatments consisted of eliminating competing individuals circumscribed to the selected tree by thinning: direct cutting (thin trees) and girdling (thicker trees). The species that had the best response in diametric increment, in Ti plot when compared to the species in TO plot, in Henhouse 1, were Phillanthus nobilis (L. F.) Choisy. with 0.15 cm and Eschweilera coriacea (DC.) S. A. Mori. with 0.17 cm. In site 2, the species that obtained the best results were Strypnodendron guianensis (Aubl.) Benth. with 0.45 cm and Inga alba (Sw.) Willd. About 100% of the treated individuals of the species Croton matourensis Aubl. and Annona paludosa Aubl. did not resist the thinning operations, while for Hymatamthus sucuuba (Spruce ex Mull. Agr.) Woodson about 100% of the individuals eliminated from this species resisted the thinning treatments. For most of the species eliminated in coppice 1 and 2, the treatments applied are not having the expected effect, since the species that were ringed are recovering their bark and those that were felled are regrowing. The small difference detected between TO and TI plots for both stands is probably due to the short period of time and/or the intense regeneration of the eliminated species, which probably increased competition with the selected species.