Análise da vegetação de caatinga arbustivo-arbórea em Floresta, PE, como subsídio ao manejo florestal

Abstract

The study aimed to analyze the floristic composition and vegetation structure of two areas of caatinga with different histories of use, in Floresta, PE, Brazil, evaluating the recovery of secondary vegetation after 22 years of fallow; to identify the uses of shrubs and trees species by the local population; to provide management prescriptions based on the diameter structure of the vegetation and potential uses of species; and to compare techniques for estimating volume and biomass of the most important species in the area. In order to reach these purposes, 60 plots of 20 x 20 m were systematically distributed, 40 plots in a disturbed area and 20 plots in a preserved area, where all plants circumference at breast height with (CBH) ≥ 6.0 cm were identified and measured and had their CBH height. Parameters of horizontal and dendrometric structure richness and diversity indices were estimated. To determine volume and biomass of Poincianella bracteosa (Tul.) L.P.Queiroz, species which represents the highest importance value in both areas, 30 trees were felled. The uses of shrubs and trees species were surveyed among indigenous people of the community Travessão do Ouro, located close to the study area. The secondary vegetation recovering for 22 years after clearcutting (Area I) differed in composition and physiognomy from the preserved vegetation (Area II), with higher species richness, concentrated in classes of lower diameters. In both areas, Fabaceae and Euphorbiaceae were the families with the higher number of species and Poincianella bracteosa had the highest Importance Value, with higher dominance in the disturbed area. Indians listed uses for 27 species found in the area. Myracrodruon urundeuva Allemão, Anadenanthera colubrina var. cebil (Griseb.) Altschul and Cnidoscolus quercifolius Pohl were the species with the largest numbers of use categories. The use as fodder was listed for the highest number of species, reflecting the most land use, which is extensive livestock. Frequency data for stem diameter classes were well adjusted to the Meyer model, with parameters estimated by a nonlinear method, allowing the development of a forest management model based on selective cutting by diameter classes, considering the relative density of the species and its potential use, depending on the objective. Management prescriptions of selective cutting for three species to be used as fuel wood are presented (Poincianella bracteosa Mimosa ophtalmocentra Mart. ex Benth. and Pityrocarpa moniliformis (Benth.) Luckow & R.W.Jobson), maintaining over 60% of the original basal area. The best volumetric and biomass equations for Poincianella bracteosa were obtained with the logarithmic model, as a function of the circumference at the base of the stems. Use the form factor appeared to be the most practical and accurate alternative to estimate the volume of Poincianella bracteosa, taken as reference the volume of the cylinder with cross-sectional area equal to the base of the tree.