Equações de volume e biomassa para plantios de Acacia mangium Willd. em área de savana, em Roraima

Abstract

The objective of the present study is to develop allometric equations to estimate the biomass and the volume of commercial wood in plantations of Acacia mangium Willd, in savanna area, aiming to assist the planning and management of planted forests in the state of Roraima. For fresh biomass, 85 trees were harvested, from which samples of the trunk, branches, leaves and roots were obtained to obtain the water content and carbon content. A total of 221 trees were harvested to obtain the volumetric data from a combination of the Hohenadl and Smalian methods, distributed in 10 plantations of different ages. Six models were tested to adjust the total fresh and commercial volume biomass data. The average total biomass stock for individual tree was 338 ± 31.07 kg, generating an estimate of 433.56 t ha-1, with the weighted water content of 0.43 and carbon was 0.48. The equations developed to estimate the total fresh biomass, above the soil, below the soil and the trunk showed good adjustment. It is possible to use the general equation (M = 0,4103 * DAP2,3315; N = 85; R2 = 0,96; Syx(%) = 1,73) to accurately estimate the total fresh biomass of all the plantations under study. The Husch model was also the one that presented the best fit for the commercial volume data for plantations of all ages, and the use of the general equation (V = 0,000185 * DAP2,42695; N = 221; R2 = 0,92; Syx(%) = 1,6; Uncertainty = 3,1%) because it presents low uncertainty. In view of this the equations developed in this work are precise tools to estimate the fresh biomass and commercial volume of the Acacia mangium plantations in Roraima.