Estimativas de produção volumétrica das madeiras de Eucalyptus sp., Acacia mangium e Azadirachta indica em povoamentos com diferentes idades visando uso como energia renovável

Abstract

The objective of this work was to determine the average annual increment and survival in the stands of Acacia mangium, Azadirachta indica and Eucalyptus sp. at different ages in the city of Touros/RN. Initially, data referring to the planting ages of each stand were accessed. Thus, for A. mangium, 3 plantations were evaluated with the age group of 9, 10 and 11 years, cultivated in a spacing of 3 x 2 m; for A. indica, 1 plantation with 12 years was evaluated, cultivated in 3 x 3 m spacing in quincunx and; for the Eucalyptus sp. Two 22-year-old plantations were evaluated, cultivated in 3 x 2 m spacing in quincunx. Ten plots were allocated and georeferenced, in each treatment, with 30 individuals at random. For Eucalyptus sp. that contained four rows, the plots were made in the inner rows, in order to minimize the effect of the edge as much as possible. The data collected were DBH and total height of each tree included in the study areas, per plot, were worked using Excel for the calculation, obtaining results through the use of diameter classes. Estimates of the real volume and the stacked volume were also worked out using the form factor of each species studied and later the average of the average annual increments were calculated for each sample tree. For the applied data analysis, descriptive statistics were used using mean, standard deviation, variance, coefficient of variation, in order to present and understand the results. The species A. mangium had an average wood volume of 249.46 m3 ha-1 at 9 years of age, 140.73 m3 ha-1 at 10 years of age and 272.78 m3 ha-1 at 11 years of age, finding IMA corrected respectively with 14 .14, 7.18 and 12.65. For A. indica it was found 62.87 m3 ha-1 with 12 years with a corrected MAI of 4.72 and for Eucalyptus sp. we have 1040.81 m3 ha-1 and 20.98 IMA. According to species survival, A. mangium obtained respectively: 68% at 11 years, 61% at 10 years and 59% at 9 years; A. indica A. Juss obtained 62% in the only 12-year-old stand and Eucalyptus sp. had 85% survival in the 22-year-old stand. We observed that, as in the corrected IMA, the Eucalyptus sp. species also presented a better survival rate when compared to the other species. Which may suggest that Eucalyptus sp. is a species of excellent physiological properties for the region, thus being a more economically viable species for planting in the target region of this study. In this way, it is recommended to study the quality of the wood of the species evaluated in this study, so that the analyzes that support the energy potential of a forest stand can be complemented, such as the basic density of the woods and the higher calorific value between others.