Gilciano Saraiva Nogueira

Modelo de distribuição diamétrica para povoamentos de Eucalyptus sp. submetidos a desbaste

Data used for this study are from a thinning essay established in stands of eucalypt carried out in the Copener Florestal enterprise, in the Northeast region of Bahia State, Brazil. Data were collected in 48 rectangular permanent plots, with an area of 2,600 m2. The first thinning was made at 58 months. Various percentages of basal area reductions were used. The objective of the study was to build and quantitatively evaluate, through statistical tests, a growth and yield model by diameter class for thinned eucalypt stands. The theoretic redistribution of diameters by class was made through equations that include both linear and non-linear relations between the Weibull function parameters in a future age (b2 and g2) and the parameters at the present age (b1 and g1) and with some stand characteristics at the present and future age. Three equations systems were analyzed. The equations were analyzed through the adjusted determination coefficient, the correlation coefficient and the graphical analyses of the residues. Tests were performed to verify the compatibility of the systems and the identity among them. The selected system is compatible and assures the property that when the future age (I2) is equal to the present age (I1), the diametric distribution at the future age is equal to the diametric distribution at the present age. This system generated accurate and consistent estimates of growth and yield per diameter class.

Individual Growth Model for Eucalyptus Stands in Brazil Using Artificial Neural Network

This work aimed to model the growth and yield of Eucalyptus stands located in northern Brazil, at the individual tree level, by using artificial neural networks (ANNs). Data from permanent plots were used for training the neural networks to predict tree height and diameter as well as mortality probability. Once trained, the networks were evaluated using an independent data set. The first group was composed of 33 plots (11 in each productive capacity class) and was used for artificial neural network training. In five measurements, this group totaled 8,735 cases (measurements of individual trees), as each plot had 53 trees on average throughout this evaluation. The second group was composed of 30 plots (10 in each productive capacity class) and was used for model validation. This group totaled 7,756 cases. Were tested different network architectures Multilayer Perceptron (MLP). Results revealed an underestimation bias for number of surviving trees. However, estimates of diameter, height, and volume per hectare were found to be accurate. This indicates that artificial neural networks are a viable alternative to the traditional growth and yield modeling approach in the forestry sector.

Um modelo de distribuição diamétrica para povoamentos de Tectona grandis submetidos a desbaste

The objective of this study was to develop and quantitatively evaluate a diametric distribution model for the management of thinned teak (Tectona grandis L. f.) stands. Model construction involved data from a net of permanent plots established in teak stands, in Mato Grosso State, Brazil, owned by Floresteca Agroflorestal Ltda. A total of 239 permanent plots with a mean area of approximately 490.8 m2 were used. The first thinning was carried out at 58 months (mean value) and consisted in the systematically reduction in approximately 36% of the tree number . The recovery of the diametric distribution was taken from equations comprising linear and non-linear relations between the Weibull function parameters at a future age (b2 and g2) and the parameters at a present age (b1 and g1), and stand characteristics in a present and a future age. Three equations systems were analyzed. Compatibility analyses of each system and identity among them were performed oo verify the consistence of the systems. The selected system guaranteed the property in which if the future age (I2) is equal to the present age (I1), the diametric distribution in the future age is equal to the diametric distribution in the present age. It was concluded that the model is compatible and recommended for thinned stands of Tectona grandis. It was also concluded that the prediction of the Weibull function parameters at a future age in function of the parameters observed at a present age is logical and generates consistent and accurate estimates.

Curvas de crescimento e de índice de local para povoamentos de Tectona grandis em Tangará da Serra, Mato Grosso

The objective of this study was to evaluate the growth tendencies of the stand variables and evaluate alternatives to construct site index curves for teak (Tectona grandis) in stands located in the Tangara da Serra, Mato Grosso state. For this purpose, data from 50 permanent plots with a minimum of four successive measurements were used. The tendencies of growth in height, diameter, basal area and volume were analyzed by means of the regression method, using the Chapman-Richards model. Two methods of construction of site index curves, with different models, were evaluated. The results of the analysis showed that Chapman-Richards model adjusted well to the observed data, describing the growth tendencies of the stand variables. The best alternative for the construction of site index curves was the guide-curve method, using the Chapman-Richards model.

INFLUENCE OF INITIAL SPACING ON THE STEM SHAPE OF Pinus Taeda L.TREES

The objective of this study was to analyze the effect of spacing on the stem shape of Pinus taeda L. trees. Data from a spacing experiment carried out at the company IGARAS, in Santa Catarina, Brazil, were used for this purpose. The analyzed spacings were: 1.5 x 1.0 m; 2.0 x 1.0 m; 2.5 x 1.0 m; 1.5 x 2.0 m; 2.0 x 2.0 m; 1.5 x 3.0 m; 2.5 x 2.0 m; 2.0 x 3.0 m; and 2.5 x 3.0 m. The taper models tested were those proposed by Demaerschalk, Garay and Biging, with the model of Garay being selected. Through model identity tests, it was verified that the smallest spacings resulted in less conical shape than the largest ones.

Avaliação de um modelo de distribuição diamétrica ajustado para povoamento de Eucalyptus sp. submetidos a desbaste

The main objective of this study was to evaluate the estimates generated by a diametric distribution model, under the biologic point of view. Another objective was to evaluate the efficiency of the percentage of entries method to determine the technical age for the first and second thinning in eucalypt stands. The qualitative evaluation of the model was carried out through the evaluation of the results obtained by the percentage of entries method, the behavior of the diametric distributions projected for the future, and the behavior of the remaining distributions after some thinning simulations, theoretically, logically and biologically speaking. According to the results it was concluded that the diametric distribution model proposed is biologically correct and consistent. Growth stagnation is stimulated after thinning. It also was concluded that the percentage of entries method is suitable to determine the technical age for the first and second thinning. The model evaluated allows the simulation of various situations, generating consistent estimates and it can be used without restrictions, that is, situations can be simulated with or without the conditions observed in the field.

Avaliação de um modelo de distribuição diamétrica ajustado para povoamentos de tectona grandis submetidos a desbaste

The objective of this study was to evaluate, under the biological point of view, a diametric distribution model. Another objective was to evaluate the efficiency of the percentage of entries method to determine the technical age for the first and second thinning in teak (Tectona grandis L. f.) stands. This evaluation was carried out by comparing the technical thinning ages obtained by the percentage of entries method, the diametric distributions projected for future ages and the behavior of the remaining distribution, after some thinning simulations, with the expected logical tendency. It was be concluded that the proposed diametric distribution model generates estimates which follow a logical tendency, biologically speaking and that the percentage of entries method is suitable to determine the technical age of the first and second thinning.

Evaluation of methods of site index curve ajustment in thinned eucalypt stands

The objective of this study was to compare the efficiency of the methods guide-curve, difference equation and parameter prediction to build site index curves in stands of thinned eucalypts. Data came from a thinning experiment belonging to the Copener Florestal, enterprise, Bahia, Brazil. Seven measurements (at 27, 40, 50, 61, 76, 87, and 101 months) from 48 plots with mean area of 2,600m² each, were used to adjust the models. The methods were analyzed individually through the determination and correlation coefficients, percentage mean errors, and graphical analysis of the site index curves. The identity among methods was tested according to Leite e Oliveira (2002). To perform the test, the guide-curve method was chosen as the standard for comparison with the other two methods. In the single analysis, the three methods fitted in the criterion adopted for the efficiency evaluation to build the site index curves, but the guide-curve method presented the best adjustment. The results of the model identity showed that the estimation of site index obtained

Análise econômica de um sistema agrossilvipastoril de área montanhosa na Zona da Mata mineira

The objective of this work was to evaluate the economic viability of an agrosilvipastoral system developed for Zona da Mata mountainous areas in Minas Gerais state, Brazil, as well as to compare different options for wood (Eucalyptus grandis and Acacia mangium) commercialization of the second thinning. The data were obtained from a 10 year-old agrosilvipastoral system established in four hectares at Embrapa Gado de Leite station in Coronel Pacheco, MG, Brazil. As evaluation criteria for the economic viability analysis, the adopted methods were the net present value (NPV) and the internal rate of return (IRR), both calculated at 6% interest rate. Despite the small difference, adding value to forest products increased the attractiveness of the proposed system. Considered separately, the agricultural activity was impracticable, whereas the forestry and livestock activities were independently viable. The studied system seems to be equally tolerant to price variations for forest and livestock products, as well as strongly tolerant to variations in production costs.

Tendência de crescimento de povoamento de eucalipto após aplicação de desbaste

Although the Clutters model (1963) is widely used for predicting growth and yield in Brazil, it has also been used in the modeling of thinned stands. The most important criticism of this last approach is the incapacity to differentiate trends before and after thinning. The data came from an experimental thinning design in a stand of E. grandis x E. urophylla, in Northern Bahia. The treatments were thinning 20%, 35% and 50% of the basal area. Using these experimental data, the modified Piennar e Shivers Model (1986) was tested, seeking more flexibility. Another objective was to make the use of Clutters Model available to identify different growth trends. The considered modified model showed statistical characteristics similar to the Clutters Model (1963), without adding to this more flexibility. It was also found that the Clutters Model can be used to thinning simulation, even if not suitable for differentiating growth trends