Natalino Calegario

Ajuste de modelos estocásticos lineares e não-lineares para a descrição do perfil longitudinal de árvores

Polynomial models are most commonly used in Brazilian forestry for taper modeling due to its straightforwardly fitting and precision. The use of nonlinear regression classic models, like Gompertz, Logistic and Weibull, is not very common in Brazil. Therefore, this study aimed to verify the best nonlinear and linear models, and among these the best model to describe the longitudinal tree profile. The comparison measures were: R 2 , syx, R 2 adjusted, residual graphics and fitting convergence. The results pointed out that among the non-linear models the best behavior, in general, was given by the Logistic model, although the Gompertz model was superior compared with the Weibull model in terms of residual standard error (syx). Among the linear models, the polynomial by Pires and Calegario proved to be better than the others. When comparing non-linear models with linear models, the Logistic model was better mainly because of the behavior of the data, the low correlation between the parameters and in meaning, facilitating convergence and adjustment.

Longitudinal analysis of wood charcoal prices in the State of Minas Gerais.

O carvao vegetal e um recurso energetico renovavel, sendo um dos insumos basicos responsaveis pelo desenvolvimento das industrias de base florestal no Brasil. O Estado de Minas Gerais e o maior produtor e consumidor desse produto. No presente estudo, dedicou-se a analise das series longitudinais dos precos do metro cubico de carvao vegetal, no Estado de Minas Gerais, utilizando os precos medios pagos por metro cubico, publicados pela ABRACAVE. Para a analise da serie, considerou-se o modelo SARIMA, com o objetivo de encontrar os parâmetros que fornecam melhores previsoes de preco. Consideraram-se os precos do periodo de janeiro de 1975 a dezembro de 2002, para ajustar o modelo e o periodo de janeiro a dezembro de 2003 para validacao das projecoes. A escolha do modelo mais adequado se baseou nas analises graficas, nos testes estocasticos e nos criterios de avaliacao da ordem do modelo. Entre os modelos estudados, o SARIMA (2,0,1)(0,1,1)12 proporcionou melhor ajuste e de forma parcimoniosa. Apesar de ter ocorrido um fator aleatorio que distorceu os valores reais dos precos do carvao vegetal, as projecoes fornecidas pelo modelo ficaram dentro dos limites de significância estabelecidos.

Effect of age and diameter class on the properties of wood from clonal Eucalyptus

The objective of this work was to evaluate the influence of age and diameter class on the physical, thermal and chemical characteristics of a clone of Eucalyptus grandis and Eucalyptus urophylla. The material originated from a reforestation site owned by GERDAU S.A. and included trees at age 34, 48, 61, 74 and 86 months. Two trees were selected per age in each diameter class, observing the proportion of each established plot. Analyses of physical characteristics included wood basic density, dry matter weight and carbon stock, and of chemical characteristics included holocellulose, total extractives content, total lignin and ash content, in addition to elemental and thermal analysis of the wood. Results led to the conclusion that most wood properties were influenced by age and diameter class. The species was found to have great potential for production of biomass and generation of heat energy, potentially convertible into mechanical energy and electricity.

Modelagem não linear do perfil longitudinal de fustes de Pinus oocarpa

Com o aumento da demanda de produtos florestais no mercado, o incentivo a pesquisas que aperfeicoem a obtencao de multiprodutos das florestas com o menor custo e cada vez maior. Objetivou-se, neste trabalho, avaliar a precisao de um modelo linear (polinomio do 5o grau) e de um modelo nao linear (logistico) na estimativa do perfil do fuste de Pinus oocarpa. A base de dados utilizada foi de um plantio de Pinus oocarpa, localizado no Triângulo Mineiro, originada da cubagem rigorosa de 140 arvores. As equacoes ajustadas foram avaliadas pelos seguintes criterios: criterio de informacao de Akaike, criterio de informacao Bayseiano, analise grafica de residuos e erro padrao da estimativa. O modelo logistico apresentou-se mais preciso na estimativa do perfil do fuste de Pinus oocarpa.

Generalized nonlinear models applied to the prediction of basal area and volume of Eucalyptus sp

This paper aims to propose the use of generalized nonlinear models for prediction of basal area growth and yield of total volume of the hybrid Eucalyptus urocamaldulensis, in a stand situation in a central region in state of Minas Gerais. The used methodology allows to work with data in its original form without the necessity of transformation of variables, and generate highly accurate models. To evaluate the fitting quality, it was proposed the Bayesian information criterion, of the Akaike, and test the maximum likelihood, beyond the standard error of estimate, and residual graphics. The models were used with a good performance, highly accurate and parsimonious estimates of the variables proposed, with errors reduced to 12% for basal area and 4% for prediction of the volume.

Sustainable Forest Management of Native Vegetation Remnants in Brazil

A region’s species diversity is an important factor, resulting as a component of social and economical development when used wisely. The correct commercialization of a region’s natural resources guaranties the preservation of local culture and habitat maintenance by means of the obtained income. Hence, the idea of sustainability arises, a widespread theoretical theme which is beginning to gain force in Brazil’s consumer market. The principal conceptual shift was the erroneous notion that timber resources from forests are inexhaustible, since the processes of recomposition/restoration naturally occur after exploration. Indeed a system is capable of regeneration, but this is tied to a series of factors that are usually not respected in areas illegally explored. According to a conference realized in Melbourne by Raison et al. (2001), the concept of sustainability must encompass social and economic conditions such as: respect the forest growth rate; legislation based control; productive capacity; ecosystem’s health and vitality; soil and water resource protection; carbon balance and preservation of biological diversity. Under this scenario, Brazil presents great potential for the use of its natural resources. This is due to the country’s vast territorial extension (8.5 million km2) and high diversity of recurrent vegetation physiognomies. The country possesses about 5.2 million km2 of forest land (60% of its territory), of this total, 98.7% consists of natural forest formation and 1.3% of planted forests. The forest types found in Brazil can be classified as Cerrado (Brazilian savanna), Amazonia (tropical rainforest), Mata Atlântica (Atlantic rainforest), Pantanal (wetlands) and Caatinga (semi-arid forest) as well of transition areas which promotes a mixture of habitats. In many cases, the deforestation of these environments is associated with illegal logging practices coupled with agriculture and cattle-raising. The damage caused by this include modifications of the carbon cycle and consequential rise of CO2 emissions; forest fragmentation; alteration of the hydraulic cycle; species extinction; rural exodus and loss of local fauna and flora diversity. Possibly the most logical use of these forests is the application of sustainable forest management for wood production destined for fire wood, charcoal and logs for industrial purposes. The motives for this strategy are evident, involving aspects attached to the reduction

MODELOS HIPSOMÉTRICOS GENERALIZADOS MISTOS NA PREDIÇÃO DA ALTURA DE Eucalyptus sp.

Conduziu-se, este trabalho, com o objetivo de avaliar a teoria dos modelos generalizados mistos e a modelagem da heterogeneidade de variância no ajuste de dois modelos nao lineares para a relacao altura-diâmetro em Eucalyptus sp. Foram utilizados dados de arvores-amostras de diferentes materiais geneticos (clone e semente) e idades. De acordo com as analises, o modelo assintotico obteve os melhores resultados em relacao ao modelo sigmoidal. A precisao dos modelos avaliados aumentou com a utilizacao da teoria dos efeitos mistos com adicao de covariaveis e a modelagem da heterogeneidade da variância.

Different strategies to estimate the commercial volume of Anadenanthera colubrina (Vell.) Brenan

This work aimed to evaluate the use of traditional models, profile and relative height method, for estimating the commercial volume of Anadenanthera colubrina (Vell.) Brenan. Data were obtained from scaling of separate lengths of the stem of 22 trees, using Smalians method. Tree stems were measured 0.1m, 0.30m, 0.70m, 1.0m, 1.30m above the ground and then every 1m. For purposes of method assessment and comparison, statistics were used that include percent standard error, bias, standard deviation of differences, in addition to graphic interpretation of residuals. Assessments showed that Stoates model is the most accurate, followed by Schumachers model. They also showed that the linearized Schumachers model reduced accuracy by an average 0.32% and that the relative height method was biased in this study.

Análise de algumas alternativas para obter o coeficiente angular da reta no método da altura relativa.

The relative height method allows the characterization of stem profile without meeding sample trees to upper diameter measurements. The analytical geometry is applied on the diameter taken on 0,3 meters and on hr = (h-2)/2, as well as dbh and total height (h), making possible the measurement of these variables, simultaneously, with others measured on the permanent sampling in forest inventory. This study evaluated some alternatives in characterizing the stem profile by using analytical geometry, comparing it to the original method according Andrade (2001). It was concluded that the use of relative diameters to dbh showed better results in regression analysis to generate straight line angular coefficient. Also, to obtain better accuracy, it is more adequate to implement the relative height method using all trees inside the inventory sample unit.

Estimativa do crescimento de povoamentos de Eucalyptus baseada em modelos lineares em multiníveis de efeito misto

The main purpose of this study was to apply the mixed-effects theory in modeling Eucalyptus stand growth. The database is from homogeneous stands located on Brazilian coastal region, Espirito Santo and Bahia States. We used two levels of sampling: sample units and individual trees inside of sample units. As an example, we considered the logarithm of the basal area as response variable and inverse of age, logarithm of the total height and their interaction as covariates. The parameter estimate quality of the linear model was significantly improved. Also, by modeling the heteroscedasticity and the autocorrelation (AR(1)), the log-likelyhood values were increased significantly.