Samuel de Pádua Chaves e Carvalho

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.

Exatidão de dendrômetros ópticos para determinação do volume de árvores em pé

The aim of this paper is to verify the accuracy of the optical dendrometers Criterion 400 and RC3H by studying the quality of measures of wood volume determination of standing trees through these dendrometers. The study was developed at the Experimental Station of Forest Sciences, in Itatinga, Sao Paulo state, which belongs to the University of Sao Paulo (ESALQ / USP). It was sampled a total of 175 trees in three plots of Eucalyptus grandis. The stem diameter of standing trees was measured by the two optical dendrometers at distances of 0.1, 0.4, 0.7, 1.0, 1.3, 2.0 meters from this point meter by meter along the stem up to 8 meters height. After measuring the standing trees they were felled and the diameter was obtained in different positions with a caliper and a tape in the same positions that the non-destructive measures were taken. With the diameters the volume was calculated by section and by individual trees by the Smalian formula for the comparison of methods. Analyzing the measurements of stem diameter and the individual tree volume realizes that the two dendrometers provided measures generally underestimated. However, the Criterion provided the best estimates. For the diameter and individual tree volume the Criterion showed underestimated errors averaging approximately 1 cm (10%), while the RC3H resulted in errors greater than 5 cm (30%) on average.Thus, when measuring observed variables in a non-destructive way with reliability and accuracy, the Criterion showed better results.

ANÁLISE ECONÔMICA DA ROTAÇÃO FLORESTAL DE POVOAMENTOS DE EUCALIPTO UTILIZANDO A SIMULAÇÃO DE MONTE CARLO

The objective of this study was to determine the economic cycle rotation of eucalyptus plantations in three productivity sites over hazardous conditions. The data used on this study, released by the company Fibria Celulose. Besides the timber production data, it was also given the company cash flow. It was from an even-aged stand and a monoclonal stand both of Eucalyptus urograndis . For the risk analysis, the study used Monte Carlo method, having as a result of the simulation the Net Present Value for Infinite Series, using as an input variable and/or source of uncertainty, the probability distributions of the land and wood prices, the costs of harvesting and transportation activities, the interest rate and also the timber production. The simulation consisted in carrying out 10,000 interactions, where it was obtained the necessary information for the development of the next analysis. As a conclusion the optimal rotation for cutting was 6, 8 and 11 years on the good sites (I), regular sites(II) and poor sites(III) respectively, being consistent with the biological laws of growth. Another conclusion is that even under the same management conditions, more productive sites generate greater economic returns and therefore lower risk in adverse economic scenarios.