African mahogany plantations: modeling growth and yield in Brazil

Abstract

Khaya ivorensis A. Chev. is a species of African origin and of recent cultivation in Brazil, not existing to date published data on the growth trends for the species. The analysis of a forestry project takes into account different types of feasibility criteria for implementation or not of the project, including the economic feasibility. But to evaluate this viability there is a need to develop models that provide estimates of the future growth of a forest in order to define the best silvicultural techniques. Therefore, the modeling of growth and yield is crucial to meet the planned objectives and the consequent profitability desired by forest managers. The present work proposes studies regarding the forest management of the species, still scarce in the literature. The data used come from commercial plantations installed in different Brazilian regions, mostly in the state of Minas Gerais. The plantations use spacing ranging from 4x5 to 12x12 meters, with ages ranging from 1.1 to 15 years, most with annual measurements starting in the year 2010. The first part of the work is composed of a theoretical reference on the state of the art of statistical modeling in the forest sciences and a brief description of financial analysis. The second part is composed of the research papers of this thesis. The first is a review article on the cultivation of African mahogany in Brazil and other parts of the world. A second article is about hypsometric modeling, in which mathematical models were evaluated under different fitting methods in order to select an equation for height prediction for African mahogany plantations. The third article was the evaluation of dominant height growth models comparing invariant dynamic models with standard age and static models (guide curve method) for site classification. The Lundqvist-Korf model with the guide curve method was efficient and recommended for site classification and prediction of dominant height in African mahogany stands. The amplitude of site indexes, at the reference age of 15 years, was 17 to 33 meters. The fourth article refers to a system of equations developed for the prognosis of growth and production of African mahogany by diameter class, in which the parameter recovery method was used with the Weibull probability density function to estimate volume and basal area. Finally, the fifth article deals with the financial analysis of the implantation and growing of African mahogany in the state of Minas Gerais, evaluating three management situations (no thinning, one thinning or two thinnings), the risks involved in the activity and their reflection in the net present value (NPV) of the enterprise for the five productivity classes.