Tesis (Ph.D.)

44 referencias bibliográficas

Fast-growing, high-yield tree plantations are an increasingly significant source of wood in the tropics. In these areas, improved wood productivity is an important economic goal. In Costa Rica and other countries in Central America, most of the tree plantations, especially those of advanced age, have not had the productivity expected of them. In the general context of a closer relationship between management practices and quality wood production, the general objective of this research was to develop a set of intensive management scenarios that could lead to alternative timber production practices with attainable and promising economic returns. Data for the different studies were collected in different regions of Costa Rica, covering almost all climatic conditions where T. grandis plantations have been established and where the species has adapted well. The study consisted fundamentally of the measurement of growth and yield parameters at the stand level and of the analysis of wood properties at the individual tree level and the interrelationship between silvicultural management and site conditions. High intensity, timely thinnings yielded both individual tree and stand volume, i.e. the objective of high individual tree growth was met without a severe reduction in stand yield. Pruning up to a reasonable height and on time caused no reduction in tree growth and stand yield. Moreover, pruning may improve stem form (higher form factor, lower stem taper) and heartwood content. Important characteristics, such as heartwood content and wood density, were found to be related more to tree age than to silvicultural management practices, especially at early plantation stages. Growth scenarios for 20 and 30 year rotations with the objectives of high individual tree growth and high stand growth were developed for high, medium, and low quality sites. Different site classes, production objectives, rotation periods, and discount rates resulted in marked differences in the financial profitability projections of the developed scenarios.