Genetic improvement has been an integral part of loblolly pine plantation forestry in southern United States for about 60 years with focus on improving timber yield, wood quality, and pest and disease resistance. Advances in techniques of genetic selection, breeding, and propagation of planting material have made it possible to achieve genetic gains that are likely to result in significant changes in loblolly pine stand dynamics. Height-age relationships, height and diameter relationships and distributions, and intraspecific competition were investigated in second generation open-pollinated, controlled-pollinated, and clonal loblolly pine with an objective of characterizing the nature and magnitude of changes in these characteristics due to genetic improvement and clonal forestry. Genetic improvement and/or clonal forestry had no practical effect on parameters of the height-age and height-diameter relationships beyond the effect on the asymptote parameter of the Chapman-Richards and Korf equations that were used to model these relationships. Genetic improvement resulted in an increase in the mean of height distribution without a corresponding increase in the mean of the diameter distribution, but had no effect the variance and skewness of the distributions. Thus, growth and yield models in which basal area is a function of height at a specific age (site index) are likely to over predict genetic gains in basal area growth and volume yield. Increase in stand density resulted in an increase in variance of the diameter distribution of non-clonal stands but had no effect on the variance of the diameter distribution of clonal stands. Thus, diameter distribution of clonal stands may differ from that of non-clonal stands after crown closure despite the distributions not being different before and during early stages of crown closure. This study also evaluated methods that may be used to predict height growth of new genetic varieties and those that may be used to asses intraspecific competition in forest stands. Mixed-model approach of calibrating a height-age relationship to a new loblolly pine clone gave biased estimates for clones that were at the extremes of the distribution of the groups. The use of maximum likelihood with simulated annealing (MLSA) to evaluate competitive interactions among trees in loblolly pine stands gave non-unique estimates of optimum competitor selection radius. A simpler technique that uses Pearson correlations was proposed and was found to work better than MLSA. / Ph. D.

Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Red Lapacho is timber species with largest market value, considered along with Mahogany, as 'green gold' in areas of natural forest logging. Therefore, the objective of this study was to analyze the different factors that influence the growth of this species, taking into consideration the spatial and temporal dependence inherent to the data. A census of Red Lapacho individuals was carried out in a natural fragment of Subtropical Deciduous Forest with approximately 13 hectares of area. Quantitative morphological and diameter increment data were obtained for each tree of this species. Competitors defined by Bitterlich plots were measured and identified, and a regular grid with infill points of soil sampling were also analyzed. Spatial patterns of distribution of Red Lapacho and its dimensions had completely spatial randomness patterns. Sampled species richness from competitors was of 60 species and the competition generated by them had a random spatial pattern as well. A model for the height – diameter relationship using Generalized Additive Mixed Models (GAMM) produced better results when the latent spatial pattern was included in the model. The spatial patterns of nutrient availability were influenced by relief of the area and distance from the edge of the forest and grassland environments. Anionic nutrients were strongly influenced by the spatial dynamics of the two vegetation types while cations were influenced mainly by pedogenesis. The spatio-temporal Bayesian diameter increment model developed for the Red Lapacho trees showed that there was considerable inter – annual variation in tree growth. The spatial variation in tree growth was closely related to the pedogenesis of the area under study, more specifically, lower increments were observed in areas where the soil had signals of water influence in tits formation. Using site proxies based on geocentric, phytocentric and dendrocentric approaches was able to take into consideration the spatial variation in the growth of Red Lapacho trees and, all approaches may be utilized in the development of growth models. / O Ipê – Roxo é uma das espécies de madeira com maior valor de mercado, sendo considerado, juntamente com o Mogno, o 'ouro verde' em áreas de exploração de florestas naturais. Assim sendo, o objetivo deste estudo foi analisar os diferentes fatores que influem no crescimento desta espécie, levando em consideração a dependência espacial e temporal inerente aos dados. Foi realizado um censo dos indivíduos de Ipê – Roxo em um fragmento natural de Floresta Estacional Decidual com aproximadamente 13 hectares. Foram levantados dados morfométricos e de incremento em diâmetro de cada uma das árvores desta espécie. Os competidores definidos por parcelas de Bitterlich foram medidos e identificados e, uma grade regular com pontos de preenchimento para amostras de solo foram avaliados. Os padrões espaciais de distribuição das árvores de Ipê – Roxo e suas dimensões se adequaram à completa aleatoriedade espacial. A riqueza de espécies amostradas como competidores foi de 60 espécies e a competição por estas gerada também teve padrão espacial aleatório. A modelagem da relação hipsométrica das árvores utilizando Generalized Additive Mixed Models (GAMM) obteve melhor ajuste quando o padrão espacial latente foi incluso no modelo. Os padrões espaciais de disponibilidade dos nutrientes foram afetados pelo relevo da área e pela distância da borda dos ambientes florestal e campestre. Nutrientes aniônicos foram fortemente influenciados pela dinâmica espacial entre os dois tipos vegetais enquanto cátions foram influenciados principalmente pelo processo pedogênico. O modelo espaço – temporal Bayesiano de incremento em diâmetro desenvolvido para as árvores de Ipê – Roxo mostrou que existe considerável variação inter - anual do crescimento. A variação espacial do crescimento também se mostrou relacionada com o processo pedogênico da área sob estudo, sendo que menores incrementos foram observados em áreas onde o solo apresentou sinais de hidromorfismo. A utilização de estimadores de sítio baseados em índices geocêntricos, fitocêntricos e dendrocêntricos foi capaz de levar em consideração a variação espacial do crescimento de árvores de Ipê – Roxo e, todos podem ser utilizados para a construção de modelos de crescimento.