Patterns of growth dominance and neighborhood effects in Eucalyptus plantations and tropical forests

Forest stands have a broad range of tree sizes, even when all trees develop as a single cohort. Differences in size might result from different rates of resource uptake or resource use efficiency. Dominant trees often account for the majority of increment, but non-dominant trees can contribute a major part of stand growth in some cases. Pattern of growth dominance may provide predictive insight into the growth of trees and forest. My dissertation contains three chapters to explore growth dominance patterns of Eucalyptus plantations in Hawaii and Brazil, and natural tropical forests in Panama.;Chapter 1. Growth dominance was assessed in young plantations of Eucalyptus saligna under different treatments of planting density and fertilization. I found that effects of density treatment on stand growth declined over time, while those of fertilization increased in ways that accentuated changes of stand development. The strong growth dominance patter was exhibited under all treatments. The growth dominance positively increased over age. High density increased growth dominance, but high fertilizer had little effect on it. The growth dominance increased slightly as stand biomass and the variation in tree sizes increased.;Chapter 2. The 70-year-old plantations were used to explore the pattern of growth dominance. The growth of trees was still influenced strongly by neighbors. The interaction with neighbors explained 52% of the variation in focal tree in Hawaii, and 32% in Brazil. The accumulated stem biomass was high in old plantations, yet growth dominance by large trees remained strong or moderate; "reverse pattern" was not supported.;Chapter 3. Pattern of growth dominance in natural tropical forests was characterized in Panama. The "reverse pattern" was exhibited as expected. Tree growth increased with tree size, but the contribution of large trees to stand growth was lower than their proportional contribution to stand biomass. The reverse growth dominance was stronger in old tropical forests than the 20-year-old one recovered from clear-cutting. Growth dominance pattern did not change in two decades.