Forest fragmentation has many negative effects on tree species. It causes edge effects, reduces population sizes and increases isolation between populations. This has potentially large implications for tree species and forest dynamics. In this thesis, the effects of forest fragmentation on tree diversity, population dynamics, and genetic diversity in Vietnam are analyzed. The objectives of the study were (1) to evaluate the effects of forest fragment size on forest structure, tree diversity, and tree composition; (2) to evaluate the effects of fragment size on the dynamics of tree species; and (3) to assess the effects of forest fragmentation on genetic diversity of tree species.