Mathematical study on global dynamics in ecological systems

点击翻译按钮获取中文摘要

This study has aimed at theoretical understanding of global spatial and temporal changes in ecological systems with reference to various aspects of environmental issues. Specific subjects include conservation of diversity of ecosystems, invasion of alien species, extinction of rare species, function of ecosystems and so on. Representative results are summarized below.1. A mathematical model for invasions of two competing species into open spaces is investigated. The effect of disturbances that cause the environment to change in both time and space is examined, and principles of coexistence between the invading and native species are explored.2. Global diversification of termites driven by the evolution of sociality and symbiosis is discussed by means of the possible mechanism of C-N balance.3. Gap formation process in forested ecosystems is analyzed by using a lattice-structured forest model. A pair approximation technique is applied to predict the dynamics of gap formation, gap expansion, regeneration, and gap closure.4. By using data on the age-specific annual fecundity and catches-at-age by each fishery in a cub mackerel population in the Pacific Ocean off Japan during 1970-1992, the long-term fluctuation in impacts of two types of fisheries, the purse-seine fishery and the dip-net fishery, is evaluated.5. Invasion process is analyzed by using a stratified diffusion model, in which both the short and long range dispersals are taken into account. Applying models to the invasion of the House Finch, the effects of long- and short- distance dispersals on the range expansion are evaluated separately.