Interactions between biological invasion and scale-dependent environments in the early stages of succession

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Biological invasion (BC) means that non-native species establishes in natural ecosystems via human impacts. In particular, BC is remarkable on severely-disturbed communities in the early stages of succession. The mechanisms are related to various spatial scales from microtopography to landscape. This study compares plant communities between Mount Usu where BC is not conspicuous and Mount Koma where BC is conspicuous, to clarify the significant differences between native and non-native species with different environmental scales. The abstracts of published papers are as follows : 1) On Mount Koma after the 1996 eruptions as well as Mount Usu, vegetative reproduction contributes revegetation more than sexual reproduction. In addition, microtopography is important to determine the community development. 2) Mycorrhizal colonization differs along elevational gradient. I confirmed that a few vascular plant species that have not been reported were inoculated by mycorrhiza. The contribution of mycorrhiza on the growth of larch was low. 3) Temporal changes in the characteristics of survival and germination on seedbank are greatly related to the experienced environments, such as temperature fluctuations. 4) BC species have higher survival rates than native species by higher morphological plasticity adapted to various disturbances and stresses, such as strong wind, drought and low nutrients.Based on those results, top-down and bottom-up analyses have been conducted on the interactions between different scales. Weather conditions have been measured by weather stations purchased by this grant on Mount Koma. By the combinations of those results, I completed that the quantification of the interactions on various life history stages (seed dispersal, germination, establishment and growth) under certain environmental gradients, e.g., ground surface moisture and microtopography.