The role of mycorrhiza on the invasion of seed plants on volcanoes

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There are wide environmental gradients on volcanoes, e.g., thickness of volcanic deposits, indicating that the areas are convenient tools for the survey on the relationships between plants and mycorrhizae with different microtopography for long-term changes. Based on these consideration, I research the plant community dynamics on volcanoes. The major results are as follows :1.Permanent plots were set up in bareground, grassland and forest in some microhabitats, i.e., understory, rill, flat, etc., to examine the relationship between microhabitats and dominant plants. The microhabitat is most important factor on tree establishment in the early stages. Furthermore, the distribution of mycorrhizae is related to microtopography.2.All dominant seed plants and some other cohabitants were excavated to examine mycorrhizal colonization on roots in each plant community. The quantification of mycorrhizal colonization was made by the frequency of root fragments colonized by mycorrhizae, instead of mesh counting method, because preliminary experiment showed that counting is inappropriate. By this way, ectomycorrhizae colonized on a few herbs that have never been reported.3.Endomycorrhizae have been considered mostly to uptake phosphates from soil and supply the excess phosphates to plants in nutrient-poor environments. The total organic matter, total nitrogen, soluble phosphates, etc. were measured. Nitrogen increased with increasing elevation, and frequency of endomycorrhiza increased. While, there was no significant relationship between elevation and endomycorrhiza frequency.4.Based on those results and literatures, the characteristics of early volcanic succession were reviewed. In particular, biological invasion, e.g., Larix kaempferi on Mount Koma, and the importance of mycorrhizae for biological invasion were discussed.