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

火山具有广泛的环境梯度，如火山沉积物的厚度，这表明该地区是调查不同微地形长期变化的植物与菌根关系的便利工具。基于这些考虑，本文对火山植物群落动态进行了研究。主要研究结果如下：1.在林下、细沟、平原等微生境中，在草地、草地和森林中设置了固定样地，考察了微生境与优势植物之间的关系。小生境是影响早期建树的最重要因素。此外，菌根的分布与微地形有关。2.挖掘所有优势种子植物和其他一些共生体，研究菌根在每个植物群落中的根部定植情况。菌根定殖率的量化是用菌根定殖率代替网目计数法，因为初步实验表明计数是不合适的。通过这种方式，外生菌根在一些从未报道过的草本植物上定居。3.内生菌根被认为主要是从土壤中吸收磷酸盐，并将多余的磷酸盐供应给营养贫乏环境中的植物。测定总有机质、总氮、可溶性磷酸盐等。氮素含量随着海拔的升高而增加，菌根出现的频率也随之增加。而海拔与内生菌根的分布没有显著关系。4.在上述研究成果和文献的基础上，对早期火山演替的特征进行了综述。特别讨论了生物入侵，如科马山上的日本落叶松，以及菌根对生物入侵的重要性。

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.