Distribution of different mycorrhizal classes on Mount Koma, northern Japan.

To investigate the role of mycorrhizae in nutrient-poor primary successional volcanic ecosystems, we surveyed mycorrhizal frequencies on the volcano Mount Koma (42 degrees 04'N, 140 degrees 42'E, 1,140 m elevation) in northern Japan. After the 1929 eruptions, plant community development started at the base of the volcano. Ammonia and nitrate levels, along with plant cover, decreased with increasing elevation, whereas phosphorus did not.