Forest ecosystems in Japan are now suffering from various environmental stresses such as global warming, urbanization and invasive diseases. The altitudinal distribution of forests from the warm-temeprate evergreen forest to the cool-temperate deciduous forests in Mt. Tanzawa in Kanto district was investigated with accompanying soil organisms. Major boundary of forest zones was at c. 900 m asl in which evergreen broad-leaved forest is replaced by deciduous broad-leaved forests with a narrow transition zones of Abies firma. In both natural and plantatin forests, population of soil invertebrates declined with altitudes, though the diversity of taxa always higher in natural than plantation. In Tanzawa mountains, decline of Fagus crenata trees results in decrease of diversity of symbiotic ectomycorrhiza on their roots. Along the gradient of urbanization from Kiyosumi (Chiba pref.) to Tokyo, symbiotic ectomycorrhizal fungi in evergreen Castanopsis sieboldii forests are found to be decreasing. In Mt. Tsukuba, where pine wilt disease caused by an introduced pathogen Bursaphelenchus xylophilus is now destroying vast areas of Japanse red pine forests, symbiotic ectomycorrizal fungi are found to be disappearing because of the host tree death. Environmental stresses are found to be causing many kind of impacts not only on forest trees but also on soil ecosystems.
Altitudinal zonation, Forest zone, Fagus crenata, Castanopsis sieboldii, soil invertebrates, ectomycorrhiza