Abstract The benefits of living mulches include not only soil erosion control and less use of herbicides but also preservation of soil organisms, which may result in improved soil productivity and sustainability. The effect of the use of living mulch of white clover (Trifolium repens L.) on the abundance of various components of the soil detritus food web was studied in maize cropping on Andosols for 2 years. Microbial substrate-induced respiration (SIR) and population densities of protozoa (flagellates, naked amoebae, ciliates), nematodes, and microarthropods (mites, collembolans), which were measured at about 1-month intervals in both years, were increased by the use of living mulch. The communities of soil organisms under the white clover living mulch systems was at a more mature stage of succession, and characterized by the enhancement of fungal pathway of organic matter decomposition and the high population density of higher trophic groups, such as mesostigmatid mites and ciliates. Higher litter decomposition rate under living mulch plots compared with no-living mulch plots, determined by a litterbag method, suggested that the function of the detritus food web was enhanced under the living mulch system. On the other hand, inorganic fertilization increased only nematodes and mesostigmatid mites in mid-summer, which was possibly attributed to better maize growth resulted from inorganic fertilization, and had neither positive nor adverse effect on other soil biological groups. It is suggested that the use of white clover living mulch in maize cropping may preserve soil organisms without reducing productions, if adequately fertilized. Keywords: Living mulch; Soil biota; Soil ecology

Research Project , Research Report 2003

Masahiko OHSAWA Institute of Environmental Sciences, Graduate School of Frontier Sciences, the University of Tokyo
Kenji FUKUDA Institute of Environmental Sciences, Graduate School of Frontier Sciences, the University of Tokyo

Abstract

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.

Keywords:

Altitudinal zonation, Forest zone, Fagus crenata, Castanopsis sieboldii, soil invertebrates, ectomycorrhiza