Abstract
This report summarizes the study on the movement of Na, Fe, Mn, Zn, Cu, Co, and Ni in the grassland ecosystems of P. longivalvis, R. sachalinensis and S. purpurascens in Obihiro and on the ability of their surface soils to supply minor elements. 1. The Na, Mn, Co and Ni contents in the litter of R. sachalinensis were the highest of the three species but there were no significant differences of those elements between P. longivplvis and S. purpurascens. The Fe and Zn contents in the litter of S. purpurascens showed highly significant difference from each other. There was no significant difference among the Cu contents in the litter of the three species. 2. As the soil horizon goes down to H, the Na, Fe, Mn, Zn, Cu Co and Ni contents increase steadily and show maximum values at H or A_0, but exchangeable Na decreases and shows maximum values at H or A_0. 3. The Na, Fe, Mn, Zn, Co and Ni contents in the litter of the there species are 0.123-0.278%, 181.7-260.8ppm, 27.1-139.6ppm, 18.0-41.1ppm, 11.3-12.5ppm, 0.43-0.53ppm and 0.33-0.48ppm respectively. Therefore, in the present time three are no deficiency of minor elements in this area. 4. Annual addition of minor elements is very large in the R. sachalinensis grassland. It is medium in the P. longivalvis grassland, while the S. purpurascens grassland shows small addition. 5. Since it takes a period of about each 0.693/r, 3/r and 5/r years to release and accumulate 50, 95 and 99% of its steady state level, their estimates for Na, Fe, Mn, Zn, Cu, Co and Ni in the three grassland ecosystems are as in Table 3. 6. The models of release and accumulation of Na and minor elements on the grassland floor are expressed as the equations (1) to (14). 7. The amount of minor elements in the surface soils of those three grasslands, when put to the plow or to the harvester, may decrease to 1% of the steady state level after about 50 to 310 years.
