Abstract
1. This investigation is carried out to clarify the cycles of organic nitrogen under the grassland ecosystems of P. longivalvis, P. sachalinensis and S. purpurascens at the Satsunai Riverside. 2. The basic differential equation for the rate of change in nitrogen storage is [Table] illustrated by build-up and turnover of organic nitrogen, particularly in three grassland ecosystems. The equations of (9), (10), (11), (12), (13) and (14) are derived from the the basic concepts of the equations (1), (2) and (3). 3. The turnover velocity fractions of nitrogen for the P. longivalvis, R. sachalinensis and S. purpurascens grasslands were r=0.148, r=0.239 and r=0.077 respectively. 4. The times required to reach 50, 95 and 99 percent to steady state levels and turnover values of nitrogen on the grassland floors are as follows: 5. The amounts of annual cycles of nitrogen are 4.047, 6.993 and 1.528g N/m^2 in the P. longivalvis-, R. sachalinensis- and S. purpurascens grasslands respectively.
