Abstract
According to my annual survey, the number of the flowering plants of Aster kantoensis Kitamura on the Tame River floodplain declined from 45, 000 in 1991 to 175 in 2001. Experiments were made in 2001 to create habitats for A. kantoensis. After cutting down trees, mostly Robinia Pseudo-acacia L., and taking the surface sand away, five types of gravel dry river bed were prepared; Type A: no treatment, Type B: covered with one layer of large stones (D>10cm), Type C: one layer of stones of different sizes (D>7cm), Type D: fine sand deposits and Type E: three layers of large stones. The rate of emergence 8 days after the sowing was the highest in Type B (29%), followed by Types C, E, A and D in the order. As fine particle deposits under stones had higher moisture contents than uncovered deposits, the favorable emergence rates in Types B and C are attributable to the covering effects of stones.
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