Sowing and transplantation of Adonis ramosa (Ranunculaceae) for the establishment of a new population in a seminatural broad-leaved deciduous forest floor

Adonis ramosa (Ranunculaceae) is a plant whose risk of extinction is increasing in Japan. In this study, we show that there is a significant possibility of establishing an A. ramosa population by sowing seeds or transplanting plants in a seminatural broad-leaved deciduous forest floor. Immediately after seed collection in early June, seeds were sown either in pots that were watered periodically or in a deciduous forest floor where the soil surface was prepared. In the following spring, 30–40% of the seeds germinated. Of the one-year-old plants buried at a depth of 2 cm and two-year-old plants buried at a depth of 2 or 8 cm in the fall, 96% sprouted leaves in the following spring. However, 79% of the one-year-old plants buried at a depth of 8 cm sprouted leaves. In spring, the number of leaves, the widths of individual plants, and the heights of the two-year-old plants were greater than those of the one-year-old plants. The dry weights of one- and two-year-old plants in fall after one spring growing season increased by 1.6–2.3 times and by 2.3–5.1 times, respectively, compared to the dry weight at the time of transplanting. Also, the dry weights of the plants transplanted at a depth of 8 cm were higher than those of plants transplanted at a depth of 2 cm for both one- and two-year-old plants. The results suggest that the growth conditions at a depth of 8 cm are more favorable than those at a depth of 2 cm.