2010 Volume 1 Pages 43-53
To elucidate the effect of inundation on the habitats of various forms of Alnus japonica in wetlands, the tree height, base level of the stem, and upper level of the root system of each A. japonica tree were investigated at 15 sites near the gauge stations of groundwater level in the Kushiro Mire, northern Japan. The base level of the stem was found to be approximately 17 cm higher than the ground surface, and the upper level of the root system was also higher than the base level of the stem. The upper level of the root system was higher than the mean water level, suggesting that the root system may affect the habitat of A. japonica. The frequency of inundation in various periods was calculated for each A. japonica tree and indicated that the population of A. japonica dramatically decreases in the areas inundated from 12 hours to 1 week. In the areas inundated for over 1 week, the population of A. japonica trees in sprouting form was higher than those in single stem form. These results indicate that A. japonica can adapt to the longer inundation environment by germinating in higher ground surface, sprouting roots higher than base level of stem, and growing in sprouting form.