Microenvironmental conditions for Japanese alder seedling establishment in a hummocky fen
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In this article, we focused on hummocky microtopography as a prominent feature of mires and explored the microenvironmental conditions suitable for alder seedling establishment. Japanese alder (Alnus japonica) forest is widely distributed in wetlands in northern Japan. However, because alder seedlings are rare in mires, alder population dynamics and conditions that favor the establishment of alder seedlings are still unknown. The study was conducted in northern Japan at a site in mesotrophic mire. We surveyed the seedling density, the microenvironmental conditions (light, litter cover, and soil quality), and the density of dispersed seeds in alder forest and in the adjacent herbaceous fen. In addition, we performed a laboratory experiment to examine the germination characteristics of alder. Seedlings grew only on hummocks in alder forest. The percentage of litter cover on hummocks was lower than in hollows, and the density of dispersed seeds in alder forest was much higher than in herbaceous fen. Seeds of Japanese alder germinated under both light and dark conditions, and the germination rate were high under light and high-temperature conditions. Our results suggest that litter cover may inhibit seedling establishment and hummocks that characterized by less litter cover are suitable place for the establishment of seedlings. We conclude that hummocky microtopography and abundant seed rain in the mire enable the establishment of Japanese alder seedlings.
KeywordsAlnus japonica Germination characteristics Hummock Hollow Litter
The authors thank Kazuo Yabe of Sapporo City University and Takatoshi Nakamura of Tokyo University of Agriculture for providing advice on the field surveys, Yuki Tamura of Kankyo Consultants Corporation and Mayumi Kubo of Hokkaido University for helping with the field surveys, Yutaka Tamai and Tetsuya Kondo of Hokkaido University for providing advice on the germination experiments, and Hiroko Fujita and Junko Morimoto of Hokkaido University for providing helpful comments that improved the manuscript.
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