Seedling emergence of Betula maximowicziana following human disturbance and the role of buried viable seeds

We observed seed rain and seedling emergence of a pioneer tree species, Betula maximowicziana Regel., for 5 years at various sites differing in canopy and soil surface conditions, and clarified that a buried seed bank contributed to the recruitment of B. maximowicziana seedlings. More seedlings emerged at sites where the soil surface had been disturbed than at sites where the soil surface had not been disturbed. Within each soil surface condition, the densities of the emerged seedlings were generally proportional to the densities of the seeds dispersed the previous year. However, the seedling densities were disproportionately higher than the dispersed seed densities at the sites where the soil surface had been disturbed in the previous year. Soil samples taken during different seasons indicated that B. maximowicziana maintained a persistent seed bank in the soil below 1 cm deep, while it formed a more transient seed bank in the top 1 cm of the soil. The seed rain in the previous year was the primary contributor to the establishment of B. maximowicziana seedlings in a year after a mast seed year. On the other hand, the soil seed bank had a compensational role in a year after a poor seed year. Canopy cover did not affect seedling emergence. Therefore, the previously reported lack of a persistent seedling bank of B. maximowicziana under a canopy will be partially attributed to a relatively rare soil surface disturbance in a stable stand.