Emergence and settlement of Magnolia kobus in urban forests of Seoul, Korea

Magnolia kobus is a deciduous, broadleaved tree native to Jeju Island of Korea and Japan. The species has been introduced in mainland Korea as a landscape plant, and some individual plants have been found in forests of the mainland. The objective of the present study was to examine whether M. kobus individuals have spontaneously formed communities as part of a natural settlement process. Diameter at breast height (DBH), flower, fruit, and GPS coordinates were recorded for all M. kobus individuals in the study sites. Age of the trees was determined using an increment borer. A total of 158 M. kobus individuals were identified. The reverse J-shaped Diameter at breast height distribution trend was confirmed. DBH and age of M. kobus samples were positively correlated, confirming that the distribution of individuals with varying DBH classes suggested an uneven-aged forest with the coexistence of trees from different generations. In all the survey sites, individuals of M. kobus with small DBH that did not reach inflorescence formation and fructification stages coexisted with individuals that flowered and produced fruits, which suggested the presence of overlapping generations of trees. Therefore, we concluded that M. kobus individuals were forming populations in the forests of mainland Korea.