Fig. 1

a Location of Torreya Forest in Jeju Island, South Korea. b The 11 plots divided by trails (Lee 2009) were categorized into three sites depending on the sex ratio and DBH gradient by Kang and Shin (2012): Site I in the southern part of the forest including plots 3–5, Site II in the middle part including plots 2–7, and Site III in the northern part including plots 1, 8, 9, and 10