Found only in the Chichibu region on the island of Honshu in Japan, Betula chichibuensis is considered a Critically Endangered species. It occurs in subpopulations with very small ranges (<10km2). Recent survey efforts have identified new subpopulations, but the overall range and number of individuals remains low.
This species is a multi-stemmed small tree which can grow up to 10m in height and is monoecious (male and female flowers on the same plant), with creamy yellow male catkins and red female catkins. The tree grows on limestone outcrops and is fairly tolerant of both wet soil and drought. Mature trees are very shade intolerant.
This species is self-compatible, meaning two trees must be close enough to cross-pollinate each other. Because these trees have such small populations, seed production is therefore difficult. Seed collecting and propagation efforts are underway. Despite some successful propagation results, seed viability seems generally low. It is easy to grow this species from cuttings but propagation from seed is the preferred method to maximise genetic diversity.
Betula chichibuensis is under threat from deforestation as well as habitat degradation in the region. It is also vulnerable to natural disaster or disease because of its restricted distribution and small population sizes. This species has no closely related living relatives and is considered a relict species – a remnant of a previously widely occurring, genetically diverse population.
Did you know?
Dayak people believe the Bornean ironwood protects them from dangerous animals, offering their own explanation for the lack of elephants and tigers on Borneo.