Yakushima's vegetation nurtured by a special mountainous environment and rainy climate
Although Yakushima is located in the subtropics at 30 degrees of latitude, one of its main features is its vertical distribution of all of Japan's climates. For example, while the average annual temperature is about 20 degrees Celsius on the coast, characteristics of subarctic and cold-temperate zones can be found on the island's mountains almost 2,000 meters in height. Also worthy of note is the island's vegetation. Yakushima is home to over 1,900 species of plants, of which over 70 are endemic. There are about 600 species of mosses alone. These play a role in storing water for Yakushima's forests, substituting for the granite soil, which has poor water retention. There are various reasons for the diversity of vegetation on the island, including the presence of mountains high enough for snow to fall in winter, as well as abundant rainfall due to water vapor carried by the warm Kuroshio Current. In addition to the diversity of Yakushima's vegetation, the island is also home to trees of exceptional longevity. For example, many of the Yakushima cedars including the Jomonsugi Cedar are thousands of years old. Why are Yakushima's cedar trees so long-lived? The answer lies in the soil generated from the granite that forms the core of the island. This soil has poor water retention and is low in nutrients, making it seemingly unfit for plant growth. However, since trees grow more slowly due to the harsh environment and soil, their trunks become harder and stronger, promoting production of resin to prevent rotting due to pests and rain. This is one integral factor behind the growth of Yakushima cedar trees several thousands of years old. Yakushima's unique vegetation is the product of multiple specific landforms, meteorological conditions, and geographic conditions almost miraculously coinciding.
References:
Yakushima: Walking on the Island of Trees, Water, and Stones (Iwanami Junior Paperbacks)
Plants of Yakushima (The Yakushima Environmental and Cultural Foundation)
Sumihiko Hatsushima, ed., Plants of Yakushima: New Edition (Nanpou Shinsha)
Illustration = Takashi Taima