Yakushima

Japanese: 屋久島 - やくしま

It is a nearly circular island located in the ocean about 60 km south of Cape Sata in Kagoshima Prefecture (its northern tip is around 30 degrees 30 minutes north latitude), and is one of the Osumi Islands. Its area is 504.88 square kilometers. Its highest point is Miyanoura-dake, which is 1,936 meters high and is the highest point in Kyushu. It belongs to Yakushima Town, Kumage District, Kagoshima Prefecture. In contrast to Tanegashima Island, which is 20 kilometers to the east and has a long, low, flat terrain, the main island is a mountainous island with a steep terrain, with more than 30 mountain peaks over 1,000 meters high. Except for a part of the northwestern part, the Kumage Group (Cretaceous to Paleogene) and terrace deposits that form the base of the island can be seen around the island, but the inner mountain area is covered entirely by intrusive granite. The topographical and geological differences between Yakushima and Tanegashima are due to the presence or absence of these intrusive rocks. The climate of the main island is complex due to these unique topographical features. It is well known that the island receives a lot of precipitation, with the average annual value exceeding 4,000 mm in coastal areas. In the interior highlands, it is estimated that the amount is more than twice that. This is due to the high number of days with rain, as expressed in the popular proverb, "It rains 33 days a month on Yakushima." It is worthy of being called an island of mountains and water. The annual average temperature on the coast is about 19°C, and even in the coldest month, there are few days when the temperature drops below 10°C. However, due to the altitude in the interior, snowfall and accumulation occurs. These topographical and climatic conditions give the island a strikingly distinctive distribution of vegetation. The first 200 meters from the edge are subtropical vegetation such as Ako, Gajumaru, and Hego trees, 200-800 meters are warm temperate forests such as camphor and chinquapin, from there to 1600 meters is a Yakusugi zone, and above that is a zone of rhododendrons and Yakuzasa. Agriculture is carried out on the coastal terraces on the edge, where sugarcane, sweet potatoes, citrus fruits such as tankan and ponkan, and gajutsu are cultivated. As the interior of the island is national forest, all settlements are scattered along the coast. Population 13,375 (2009). It belongs to Yakushima National Park, and many tourists come to see the flora and fauna and go mountain climbing. There are daily boat services from Kagoshima City, and planes can also be used.

[Kimihiko Tsukada]

Vegetation

Yakushima is home to a variety of plant communities that grow from the subtropics to the subarctic, with a certain vertical distribution. Due to the large amount of rainfall and the nutrient-poor parent rock of granite origin, coniferous forests have developed well on the middle and upper slopes of the island, and the natural forests of Yakusugi (Takasago Fern-Sugi communities and others) that are over 2,000 years old are particularly prominent. Furthermore, on high altitude areas, communities unique to the island, such as Yakushima Rhododendron, Yakushima Bamboo, and Issun Kinka, have developed. The "Yakushima Cedar Primeval Forest" is a special natural monument. Yakushima was registered as a natural World Heritage Site in 1993 (Heisei 5). Nagatahama Beach in the northwest of Yakushima was registered as a Ramsar Convention wetland in 2005.

[Shigetoshi Okuda]

"The Nature of Yakushima" by Kiyoshi Kusada (1984, Yaegake Shobo) " "Yakushima - Nature and Culture" by Koji Matsuda (1985, Nangoku Publishing)

Mount Miyanoura
Yakushima National Park. Part of the World Heritage Site "Yakushima" (registered in 1993) Yakushima Town, Kumage District, Kagoshima Prefecture ©Ministry of the Environment ">

Mount Miyanoura

Jomon Cedar in Yakushima Cedar Primeval Forest
Yakushima National Park. Part of the World Natural Heritage Site "Yakushima" (registered in 1993) Nationally designated special natural monument Yakushima Town, Kumage District, Kagoshima Prefecture © Kagoshima Prefecture Tourism Federation ">

Jomon Cedar in Yakushima Cedar Primeval Forest

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

鹿児島県佐多岬の南約60キロメートルの洋上（北端が北緯30度30分付近）に位置する、ほぼ円形の島で大隅諸島(おおすみしょとう)の1島。面積504.88平方キロメートル。最高点は宮之浦岳(みやのうらだけ)の1936メートル、九州の最高地点である。鹿児島県熊毛(くまげ)郡屋久島町に属する。東方20キロメートルにある種子島(たねがしま)が細長い低平な地形であるのとは対照的に、本島には1000メートルを超す山峰が30座以上もあり、急峻(きゅうしゅん)な地形の山岳島である。北西部の一部を除き島の周囲には基盤をなす熊毛層群（白亜紀から古第三紀）や段丘堆積(たいせき)物がみられるが、内側の山地はすべて貫入した花崗(かこう)岩類で覆われる。種子島との地形・地質上の相違はこの貫入岩の有無に起因する。本島の気候は、これら地形的特異性と相まって複雑である。降水量の多いことはよく知られ、海岸部の平年値でも4000ミリメートルを超える。内部の高地では、その2倍以上とも推定される。これは「屋久島では月に33日雨が降る」という俗諺(ぞくげん)に言い表されるように、降水日数の多いことによる。山と水の島とよぶにふさわしい。気温は、海岸部では年平均19℃ぐらいで最寒月でも10℃を下回る日は少ない。しかし、内部ではその高度のため降雪や積雪もある。これら地形や気候条件により、植生分布に著しい特色がある。縁辺の200メートルまでは、アコウ、ガジュマル、ヘゴなどの亜熱帯植生、200～800メートルは、クス、シイなど暖帯林、そこから1600メートルまでがヤクスギ帯、それ以上がシャクナゲ、ヤクザサ帯となっている。農業は縁辺部の海岸段丘上で行われ、サトウキビ、サツマイモ、タンカン、ポンカンなどの柑橘(かんきつ)類、ガジュツなどが栽培される。集落は、島の内部が国有林であるため、すべて海岸部に分散立地する。人口1万3375（2009）。屋久島国立公園に属し、動・植物相の観賞や登山を目的とする観光客が多い。鹿児島市から毎日船便があり飛行機も利用できる。

［塚田公彦］

植生

屋久島には亜熱帯から亜寒帯にわたって生育する多様な植物群落が一定の垂直分布を示しながら凝集している。多量の降水量と花崗岩起源の貧養性の母岩(ぼがん)のため、中腹以上には針葉樹林がよく発達し、なかでも樹齢2000年以上ものヤクスギの自然林（タカサゴシダ‐スギ群集他）の生育はきわめて顕著である。さらに高海抜地にはヤクシマシャクナゲ、ヤクシマダケ、イッスンキンカといった同島固有の群落が発達している。「屋久島スギ原始林」は特別天然記念物。なお、屋久島は1993年（平成5）、世界遺産の自然遺産として登録されている（世界自然遺産）。また、屋久島北西部の永田浜は、2005年にラムサール条約登録湿地となった。

［奥田重俊］

『日下田紀三著『屋久島の自然』（1984・八重岳書房）』▽『松田幸治著『屋久島――自然と文化』（1985・南国出版）』

宮之浦岳

屋久島スギ原始林の縄文杉

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例

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