Because Japan stretches from north to south and has mountainous terrain, its biomes change both through latitudinal distribution and through altitudinal distribution.
Basic Knowledge
Latitudinal distribution (change with latitude):
・Subtropical rainforest: Okinawa and the Ogasawara Islands. Akou, banyan, and mangrove trees.
・Laurel forest: Kyushu to Kanto (warm-temperate zone). Sudajii, tabunoki, and arakashi.
・Deciduous broad-leaved forest: Tohoku and southern Hokkaido (cool-temperate zone). Buna, mizunara, and maple.
・Coniferous forest: Eastern and northern Hokkaido (subarctic zone). Ezomatsu and todomatsu.
Altitudinal distribution (change with elevation, central Honshu):
・Hill zone (lowland zone): Up to around 700m. Laurel forest.
・Mountain zone: Around 700–1700m. Deciduous broad-leaved forest (buna and others).
・Subalpine zone: Around 1700–2500m. Coniferous forest (shirabiso and kometsuga).
・Alpine zone: Above 2500m. Above the tree line, there are creeping pine zones and alpine flower meadows.
Because temperature decreases by approximately 0.6℃ for every 100m increase in elevation, mountain climbing allows people to experience a climatic change equivalent to traveling northward in latitude.
Latitudinal distribution (biome changes caused by changes in latitude)
Altitudinal distribution (biome changes caused by changes in elevation)
Hill, mountain, subalpine, and alpine zones (the four divisions of altitudinal distribution)
Tree line (the upper elevation limit at which trees can grow)
Creeping pine zone (a wind-exposed alpine shrub forest in which creeping pine grows along the ground)
Alpine flower meadow (grassland-like vegetation in the alpine zone)
Further Exploration
The distribution of biomes in Japan is determined by the warmth index, the total of (monthly mean temperature−5) for months whose monthly mean temperature exceeds 5℃. It was proposed by geographer Tatsuo Kira. The warmth index ranges are 85–180 for laurel forests, 45–85 for deciduous broad-leaved forests, and 15–45 for coniferous forests.
The elevation of boundaries between zones in altitudinal distribution varies with latitude. The lower the latitude, the higher the boundaries are; at higher latitudes, the boundaries are lower. In central Honshu, the tree line is about 2500m, but on an isolated peak such as Mount Fuji it is nearly 500m lower because of strong winds. Alpine plants in Honshu, such as komakusa, chinguruma, and hakusankozakura, are relict species from the ice age, and their decline due to global warming is a concern.
- Latitudinal distribution runs north and south; altitudinal distribution runs upward and downward
- Central Honshu has four altitudinal zones: hill, mountain, subalpine, and alpine
- The tree line is the upper limit for tree growth
- Above the tree line are creeping pine zones and alpine flower meadows
- A 100m increase means a decrease of about 0.6℃
- Okinawa = subtropical rainforest; Kanto = laurel forest
- Tohoku = deciduous broad-leaved forest; northeastern Hokkaido = coniferous forest
Points to Note
① Do not confuse latitudinal distribution (latitude) with altitudinal distribution (elevation). ② Remember the order in central Honshu—hill zone → mountain zone → subalpine zone → alpine zone—and the corresponding biomes: laurel forest → deciduous broad-leaved forest → coniferous forest → creeping pine and alpine flower meadow. ③ The tree line is the boundary between the alpine and subalpine zones. ④ Temperature decreases by about 0.6℃ per 100m of elevation, nearly the same difference as moving 1 degree north in latitude (about 110km).
Practice
- What is the line at about 2500m that forms the boundary between the subalpine and alpine zones in central Honshu?
- By approximately how many degrees Celsius does temperature decrease when elevation rises by 100m?
- Name one representative tree that forms the mangrove forests of Okinawa or the Ogasawara Islands.