History of Japan Ancient Japan to 1185

Soils of Japan

The soils of Japan are customarily divided from northeast to southwest into a weak podzolic (soils with a thin organic mineral layer over a gray leached layer) zone, a brown earth zone, and a red earth zone. There are some local variations. The northern half of the Tōhoku area of northern Honshu is included in the area of brown forest soils. The northern tip of Hokkaido is classed as a subzone of the podzolic soils; the remainder of the island is included in the subzone of the acidic brown forest soils. Most of western Honshu is a transitional zone. Yellow-brown forest soils extend along the Pacific coast from southern Tōhoku to southern Kyushu, while red and yellow soils are confined to the Ryukyu Islands. The widespread reddish soils are generally regarded as the products of a former warmer, more humid climate. Immature volcanic ash soils occur on the uplands.
Kuroboku soils (black soils rich in humus content) are found on terraces, hills, and gentle slopes throughout Japan, while gley (sticky, blue-gray compact) soils are found in the poorly drained lowlands. Peat soils occupy the moors in Hokkaido and Tōhoku. Muck (dark soil, containing a high percentage of organic matter) and gley paddy soils are the products of years of rice cultivation. Polder soils (those reclaimed from the sea) are widely distributed. Soil fertility increases in the lowlands where agriculture is practiced, the result of a combination of natural alluvium washed down from the uplands and centuries of intense reworking of the soil medium by rice farmers.

Climate

In general, Japan’s climate is characterized as monsoonal (i.e., governed by wet and dry seasonal winds). The main influences are the country’s latitudinal extent, the surrounding oceans, and its proximity to the neighbouring Asian landmass. There are numerous local climatic variations, the result of relief features. In winter the high pressure zone over eastern Siberia and the low pressure zone over the western Pacific result in an eastward flow of cold air (the winter monsoon) from late September to late March that picks up moisture over the Sea of Japan. The winter monsoon deposits its moisture as rain or snow on the side of Japan facing the Sea of Japan and brings dry, windy weather to the Pacific side. The pressure systems are reversed during the summer, and air movements from the east and south (the summer monsoon) from mid-April to early September bring warmer temperatures and rain. Cyclonic storms and frequent and destructive typhoons (tropical cyclones) occur during late summer and early fall, especially in the southwest.
The warm waters of the Kuroshio (Japan Current), which corresponds in latitude and general directional flow to the Gulf Stream of the Atlantic, flow northward along Japan’s Pacific coast as far as latitude 35° N. The Tsushima Current branches westward from the Kuroshio off southern Kyushu and washes the coasts of Honshu and Hokkaido along the Sea of Japan; it is this current that lends moisture to the winter monsoon. The Pacific counterpart of the Atlantic’s Labrador Current, the cold Oya (Kuril) Current, flows southeastward from the Bering Sea along the east coast of Hokkaido and northeastern Honshu. Its waters meet those of the Kuroshio, causing dense sea fogs in summer, especially off Hokkaido.