Geography of Korea: I. Natural Environment > 4. Soil and Vegetation > 1) Soil
(1) Soil separates according to general soil characteristics
Factors that determine the characteristics of soil include such things as climate, vegetation, rock forms, and terrain. In terms of its climate and vegetation, the Korean Peninsula’s representative soil type is brown earth. This type of soil is typical of regions with high summer temperatures and ample rainfall distribution, and in Korea can be found throughout the peninsula’s central and southern regions. In the Kaema Plateau in the north podzol soils are well developed, reflecting the area’s low temperatures and rich organic matter.
Because the most basic component of soil is rock, the properties of any given soil are intimately related to rock types. In Korea the coarse crystalline granite rock is widely distributed, and in such places the soil is sandy and has good drainage. On the other hand, in regions with microcrystalline gneiss, clayey soils are prevalent.
Terrain conditions also have a significant impact on soil characteristics. River floodplains for instance are rich in alluvial soils due to the sedimentation of the rivers, though the ratios of sand, silt, and clay in these alluvial soils will vary by location. For instance, soils around natural levees are loamy—equal mixtures of sand, silt, and clay, while the soil of backswamps is predominantly clay soil. Due to its good drainage and water-holding capacity, loamy soil makes optimal agricultural fields, whereas clayey soil is often converted to wet paddy fields due to its poor drainage. In the reclaimed land of the southern and western coastal regions saline soil can be found. This is actually quite rich soil once the saline is removed.
(2) Laterite: red soil
Usually termed “loess,” laterite soil or red soil is found extensively in regions of gently sloping, low-lying hills (under 150 meters in altitude). The laterite soil layer is about 1–1.5 meters in depth, with the topsoil portion red in color, and the subsoil portion a red to reddish-yellow color. A distinguishing characteristic of laterite soil is its heavy clay component, this due to the fact that it is weathered gneiss. Soil created by weathered granite has a heavy sand component and is gravelly soil.
Another characteristic of laterite soil from weathered gneiss is that it does not exhibit soil layering. While laterite soil has extremely low levels of alkalis and organic matter, it is rich in silica, iron oxide, and aluminum oxide. This type of laterite soil is produced under hot and humid climatic conditions. The laterite soil of the Korean Peninsula. There is still wide debate among scholars as to whether these laterite soils were created under the hot and humid conditions that currently characterize the Korean Peninsula or whether they were created in more extreme climatic conditions in the distant past. However, there is broad support of the view that a laterite paleosol was formed during the Cenozoic Tertiary period.
(3) Soil classification according to the new U.S. system of soil taxonomy
In 1975, the United States Department of Agriculture (USDA) introduced its Soil Taxonomy System, a system that classifies soils according to their soil profile. This system has since gained widespread use worldwide and has become a primary classification system in such fields as geography.
According to USDA Soil Taxonomy System, among the 12 soil orders found worldwide, 7 are found in the central and southern Korean Peninsula (i.e. South Korea), namely: Inceptisol, Entisol, Ultisol, Alfisol, Andisol, Mollisol, and Histisol. Among these seven soil orders found in South Korea, the most widespread is Inceptisol, which has no discernible soil layering. Inceptisol covers some 6,670,000 hectares of South Korea, or about 74.71 percent of the national territory (Table 1-5). This reflects the development of Korea’s natural environment, namely, a very mountainous landscape and a climate with rainy summers, resulting in the continual loss of topsoil as well as sedimentation, which hinders the development soil cross-stratification. Further, hot and humid summer climate inhibits the accumulation of layers of organic material, while freezing in winter also makes soil cross-stratification difficult.
|Percentage of total||74.71||15.06||4.99||3.67||1.47||0.09||0.01|
In general, we know that the climatic characteristics of the central and southern regions of the peninsula contribute to the development there of Alfisol and Ultisol soil orders. However, because of Korea’s highly mountainous topography clay minerals tend more often to migrate along the surface rather than vertically. Accordingly, in the southern and central regions of the Korean Peninsula Inceptisols and Entisols are comparatively more widely distributed than Alfisols and Ultisols.