and buildings or to create artificial topography for recreation
areas consist of the same soil materials as at the excavated
site. In such cases, the soil profile can be classified as the
original soil with a description of the soil phase as a
Human-made soil phase. Banking soil is not called Reformed
soil when there is consistency between the dressed soil and
the underlying soil; instead, it is usually named according to
the properties of the filled and covered soils. Soil dressing
using soil excavated from nearby hills, mountains, and terraces is a common practice when constructing greenery areas.
The soils formed by these civil engineering works do not fit
the definition of Reformed soils or Artifactual soils because of
the vertical consistency of soil materials.
(2) Distribution of Human-made soils in Japan
Based on the Soil Classification System of Japan, the area of
Human-made soils is estimated to be less than 1% of Japan’s
total land area, indicating that the Human-made soils are sporadically distributed in civil engineering areas. The Soil Classification System of Japan states that the distribution of
Human-made soils is unknown because of the scarcity of
information about soil descriptions and general soil physicochemical properties of such soils (The Fifth Committee for Soil
Classification and Nomenclature 2017). Furthermore, there is
no surveillance of the present status of Human-made soils in
urban, industrial, traffic, mining, and waste disposal areas. The
acquisition of further data and information about these soils is
required in order to recognize them in spite of the difficulties
involved with conducting soil surveys in these types of areas.
About half of the excavated soil released from civil
engineering works in Japan are not used for banking at the
excavated site, but rather are moved to landfill areas, commonly along the sea coast. Some greenery areas in reclamation areas can have Artifactual soils in the case of mixing
with plenty of construction debris as artifacts within a proposed depth. Reclamation areas also have a role as a final
disposal site, which results in the presence of artifacts in the
soil. Soils mounded on ground using excavated soil can be
classified as Reformed soils in greenery areas. However,
irregular thickness of covered soil volume can cause the
sporadic distribution of Human-made soils in artificial
greenery areas used as urban parks and artificial forests.
Although a land use map is one possible way to estimate the
area and distribution of Human-made soils, the irregularity of
artifacts or top-dressed soil materials brought by the process
of civil engineering works make it difficult to estimate them
through soil surveys. This is also one of the barriers to recognizing Human-made soils and is different from the case of
other soils in Japan. Other soil types are usually expressed on
a soil map containing topographical information because this
can indicate the distribution of their soil parent materials.
4.1.5 Land Uses of Human-Made Soils
Unlike most soils, the properties of Human-made soils
usually depend on the land use. Any land uses that require
appropriate soil management create Human-made soils
through civil engineering processes. However, in order to
achieve stable ground for land-use purposes, civil engineering usually forms Artifactual soils with highly compacted subsoil and a soil profile consisting of unexpected
combinations of soil horizons. In this case, the Human-made
soil is not suitable for plant growth. After the construction of
Human-made soils, the soil is usually no longer suitable for
primary productivity. A suitable civil engineering process is
necessary to construct a greenery area on landfill with waste
disposal or on soil remaining after civil engineering.
Although land uses such as urban, industry, and traffic
have replaced land uses for primary production in Japan’s
modern history, this trend will not continue in the future. It is
necessary to consider land use change from the opposite
direction. We are facing population decline accompanied by
the downsizing of urban areas. A strategy for shifting land
use may be required in the near future. Soil information for
anthropized land should be collected for future land-use
planning.
4.2 Organic Soils
4.2.1 Definition and Classification of Organic
Soils in Japan
Organic soils form under wetland conditions where the rate
of organic matter production exceeds the rate of organic
matter decomposition, and when composed of partially
decomposed hygrophytes, they are regarded as peats (Buol
et al. 2011).
The Soil Classification System of Japan states that soils of
the Organic soil great group must meet one of the following
criteria (The Fifth Committee for Soil Classification and
Nomenclature 2017):
(1) The thickness of Organic soil material totals 25 cm or
more between the surface and a depth of 50 cm; or
(2) When non-organic soil material is dressed for less than
35 cm, the thickness of organic soil material total
25 cm or more consecutively below this non-organic
soil material.
Organic soil material is mainly made up of undecomposed or decomposed plant materials that accumulated
underwater and satisfy all of the following criteria:
74
Y. Takata et al.
areas consist of the same soil materials as at the excavated
site. In such cases, the soil profile can be classified as the
original soil with a description of the soil phase as a
Human-made soil phase. Banking soil is not called Reformed
soil when there is consistency between the dressed soil and
the underlying soil; instead, it is usually named according to
the properties of the filled and covered soils. Soil dressing
using soil excavated from nearby hills, mountains, and terraces is a common practice when constructing greenery areas.
The soils formed by these civil engineering works do not fit
the definition of Reformed soils or Artifactual soils because of
the vertical consistency of soil materials.
(2) Distribution of Human-made soils in Japan
Based on the Soil Classification System of Japan, the area of
Human-made soils is estimated to be less than 1% of Japan’s
total land area, indicating that the Human-made soils are sporadically distributed in civil engineering areas. The Soil Classification System of Japan states that the distribution of
Human-made soils is unknown because of the scarcity of
information about soil descriptions and general soil physicochemical properties of such soils (The Fifth Committee for Soil
Classification and Nomenclature 2017). Furthermore, there is
no surveillance of the present status of Human-made soils in
urban, industrial, traffic, mining, and waste disposal areas. The
acquisition of further data and information about these soils is
required in order to recognize them in spite of the difficulties
involved with conducting soil surveys in these types of areas.
About half of the excavated soil released from civil
engineering works in Japan are not used for banking at the
excavated site, but rather are moved to landfill areas, commonly along the sea coast. Some greenery areas in reclamation areas can have Artifactual soils in the case of mixing
with plenty of construction debris as artifacts within a proposed depth. Reclamation areas also have a role as a final
disposal site, which results in the presence of artifacts in the
soil. Soils mounded on ground using excavated soil can be
classified as Reformed soils in greenery areas. However,
irregular thickness of covered soil volume can cause the
sporadic distribution of Human-made soils in artificial
greenery areas used as urban parks and artificial forests.
Although a land use map is one possible way to estimate the
area and distribution of Human-made soils, the irregularity of
artifacts or top-dressed soil materials brought by the process
of civil engineering works make it difficult to estimate them
through soil surveys. This is also one of the barriers to recognizing Human-made soils and is different from the case of
other soils in Japan. Other soil types are usually expressed on
a soil map containing topographical information because this
can indicate the distribution of their soil parent materials.
4.1.5 Land Uses of Human-Made Soils
Unlike most soils, the properties of Human-made soils
usually depend on the land use. Any land uses that require
appropriate soil management create Human-made soils
through civil engineering processes. However, in order to
achieve stable ground for land-use purposes, civil engineering usually forms Artifactual soils with highly compacted subsoil and a soil profile consisting of unexpected
combinations of soil horizons. In this case, the Human-made
soil is not suitable for plant growth. After the construction of
Human-made soils, the soil is usually no longer suitable for
primary productivity. A suitable civil engineering process is
necessary to construct a greenery area on landfill with waste
disposal or on soil remaining after civil engineering.
Although land uses such as urban, industry, and traffic
have replaced land uses for primary production in Japan’s
modern history, this trend will not continue in the future. It is
necessary to consider land use change from the opposite
direction. We are facing population decline accompanied by
the downsizing of urban areas. A strategy for shifting land
use may be required in the near future. Soil information for
anthropized land should be collected for future land-use
planning.
4.2 Organic Soils
4.2.1 Definition and Classification of Organic
Soils in Japan
Organic soils form under wetland conditions where the rate
of organic matter production exceeds the rate of organic
matter decomposition, and when composed of partially
decomposed hygrophytes, they are regarded as peats (Buol
et al. 2011).
The Soil Classification System of Japan states that soils of
the Organic soil great group must meet one of the following
criteria (The Fifth Committee for Soil Classification and
Nomenclature 2017):
(1) The thickness of Organic soil material totals 25 cm or
more between the surface and a depth of 50 cm; or
(2) When non-organic soil material is dressed for less than
35 cm, the thickness of organic soil material total
25 cm or more consecutively below this non-organic
soil material.
Organic soil material is mainly made up of undecomposed or decomposed plant materials that accumulated
underwater and satisfy all of the following criteria:
74
Y. Takata et al.