reductive soil conditions unfavorable for plant growth.
When the artifact content is higher in subsoil horizons, the
soil is referred to as Artifactual soil. Artifacts originating
from construction debris promote soil alkalinization,
adversely affecting plant growth.
If the covered soil has properties similar to those of base
soils taken from near the reclamation area, it cannot be
classified as Human-made soil, but rather as the soil great
group of the base soils with supplementary description of a
soil phase. For example, although urban forestry parks in
Tokyo have undergone various changes in land use
throughout their history, accompanying large-scale earthworks and constructions that have left records in the soil, the
soil is classified not as Human-made soil, but rather as
Andosol (Kawai et al. 2015).
The area of human-modified land extends along river and
sea coasts because of protection against flood and tsunami
and on mountain hills because of construction of recreation
areas such as golf courses and ski slopes accompanied by
land form modification. Human-modified soils associated
with large-scale civil engineering works are also highly
compacted, leading to a high bulk density and undeveloped
soil structure (Ono et al. 2018). The soil condition leads to
severe surface soil erosion under low vegetation density,
resulting in a low stock of organic carbon and low-fertility
soils (Uoi et al. 2013). After construction of the land, periodic assessment for monitoring of the physical and chemical
properties of the soil is necessary for disaster prevention.
4.1.2 Significance in the Classification System
(1) Change in the concept of Human-made soils
In Japanese soil classification systems, as well as in the
United States Department of Agriculture (USDA) and WRB
soil classification systems, new revisions of the soil classification system always include major and/or minor changes
regarding Human-made soils. This means that the definition,
criteria, and concept of Human-made soils are still under
debate in most soil classification systems. Since the impact
of human activity on agricultural soils has long been recognized in Japan, Reformed soils were separated from other
soil great groups in the revised second version of the Classification of Cultivated Soils in Japan (Cultivated Soil
Classification Committee 1983). The agricultural reformation process was considered as a special activity to produce
flat land for agriculture in Japan, which is dominated by
mountainous terrain. On the other hand, in the same period,
soils affected by anthropogenic activities have been classified as subgroups in the immature soil group [Regosols in
WRB (FAO 1998) and Entisols in the USDA (Soil Survey
staff 1999)] in the old version of the soil classification system released by the USDA and FAO. In the twenty-first
century, the impact of humans on soil formation processes
has been discussed in a broad sense, including
non-agricultural areas in the soil classification systems. In
the Unified Soil Classification System of Japan (second
approximation) of 2002 (The Fourth Committee for Soil
Classification and Nomenclature, Japanese Society of
Pedology 2002), artifact contents and banking of transported
soil materials were addressed as diagnostics to identify a
surveyed soil as a Human-made soil at the first stage when
the soil is classified. The Human-made soil great group is
keyed out first in the Soil Classification System of Japan
because human activity has been considered as a strong
affecting factor to differentiate Human-made soils from the
other soil great groups, which arise from pedogenic processes under natural conditions and/or agricultural management. This classification system is considered well about
human impact on soil in categorizing Human-made soils,
because human activity had not been sufficiently discussed
to classify Human-made soils in the international soil classification systems.
(2) Relationship between Human-made soils and other
soil groups
When diagnostic properties relating to pedogenic processes
are recognized in soils under anthropogenic activities, the
soils are not classified as Human-made soils, but rather as
another soil type having specific diagnostic properties, indicating that no soil formation processes have ever been recognized for Human-made soil. Soil formation processes
occurring in a soil have higher priorities in the classification
and/or characterization of soils than any soil construction
processes. Although human activity has a crucial influence on
soils, it is not one of the soil-forming factors in the history of
the Japanese soil classification system. Soils that have been
artificially constructed by human activity are also naturally
processed under climatic pedogenic factors. The concept of
Human-made soil, which is considered as immature soil
without any changes in soil, is the same as the concept of
anthropogenic soils in the USDA Soil Taxonomy (Soil Survey Staff 2014) and WRB (IUSS Working Group WRB
2006).
4 Major Soil Types
71
When the artifact content is higher in subsoil horizons, the
soil is referred to as Artifactual soil. Artifacts originating
from construction debris promote soil alkalinization,
adversely affecting plant growth.
If the covered soil has properties similar to those of base
soils taken from near the reclamation area, it cannot be
classified as Human-made soil, but rather as the soil great
group of the base soils with supplementary description of a
soil phase. For example, although urban forestry parks in
Tokyo have undergone various changes in land use
throughout their history, accompanying large-scale earthworks and constructions that have left records in the soil, the
soil is classified not as Human-made soil, but rather as
Andosol (Kawai et al. 2015).
The area of human-modified land extends along river and
sea coasts because of protection against flood and tsunami
and on mountain hills because of construction of recreation
areas such as golf courses and ski slopes accompanied by
land form modification. Human-modified soils associated
with large-scale civil engineering works are also highly
compacted, leading to a high bulk density and undeveloped
soil structure (Ono et al. 2018). The soil condition leads to
severe surface soil erosion under low vegetation density,
resulting in a low stock of organic carbon and low-fertility
soils (Uoi et al. 2013). After construction of the land, periodic assessment for monitoring of the physical and chemical
properties of the soil is necessary for disaster prevention.
4.1.2 Significance in the Classification System
(1) Change in the concept of Human-made soils
In Japanese soil classification systems, as well as in the
United States Department of Agriculture (USDA) and WRB
soil classification systems, new revisions of the soil classification system always include major and/or minor changes
regarding Human-made soils. This means that the definition,
criteria, and concept of Human-made soils are still under
debate in most soil classification systems. Since the impact
of human activity on agricultural soils has long been recognized in Japan, Reformed soils were separated from other
soil great groups in the revised second version of the Classification of Cultivated Soils in Japan (Cultivated Soil
Classification Committee 1983). The agricultural reformation process was considered as a special activity to produce
flat land for agriculture in Japan, which is dominated by
mountainous terrain. On the other hand, in the same period,
soils affected by anthropogenic activities have been classified as subgroups in the immature soil group [Regosols in
WRB (FAO 1998) and Entisols in the USDA (Soil Survey
staff 1999)] in the old version of the soil classification system released by the USDA and FAO. In the twenty-first
century, the impact of humans on soil formation processes
has been discussed in a broad sense, including
non-agricultural areas in the soil classification systems. In
the Unified Soil Classification System of Japan (second
approximation) of 2002 (The Fourth Committee for Soil
Classification and Nomenclature, Japanese Society of
Pedology 2002), artifact contents and banking of transported
soil materials were addressed as diagnostics to identify a
surveyed soil as a Human-made soil at the first stage when
the soil is classified. The Human-made soil great group is
keyed out first in the Soil Classification System of Japan
because human activity has been considered as a strong
affecting factor to differentiate Human-made soils from the
other soil great groups, which arise from pedogenic processes under natural conditions and/or agricultural management. This classification system is considered well about
human impact on soil in categorizing Human-made soils,
because human activity had not been sufficiently discussed
to classify Human-made soils in the international soil classification systems.
(2) Relationship between Human-made soils and other
soil groups
When diagnostic properties relating to pedogenic processes
are recognized in soils under anthropogenic activities, the
soils are not classified as Human-made soils, but rather as
another soil type having specific diagnostic properties, indicating that no soil formation processes have ever been recognized for Human-made soil. Soil formation processes
occurring in a soil have higher priorities in the classification
and/or characterization of soils than any soil construction
processes. Although human activity has a crucial influence on
soils, it is not one of the soil-forming factors in the history of
the Japanese soil classification system. Soils that have been
artificially constructed by human activity are also naturally
processed under climatic pedogenic factors. The concept of
Human-made soil, which is considered as immature soil
without any changes in soil, is the same as the concept of
anthropogenic soils in the USDA Soil Taxonomy (Soil Survey Staff 2014) and WRB (IUSS Working Group WRB
2006).
4 Major Soil Types
71