physical protection of the SOM in stable microaggregates;
(4) the sorption and deactivation of exoenzymes involved in
the extracellular depolymerization process of SOM decomposition; (5) the burial of surface horizons with high SOM
contents by additional tephra deposition; and (6) the presence of microbial-resistant charcoal (Takahashi and Dahlgren 2016).
According to a statistical analysis using data from 293 “A
horizons,” it is considered that, in the humic horizons of
many Andosols, Al–humus complexation strongly contributes to SOM accumulation, and low soil pH and Al
toxicity may be partially responsible for humus accumulation (Takahashi and Dahlgren 2016).
(2) Water storage and water quality improvement
Andosols have well-developed soil structures with various
pore diameters and therefore can hold a large amount of
plant-available water. These soils can supply enough water
to grow most agricultural plants and natural vegetation.
Andosols under forests can decrease flooding during the
rainy season and can relieve water shortage during the dry
season. Shoji and Takahashi (2002) indicated that water
storage is remarkably enhanced when both Andosols and
their substratum are very thick, by using the analytical data
of several factors contributing to the water storage capacity
of forest soils, such as type of soil, depositional mode, type
of substrata, altitude, topography, and so on.
Andosols commonly contain a large amount of
short-range-order minerals (allophane, imogolite, ferrihydrite) which have a large anion exchange capacity and
contain active Al and Fe. These minerals can contribute to
the maintenance and improvement of the quality of
groundwater, river water, and other water bodies by
removing and retaining nitrate and phosphate originating
from fertilizers and other sources.
(3) Amenity in Andosol areas
Among Japan’s 111 active volcanoes, 62 volcanoes are
located in national parks (21 parks), while another 10 active
volcanoes are located in quasi-national parks (9 parks). One
of the purposes of national parks and quasi-national parks is
to restrict development projects and other human activities to
exceptional national landscapes, and another is to foster a
joyful experience of nature, including an appreciation of
landscape (Ministry of the Environment 2017). Thus, many
volcanoes and their surrounding areas including Andosols
are valuable resources for sightseeing and outdoor activities
because of their unique topography and vegetation.
(4) Ancient human activity and Andosols
Intermittent volcanic deposition and repeated pedogenesis
commonly create multi-storied soils in Japan. Multi-storied
Andosols notably resist soil disturbance, truncation, and
displacement by natural and human activities. These facts
contribute to the preservation of heritage.
Many archaeological remains, and artifacts have been
found in Holocene Andosols in Japan. There has been found
to be a close relationship between the distribution of
Jomon-age ruins (ca. 15,000–2300 YBP) and the distribution
of dark-colored Andosols in Japan (Edamura and Kumagai
2009). Therefore, Melanic Andosols are thought to be created under ecosystems largely influenced by human beings
(Hosono and Sase 2015). Thus, dark-colored Andosols can
be regarded as a heritage.
(5) Agricultural use of Andosols
Andosols are among the most productive soils in the world
(Shoji and Takahashi 2002). Andosols in Japan that formed
under a humid-temperate climate were originally regarded as
poorly productive soils because of their very low content of
plant-available phosphorus, low concentrations of
exchangeable bases, and strong acidity. However, these
chemical constraints are easily overcome by the application
of phosphorus fertilizer and liming. Some Andosols are
especially productive for upland crops, and their notable
properties are as follows: soil morphology is pachic (thick
humus-rich horizon); physical properties show a
medium-grained texture, friable consistency, free drainage,
and high plant-available water content; and chemical properties show a high base saturation, a pH(H 2 O) more than 6,
and an absence of toxic Al (Shoji and Takahashi 2002).
Nowadays, Andosols are most extensively used for
high-value horticultural crops, such as cabbage, Chinese
cabbage, Chinese yam, edible burdock, Japanese radish, and
ginger. These are described in detail in the “Andosols in
Tohoku Region” chapter of this book.
4.4 Podzols
4.4.1 Introduction
Podzols, as defined in the Soil Classification System of
Japan and the WRB (IUSS Working Group WRB 2015), or
Spodosols, as defined in the USDA Soil Taxonomy (Soil
Survey Staff 2014), are characterized by the eluviation of
aluminum (Al) and iron (Fe) from the albic E horizon and
90
Y. Takata et al.
(4) the sorption and deactivation of exoenzymes involved in
the extracellular depolymerization process of SOM decomposition; (5) the burial of surface horizons with high SOM
contents by additional tephra deposition; and (6) the presence of microbial-resistant charcoal (Takahashi and Dahlgren 2016).
According to a statistical analysis using data from 293 “A
horizons,” it is considered that, in the humic horizons of
many Andosols, Al–humus complexation strongly contributes to SOM accumulation, and low soil pH and Al
toxicity may be partially responsible for humus accumulation (Takahashi and Dahlgren 2016).
(2) Water storage and water quality improvement
Andosols have well-developed soil structures with various
pore diameters and therefore can hold a large amount of
plant-available water. These soils can supply enough water
to grow most agricultural plants and natural vegetation.
Andosols under forests can decrease flooding during the
rainy season and can relieve water shortage during the dry
season. Shoji and Takahashi (2002) indicated that water
storage is remarkably enhanced when both Andosols and
their substratum are very thick, by using the analytical data
of several factors contributing to the water storage capacity
of forest soils, such as type of soil, depositional mode, type
of substrata, altitude, topography, and so on.
Andosols commonly contain a large amount of
short-range-order minerals (allophane, imogolite, ferrihydrite) which have a large anion exchange capacity and
contain active Al and Fe. These minerals can contribute to
the maintenance and improvement of the quality of
groundwater, river water, and other water bodies by
removing and retaining nitrate and phosphate originating
from fertilizers and other sources.
(3) Amenity in Andosol areas
Among Japan’s 111 active volcanoes, 62 volcanoes are
located in national parks (21 parks), while another 10 active
volcanoes are located in quasi-national parks (9 parks). One
of the purposes of national parks and quasi-national parks is
to restrict development projects and other human activities to
exceptional national landscapes, and another is to foster a
joyful experience of nature, including an appreciation of
landscape (Ministry of the Environment 2017). Thus, many
volcanoes and their surrounding areas including Andosols
are valuable resources for sightseeing and outdoor activities
because of their unique topography and vegetation.
(4) Ancient human activity and Andosols
Intermittent volcanic deposition and repeated pedogenesis
commonly create multi-storied soils in Japan. Multi-storied
Andosols notably resist soil disturbance, truncation, and
displacement by natural and human activities. These facts
contribute to the preservation of heritage.
Many archaeological remains, and artifacts have been
found in Holocene Andosols in Japan. There has been found
to be a close relationship between the distribution of
Jomon-age ruins (ca. 15,000–2300 YBP) and the distribution
of dark-colored Andosols in Japan (Edamura and Kumagai
2009). Therefore, Melanic Andosols are thought to be created under ecosystems largely influenced by human beings
(Hosono and Sase 2015). Thus, dark-colored Andosols can
be regarded as a heritage.
(5) Agricultural use of Andosols
Andosols are among the most productive soils in the world
(Shoji and Takahashi 2002). Andosols in Japan that formed
under a humid-temperate climate were originally regarded as
poorly productive soils because of their very low content of
plant-available phosphorus, low concentrations of
exchangeable bases, and strong acidity. However, these
chemical constraints are easily overcome by the application
of phosphorus fertilizer and liming. Some Andosols are
especially productive for upland crops, and their notable
properties are as follows: soil morphology is pachic (thick
humus-rich horizon); physical properties show a
medium-grained texture, friable consistency, free drainage,
and high plant-available water content; and chemical properties show a high base saturation, a pH(H 2 O) more than 6,
and an absence of toxic Al (Shoji and Takahashi 2002).
Nowadays, Andosols are most extensively used for
high-value horticultural crops, such as cabbage, Chinese
cabbage, Chinese yam, edible burdock, Japanese radish, and
ginger. These are described in detail in the “Andosols in
Tohoku Region” chapter of this book.
4.4 Podzols
4.4.1 Introduction
Podzols, as defined in the Soil Classification System of
Japan and the WRB (IUSS Working Group WRB 2015), or
Spodosols, as defined in the USDA Soil Taxonomy (Soil
Survey Staff 2014), are characterized by the eluviation of
aluminum (Al) and iron (Fe) from the albic E horizon and
90
Y. Takata et al.