1. Forest and forestry in the Kinki–Chugoku–Shikoku
region
The Kinki–Chugoku–Shikoku region is rich in forest
resources as a result of its mild temperatures and precipitation. Forest covers an average of 63% (31–77%) of the Kinki
region (close to the national average of 67%), an average of
73% (68–78%) of the Chugoku region, and an average of
70% (47–84%) of the Shikoku region (Forestry Agency
2016). Forest covers only 31% of Osaka Prefecture, the
lowest percentage of any Japanese prefecture, but this is the
result of human influences rather than natural conditions.
The forests of the Kinki–Chugoku–Shikoku region are
mainly evergreen forests consisting of Castanopsis and
Quercus sp. The mountain areas are home to deciduous
forest, including Fagus crenata and Quercus cripula Blume,
and intermediate temperate forest; Abies firma and Tsuga
sieboldii grow on the Kii Peninsula and the high-elevation
areas of Shikoku Island. Along the Seto Inland Sea, Pinus
densiflora is the dominant species and is adapted to dry
conditions. Forest fires often occur in this dry region,
although these events support Pinus densiflora regrowth.
P. densiflora, Quercus serrata, and Quercus acutissima are
popular species in “Satoyama” (the Japanese term for areas
between mountain foothills and arable flat land) and are
influenced by anthropomorphic factors. Additionally, a
decrease in biodiversity caused by invading bamboo is a
recent major concern.
Plantation forests cover 51, 42, and 53% of the Kinki,
Chugoku, and Shikoku regions, respectively, all exceeding
the national average of 41%. These plantations are privately
owned. Since ancient times, the population and forest usage
have been high in the Kansai region. The main plantation
species are Cryptomeria japonica and Chamaecyparis
obtuse, most of which were planted between 1950 and 1960.
These plantations now need thinning, as in other areas.
However, it is difficult to maintain these forests since the
price of wood is low and the number of foresters has
decreased.
2. Forest soil in the Kinki–Chugoku–Shikoku region
The influence of volcanic ash is weaker in the Kinki–Chugoku–Shikoku region than in Eastern Japan and the Kyushu
region, except for in Non-allophanic Andosols in the vicinity
of Mt. Daisen (Saigusa and Matsuyama 1994; Matsuyama
and Saigusa 1994).
As already mentioned, the Kinki–Chugoku–Shikoku
region has a long history. Many temples are located in this
area and the old capital buildings were built from wood. The
Tanakami mountains in Shiga Prefecture once hosted a
natural Chamaecyparis japonica forest. However, people
repeatedly used the wood from this area for building during
the Heian period (794–1185 AD), denuding it. In the
Tanakami mountains, the bedrock is granite. Once the area
was denuded, this granite was readily subjected to erosion,
making regrowth difficult; when it rains, the soil is transported into rivers where it accumulates on the riverbed.
People built dikes to prevent the river from overflowing its
banks, and ultimately the riverbed became higher than the
surrounding area. This kind of construction is called “tenjogawa,” which means a river with a bed higher than the
surrounding plains. In the denuded mountain area in the
Tanakami mountains, afforestation was started by foreign
technicians in the Meiji period (1868–1912 AD), and the
mountains are now covered by forest. Soil formation processes in relation to the period of afforestation in the Tanakami mountains is reported (Tsukimori et al. 1992).
Generally, almost no nitrogen (N) leaches into streams
from forested ecosystems. However, recent reports showed
that N concentrations in stream water are increasing (e.g.,
Vitousek et al. 1997). This is the result of increased fossil
fuel emissions, which have increased N deposition in
forested ecosystems. The deposited N exceeds the biological
demand of the forested ecosystems and ultimately leaches
into streams. This phenomenon is called N saturation (Aber
et al. 1998).
Makino et al. (2017) found a large difference in N concentrations in streams between two adjacent hills in Toyama
Prefecture in the northern part of the Kinki region. The hills
are only 5 km apart, a small distance that implies there
should be no significant difference in N deposition. The
largest N pool is soil, but there was no clear difference in soil
type between the two hills. The researchers therefore concluded that N saturation was caused by other factors in
addition to N deposition. Further study is needed to clarify
the N dynamics in this soil.
9.3 Environmental Conservation
9.3.1 Environmental Conservation in Paddy
Fields in Shiga Prefecture
Among the 47 prefectures in Japan, Shiga Prefecture has
promoted the production of specially cultivated rice most
extensively. This is because Lake Biwa, which is the largest
inland lake in Japan and supplies water to about 14 million
people in the Kinki region, is located in the center of the
prefecture, and also because more than 90% of the agricultural land in the prefecture is classified as paddy field (the
second highest percentage in Japan as of 2017); this paddy
field is used for the production of rice, wheat, soybean, and
vegetables in an open system. The prefecture established
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J. Yanai et al.
region
The Kinki–Chugoku–Shikoku region is rich in forest
resources as a result of its mild temperatures and precipitation. Forest covers an average of 63% (31–77%) of the Kinki
region (close to the national average of 67%), an average of
73% (68–78%) of the Chugoku region, and an average of
70% (47–84%) of the Shikoku region (Forestry Agency
2016). Forest covers only 31% of Osaka Prefecture, the
lowest percentage of any Japanese prefecture, but this is the
result of human influences rather than natural conditions.
The forests of the Kinki–Chugoku–Shikoku region are
mainly evergreen forests consisting of Castanopsis and
Quercus sp. The mountain areas are home to deciduous
forest, including Fagus crenata and Quercus cripula Blume,
and intermediate temperate forest; Abies firma and Tsuga
sieboldii grow on the Kii Peninsula and the high-elevation
areas of Shikoku Island. Along the Seto Inland Sea, Pinus
densiflora is the dominant species and is adapted to dry
conditions. Forest fires often occur in this dry region,
although these events support Pinus densiflora regrowth.
P. densiflora, Quercus serrata, and Quercus acutissima are
popular species in “Satoyama” (the Japanese term for areas
between mountain foothills and arable flat land) and are
influenced by anthropomorphic factors. Additionally, a
decrease in biodiversity caused by invading bamboo is a
recent major concern.
Plantation forests cover 51, 42, and 53% of the Kinki,
Chugoku, and Shikoku regions, respectively, all exceeding
the national average of 41%. These plantations are privately
owned. Since ancient times, the population and forest usage
have been high in the Kansai region. The main plantation
species are Cryptomeria japonica and Chamaecyparis
obtuse, most of which were planted between 1950 and 1960.
These plantations now need thinning, as in other areas.
However, it is difficult to maintain these forests since the
price of wood is low and the number of foresters has
decreased.
2. Forest soil in the Kinki–Chugoku–Shikoku region
The influence of volcanic ash is weaker in the Kinki–Chugoku–Shikoku region than in Eastern Japan and the Kyushu
region, except for in Non-allophanic Andosols in the vicinity
of Mt. Daisen (Saigusa and Matsuyama 1994; Matsuyama
and Saigusa 1994).
As already mentioned, the Kinki–Chugoku–Shikoku
region has a long history. Many temples are located in this
area and the old capital buildings were built from wood. The
Tanakami mountains in Shiga Prefecture once hosted a
natural Chamaecyparis japonica forest. However, people
repeatedly used the wood from this area for building during
the Heian period (794–1185 AD), denuding it. In the
Tanakami mountains, the bedrock is granite. Once the area
was denuded, this granite was readily subjected to erosion,
making regrowth difficult; when it rains, the soil is transported into rivers where it accumulates on the riverbed.
People built dikes to prevent the river from overflowing its
banks, and ultimately the riverbed became higher than the
surrounding area. This kind of construction is called “tenjogawa,” which means a river with a bed higher than the
surrounding plains. In the denuded mountain area in the
Tanakami mountains, afforestation was started by foreign
technicians in the Meiji period (1868–1912 AD), and the
mountains are now covered by forest. Soil formation processes in relation to the period of afforestation in the Tanakami mountains is reported (Tsukimori et al. 1992).
Generally, almost no nitrogen (N) leaches into streams
from forested ecosystems. However, recent reports showed
that N concentrations in stream water are increasing (e.g.,
Vitousek et al. 1997). This is the result of increased fossil
fuel emissions, which have increased N deposition in
forested ecosystems. The deposited N exceeds the biological
demand of the forested ecosystems and ultimately leaches
into streams. This phenomenon is called N saturation (Aber
et al. 1998).
Makino et al. (2017) found a large difference in N concentrations in streams between two adjacent hills in Toyama
Prefecture in the northern part of the Kinki region. The hills
are only 5 km apart, a small distance that implies there
should be no significant difference in N deposition. The
largest N pool is soil, but there was no clear difference in soil
type between the two hills. The researchers therefore concluded that N saturation was caused by other factors in
addition to N deposition. Further study is needed to clarify
the N dynamics in this soil.
9.3 Environmental Conservation
9.3.1 Environmental Conservation in Paddy
Fields in Shiga Prefecture
Among the 47 prefectures in Japan, Shiga Prefecture has
promoted the production of specially cultivated rice most
extensively. This is because Lake Biwa, which is the largest
inland lake in Japan and supplies water to about 14 million
people in the Kinki region, is located in the center of the
prefecture, and also because more than 90% of the agricultural land in the prefecture is classified as paddy field (the
second highest percentage in Japan as of 2017); this paddy
field is used for the production of rice, wheat, soybean, and
vegetables in an open system. The prefecture established
318
J. Yanai et al.