since the restoration. It also stated that the required amount
of nitrogen fertilizer can be reduced by up to 50% 30 years
after the restoration compared to the amount of nitrogen
required immediately after the restoration.
In Toyama Prefecture, soil dressing was completed in
2011 fiscal year after 33 years of restoration measures.
However, as shown by the fact that there are still patients
who have itai-itai disease and that the activities of victim
groups are still continuing, the problems caused by cadmium
pollution have not been solved completely.
The concentration of Cd in the Jinzu River has now
returned to the natural environmental level due to the efforts
of victim organizations and companies. However, it should
not be forgotten that once heavy metal contamination occurs,
it causes many losses, and its restoration requires significant
amounts of labor and funds. I sincerely hope that the
development of the economy and the maintenance of the
environment will proceed simultaneously by making use of
the lessons learned from the case of Toyama Prefecture.
8.2.2 Forestry in the Central Highland Area
Gifu is an inland prefecture that occupies the extreme western
part of the Central Highland area and the center of Honshu
Island in the western part of the Hida and Kiso Mountains
(Fig. 8.1). From geographical viewpoint, the prefecture is
divided into two regions, the northern part (Hida area) and
the southern part (Mino area). The elevation ranges from
under 0 m a.s.l. in the southern part to over 3000 m a.s.l. in
the Hida Mountains. Most areas comprise plateaus and steep
mountains, and 82% of the area is forest (Gifu Prefectural
Forestry Policy Division, 2017). Therefore, there are various
types of soils and forests depending on the elevation.
The forestry industry harvests timbers from plantations of
trees suitable for the local climatic and environmental conditions and conducts appropriate thinning and other management. In many areas, according to local conditions, forest
management is conducted continuously. Recently, local
municipalities have made original regional forest plans, and
these municipalities support forestry works in their regions.
For example, Gujo City in Gifu Prefecture, is trying to
develop a forest zoning plan that takes into account local
conditions such as soil type, snow accumulation, and risk of
sediment disasters.
Forest management that does not account for local conditions leads to high environmental burden or natural disaster. In the following, some examples are presented in order
to review various forests and soils of the Central Highland
area, mainly Gifu Prefecture.
Most Podzols are distributed in high mountainous areas,
such as the Hida Mountains and Ryohaku Mountains. Under
the timberline, subalpine evergreen coniferous forest appears
at elevations of 1500 to 2500 m a.s.l. (Namikawa 2005); the
main species are fir (Abies veitchii var. veitchii and A.
mariesii), Japanese hemlock (Tsuga diversifolia) and spruce
(Picea jezoensis var. hondoensis) often accompanied by
white pine (Pinus parviflora) and birch (Betula ermanii var.
ermanii). Because of the low land productivity and the lack
of suitable species and management technology, these high
mountainous areas have not been used as afforestation sites.
Additionally, because of legal regulations such as the Natural Parks Law, it is thought that forestry work should, for
the most part, not be conducted in the future.
After World War II, in an “expansive afforestation stage”,
broad-leaved forests such as beech (Fagus crenata) were cut
widely, and coniferous trees such as Japanese cedar (Cryptomeria japonica) and Japanese larch (Larix kaempferi) were
planted at the same time in high-altitude or snowy regions.
However, due to the snow cover and its glide pressure,
planted trees were damaged, and afforestation was unsuccessful (Aiura, 2014). These places are called “unsuccessful
plantations” (Yokoi and Yamaguchi, 1998). Especially in
heavy snowfall regions, landslides caused by snow erosion
(Fig. 8.17) occurred frequently, and soil pedogenesis has
been influenced. These areas faced routine avalanches and
the deterioration of water conservation function by soil
erosion, accompanied by sediment production derived from
this phenomenon (Aiura 2014).
Andosols are mainly distributed in the northeastern and
southern parts of the Hida area, while Allophanic Andosols
are only developed on the eastern part of Mt. Haku and
around Mt. Ontake. Because Andosols are difficult to compact, the risk of subsidence may be increased on forestry
work roads (Forestry Agency, 2015). On the other hand, soil
subsidence caused by the driving of large forestry machines
can lead to the early death of saplings. Figure 8.18 shows the
ratio of pores in the soil. The number of coarse pores is
remarkably lower in tracks of forestry machine sites than in a
control site.
Brown Forest soils are most widespread in mountains or
hilly lands in Mino area. This area is steep, and its soils tend
to be dry, making it suitable for the afforestation of Japanese
cypress (Chamaecyparis obtusa). There may be a risk of
surface soil erosion in planted cypress forests, depending on
management. Surface soil erosion caused by rainfall is
decreased by the presence of undergrowth vegetation, as the
vegetation and litter cover reduce the impact of raindrops on
the soil. Any type of forest, regardless of species, is expected
to reduce the impact of raindrops on the soil, but in
unmanaged cypress forests, it is difficult to lessen the erosion
(Kosugi 2014). The fallen leaves of the cypress are broken
into smaller pieces by the throughfall and are transported
away from the forest floor by overland flow. There is the risk
that large amounts of sediment may erode from the surface
due to interference with the invasion or growth of
8 Chubu Region (Hokuriku/Tokai)
289
of nitrogen fertilizer can be reduced by up to 50% 30 years
after the restoration compared to the amount of nitrogen
required immediately after the restoration.
In Toyama Prefecture, soil dressing was completed in
2011 fiscal year after 33 years of restoration measures.
However, as shown by the fact that there are still patients
who have itai-itai disease and that the activities of victim
groups are still continuing, the problems caused by cadmium
pollution have not been solved completely.
The concentration of Cd in the Jinzu River has now
returned to the natural environmental level due to the efforts
of victim organizations and companies. However, it should
not be forgotten that once heavy metal contamination occurs,
it causes many losses, and its restoration requires significant
amounts of labor and funds. I sincerely hope that the
development of the economy and the maintenance of the
environment will proceed simultaneously by making use of
the lessons learned from the case of Toyama Prefecture.
8.2.2 Forestry in the Central Highland Area
Gifu is an inland prefecture that occupies the extreme western
part of the Central Highland area and the center of Honshu
Island in the western part of the Hida and Kiso Mountains
(Fig. 8.1). From geographical viewpoint, the prefecture is
divided into two regions, the northern part (Hida area) and
the southern part (Mino area). The elevation ranges from
under 0 m a.s.l. in the southern part to over 3000 m a.s.l. in
the Hida Mountains. Most areas comprise plateaus and steep
mountains, and 82% of the area is forest (Gifu Prefectural
Forestry Policy Division, 2017). Therefore, there are various
types of soils and forests depending on the elevation.
The forestry industry harvests timbers from plantations of
trees suitable for the local climatic and environmental conditions and conducts appropriate thinning and other management. In many areas, according to local conditions, forest
management is conducted continuously. Recently, local
municipalities have made original regional forest plans, and
these municipalities support forestry works in their regions.
For example, Gujo City in Gifu Prefecture, is trying to
develop a forest zoning plan that takes into account local
conditions such as soil type, snow accumulation, and risk of
sediment disasters.
Forest management that does not account for local conditions leads to high environmental burden or natural disaster. In the following, some examples are presented in order
to review various forests and soils of the Central Highland
area, mainly Gifu Prefecture.
Most Podzols are distributed in high mountainous areas,
such as the Hida Mountains and Ryohaku Mountains. Under
the timberline, subalpine evergreen coniferous forest appears
at elevations of 1500 to 2500 m a.s.l. (Namikawa 2005); the
main species are fir (Abies veitchii var. veitchii and A.
mariesii), Japanese hemlock (Tsuga diversifolia) and spruce
(Picea jezoensis var. hondoensis) often accompanied by
white pine (Pinus parviflora) and birch (Betula ermanii var.
ermanii). Because of the low land productivity and the lack
of suitable species and management technology, these high
mountainous areas have not been used as afforestation sites.
Additionally, because of legal regulations such as the Natural Parks Law, it is thought that forestry work should, for
the most part, not be conducted in the future.
After World War II, in an “expansive afforestation stage”,
broad-leaved forests such as beech (Fagus crenata) were cut
widely, and coniferous trees such as Japanese cedar (Cryptomeria japonica) and Japanese larch (Larix kaempferi) were
planted at the same time in high-altitude or snowy regions.
However, due to the snow cover and its glide pressure,
planted trees were damaged, and afforestation was unsuccessful (Aiura, 2014). These places are called “unsuccessful
plantations” (Yokoi and Yamaguchi, 1998). Especially in
heavy snowfall regions, landslides caused by snow erosion
(Fig. 8.17) occurred frequently, and soil pedogenesis has
been influenced. These areas faced routine avalanches and
the deterioration of water conservation function by soil
erosion, accompanied by sediment production derived from
this phenomenon (Aiura 2014).
Andosols are mainly distributed in the northeastern and
southern parts of the Hida area, while Allophanic Andosols
are only developed on the eastern part of Mt. Haku and
around Mt. Ontake. Because Andosols are difficult to compact, the risk of subsidence may be increased on forestry
work roads (Forestry Agency, 2015). On the other hand, soil
subsidence caused by the driving of large forestry machines
can lead to the early death of saplings. Figure 8.18 shows the
ratio of pores in the soil. The number of coarse pores is
remarkably lower in tracks of forestry machine sites than in a
control site.
Brown Forest soils are most widespread in mountains or
hilly lands in Mino area. This area is steep, and its soils tend
to be dry, making it suitable for the afforestation of Japanese
cypress (Chamaecyparis obtusa). There may be a risk of
surface soil erosion in planted cypress forests, depending on
management. Surface soil erosion caused by rainfall is
decreased by the presence of undergrowth vegetation, as the
vegetation and litter cover reduce the impact of raindrops on
the soil. Any type of forest, regardless of species, is expected
to reduce the impact of raindrops on the soil, but in
unmanaged cypress forests, it is difficult to lessen the erosion
(Kosugi 2014). The fallen leaves of the cypress are broken
into smaller pieces by the throughfall and are transported
away from the forest floor by overland flow. There is the risk
that large amounts of sediment may erode from the surface
due to interference with the invasion or growth of
8 Chubu Region (Hokuriku/Tokai)
289