As with special topographical features, the flora associated with particular substrates, such as calcareous and serpentine soil (or rocks), is rich in endemic species. Limestone
is rich in calcium, and serpentine is rich in magnesium,
while both tend to be deficient in essential macronutrients
(N, P, K). Under edaphically stressful conditions, flora in
these habitats tends to contain recently formed taxa, that is,
other types of endemics different from the relict species.
Serpentine is an ultramafic rock derived from oceans on
the margins of former tectonic plates and is particularly
distributed along tectonic lines in Japan. Horie (2002)
defined 65 taxa from 22 families as “serpentine plants” in
Japan; a total of 46 of these taxa occur in Hokkaido, where
the largest serpentine area in Japan is located along the
Kamuikotan and Hidaka metamorphic belt (Horie 2002,
Mizuno et al. 2009). Most of these members are herbs or
shrubs, such as Asteraceae (Compositae), Primulaceae,
Ranunculaceae and Rosaceae. Betula apoiensis and Picea
glehnii are characteristic woody species in serpentine areas.
Masses of limestone are also patchy distributed and are
somewhat near to serpentine. Shimizu (1962, 1963) studied
200 taxa linked to limestone areas in Japan and Taiwan, and
reported 75 taxa which were endemic to limestone but not
found on other substrates, such as Crepidiastrum yoshinoi,
Senecio furusei and Adenophora maximowicziana. Betula
chichibuensis and Carpinus turczaninovii are characteristic
woody species of limestone areas.
(2) Historical aspect of vegetation
Vegetation in the last glacial periods has been estimated by
analysis of fossil pollen in soils (Yasuda and Miyoshi 1998).
Cryptomeria japonica was a dominant species until
100,000 years ago. After that, the species dramatically
decreased, while birch and coniferous species such as fir,
hemlock and pine increased. Even in the coldest times in the
last glacial periods, glaciers were only distributed in higher
mountains, while forest persisted in most of the Japanese
territory throughout whole glacial periods. After the glacial
periods ended, the distribution of beech expanded (Yasuda
and Miyoshi 1998); it occupied most of northeast Honshu
and the southern parts of Hokkaido. The distribution of
evergreen broad-leaved trees expanded in Western Japan,
where the population density was high enough that forests
might be influenced by human activities. In the Jōmon
period (13,000–800 BC), shifting cultivation must have
taken place in forest areas. Rice cultivation was introduced
in the Yayoi period (800 BC–250 AD), and the area of
original natural forests gradually decreased and was replaced
by early successional deciduous broad-leaved trees (Matsugi
2007). In the Yayoi period, the density of red pine (Pinus
densiflora) increased.
The impact of humans on forests increased along with
population growth and the development of civilization. In
western Honshu, bare land was formed in granite hills where
severe erosion occurred due to the excessive utilization of
forests in the Edo period (Chiba 1991). In the Meiji period
(1868–1912 AD), the new government decided to undertake
afforestation on bare land in order to prevent soil erosion.
The rehabilitation effort continued into the Showa period
(1925–1988 AD), and the bare land changed to forest;
however, at present biomass is poor and soil is still immature
in forests (Kaneko et al. 2007). The Meiji government also
promoted coniferous plantations to increase timber supply,
and after World War II coniferous plantation became more
popular since large amounts of timber were required for
house construction to support economic development.
Because of this, a great number of trees were cut down in
natural forests, with the trees being replaced with coniferous
trees such as C. japonica and Chamaecyparis obtusa. Larch
(Larix kaempferi) was also planted in high-altitude areas and
in Hokkaido and the northern Honshu. Spruce (Picea
jezoensis) and fir (Abies sachalinensis) were planted in
Hokkaido, which it is not suitable for the growth of Japanese
cedar and Japanese cypress. As of 2012, 41% of Japan’s
total forest area of 250,810 km
2 was planted coniferous
forest, with the remaining fraction consisting of natural
forest (Statistics Department 2018). Most of the natural
forests are secondary, while the primary forests are distributed in only low-accessibility locations such as
high-altitude areas and religious sanctuaries.
(3) Forest vegetation zones
Forest ecosystems in the Japanese archipelago are divided
into four forest zones: subtropical evergreen broad-leaved,
warm-temperate evergreen broad-leaved, cool-temperate
deciduous broad-leaved and cold temperate/subalpine
coniferous forest zones (Fig. 2.27). Since most of Japan
receives adequate precipitation for the development of forest,
indices using accumulated temperature are often used to
explain the distribution of forest zones. For example, the
warmth index (WI) and coldness index (CI) proposed by
Kira (1949; 1977) are useful in defining the boundaries of
forest zones in Japan and throughout the monsoon area of
East Asia. The indices are calculated by totaling monthly
mean temperatures (t) as follows:
WI ¼
X ðtÀ5Þ; for months in which t [ 5
C
CI ¼ À
X
ð5 À tÞ; for months in which t\5
C
The composition and structure of each forest zone are
described in the following sections on the basis of Numata
(1974) and Shimizu (2014).
2 Soil-Forming Factors
41
is rich in calcium, and serpentine is rich in magnesium,
while both tend to be deficient in essential macronutrients
(N, P, K). Under edaphically stressful conditions, flora in
these habitats tends to contain recently formed taxa, that is,
other types of endemics different from the relict species.
Serpentine is an ultramafic rock derived from oceans on
the margins of former tectonic plates and is particularly
distributed along tectonic lines in Japan. Horie (2002)
defined 65 taxa from 22 families as “serpentine plants” in
Japan; a total of 46 of these taxa occur in Hokkaido, where
the largest serpentine area in Japan is located along the
Kamuikotan and Hidaka metamorphic belt (Horie 2002,
Mizuno et al. 2009). Most of these members are herbs or
shrubs, such as Asteraceae (Compositae), Primulaceae,
Ranunculaceae and Rosaceae. Betula apoiensis and Picea
glehnii are characteristic woody species in serpentine areas.
Masses of limestone are also patchy distributed and are
somewhat near to serpentine. Shimizu (1962, 1963) studied
200 taxa linked to limestone areas in Japan and Taiwan, and
reported 75 taxa which were endemic to limestone but not
found on other substrates, such as Crepidiastrum yoshinoi,
Senecio furusei and Adenophora maximowicziana. Betula
chichibuensis and Carpinus turczaninovii are characteristic
woody species of limestone areas.
(2) Historical aspect of vegetation
Vegetation in the last glacial periods has been estimated by
analysis of fossil pollen in soils (Yasuda and Miyoshi 1998).
Cryptomeria japonica was a dominant species until
100,000 years ago. After that, the species dramatically
decreased, while birch and coniferous species such as fir,
hemlock and pine increased. Even in the coldest times in the
last glacial periods, glaciers were only distributed in higher
mountains, while forest persisted in most of the Japanese
territory throughout whole glacial periods. After the glacial
periods ended, the distribution of beech expanded (Yasuda
and Miyoshi 1998); it occupied most of northeast Honshu
and the southern parts of Hokkaido. The distribution of
evergreen broad-leaved trees expanded in Western Japan,
where the population density was high enough that forests
might be influenced by human activities. In the Jōmon
period (13,000–800 BC), shifting cultivation must have
taken place in forest areas. Rice cultivation was introduced
in the Yayoi period (800 BC–250 AD), and the area of
original natural forests gradually decreased and was replaced
by early successional deciduous broad-leaved trees (Matsugi
2007). In the Yayoi period, the density of red pine (Pinus
densiflora) increased.
The impact of humans on forests increased along with
population growth and the development of civilization. In
western Honshu, bare land was formed in granite hills where
severe erosion occurred due to the excessive utilization of
forests in the Edo period (Chiba 1991). In the Meiji period
(1868–1912 AD), the new government decided to undertake
afforestation on bare land in order to prevent soil erosion.
The rehabilitation effort continued into the Showa period
(1925–1988 AD), and the bare land changed to forest;
however, at present biomass is poor and soil is still immature
in forests (Kaneko et al. 2007). The Meiji government also
promoted coniferous plantations to increase timber supply,
and after World War II coniferous plantation became more
popular since large amounts of timber were required for
house construction to support economic development.
Because of this, a great number of trees were cut down in
natural forests, with the trees being replaced with coniferous
trees such as C. japonica and Chamaecyparis obtusa. Larch
(Larix kaempferi) was also planted in high-altitude areas and
in Hokkaido and the northern Honshu. Spruce (Picea
jezoensis) and fir (Abies sachalinensis) were planted in
Hokkaido, which it is not suitable for the growth of Japanese
cedar and Japanese cypress. As of 2012, 41% of Japan’s
total forest area of 250,810 km
2 was planted coniferous
forest, with the remaining fraction consisting of natural
forest (Statistics Department 2018). Most of the natural
forests are secondary, while the primary forests are distributed in only low-accessibility locations such as
high-altitude areas and religious sanctuaries.
(3) Forest vegetation zones
Forest ecosystems in the Japanese archipelago are divided
into four forest zones: subtropical evergreen broad-leaved,
warm-temperate evergreen broad-leaved, cool-temperate
deciduous broad-leaved and cold temperate/subalpine
coniferous forest zones (Fig. 2.27). Since most of Japan
receives adequate precipitation for the development of forest,
indices using accumulated temperature are often used to
explain the distribution of forest zones. For example, the
warmth index (WI) and coldness index (CI) proposed by
Kira (1949; 1977) are useful in defining the boundaries of
forest zones in Japan and throughout the monsoon area of
East Asia. The indices are calculated by totaling monthly
mean temperatures (t) as follows:
WI ¼
X ðtÀ5Þ; for months in which t [ 5
C
CI ¼ À
X
ð5 À tÞ; for months in which t\5
C
The composition and structure of each forest zone are
described in the following sections on the basis of Numata
(1974) and Shimizu (2014).
2 Soil-Forming Factors
41