2. Warm-temperate evergreen broad-leaved forest zone
The warm-temperate evergreen broad-leaved forest zone
corresponds to WI values of 85 to 180, and in Japan stretches from 30° N to nearly 38° N. Here, forests with species
strongly similar to those of subtropical forest and
lauro-fagaceous trees are dominant. The diversity of evergreen broad-leaved species becomes less rich with increasing latitude. Near the northern or upper limit of evergreen
forests, there are particular types of forest which lack both
tall evergreen broad-leaved trees and a representative tree in
the cool-temperate zone, Fagus crenata, but are instead
characterized by warm-temperate deciduous trees such as
Quercus serrata, Carpinus spp. and Fagus japonica,
sometimes mixed with temperate conifers such as Abies
firma. This forest is called “warm temperate deciduous forest” (Kira 1949, 1977) and is explained as an area where the
warmth of the growing season is still within the range of the
warm-temperate zone (WI > 85) but cannot support the
growth of broad-leaved evergreen tree species due to
increased winter coldness (CI < −10).
3. Cool-temperate deciduous broad-leaved forest zone
The cool-temperate deciduous broad-leaved forest zone
corresponds to WI values of 45 to 85, and in Japan extends
northward to the southern part of Hokkaido. This zone is
dominated by deciduous fagaceous species such as F. crenata and Quercus crispula mixed with Acer and Carpinus.
On the Sea of Japan side, where the snow cover is heavy in
winter, the dominancy of F. crenata is high. Other associated tree species are Viburnum furcatum, Lindera umbellata
var. membranacea, etc., in the shrub layer. The shrub layer
is also characterized by the dense growth of a dwarf bamboo,
Sasa kurilensis, and the occurrence of evergreen
broad-leaved shrubs such as Camellia rusticana and Ilex
leucoclada that can endure winter coldness under snow
cover. On the Pacific Ocean side, the canopy layer is dominated by species such as F. crenata, F. japonica, Q. crispula, Carpinus tschonoskii and Betula grossa. The shrub
layer in most areas is dominated by dwarf bamboos such as
Sasa nipponica or Sasamorpha borealis. In the region
northward from the northern limit of F. crenata, the lowlands
of
Hokkaido,
mixed
cool-temperate
deciduous/subalpine coniferous forest occurs, dominated
by Q. crispula, Acer pictum subsp. mono, Betula spp., Abies
sachalinensis and Picea jezoensis.
4. Cold temperate/subalpine coniferous forest zone
The cold temperate/subalpine coniferous forest zone corresponds to WI values of 15 to 45 and is dominated by
evergreen conifers such as Abies and Picea. This forest zone
is not found in Kyushu. The dominant species of the forest
zone in Hokkaido is A. sachalinensis and Picea jezoensis,
whereas P. glehnii also dominates in wetlands and rocky
areas with shallow soil. Abies mariesii is the dominant
species in the north of Honshu. In central Honshu, both A.
mariesii and A. veitchii are commonly dominant. A. mariesii
is not found on Shikoku or the Kii Peninsula of Honshu. In
the forest zones, except in Hokkaido and northern Honshu,
other conifers, such as Chamaecyparis pisifera, Thuja
standishii, Tsuga diversifolia and P. jezoensis var. hondoensis (not in Shikoku) are also common species present.
5. Alpine zone
As an altitudinal vegetation zone, the regions above the
tree line of the cold temperate/subalpine coniferous forest
zone have been conventionally called the “alpine zone” in
Japan. Many of the components of this zone came from
subarctic and arctic zones in the glacial period and were left
as relics on the summits of its high mountains. There are
various types of vegetation in the alpine zone, and their
distribution is governed by wind and snow as well as
edaphic and topographic factors.
Most representative vegetation in the habitats where snow
melts early is alpine scrubs dominated by Pinus pumila, a
dwarf pine that occurs widely in northeastern Asia including
Hokkaido and Honshu. Mt. Tekari (35° 20′ N) of Akaishi
Mountains is the southernmost point at which P. pumila is
found throughout the world, although this species is not
found on Mt. Fuji (35° 21′ N). This species forms carpet-like
monodominant stands of about 1 m in height, sometimes
mixed with evergreen Rhododendron, such as R. brachycarpum and R. aureum, and dwarf tree components of the
subalpine zone such as Alnus viridis subsp. maximowiczii,
Betula ermanii, Acer tschonoskii and Sorbus commixta in
the canopy layer.
(4) Human influence on soil formation through vegetation change
In Japan, forest has been converted to grassland by burning
to obtain materials such as manure for agricultural production, feedstuff for livestock and material for making thatched
roofs in the Edo period (Ogura 2009). A recent study
revealed that savanna-like grasslands with small trees and
bushes were widely distributed in areas surrounding human
settlements throughout the country until the early Meiji
period (the late nineteenth century) (Ogura 2009). Here, we
will introduce a hypothesis that human activities for maintaining grassland vegetation affect the formation of “black
soils.”
2 Soil-Forming Factors
43
The warm-temperate evergreen broad-leaved forest zone
corresponds to WI values of 85 to 180, and in Japan stretches from 30° N to nearly 38° N. Here, forests with species
strongly similar to those of subtropical forest and
lauro-fagaceous trees are dominant. The diversity of evergreen broad-leaved species becomes less rich with increasing latitude. Near the northern or upper limit of evergreen
forests, there are particular types of forest which lack both
tall evergreen broad-leaved trees and a representative tree in
the cool-temperate zone, Fagus crenata, but are instead
characterized by warm-temperate deciduous trees such as
Quercus serrata, Carpinus spp. and Fagus japonica,
sometimes mixed with temperate conifers such as Abies
firma. This forest is called “warm temperate deciduous forest” (Kira 1949, 1977) and is explained as an area where the
warmth of the growing season is still within the range of the
warm-temperate zone (WI > 85) but cannot support the
growth of broad-leaved evergreen tree species due to
increased winter coldness (CI < −10).
3. Cool-temperate deciduous broad-leaved forest zone
The cool-temperate deciduous broad-leaved forest zone
corresponds to WI values of 45 to 85, and in Japan extends
northward to the southern part of Hokkaido. This zone is
dominated by deciduous fagaceous species such as F. crenata and Quercus crispula mixed with Acer and Carpinus.
On the Sea of Japan side, where the snow cover is heavy in
winter, the dominancy of F. crenata is high. Other associated tree species are Viburnum furcatum, Lindera umbellata
var. membranacea, etc., in the shrub layer. The shrub layer
is also characterized by the dense growth of a dwarf bamboo,
Sasa kurilensis, and the occurrence of evergreen
broad-leaved shrubs such as Camellia rusticana and Ilex
leucoclada that can endure winter coldness under snow
cover. On the Pacific Ocean side, the canopy layer is dominated by species such as F. crenata, F. japonica, Q. crispula, Carpinus tschonoskii and Betula grossa. The shrub
layer in most areas is dominated by dwarf bamboos such as
Sasa nipponica or Sasamorpha borealis. In the region
northward from the northern limit of F. crenata, the lowlands
of
Hokkaido,
mixed
cool-temperate
deciduous/subalpine coniferous forest occurs, dominated
by Q. crispula, Acer pictum subsp. mono, Betula spp., Abies
sachalinensis and Picea jezoensis.
4. Cold temperate/subalpine coniferous forest zone
The cold temperate/subalpine coniferous forest zone corresponds to WI values of 15 to 45 and is dominated by
evergreen conifers such as Abies and Picea. This forest zone
is not found in Kyushu. The dominant species of the forest
zone in Hokkaido is A. sachalinensis and Picea jezoensis,
whereas P. glehnii also dominates in wetlands and rocky
areas with shallow soil. Abies mariesii is the dominant
species in the north of Honshu. In central Honshu, both A.
mariesii and A. veitchii are commonly dominant. A. mariesii
is not found on Shikoku or the Kii Peninsula of Honshu. In
the forest zones, except in Hokkaido and northern Honshu,
other conifers, such as Chamaecyparis pisifera, Thuja
standishii, Tsuga diversifolia and P. jezoensis var. hondoensis (not in Shikoku) are also common species present.
5. Alpine zone
As an altitudinal vegetation zone, the regions above the
tree line of the cold temperate/subalpine coniferous forest
zone have been conventionally called the “alpine zone” in
Japan. Many of the components of this zone came from
subarctic and arctic zones in the glacial period and were left
as relics on the summits of its high mountains. There are
various types of vegetation in the alpine zone, and their
distribution is governed by wind and snow as well as
edaphic and topographic factors.
Most representative vegetation in the habitats where snow
melts early is alpine scrubs dominated by Pinus pumila, a
dwarf pine that occurs widely in northeastern Asia including
Hokkaido and Honshu. Mt. Tekari (35° 20′ N) of Akaishi
Mountains is the southernmost point at which P. pumila is
found throughout the world, although this species is not
found on Mt. Fuji (35° 21′ N). This species forms carpet-like
monodominant stands of about 1 m in height, sometimes
mixed with evergreen Rhododendron, such as R. brachycarpum and R. aureum, and dwarf tree components of the
subalpine zone such as Alnus viridis subsp. maximowiczii,
Betula ermanii, Acer tschonoskii and Sorbus commixta in
the canopy layer.
(4) Human influence on soil formation through vegetation change
In Japan, forest has been converted to grassland by burning
to obtain materials such as manure for agricultural production, feedstuff for livestock and material for making thatched
roofs in the Edo period (Ogura 2009). A recent study
revealed that savanna-like grasslands with small trees and
bushes were widely distributed in areas surrounding human
settlements throughout the country until the early Meiji
period (the late nineteenth century) (Ogura 2009). Here, we
will introduce a hypothesis that human activities for maintaining grassland vegetation affect the formation of “black
soils.”
2 Soil-Forming Factors
43