The Humid Temperate Ecoregions
6
6.1
200 Humid Temperate Domain
Both tropical and polar air masses govern the
climate of the humid temperate domain, located
in the mid-latitudes (30
–60
) on all the
continents. The mid-latitudes are subject to
cyclones; much of the precipitation in this belt
comes from rising moist air along fronts within
those cyclones. Pronounced seasons are the rule,
with strong annual cycles of temperature and
precipitation. The seasonal fluctuation of solar
energy and temperature is greater than the diurnal (see Fig. 4.2, p. 29). The climates of the midlatitudes have a distinctive winter season, which
tropical climates do not. The lower temperatures
of the winter season are due to two factors:
reduced solar radiation and the inflow of cold
air streams.
In the tropics (see Chap. 8), the different
environments are distinguished on the basis of
seasonal moisture pattern. There are regions with
a high frequency of precipitation and regions
with strong seasonal contrasts. Although the
tropics are subject to one annual periodicity,
most humid temperate regions are subject to
two major annual cycles, one of solar energy
and another of moisture.
In the temperate latitudes, probably the most
important aspect of the hydrologic cycle is the
periodic freezing of lakes, streams, and soil
moisture. This freezing stops the flow of water
runoff. At the same time, it decreases the water
supply available to the plants, producing drought.
Most streams will reflect the winter season in the
flow pattern. When the spring thaw occurs,
flooding may occur if there are large amounts
of snow in the watershed and melting takes
place rapidly. Removal of headwater forests
leads to increased flooding.
Many of the same process of soil development
which operate in tropical forest lands are active
here, but go on more slowly, owing to lower
temperatures and less extreme humidity. Humus
accumulates, too, for the slower decay of organic
litter on the forest floor, when mixed with the soil
layers, imparts a brownish color.
Three zonal soil types are recognized in the
regions of this group (Fig. 6.1). The red and
yellow lateritic soils of the humid tropical
group extend poleward into the warmer parts of
the humid temperate lands, and are known as
yellow forest soils (Ultisols). Farther poleward,
however, humus accumulation is sufficiently
rapid so that soil color is darkened. With the aid
of earthworms, the organic matter is mixed with
the upper soil layers to form the brown forest
soils (Alfisols). The podzols (Spodosols) lie on
the northern borders of this group, extending into
the polar group. In the profiles of the podzol, the
absence of earthworms is indicated by the concentration of humus at the surface, and the light,
ashy color of the soil below (the name podzol is
derived from a Russian word meaning ashes).
The depth of these profiles decreases as the
length of the frozen period of winter increases.
None of these soils are fertile.
R.G. Bailey, Ecoregions, DOI 10.1007/978-1-4939-0524-9_6, # Springer Science+Media, LLC 2014
55
6
6.1
200 Humid Temperate Domain
Both tropical and polar air masses govern the
climate of the humid temperate domain, located
in the mid-latitudes (30
–60
) on all the
continents. The mid-latitudes are subject to
cyclones; much of the precipitation in this belt
comes from rising moist air along fronts within
those cyclones. Pronounced seasons are the rule,
with strong annual cycles of temperature and
precipitation. The seasonal fluctuation of solar
energy and temperature is greater than the diurnal (see Fig. 4.2, p. 29). The climates of the midlatitudes have a distinctive winter season, which
tropical climates do not. The lower temperatures
of the winter season are due to two factors:
reduced solar radiation and the inflow of cold
air streams.
In the tropics (see Chap. 8), the different
environments are distinguished on the basis of
seasonal moisture pattern. There are regions with
a high frequency of precipitation and regions
with strong seasonal contrasts. Although the
tropics are subject to one annual periodicity,
most humid temperate regions are subject to
two major annual cycles, one of solar energy
and another of moisture.
In the temperate latitudes, probably the most
important aspect of the hydrologic cycle is the
periodic freezing of lakes, streams, and soil
moisture. This freezing stops the flow of water
runoff. At the same time, it decreases the water
supply available to the plants, producing drought.
Most streams will reflect the winter season in the
flow pattern. When the spring thaw occurs,
flooding may occur if there are large amounts
of snow in the watershed and melting takes
place rapidly. Removal of headwater forests
leads to increased flooding.
Many of the same process of soil development
which operate in tropical forest lands are active
here, but go on more slowly, owing to lower
temperatures and less extreme humidity. Humus
accumulates, too, for the slower decay of organic
litter on the forest floor, when mixed with the soil
layers, imparts a brownish color.
Three zonal soil types are recognized in the
regions of this group (Fig. 6.1). The red and
yellow lateritic soils of the humid tropical
group extend poleward into the warmer parts of
the humid temperate lands, and are known as
yellow forest soils (Ultisols). Farther poleward,
however, humus accumulation is sufficiently
rapid so that soil color is darkened. With the aid
of earthworms, the organic matter is mixed with
the upper soil layers to form the brown forest
soils (Alfisols). The podzols (Spodosols) lie on
the northern borders of this group, extending into
the polar group. In the profiles of the podzol, the
absence of earthworms is indicated by the concentration of humus at the surface, and the light,
ashy color of the soil below (the name podzol is
derived from a Russian word meaning ashes).
The depth of these profiles decreases as the
length of the frozen period of winter increases.
None of these soils are fertile.
R.G. Bailey, Ecoregions, DOI 10.1007/978-1-4939-0524-9_6, # Springer Science+Media, LLC 2014
55