Environmental Engineering Reference
In-Depth Information
45
Emergent
layer
Harpy
eagle
40
35
Toco
toucan
Canopy
30
25
20
Understory
Wooly
opossum
15
10
Shrub
layer
Brazilian
tapir
5
Ground
layer
Black-crowned
antpitta
0
Figure 5-17
Natural capital:
stratification of specialized plant and animal niches in a
tropical rain forest.
Fill-
ing such specialized niches enables species to avoid or minimize competition for resources and results in the
coexistence of a great variety of species.
Temperate deciduous forests
(Figure 5-18, p. 92) grow
in areas with moderate average temperatures that
change significantly with the season. These areas have
long, warm summers, cold but not too severe winters,
and abundant precipitation, often spread fairly evenly
throughout the year.
This biome is dominated by a few species of
broadleaf deciduous trees
such as oak, hickory, maple,
poplar, and beech. They survive cold winters by be-
coming dormant through the winter (photo in Fig-
ure 5-18, right). Each spring they grow new leaves
whose colors change in the fall into an array of reds
and golds before the leaves drop (photo in Figure 5-18,
left). Because of a slow rate of decomposition, these
forests accumulate a thick layer of slowly decaying
leaf litter that is a storehouse of nutrients
Evergreen coniferous forests,
also called
boreal forests
and
taigas
(“TIE-guhs”), are found just south of the arc-
tic tundra in northern regions across North America,
Asia, and Europe (Figure 5-7). In this subarctic climate,
winters are long, dry, and extremely cold; in the north-
ernmost taiga, sunlight is available only 6-8 hours per
day. Summers are short, with mild to warm tempera-
tures, and the sun typically shines 19 hours per day.
Most boreal forests are dominated by a few
species of
coniferous
(cone-bearing)
evergreen trees
such
as spruce, fir, cedar, hemlock, and pine that keep some
of their narrow-pointed leaves (needles) year-round
(Figure 5-19, p. 93). The small, needle-shaped, waxy-
coated leaves of these trees can withstand the intense
cold and drought of winter when snow blankets the
ground. The trees are ready to take advantage of the
brief summers in these areas without taking time to
grow new needles. Plant diversity is low in these
forests because few species can survive the winters
when soil moisture is frozen.
