Download Terrestrial Biomes

TERRESTRIAL BIOMES
34.8 Terrestrial biomes reflect regional
variations in climate
• Terrestrial ecosystems are grouped into nine major types
of biomes, distinguished primarily by their predominant
vegetation.
• The geographic distribution of plants and thus terrestrial
biomes largely depends on climate. The key climate
factors are
• temperature and
• precipitation
• The same type of biome may occur in geographically
distant places if the climate is similar.
34.8 Terrestrial biomes reflect regional
variations in climate
• The current concern about global warming is generating
intense interest in the effect of climate on vegetation
patterns.
• Scientists are documenting
• shifts in latitudes of biome borders,
• changes in snow and ice coverage, and
• changes in length of the growing season.
• A high rate of biome alteration by humans is correlated
with an unusually high rate of species loss throughout
the globe.
Figure 34.8
30°
N
Tropic
of
Cancer
Equator
Tropic of Capricorn
30°
S
Key
Tropical forest
Chaparral
Coniferous forest
Savanna
Temperate grassland
Arctic tundra
Desert
Temperate broadleaf
forest
Polar ice
High mountains
(coniferous forest
and alpine tundra)
34.9 Tropical forests cluster near the equator
• Tropical forests
• occur in equatorial areas,
• experience warm temperatures and days that are 11–12 hours long yearround, and
• have variable rainfall.
34.9 Tropical forests cluster near the equator
• The tropical rain forest is among the most complex of all biomes.
• Tropical rain forests harbor enormous numbers of species.
• Large-scale human destruction of tropical rain forests continues to endanger
many species.
Precipitation
Temperature
range
Figure 34.9
34.10 Savannas are grasslands with scattered
trees
• Savannas
•
•
•
•
•
are warm year-round,
have 30–50 cm annual rainfall,
experience dramatic seasonal variation,
are dominated by grasses and scattered trees, and
have insects as the dominant herbivores.
Fire
Precipitation
Temperature
range
Figure 34.10
34.11 Deserts are defined by their dryness
• Deserts are the driest of all terrestrial biomes.
• They are characterized by low and unpredictable rainfall.
• The cycles of growth and reproduction in the desert are keyed
to rainfall.
• Deserts can be very hot or very cold.
• Desertification, the conversion of semi-arid regions to desert,
is a significant environmental problem.
Precipitation
Temperature
range
Figure 34.11
34.12 Spiny shrubs dominate the chaparral
• The chaparral is a shrubland characterized by dense, spiny shrubs
with tough, evergreen leaves.
• Chaparral experiences
• cool, rainy winters,
• hot, dry summers, and
• vegetation adapted to periodic fires. Firestorms that race through the densely
populated canyons of Southern California can be devastating.
Fire
Precipitation
Temperature
range
Figure 34.12
34.13 Temperate grasslands include the North
American prairie
• Temperate grasslands
• are mostly treeless, except along rivers or streams,
• are found in regions of relatively cold winter temperatures.
• experience precipitation of about 25–75 cm per year, with periodic droughts,
and
• in North America have historically been grazed by large bison and pronghorn.
• Very productive farms have replaced most of North America’s
temperate grasslands.
Fire
Precipitation
Temperature
range
Figure 34.13
34.14 Broadleaf trees dominate temperate
forests
• Temperate broadleaf forests
• grow where there is sufficient moisture to support the growth of large trees
and
• experience wide-ranging temperatures (–30°C to 30°C) and high annual
precipitation (75–150 cm).
• Nearly all of the original broadleaf forests in North America have been
drastically altered by agriculture and urban development.
• These forests typically have a growing season of 5 to 6 months and a
distinct annual rhythm of leaf drop in the fall and the production of new
leaves in the spring.
Precipitation
Temperature
range
Figure 34.14
34.15 Coniferous forests are often dominated
by a few species of trees
• Cone-bearing evergreen trees, such as spruce, pine, fir, and hemlock,
dominate coniferous forests.
• The northern coniferous forest, or taiga, is the largest terrestrial
biome on Earth. The taiga is characterized by
• long, cold winters and
• short, wet summers.
• Temperate rain forests of coastal North America are also coniferous
forests.
Precipitation
Temperature
range
Figure 34.15
34.16 Long, bitter-cold winters characterize
the tundra
• The tundra covers expansive areas of the Arctic between the taiga
and the permanently frozen polar ice.
• The treeless arctic tundra
• is characterized by permafrost, continuously frozen subsoil, and
• may receive as little precipitation as some deserts.
Precipitation
Temperature
range
Figure 34.16
34.17 Polar ice covers the land at high
latitudes
• Polar ice covers
• land north of the tundra,
• much of the Arctic Ocean, and
• the continent of Antarctica.
• Temperatures are extremely cold year-round and precipitation is very
low.
• The terrestrial polar biome is closely intertwined with the neighboring
marine biome.
Precipitation
Temperature
range
Figure 34.17
34.18 The global water cycle connects aquatic
and terrestrial biomes
• Ecological subdivisions such as biomes are linked by
• nutrient cycles and
• the water cycle.
• Water in the form of precipitation and evaporation moves between
the land, oceans, and atmosphere.
• Over the oceans, evaporation exceeds precipitation.
• Over the land, precipitation exceeds evaporation and transpiration.
34.18 The global water cycle connects aquatic
and terrestrial biomes
• Human activities affect the global water cycle.
• The destruction of tropical rain forests reduces the amount of water vapor in
the air.
• Pumping large amounts of groundwater to the surface for irrigation can
increase the rate of evaporation over land, resulting in higher humidity and
depleting groundwater supplies.
Figure 34.18
Solar
heat
Water vapor
over the sea
Net movement
of water vapor
by wind
Evaporation
from the sea
Precipitation
over the sea
Water vapor
over the land
Precipitation
over the land
Evaporation
and
transpiration
Oceans
Flow of water
from land to sea
Surface water
and groundwater
Figure 34.UN01
Organismal
ecology
(individual)
Population
ecology
(group of
individuals
of a species)
Community ecology
(all organisms in
a particular area)
Ecosystem ecology
(all organisms and
abiotic factors)
Figure 34.UN02
Equator