Life on Land
Chapter 2
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Terrestrial Biomes
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Biomes are distinguished primarily by their
predominant plants and are associated with
particular climates.
 Geographic and seasonal variations in
temperature and precipitation are
fundamental components.
 Predominant plants share similar growth
characteristics although species may vary.
 Soil types of a biome are often similar due
to similar climate and plant type influences.
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Uneven Solar Heating of Earth
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Solar-Driven Air Circulation (convection)
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Temperature, Atmospheric
Circulation, and Precipitation
Spherical shape and tilt of earth’s axis cause
uneven heating of earth’s surface.
 Drives air circulation patterns and
consequently precipitation patterns.
 Warm, moist air rises.
 Cools, condenses, and falls as rain.
 Cooler, dry air falls back to surface.
 Rainforests found near equator.
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 Major deserts found near 30 N / S.
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Solar-Driven Air Circulation
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Temperature, Atmospheric
Circulation, and Precipitation
Coriolis effect causes apparent deflection of
winds clockwise in the N hemisphere and
counterclockwise in the S hemisphere.
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Seasons due to tilt of the Earth and its
annual orbit around the Sun.
Winter solstice
Dec 22nd
Vernal equinox
Mar 22nd
Summer solstice
June 22nd
Autumn equinox
Sept 22nd
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Climate
Diagrams
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Mean annual
temperature.
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Mean annual
precipitation.
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Soil : Foundation of Terrestrial Biomes
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Soil is a complex mixture of living and nonliving material.
Development of soil:
 Weathering (fracture and dissolution) of
parent rocks and other minerals portions.
 Organic matter deposition by roots and
litter (leaves, twigs, logs).
 Infiltration of water leaches material to
deeper layers (horizons) in the soil profile.
 Climate influences weathering processes.
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Soil Horizons
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O horizon: Organic Layer freshly fallen and
decomposing organic material – the most
obvious surface layer (humifications begins).
A horizon: Mixture of minerals, clay, silt,
sand, mixed with humus (older dark organic
matter – what makes dirt brown).
B horizon: Clay, humus, and other materials
leached from A horizon - often contains plant
roots.
C horizon: Weathered parent material.
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Soil Profile
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Terrestrial Biomes
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Biomes are distinguished primarily by their
predominant plants and are associated with
particular climates.
 Tropical Rainforests
 Tropical Dry Forest
 Tropical Savanna
 Desert
 Mediterranean Woodland and Shrubland
 Temperate Grassland
 Temperate Forest (Deciduous & Evergreen)
 Boreal Forest (Tiaga)
 Tundra
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Tropical Rainforest
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A broadleaf
tropical forest
growing in
tropical regions
where conditions
are warm and
wet year-round.
Vertical structure.
Epiphytes
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Tropical Rainforests
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Tropical Rainforests
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Most occur within 10o latitude of equator.
Little temperature variation between months.
Annual rainfall of 2,000 - 4,000 mm relatively
evenly distributed.
Soils low organic and nutrient poor.
 Rain quickly leaches soil nutrients.
 High decomposition and fast nutrient cycle.
 Mycorrhizae help gather nutrients.
Harbor staple foods and medicines for world’s
human populations - increasingly exploited.
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Tropical Dry Forest
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Mostly broadleaf forests in tropical regions
with pronounced wet and dry seasons where
trees drop their leaves during the dry season
(“dry deciduous forest”).
Tropical dry coniferous forests are rare.
http://www.cas.vanderbilt.edu/bioimages/ecoregions/nam-ecoregions-list.htm
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Tropical Dry Forest
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Tropical Dry Forest
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Usually located between 10o - 25o latitude.
Climate more seasonal than tropical
rainforest (wet versus dry)
Soils generally richer in nutrients than
rainforests, but vulnerable to erosion.
Shares many animal and plant species with
tropical rainforests.
Heavily settled by humans with extensive
clearing for agriculture.
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Tropical Savanna
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Tropical grassland with a few scattered
trees; characterized by pronounced wet and
dry seasons, with periodic fires.
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Tropical Savanna
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Tropical Savanna
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Most occur north and south of tropical dry
forests within 10o - 20o of the equator.
Climate alternates between wet / dry
seasons.
 Drought associated with dry season leads
to lightning-caused wildfires.
Soils have low water permeability.
 Saturated soils in wet season inhibit trees.
Landscape is more two-dimensional with
increasing pressure to produce livestock.
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Desert
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Arid lands occupying 20% of global land
area, where evapotranspiration exceeds
precipitation for most of the year.
http://helios.bto.ed.ac.uk/bto/desertecology/creosot3.jpg
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Desert
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Desert
Major bands at 30o N and 30o S latitude.
Water loss usually exceeds precipitation.
Soil usually extremely low in organic matter
(lithosols) and often with mineral deposits of
calcium carbonate (caliches).
Plant cover ranges from sparse to absent.
Animal abundance low, but biodiversity may
be high; many are nocturnal and burrowers.
Human intrusion increasing.
Rain shadow quiz.
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Mediterranean
Woodland and
Shrubland
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Mild and moist winters
and dry hot summers,
between 30º and 40º
latitude, vegetation is
short with small, tough
leaves, adapted to
periodic fires, found in
dry coastal regions
(e.g. California
chapparal).
http://pix.botany.org/set01/01-110h_700.jpg
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Mediterranean Woodland and Shrubland
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Mediterranean Woodland and Shrubland
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Occur in all continents except Antarctica.
Climate cool and moist in fall, winter, and
spring, but can be hot and dry in summer.
Fragile soils with moderate fertility.
Trees and shrubs typically evergreen.
Fire-resistant plants due to fire regime.
Long history of human intrusion.
 Cleared for agriculture.
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Temperate Grassland
Midlatitude grasslands receiving
0.3 to 1.0 m rainfall per year,
falling mostly during summers.
http://taggart.glg.msu.edu/bs110/PRAIRIE.JPG
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Temperate Grassland
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Temperate Grassland
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Extremely widespread distribution.
Annual rainfall 300 - 1,000 mm.
Experience periodic droughts.
Soils tend extremely nutrient rich and deep.
Thoroughly dominated by herbaceous
vegetation.
Large roaming ungulates.
 Bison vs. cattle
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Temperate Forests
Coniferous or deciduous forests of 40º to
50º latitude with precipitation of 0.65 to
3.0 m per year, with more precipitation in
winter than at temperate grasslands.
http://nebraska.sierraclub.org/movalley/images/Hitchcock-Forest.jpg
http://homepages.caverock.net.nz/~bj/beech/sustainable/Forest_floor2.jpg
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Temperate Forest (Old Growth)
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Temperate Forest (Old Growth)
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Majority lie between 40o and 50o latitude.
Rainfall averages 650 - 3,000 mm.
Fertile soils
 Long growing seasons dominated by
deciduous plants.
 Short growing seasons dominated by
conifers.
Biomass production can be very high.
Many major human population centers.
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Boreal Forest (Taiga)
Northern forest
south of the arctic
tundra, mostly
containing conifers
(spuce) and some
aspen and birch.
http://earthobservatory.nasa.gov/Study/BorealMigration/Images/boreal_forest_combined.jpg
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Boreal Forest (Taiga)
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Boreal Forest (Taiga)
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Confined to Northern Hemisphere.
 Covers 11% of earth’s land area.
Thin, acidic soils low in fertility.
Generally dominated by evergreen conifers.
Relatively high animal density.
Historically, low levels of human intrusion.
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Tundra
Northern most biome dominated by
mosses, lichens, and dwarfed willows
and birch, low to moderate precipitation
and very short growing season.
http://www.heritage.nf.ca/environment/images/tundra.jpg
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Tundra
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Tundra
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Covers most of lands north of Arctic Circle.
 Climate typically cool and dry with short
summers.
 200 - 600 mm precipitation.
Low decomposition rates.
Supports substantial numbers of native
mammals.
Human intrusion historically low, but
increasing as resources become scarce.
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Mountains: Islands in the Sky
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Mountains: Islands in the Sky
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Built by geological processes and thus
concentrated in belts of geological activity.
Climate changes with elevation and latitude.
Soils are generally well-drained and thin.
Flora and fauna change with elevation.
Rare or unique flora and fauna due to
geographic isolation.
Historically used as a source of raw
materials for human settlements.
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