Global Climate
Life on Land
Biomes
Chapter 2
1
1
Outline
• Intro
• Temperature, Atmospheric Circulation, and
Precipitation
• Climate Diagrams
• Soil Horizons
• Terrestrial Biomes
2
2
Restoration
using Natural
History
• Janzen studied natural
history of tropical dry
forests in Costa Rica to
aid restoration efforts.
– Guanacaste tree (E.
cyclocarpum) has no
current dependable
dispersers, thus trees
produce massive
numbers of fruits.
• Last native dispersers
went extinct 10,000
years ago.
– Cattle and horses
(exotics) now act as
dispersers.
3
3
Dispersers of Guanacaste
Seeds
4
4
Terrestrial Biomes
• 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.
5
5
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.
– Major deserts found near 30o N / S.
6
6
Solar-Driven Air Circulation
7
7
Temperature, Atmospheric
Circulation, and Precipitation
• Coriolis effect causes apparent deflection
of winds clockwise in the N hemisphere
and counterclockwise in the S
hemisphere.
8
8
Climate Diagrams
• Summarize climatic information using a
standardized structure.
– Temperature plotted on left vertical axis.
– Precipitation plotted on right vertical axis.
• 10o C equivalent to 20 mm precipitation.
– Relative position of lines reflect water availability.
» Adequate moisture for plant growth when
precipitation above temperature.
9
9
Climate Diagrams
10
10
Soil : Foundation of Terrestrial
Biomes
• Soil is a complex mixture of living and nonliving material.
– Classification based on vertical layering (soil
horizons).
• Profile provides a snapshot of soil structure in a
constant state of flux.
11
11
Soil Horizons
• O horizon: Organic Layer freshly fallen
organic material - most superficial layer.
• A horizon: Mixture of minerals, clay, silt
and sand.
• B horizon: Clay, humus, and other
materials leached from A horizon - often
contains plant roots.
• C horizon: Weathered parent material.
12
12
Soil Profile
13
13
Soil – considerations
• Parent material
• Time (age)
• Climate
• Biotic processes – humus
• Topography
• pH (hydrogen ion concentration)
14
14
Climate
• major factors: temp, ppt.
• high in both  high rate of nutrient cycling
• high ppt.  leeching
• high biologic processes characteristic of
warm conditions
 high CO2 production carbonic acid  acts
on rock causing decay, nutrient release
15
15
Biotic processes - Impact formation of
humus
• acts to:
– bind soil particles
– retain water
– maintain soil structure under varied moisture
conditions
16
16
• pH (acidity) impacts:
• Nutrient availability
– May increase  nutrient toxicities
– Decrease  deficiencies
• Different species adapted to different conditions
• Microbial activity
– Affects nutrient cycling – breakdown of
organic matter
17
17
Chart of the Effect of Soil pH on Nutrient Availability
18
18
Acidic Bogs – Special
conditions - Plants from
acidic bogs
19
19
Acidic
conditions
slow decay
processes
20
20
• Topography
and soil
formation
21
21
• Nutrient poor soil - serpentine
22
22
Nutrient loss: impacted by
• water flow
• underlying geology
• vegetation present
• soluble nutrients lost more quickly
following removal of vegetation (Hubbard
Brook studies)
23
23
Consequences of Vegetation removal:
• increased water runoff
– increased nutrient loss
– pollution of adjacent aquatic ecosystems
– soil erosion
• Closed system: nutrients contained/cycled
w/i system
• open system: nutrients move out of
system
– All systems are open!
24
24
Major Biomes
25
25
Tropical Rainforests
• Most occur within 10o latitude of equator.
• Little temperature variation between months.
• Annual rainfall of 2,000 - 4,000 mm relatively
evenly distributed.
– Quickly leaches soil nutrients.
– Mycorrhizae help gather nutrients.
• Organisms add vertical dimension.
• Harbor staple foods and medicines for
world’s human populations - increasingly
exploited.
26
26
Tropical rain forest
•
•
•
•
•
Found worldwide (at least in times past) around the equator
Extremely high levels of rainfall
Poor nutrient content in soils due to high levels of rainfall
Tremendous plant diversity; large trees have shallow root systems
evolved to be able to quickly absorb nutrients as soon as they become
available (due to decay of dead things), before the rains wash them
away.
Typical vertebrates: You name it! More than 50% of all the earth's
terrestrial animal species are found in the tropical rainforest. Picture:
monkeys, toucans, parrots, reptiles of all types, amphibians, and
representatives of just about any major animal group.
27
27
Tropical Rainforests
28
28
Tropical Dry Forest
• Usually located between
10o - 25o latitude.
• Climate more seasonal
than tropical rainforest.
• Soils generally richer in
nutrients, but vulnerable
to erosion.
• Shares many animal and
plant species with tropical
rainforests.
• Heavily settled by humans
with extensive clearing for
agriculture.
29
29
Tropical Dry Forest
30
30
Tropical Savanna
• 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 lightningcaused wildfires.
• Soils have low water permeability.
– Saturated soils keeps trees out.
• Landscape is more two-dimensional with increasing pressure to
produce livestock.
31
31
Tropical Savanna
32
32
Desert
• Major bands at 30o N and
30o S latitude.
– Occupy about 20% of
earth’s land surface.
• Water loss usually exceeds
precipitation.
• Soil usually extremely low in
organic matter.
• Plant cover ranges from
sparse to absent.
• Animal abundance low, but
biodiversity may be high.
– Strong behavioral
adaptations.
• Human intrusion increasing.
33
33
Desert
•
•
•
•
•
•
Extremely arid. Very hot in the daytime; in some regions, extremely cold at night
High nutrient levels in the soil due to very little rainfall
Sparse plant life due to very low humidity and available water
Plantlife is evolved to have special adaptations to store and avoid losing water.
typical plants: cactus, Yucca, xeriphytic shrubs of various species, spectacular
explosion of flowering annuals comes with the spring rains
typical vertebrates: drought-tolerant mammals such as desert foxes, burros,
jackrabbits, high diversity of snakes and lizards, tortoises, Roadrunner and some
other desert-adapted birds (plenty of hawks and eagles)
34
34
Desert
35
35
Mediterranean Woodland and
Shrubland
• 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.
36
36
Mediterranean scrub forest
• Found in arid regions with Mediterranean climate
(e.g., southern California, Spain, European and
African areas bordering the Mediterranean Sea;
southern tip of Africa, southwestern tip of
Australia)
• Winters are rainy and mild; summer days are
long, hot, and very dry
• Characterized by periodic, seasonal fires
• Major plant forms: Dense, spiny, evergreen
shrubs (some of these produce seeds that will
germinate and grow only after they've been
through a fire.)
• Typical vertebrates: mountain lion, coyote, mule
deer, various rodents, many lizards, snakes,
migratory birds, etc.
37
37
Mediterranean Woodland and
Shrubland
38
38
Temperate Grassland
•
•
•
•
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
39
39
•
•
•
•
•
Temperate
grasslands
Characterized by distinct seasonal
changes, moderate rainfall, extremely
rich, organic soil.
Major plant forms: annual grasses and
flowering plants; some areas with more
standing water become marshes
characterized by small trees such as
willows, cottonwoods, etc.
Very fertile land, but with harsh seasonal
variations: hot summers, cold winters
Most of these grasslands have been
converted to farmland for human use,
but some native grasslands have been
preserved.
Typical vertebrates: American Bison
(sometimes erroneously called
"buffalo"), prairie dog, jackrabbit, fox,
coyote, deer, many migratory birds
(especially predatory birds such as
hawks and falcons), etc. Many animals
undergo winter hibernation.
40
40
Temperate Grassland
41
41
Temperate Forest (Old Growth)
• 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.
42
42
Temperate Forest
• Found south of the coniferous forest in areas of relatively
high rainfall and relatively high elevation, but with longer
day length than in coniferous regions
• Major plant form: deciduous (i.e., trees that seasonally
drop their leaves) flowering trees and shrubs.
• Typical temperate deciduous forest areas are the
northeastern U.S. and most of Europe.
• Typical vertebrates: deer, wolf, bear, foxes, many
migratory birds, squirrels, rabbits, etc. Somewhat higher
species diversity than coniferous forest. Some species
hibernate through the winter, when food is scarce in the
snowy landscape.
43
43
Temperate Forest (Old Growth)
44
44
Boreal Forest (Taiga)
• 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.
45
45
Taiga
• Found south of the arctic and tundra regions, primarily in the
northern hemisphere
• Northern boreal forest receives tremendous snowfall in winter; the
conical shape of pines may help them shed snow and avoid damage
to their branches from the weight of snow.
• Highly endangered, these ecosystems are being rapidly logged out,
especially in North America.
• Also found along the the Andes of South America
• Major plant form: evergreen, coniferous trees such as pines, firs,
spruce, etc. (Cone-bearing trees). Under the trees grow shrubs,
mosses, ferns, etc.
• Relatively high levels of rainfall, but short days in the winter.
• Typical vertebrates: deer, wolf, bear, foxes, many migratory birds,
squirrels, rabbits, etc. Higher species diversity than tundra.
46
46
Boreal Forest (Taiga)
47
47
Tundra
• Located just south of the
polar regions in the
northern hemisphere.
– High winds and cold
temperatures prevail
– Climate typically cool
to cold and dry with
short summer
season.
• 200 - 600 mm
precipitation.
48
48
Tundra
•
•
•
Arid (as are the polar regions)
Characterized by PERMAFROST: a permanently frozen layer of soil, which
may be deeper in summer than in winter, but still prevents the growth of
large trees with deep root systems. Low decomposition rates.
Human intrusion historically low, but increasing as resources become
scarce.
•
•
most plants are scrubby and small
lichens (fungus/algae symbiosis) are a major photosynthetic food source
•
Supports substantial numbers of native mammals: reindeer/caribou, Snowy
Owls, Grizzly Bear, Brown Bear, Wolf, Arctic Fox, Ptarmigan (a partridgelike bird), migratory birds, lemmings (small rodents), voles (another rodent).
49
49
Tundra
50
50
Mountains: Islands in the Sky
• 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.
• Historically used as a source of
raw materials for human
settlements.
51
51
Mountains: Islands in the Sky
52
52
Mountains Create Their Own Weather
•Windward side of mountain:
•Moist, warm air carried by prevailing winds
up-slope
•Encounters cooler air
•Water vapor in air condenses  clouds,
precipitation
•Creation of ecosystems related to available
moisture
•Lee side of mountains are dry - rainshadow
http://www.pbs.org/wgbh/nova/kilimanjaro/weather.html
53
53
54
54
55
55
56
56
Ecosystems in the Sierra Nevada – Affected by
precipitation and altitude
57
57
• Summary
• Terrestrial ecosystems are affected by climate
which in turn is affected by global wind and
oceanic circulation patterns
• Soil is an important factor affecting terrestrial
ecosystems as it provides nutrients to plants
forming the basis of those ecosystems
• Many unique local ecosystems exist due to
localized climatic conditions and factors
• The geographic distribution of terrestrial biomes
correspond closely to variation in climate,
especially prevailing temperature and
precipitation.
58
58