Chapter 2 Land
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Announcements?
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IN AFS tonight
 5 pm, CL 167 Nick Haunert, Eagle Creek
Reservoir Fish
Molles: Ecology 2nd Ed.
Objectives:
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Describe climate based on climate diagrams
Explain how climate controls geographic
distribution of biomes based on:
 Temperature extremes
 Temperature and precipitation seasonality
Match biomes to their geographic locations
Describe soil characteristics that influence
plant species distribution within biomes
Molles: Ecology 2nd Ed.
Chapter Concepts
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Uneven heating of earth’s surface by sun
and tilt of earth’s axis, combine to produce
predictable latitudinal variation in climate
Molles: Ecology 2nd Ed.
Chapter Concepts
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Geographic distribution of terrestrial biomes
closely corresponds to variations in climate,
especially temperature and precipitation
Molles: Ecology 2nd Ed.
Introduction
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Janzen studied tropical dry forests in Costa
Rica for restoration efforts
 Guanacaste tree (E. cyclocarpum)
Molles: Ecology 2nd Ed.
Introduction
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Janzen studied tropical dry forests in Costa
Rica for restoration efforts.
 Guanacaste tree (E. cyclocarpum)
 No current dependable dispersers; trees
produce massive numbers of fruits
Molles: Ecology 2nd Ed.
Introduction
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Janzen studied tropical dry forests in Costa
Rica for restoration efforts.
 Guanacaste tree (E. cyclocarpum)
 No current dependable dispersers; trees
produce massive numbers of fruits.
 Last native dispersers extinct 10,000
years ago (sloths, camels).
– Cattle and horses (exotics)
dispersers.
Molles: Ecology 2nd Ed.
Natural history info is
important!
Molles: Ecology 2nd Ed.
Soil Factors that
Determine Species
Distributions
Molles: Ecology 2nd Ed.
Mineral composition
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Nutrient availability
Toxic substances (metals)
pH
Solubility of nutrients / toxic
metals
Molles: Ecology 2nd Ed.
Soil Texture
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Relative amounts of gravel, sand, silt, clay
 Silt & Clay
 Water retention
 Nutrient retention and availability
 Gravel & Sand
 Aeration (oxygen for roots)
Organic matter has beneficial influence on
water/nutrient availability AND aeration
Molles: Ecology 2nd Ed.
Texture, Aeration, and Soil Water
Molles: Ecology 2nd Ed.
Molles: Ecology 2nd Ed.
Soil : Foundation of Terrestrial Biomes
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Soil: Complex mixture of living and non-living
material.
 Classification based on vertical layering
(soil horizons).
 O Horizon
 A Horizon
 B Horizon
 C Horizon
Molles: Ecology 2nd Ed.
Soil Horizons
O: Organic Layer freshly fallen organic
material – most superficial layer.
Fig. 2.3
Molles: Ecology 2nd Ed.
Soil Horizons
O: Organic Layer freshly fallen organic
material – most superficial layer.
A: Mixture of minerals, clay, silt and sand.
Fig. 2.3
Molles: Ecology 2nd Ed.
Soil Horizons
O: Organic Layer freshly fallen organic
material – most superficial layer.
A: Mixture of minerals, clay, silt and sand.
B: Clay, humus, and other materials leached
from A horizon – often contains plant roots.
Fig. 2.3
Molles: Ecology 2nd Ed.
Soil Horizons
Fig. 2.3
O: Organic Layer freshly fallen organic
material – most superficial layer.
A: Mixture of minerals, clay, silt and sand.
B: Clay, humus, and other materials leached
from A horizon – often contains plant roots.
C: Weathered parent material.
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Soil profile = snapshot of soil structure in
constant state of flux.
Molles: Ecology 2nd Ed.
Molles: Ecology 2nd Ed.
Drainage
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Water retention & Aeration
 Topography
Run-off
 Flat vs. Sloped
 Upper vs. Lower Slope
 Convex vs. Concave
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Impervious soil layers
Infiltration
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Soil texture
Molles: Ecology 2nd Ed.
Soils influence local distribution of plants
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Texture: water, nutrients
Parent rock: pH, nutrients, toxic metals
Organics: water, nutrients
pH: nutrient availability, solubility of metals
Drainage: aeration of roots, solubility of
metals
Plants add organics, influence weathering
Molles: Ecology 2nd Ed.
Climate
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Temperature and precipitation regime
that is typical for a specific location
or region:
 Average temp. and precipitation
 Temp. extremes (especially minimum)
 Seasonality of temp. and /or
precipitation
Molles: Ecology 2nd Ed.
Factors That Control Regional
Climate
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Latitude (affects solar radiation)
Direction of prevailing winds
 From ocean or from land (moist vs.
dry)
 From tropical or polar (warm vs. cold)
 Rain shadow of mountains
Proximity to large water bodies
Elevation
Molles: Ecology 2 Ed.
nd
Climate variability
Large-scale patterns
Molles: Ecology 2nd Ed.
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Large Scale Patterns of Climatic Variation:
Temp., Atmospheric Circulation, and Precip.
Spherical shape, tilt of earth’s axis:
 uneven heating of earth’s surface.
Molles: Ecology 2nd Ed.
Fig 2.5
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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.
Molles: Ecology 2nd Ed.
Fig 2.5
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Rainforests at equator.
Major Deserts at 30o N and S.
Molles: Ecology 2
Fig
2.5
nd
Ed.
Molles: Ecology 2
Fig
2.5
nd
Ed.
Temp., Atmospheric Circulation, and Precip.
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Coriolis Effect =
 winds clockwise in N hemisphere;
counterclockwise in S hemisphere.
Molles: Ecology 2nd Ed.
Fig 2.5
Climate Diagrams
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Summarize various env. variables for area.
 Allows quick comparison between areas
for vegetative growth predictions.
Molles: Ecology
2nd
Ed.
Fig 2.7
Molles: Ecology 2
Fig
2.7
nd
Ed.
Molles: Ecology 2
Fig
2.8
nd
Ed.
Molles: Ecology 2
Fig
2.8
nd
Ed.
Terrestrial Biomes
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Biomes: distinguished by plants –
associated with particular climates
Molles: Ecology 2nd Ed.
Biome
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A major geographic region
characterized by a distinctive
assemblage of life forms.
 Defined by dominant plant life forms
on land.
 Defined by dominant plants or
animals in sea.
Terrestrial biomes generally the result of
large-scale climate patterns.
Molles: Ecology 2nd Ed.
Natural History and Geography of Biomes
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Main factors determining biomes are:
 Temperature and Precipitation
Molles: Ecology 2nd Ed.
Molles: Ecology 2nd Ed.
Tropical Rainforests
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Within 10o lat. of equator
Little temp variation
Annual rainfall 2,000 – 4,000 mm
 Heavy rainfall leaches soil nutrients
Organisms add vertical dimension
Staple foods + medicines for human pop’s –
increasingly exploited
Molles: Ecology 2nd Ed.
Ecology 2
FigMolles:
2.10
nd
Ed.
Tropical Dry Forest
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10o – 25o latitude
More seasonal than tropical rainforest
Soils richer in nutrients, but erosion
Shares many animal and plant spp. w/ tropical
rainforests
Heavily settled by humans – extensive clearing
for ag
Molles: Ecology 2nd Ed.
Molles: Ecology 2nd Ed.
Fig 2.13
Fig 2.14
Molles: Ecology 2nd Ed.
Tropical Savanna
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N / S of Dry Forests
Alternate between wet / dry seasons
 Drought w/ dry season = dry conditions;
lightning-caused wildfires.
Soils low water permeability.
 Saturated soils keeps trees out.
Increasing pressure to produce livestock.
Molles: Ecology 2nd Ed.
Fig 2.16
Molles: Ecology 2nd Ed.
Desert
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30o N and 30o S
~ 20% of earth’s land surface
Water loss > precip. most of year
Soil usually extremely low in organics
Plant cover sparse to absent
Animal abundance low; biodiversity may be
relatively high
 Strong behavioral adaptations
Human intrusion increasing.
Molles: Ecology 2nd Ed.
Fig 2.19
Molles: Ecology 2nd Ed.
Warm Desert
Molles: Ecology 2nd Ed.
Cold Desert
Molles: Ecology 2nd Ed.
Temperate Woodland and Shrubland
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All continents except Antarctica
Cool and moist in fall, winter, and spring, can
be hot / dry in summer
Fragile soils w/ moderate fertility
Trees and shrubs typically evergreen
Fire-resistant plants due to fire regime
Long history of human intrusion
Molles: Ecology 2nd Ed.
Fig 2.22
Molles: Ecology 2nd Ed.
Temperate Grassland
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Extremely widespread
Annual rainfall 300 – 1,000 mm
Periodic droughts
Soils extremely nutrient rich / deep
Dominated by herbaceous vegetation
Large roaming ungulates
 Bison vs. cattle
Molles: Ecology 2nd Ed.
Fig 2.25
Molles: Ecology 2nd Ed.
Tall Grass Prairie
Molles: Ecology 2nd Ed.
Mixed Grass Prairie
Molles: Ecology 2nd Ed.
Short Grass Prairie
Molles: Ecology 2nd Ed.
Why No Trees In Chaparral or
Grasslands ???
Drought-free growing season too
short
Not enough time to accumulate
energy to produce large woody stem.
Seasonal precipitation causes Fire
Climate
Frequent fires more likely to kill trees
than to kill shrubs and grasses.
Molles: Ecology 2nd Ed.
Molles: Ecology 2nd Ed.
Temperate Forest
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40o and 50o latitude
Rainfall averages 650 – 3,000 mm
Fertile soils
 Long growing seasons = deciduous plants
 Short growing seasons = conifers
Biomass production can be very high
Many major human population centers
Molles: Ecology 2nd Ed.
Fig 2.28
Molles: Ecology 2nd Ed.
Boreal Forest (Taiga)
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N. hemisphere
 11% of earth’s land
Thin, acidic soils low in fertility
Dominated by evergreen conifers
High animal density
Historically, low levels of human intrusion
Molles: Ecology 2nd Ed.
Molles: Ecology 2nd Ed.
Fig 2.31
Molles: Ecology 2nd Ed.
Tundra
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Most of land N of Arctic Circle
 Cool + dry w/ short summers
 200-600mm precip.
 Low decomposition rates
 Substantial numbers of native mammals
 Human intrusion historically low,
increasing as resources become scarce
Molles: Ecology 2nd Ed.
Molles: Ecology 2nd Ed.
Fig 2.34
Molles: Ecology 2nd Ed.
Biomes of North America
Molles: Ecology 2nd Ed.
Summary
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Uneven heating of earth’s surface drives
global precipitation patterns.
Distribution of terrestrial biomes corresponds
to variation in climate.
 Temperature
 Precipitation
Within a single biome (climate region), soil
characteristics influence the distribution of
plant species, which in turn influences the
distribution of other species.
Molles: Ecology 2nd Ed.
Molles: Ecology 2nd Ed.