Environmental Science
A Study of Interrelationships
Thirteenth Edition
Enger & Smith
Unit 4 - Chapter 6, Part 1
Kinds of Ecosystems and Communities
David Rude
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Kinds of Ecosystems and Communities
Outline
 6.1 Succession
 6.2 Biomes Are Determined by Climate
 6.3 Major Biomes of the World
Succession
Communities proceed through is a series of regular,
predictable changes in community structure over time.
Activities of organisms change their surroundings
& make the environment suitable for other kinds of
organisms.
Succession
Climax community
• A relatively stable, long-lasting community that is the
result of succession.
• Not always predictable
• Ecological Succession of the Climax Forest video
Succession
 Types of factors that determine the kind of
climax community
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•
•
•
Climate
Water
Substrate/soil
Colonizing organisms
Succession
 Primary succession
• Begins with
– Total lack of organisms
– Bare mineral surfaces or water
Succession
 Primary succession (continued)
• Examples
– Volcanic lava flow
– Glaciers retreating
– Lower of sea level
• Takes a long time
– Few available nutrients for plants
Succession
 Secondary succession
• Begins with
– Disturbance of an existing ecosystem.
• Much more commonly observed
• Proceeds more rapidly than primary succession.
Primary Succession
 Terrestrial primary succession
• Pioneer community
– A collection of organisms able to colonize bare rock
– Lichens
–
–
–
–
Break down rock and accumulate debris
Helps to form a thin soil layer
Soil begins to support small forms of life
May take 100 years to grow as large as dinner plate
Primary Succession
Pioneer organisms
Primary Succession
 Later Stages
•
•
•
•
•
•
Lichen community replaced by annual plants.
Annuals replaced by perennial community.
Perennial community replaced by shrubs.
Shrubs replaced by shade-intolerant trees.
Shade-intolerant trees replaced by shade-tolerant trees.
Stable, complex, climax community eventually reached.
Primary Succession
Primary succession on land
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Primary Succession
 Successional (seral) stage
• Each step in the process of succession
 Sere
• The entire sequence of stages
Primary Succession
 Characteristics of climax communities
•
•
•
•
•
Maintain species diversity for an extended period.
Contain multiple specialized ecological niches.
Maintain high levels of organism interactions.
Recycle nutrients
Maintain a relatively constant biomass.
Primary Succession
 The general trend in succession
• Increasing complexity
• More efficient use of matter and energy
Primary Succession
 Aquatic primary succession
• Except for oceans, most are considered temporary
– All receive inputs of
– Soil particles
– Organic matter from surrounding land
– Results in gradual filling of shallow bodies of water
Primary Succession
• Early stages
– In deeper parts only floating plants and algae
– As water depth becomes less
– Submerged plants establish roots in sediment
– Roots and stems below water accumulate more
material
– Help to trap sediments
Primary Succession
• As water depth becomes less
– Submerged plants establish roots in the sediments
– Elodea and algal mats
– Emergent plants become established
– Have leaves that float on the surface of the water or
project into the air.
– Water lilies and cattails
Primary Succession
• Later Stages – Transition to Terrestrial Community
– Wet meadow forms
– Grasses & sedges that can tolerate wet roots
– Sometimes sphagnum moss forms a thick floating
mat
» Bog
– Eventually becomes dryer
– Transitions to climax community typical of the area
Primary Succession
Primary succession from a pond to a wet meadow.
Page 112
Floating Bog
Bog
Rainforest Bog
Secondary Succession
 Secondary succession
• Occurs when an existing community is disturbed or
destroyed
– Much of the soil and some organisms remain
• Soil and nutrients allow process to advance more rapidly
than primary succession
• Plants and organisms that survive disturbance can grow
quickly and reestablish themselves
Secondary Succession
• Nearby undamaged communities serve as sources of
seeds and animals.
• New climax community likely resembles the destroyed
community.
Secondary Succession
 Example of seral stages
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•
•
•
•
Annual plants
Grasses and biennial herbs
Perennial herbs & shrubs
Pines
Oak & Hickory trees
Secondary Succession
Secondary succession on land
Page 113
Historical Perspective on
Succession and Climax
 Original communities that European explorers
found:
•
•
•
•
East – hardwood forests
North – evergreen forests
Central – grasslands
South - desert
 Early ecologists saw these as the endpoint
Historical Perspective on
Succession and Climax
 Settlers changed “original” ecosystems to
agriculture
• Poor farming practices destroyed soil
• When farms were abandoned, began returning to its
“original” condition.
 New climax forest resembled original
• Fewer species
• Sometimes entirely different kinds of communities
Historical Perspective on
Succession and Climax
• New species from other parts of the world changed
the mix of organisms
• Diseases removed species that were formerly
dominant
– Chestnut blight
– Dutch Elm disease
Modern Concepts of
Succession and Climax
 Not a fixed, pre-determined community for each
part of the world.
• Main difference between climax community and
successional community is its time scale.
• Climate is only one of many factors that determine
climax community
Modern Concepts of
Succession and Climax
• Human activities that alter climax communities
– Agricultural practices
– Logging
– Suppression of fire
– Changing the amount of water present
– Draining an area
– Irrigation and flooding
Biomes Are Determined By Climate
 Biomes
• Terrestrial climax communities with wide geographic
distributions.
• Different communities within a biome will show
differences in exact species present
• General structure and the kinds of niches and
habitats present are similar
Biomes: Major Types of
Terrestrial Climax Communities
 Two primary non-biological factors that
determine climax communities
• Temperature
• Patterns of precipitation
– Total amount
– Form – rain, snow, sleet
– Distribution
Biomes: Major Types of
Terrestrial Climax Communities
 Major Biomes
• Rainforest
– Tropical
– Temperate
Biomes: Major Types of
Terrestrial Climax Communities
 Major Biomes
• Forest
– Deciduous
– Northern Coniferous
– Dry
Biomes: Major Types of
Terrestrial Climax Communities
Biomes: Major Types of
Terrestrial Climax Communities
 Major Biomes
• Grassland
– Savanna
American Prairie
Pampas – South America
Savanna - Tanzania
Biomes: Major Types of
Terrestrial Climax Communities
 Major Biomes
• Tundra
Caribou Crossing
the Tundra
Tundra
Biomes: Major Types of
Terrestrial Climax Communities
 Major Biomes
• Desert
– Hot
– Cold
Northern India
Gobi Desert - Mongolia
Biomes: Major Types of
Terrestrial Climax Communities
Biomes of the world
The Effect of Elevation
on Climate and Vegetation
 Temperature
• Warmest near equator, cooler toward the poles
• Temperature decreases as altitude increases
• Moving from sea level to mountain tops
– Possible to pass through a series of biomes
– Similar moving from the equator to the North Pole
The Effect of Elevation
on Climate and Vegetation
Relationship between height above sea level, latitude, and vegetation.
The Effect of Elevation
on Climate and Vegetation
 Other non-biological factors
• Periodic fires help maintain some grasslands
• Frequent strong winds prevent establishment of trees
• Type of soil
– Sandy soil dry out quickly
– Hinders water demanding species such as trees
– Wet soils only allow certain types of trees