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									Environmental Science
      ——A Study of Interrelationships

 Cui Jiansheng
 Hebei University of Science and Technology

CH06 Kinds of Ecosystems
        and Communities
Chapter Objectives

After reading this chapter, you should be able to:

● Recognize the difference between primary and secondary
● Describe the process of succession from pioneer to climax
community in both terrestrial and aquatic situations.
● Associate typical plants and animals with the various terrestrial
● Recognize the physical environmental factors that determine the
kind of climax community that will develop.
● Differentiate the forest biomes that develop based on temperature
and rainfall.
● Describe the various kinds of aquatic ecosystems and the factors
that determine their characteristics.

Chapter Outline
Succession                             Global Perspective: Tropical
   Primary Succession                  Rainforests—A Special Case?
   Secondary Succession                  Tropical Rainforest
   Modern Concepts of Succession       Environmental Close-Up: Forest
and Climax                             Canopy Studies
Biomes: Major Types of Terrestrial       Temperate Deciduous Forest
Climax Communities                       Taiga, Northern Coniferous
   The Effect of Elevation on          Forest, or Boreal Forest
Climate and Vegetation                   Tundra
   Desert                              Major Aquatic Ecosystemsd
   Grassland                             Marine Ecosystems
Environmental Close-Up:                  Freshwater Ecosystems
Grassland Succession                   Issues—Analysis: Protecting Old-
   Savanna                             Growth Temperate Rainforests of
   Mediterranean Shrublands            the
(Chaparral)                            Pacific Northwest
   Tropical Dry Forest

   The concept that communities proceed through a
series of recognizable, predictable changes in
structure over time is called succession. The relatively
stable, long-lasting community that is the result of
succession is called a climax community.
   Primary succession is a successional progression
that begins with a total lack of organisms and bare
mineral surfaces or water.
   Secondary succession is much more commonly
observed and generally proceeds more rapidly,
because it begins with the destruction or disturbance of
an existing ecosystem.

Primary Succession
  Terrestrial Primary Succession
  Terrestrial Primary Succession

     Pioneer Organism

   The lichen growing on this rock is able to accumulate
bits of debris, carry on photosynthesis, and aid in breaking
down the rock. All of these activities contribute to the
formation of a thin layer of soil, which is necessary for
plant growth in the early stages of succession. This
collection of organisms is known as the pioneer
community because it is the first to
colonize bare rock.
Primary Succession on Land

   Each step in this process from pioneer community to
climax community is called a successional stage, or seral
stage, and the entire sequence of stages—from pioneer
community to climax community—is called a sere.

 Primary Succession
   Aquatic Primary Succession
   Aquatic Primary Succession

  Primary Succession from a Pond to a Wet Meadow
  Aquatic Primary Succession
  Aquatic Primary Succession

                               Floating Bog
   In many northern regions, sphagnum moss forms a
floating mat that can be colonized by plants that tolerate
wet soils. A network of roots ties the mat together to form
a floating community.

Secondary Succession

               Secondary Succession on Land
Secondary Succession

      Secondary Succession from a Beaver Pond

Biomes: Major Types of Terrestrial Climax Communities

  Biomes are terrestrial climax communities with wide
geographic distribution.

                              Biomes of the World
Influence of Precipitation and Temperature on Vegetation

 The Effect of Elevation on Climate and Vegetation

Relationship Between Height above Sea Level, Latitude, and Vegetation

  Deserts are areas that generally average less than
25 centimeters (10 inches) of precipitation per year.



  Grasslands, also known as prairies or steppes, are
widely distributed over temperate parts of the world.


   Tropical parts of Africa, South America, and Australia
have extensive grasslands spotted with occasional
trees or patches of trees. This kind of a biome is often
called a savanna.


Mediterranean Shrublands (Chaparral)

  The Mediterranean shrublands are located near an
ocean and have wet, cool winters and hot, dry
summers. Rainfall is 40 to 100 centimeters (15 to
40 inches) per year.

                              Mediterranean Shrublands
Tropical Dry Forest

  Another biome that is heavily influenced by
seasonal rainfall is known as the tropical dry forest.

                                  Tropical Dry Forest

Tropical Rainforest

  Tropical rainforests are located near the equator in
Central and South America, Africa, Southeast Asia, and
some islands in the Caribbean Sea and Pacific Ocean.

                                 Tropical Rainforest
Temperate Deciduous Forest

  Forests in temperate areas of the world that have a
winter-summer change of seasons typically have trees
that lose their leaves during the winter and replace
them the following spring. This kind of forest is called
a temperate deciduous forest.

                              Temperate Deciduous Forest

Taiga, Northern Coniferous Forest, or Boreal Forest

  Throughout the southern half of Canada, parts of
northern Europe, and much of Russia, there is an
evergreen coniferous forest known as the taiga,
northern coniferous forest, or boreal forest.

                                Taiga, Northern Coniferous
                                Forest, or Boreal Forest

   North of the taiga is the tundra, a biome that lacks
trees and has a permanently frozen subsurface soil.
This frozen soil layer is known as permafrost.


Major Aquatic Ecosystems

Marine Ecosystems

   An important determiner of the nature of aquatic
ecosystems is the amount of salt dissolved in the
water. Those that have little dissolved salt are called
freshwater ecosystems, and those that have a high
salt content are called marine ecosystems.
Pelagic Marine Ecosystems
Pelagic Marine Ecosystems

  Organisms that are not attached to the bottom are
called pelagic organisms, and the ecosystem they are a
part of is called a pelagic ecosystem.
  The term plankton is used to describe aquatic
organisms that are so small and weakly swimming that
they are simply carried by currents. As with all
ecosystems, the organisms at the bottom of the energy
pyramid carry on photosynthesis. The planktonic
organisms that carry on photosynthesis are called
  The upper layer of the ocean, where the sun’s rays
penetrate, is known as the euphotic zone.
  Small, weakly swimming animals of many kinds,
known as zooplankton, feed on the phytoplankton.

                                    Marine Ecosystems
Benthic Marine Ecosystems
Benthic Marine Ecosystems

   Organisms that live on the ocean bottom, whether
attached or not, are known as benthic organisms, and
the ecosystem of which they are a part is called a
benthic ecosystem. Some fish, clams, oysters, various
crustaceans, sponges, sea anemones, and many other
kinds of organisms live on the bottom. In shallow water,
sunlight can penetrate to the bottom, and a variety of
attached photosynthetic organisms commonly called
seaweeds are common. Since they are attached and
some, like kelp, can grow to very large size, many other
bottom-dwelling organisms, such as sea urchins,
worms, and fish, are associated with them.

                                             Rocky Shore
                Sandy Shore

Coral reef ecosystems are
produced by coral animals
that build cup-shaped
external skeletons around
       Mangrove swamp ecosystems occupy a region
    near the shore. The dominant organisms are
    special kinds of trees that are able to tolerate the
    high salt content of the ocean. In areas where the
    water is shallow and wave action is not too great,
    the trees can become established.


  An estuary is a special category of aquatic
ecosystem, that consists of shallow, partially enclosed
areas where freshwater enters the ocean.
Freshwater Ecosystems
Lakes and Ponds
Lakes and Ponds

   Along the shore and in the shallower parts of
lakes, many kinds of flowering plants are rooted in
the bottom. Some have leaves that float on the
surface or protrude above the water and are called
emergent plants.
   Rooted plants that stay submerged below the
surface of the water are called submerged plants.
     littoral zone

                     limnetic zone

                                           Lake Ecosystem

   Farming and construction expose soil and
release nutrients, as do other human activities such as
depositing sewage into streams and lakes. Deep,
clear, cold, nutrient-poor lakes are low in productivity
and are called oligotrophic lakes. Shallow, murky,
warm, nutrient-rich lakes are called eutrophic lakes.

  The amount of oxygen used by decomposers to
break down a specific amount of organic matter is
called the biochemical oxygen demand or BOD.
Streams and Rivers
Streams and Rivers

   Streams and rivers are a second category of
freshwater ecosystem. Since the water is moving,
planktonic organisms are less important than are
attached organisms. Most algae grow attached to
rocks and other objects on the bottom. This collection
of attached algae, animals, and fungi is called the
   Swamps are wetlands that contain trees that are
able to live in places that are either permanently
flooded or flooded for a major part of the year.
   Marshes are wetlands that are dominated by
grasses and reeds. Many swamps and marshes are
successional states that eventually become totally
terrestrial communities.

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