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 succession. 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 biomes. 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 Primary Succession Secondary Succession Modern Concepts of Succession and Climax Biomes: Major Types of Terrestrial Climax Communities The Effect of Elevation on Climate and Vegetation Desert Grassland Environmental Close-Up: Grassland Succession Savanna Mediterranean Shrublands (Chaparral) Tropical Dry Forest Global Perspective: Tropical Rainforests A Special Case? Tropical Rainforest Environmental Close-Up: Forest Canopy Studies Temperate Deciduous Forest Taiga, Northern Coniferous Forest, or Boreal Forest Tundra Major Aquatic Ecosystemsd Marine Ecosystems Freshwater Ecosystems Issues Analysis: Protecting Old- Growth Temperate Rainforests of the Pacific Northwest
Succession 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 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 Primary Succession from a Pond to a Wet Meadow
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
Desert Deserts are areas that generally average less than 25 centimeters (10 inches) of precipitation per year. Desert Grassland Grasslands, also known as prairies or steppes, are widely distributed over temperate parts of the world. Grassland
Savanna 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. 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
Tundra 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. Tundra 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 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 phytoplankton. 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 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 themselves.
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. Estuaries 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 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 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 periphyton. 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.