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Lecture 6 kinds_of_ecosystems

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  • 1. Environmental Science A Study of Interrelationships Eleventh Edition Enger & Smith Chapter 6Kinds of Ecosystems and Communities Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  • 2. Kinds of Ecosystems and Communities
  • 3. Outline Succession Biomes: Major Types of Terrestrial Climax Communities Major Aquatic Ecosystems
  • 4. Succession Succession is a series of regular, predictable changes in community structure over time. Activities of organisms change their surroundings and make the environment suitable for other kinds of organisms. A climax community is a relatively stable, long- lasting community that is the result of succession. The kind of climax community that develops is primarily determined by climate.
  • 5. Succession Primary succession begins with a total lack of organisms and bare mineral surfaces or water. Secondary succession begins with the disturbance of an existing ecosystem. • It is much more commonly observed, and generally proceeds more rapidly than primary succession.
  • 6. Primary Succession Terrestrial primary succession • A pioneer community is a collection of organisms able to colonize bare rock (e.g., lichens). – Lichens help break down rock and accumulate debris, helping to form a thin soil layer. – The soil layer begins to support small forms of life.
  • 7. Primary SuccessionPioneer organisms
  • 8. Primary Succession 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. • Each step in the process is known as a successional (seral) stage, and the sequence of stages is called a sere.
  • 9. Primary SuccessionPrimary succession on land
  • 10. Primary Succession Climax communities show certain characteristics when compared with successional communities. • Climax communities maintain species diversity for an extended period. • They contain multiple specialized ecological niches. • They maintain high levels of organism interactions. • Climax communities recycle nutrients while maintaining a relatively constant biomass. The general trend in succession is toward increasing complexity and more efficient use of matter and energy.
  • 11. Primary Succession Aquatic primary succession • Except for oceans, most aquatic systems are considered temporary. • All aquatic systems receive inputs of soil particles and organic matter from surrounding land. • This results in the gradual filling of shallow bodies of water. – Roots and stems below water accumulate more material. – Establishment of wet soil.
  • 12. Primary SuccessionPrimary succession from a pond to a wet meadow.
  • 13. Secondary Succession Secondary succession occurs when an existing community is disturbed or destroyed but much of the soil and some of the organisms remain. • Because the soil and nutrients remain, this process can advance more rapidly than primary succession. • Plants and organisms that survive the disturbance can grow quickly and reestablish themselves. • Nearby undamaged communities can serve as sources of seeds and animals. • The new climax community is likely to resemble the destroyed community.
  • 14. Secondary SuccessionSecondary succession on land
  • 15. Modern Concepts of Succession and Climax As settlers changed “original” ecosystems to agriculture, climax communities were destroyed. • Many farms were abandoned, and land began to return to its “original” condition. Ecologists began to recognize there was not a fixed, pre-determined community for each part of the world. • The only thing differentiating a climax community from any other successional community is its time scale.
  • 16. Biomes: Major Types of Terrestrial Climax Communities Biomes are terrestrial climax communities with wide geographic distributions. • When different communities within a biome are examined, they will show differences in the exact species present, but the general structure of the ecosystem and the kinds of niches and habitats present are similar throughout.
  • 17. Biomes: Major Types of Terrestrial Climax Communities Two primary nonbiological factors have major impacts on the kinds of climax communities that develop in any part of the world. • Temperature • Patterns of precipitation.
  • 18. Biomes: Major Types of Terrestrial Climax CommunitiesBiomes of the world
  • 19. The Effect of Elevation on Climate and Vegetation The distribution of terrestrial ecosystems is primarily related to precipitation and temperature. • Temperature is warmest near the equator and cooler toward the poles. • As altitude increases, average temperature decreases. • Moving from sea level to mountain tops, it is possible to pass through a series of biomes similar to what would be encountered moving from the equator to the North Pole.
  • 20. The Effect of Elevation on Climate and VegetationRelationship between height above sea level, latitude, and vegetation.
  • 21. Desert Deserts are areas that average less than 25 cm annual precipitation. • Unevenly distributed throughout the year. They are likely to be windy. They experience large daily temperature fluctuations. There is infrequent cloud cover. There are many species, but they are present in low numbers. Many species exhibit specialized adaptations to climate, such as the ability to conserve water.
  • 22. Desert Human impact on deserts: • Humans have historically had little impact on deserts. • Modern technology allows for the transport of water to the desert. • This has resulted in the development of cities in some desert areas and some limited agriculture as a result of irrigation.
  • 23. Desert
  • 24. Grassland Temperate grasslands, also known as prairies or steppes, are widely distributed over temperate parts of the world. They typically receive 25 -75 cm of annual precipitation. Fire is an important force in preventing the invasion of trees and releasing nutrients from dead plants to the soil. The primary consumers are large herds of migratory grazing mammals. Many insect species are also common.
  • 25. Grassland Human impact on grassland: • Most of the moist grasslands of the world have been converted to agriculture. • Most of the drier grasslands have been converted to the raising of domesticated grazers like sheep, cattle, and goats. • Little undisturbed grassland is left, and those fragments that remain need to be preserved as refuges for the grassland species that once occupied huge portions of the globe.
  • 26. Grassland
  • 27. Savanna Savannas are found in tropical parts of Africa, South America, and Australia. They are characterized by extensive grasslands spotted with occasional patches of trees. They receive 50-150 cm annual precipitation, unevenly distributed throughout year. Rainfall patterns produce a seasonally structured ecosystem. Fire is a common feature. Many trees are involved in nitrogen fixation.
  • 28. Savanna Human impact: • Savannas have been heavily impacted by agriculture. • Because of long periods of drought, raising crops is difficult without irrigation. • Some areas support nomadic herding. • In Africa, there are extensive areas set aside as parks and natural areas and ecotourism is an important source of income.
  • 29. Savanna
  • 30. Mediterranean Shrublands (Chaparral) Mediterranean shrublands are located near oceans and are dominated by shrubby plants. Their climate features wet, cool winters and hot, dry summers. They receive 40-100 cm annual precipitation. This biome is typical of the Mediterranean coast, coastal southern California, as well as parts of Africa, Chile, and Australia. Vegetation is dominated by woody shrubs adapted to hot, dry summers. Fire is a common feature.
  • 31. Mediterranean Shrublands (Chaparral) Human impact: • Very little undisturbed Mediterranean shrubland still exists. • Agriculture is common, often with the aid of irrigation. • Major cities are located in this biome.
  • 32. Mediterranean Shrubland (Chaparral)
  • 33. Tropical Dry Forest The tropical dry forest is another biome heavily influenced by seasonal rainfall. These biomes are found in Central and South America, Australia, Africa, and Asia. Annual precipitation ranges 50-200cm. Many exhibit a monsoon climate with highly seasonal rainfall. Plants have developed special adaptations to survive drought.
  • 34. Tropical Dry Forest Human impact: • Many of these forests occur in areas of very high human population. • Harvesting of wood for fuel and building materials has heavily affected these forests. • Many of the forests have been converted to farming or the grazing of animals.
  • 35. Tropical Dry Forest
  • 36. Tropical Rainforest Tropical rainforests are located near the equator where temperature is relatively warm and constant. Most areas receive 200+ cm annual rainfall, and some receive in excess of 500 cm. The soil allows high levels of leaching, thus most nutrients are tied up in biomass. Tropical rainforests have a multi-layered canopy. • Epiphytic plants They also host a very high diversity of species.
  • 37. Tropical Rainforest Human impact • Tropical rainforests are under intense pressure from logging and agriculture. • Many of the countries where tropical rainforests occur are poor and seek to obtain jobs and money by exploiting this resource. • Forestry can be a sustainable activity, but in many cases it is not.
  • 38. Tropical Rainforest
  • 39. Temperate Deciduous Forest Temperate deciduous forests are typical of the eastern half of the United States, south-central and southeastern Canada, southern Africa, and many parts of Europe and Asia. These areas receive 75-100 cm annual precipitation, evenly distributed throughout the year. Trees typically lose their leaves during the winter and replace them the following spring.
  • 40. Temperate Deciduous Forest This biome features mild winters and a long growing season (6 months). In contrast to tropical rainforests, where individuals of a tree species are scattered throughout the forest, temperate deciduous forests have many fewer species; some may have two or three dominant tree species.
  • 41. Temperate Deciduous Forest Human impact: • Most of the temperate deciduous forests have been heavily affected by human activity. • Much has been cleared for farming. • Much of the current forest is subjected to periodic logging. • Major populations centers of eastern North America and Europe are in areas that were originally temperate deciduous forest.
  • 42. Temperate Deciduous Forest
  • 43. 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. This biome receives 25-100 cm precipitation annually.
  • 44. Taiga, Northern Coniferous Forest, or Boreal Forest It features short, cool summers and long winters with abundant snowfall. The climate is humid because of the great deal of spring snowmelt; low temperatures reduce evaporation. The trees are adapted to winter conditions: • Needle-shaped leaves prevent water loss. • Flexible branches
  • 45. Taiga, Northern Coniferous Forest, or Boreal Forest Human impact: • Human impact is less severe than with many other biomes because population density is low. • Logging is common. • Herding of reindeer occurs in northern Scandinavia.
  • 46. Taiga, Northern Coniferous Forest, or Boreal Forest
  • 47. Tundra North of the taiga is the tundra, an extremely cold region that lacks trees and has a permanently frozen subsurface soil. The permanently frozen soil layer is called permafrost. The tundra receives less than 25 cm annual precipitation.
  • 48. Tundra This biome has a short, wet summer. Waterlogged soils and shallow ponds and pools are present in spring and summer. Plants are usually less than 20 cm tall. Tundralike communities known as alpine tundra are found on mountaintops throughout the world.
  • 49. Tundra Human impact: • Few people live in this region. • Local native people often rely on subsistence hunting for food. • Because of the very short growing season, damage to this kind of ecosystem is slow to heal, so the land must be handled with great care.
  • 50. Tundra
  • 51. Major Aquatic Ecosystems Aquatic ecosystems are shaped by key environmental factors: • The ability of the sun’s rays to penetrate the water • Depth of the water • The nature of the bottom substrate • The water temperature • The amount of dissolved salts.
  • 52. Major Aquatic Ecosystems Aquatic ecosystems with little dissolved salt are called freshwater ecosystems. Marine ecosystems have a high dissolved salt content.
  • 53. Marine Ecosystems The pelagic region is the open sea above the sea floor. The euphotic zone is the upper layer of ocean where the sun’s rays penetrate. Phytoplankton are microscopic plants floating in the ocean (perform photosynthesis). Zooplankton are microscopic animals of many kinds that feed on phytoplankton. Productive aquatic ecosystems contain a plentiful supply of essential nutrients.
  • 54. Marine Ecosystems
  • 55. Marine Ecosystems Benthic marine ecosystems • Benthic organisms, attached or non-attached, live on the ocean bottom. • Substrate and temperature are very important characteristics in determining benthic community development. • An abyssal ecosystem is a benthic ecosystem that occurs at great depths in the ocean. – There is no light to support photosynthesis. – Animals are scavengers; many are small and generate light for finding or attracting food.
  • 56. Marine Ecosystems The substrate is important in determining the kind of benthic community that develops. • Large plants and algae cannot become established in shifting sand substrate. • Mud usually contains little oxygen but is a good substrate for some kinds of rooted plants. • Rocky surfaces in the ocean provide a good substrate for many kinds of algae. – A profuse growth of algae is associated with a large variety of animals.
  • 57. Marine Ecosystems Coral reef ecosystems are composed primarily of coral animals that build cup-shaped external skeletons. Corals contain single-celled algae and carry on photosynthesis. They require warm water, thus are found only near the equator. Most require clear, shallow water with ample sunlight penetration.
  • 58. Marine EcosystemsCoral reef.
  • 59. Marine Ecosystems Mangrove swamp ecosystems are tropical forest ecosystems that occupy shallow water near the shore and adjacent land. Their trees tolerate high salt content and excrete salt from their leaves. They have extensively developed roots that can extend above water. The trees trap sediment in shallow areas, which results in the development of terrestrial ecosystems.
  • 60. Marine EcosystemsMangrove swamp
  • 61. Marine Ecosystems Estuaries consist of shallow, partially enclosed areas where freshwater enters the ocean. Organisms are specially adapted to varying levels of salinity from tides and river flow. Estuaries are extremely productive ecosystems because areas are shallow, warm, and nutrient- rich. These areas are important nursery sites for fish and crustaceans.
  • 62. Marine Ecosystems Human impact: • Oceans cover about 70% of the Earth’s surface. • Overfishing has destroyed many of the traditional fishing industries of the world. • Fish farming results in the addition of nutrients and has caused diseases to spread from farmed fish to wild fish. • Estuaries are affected by fertilizers, animal wastes, and pesticides that flow down rivers from farmland. • Use of the oceans as transportation results in oil pollution and trash floating onto the shore.
  • 63. Freshwater Ecosystems Freshwater ecosystems may be divided into two broad categories: • Stationary water (lakes, ponds, and reservoirs) • Running water (streams and rivers)
  • 64. Freshwater Ecosystems Lakes and Ponds • The littoral zone of a lake is the region of a lake with rooted vegetation. – Emergent plants have leaves that float on, or protrude above, the water’s surface. – Submerged plants stay submerged below the water’s surface. • The limnetic zone is the region of lake with no rooted vegetation.
  • 65. Freshwater EcosystemsLake ecosystem
  • 66. Freshwater Ecosystems The productivity of a lake is determined by many factors. • Cold temperature reduces rate of photosynthesis. • Shallow water allows more photosynthesis. • Erosion from land increases nutrient levels. • Dissolved oxygen, input via wave action and photosynthesis from aquatic plants, determines the kinds of organisms that can inhabit the lake.
  • 67. Freshwater Ecosystems Lakes and Ponds • Oligotrophic lakes are deep, cold, nutrient-poor. • Eutrophic lakes are shallow, warm, nutrient-rich. • Biochemical oxygen demand (BOD) is the amount of oxygen used by decomposers to break down a specific amount of organic matter.
  • 68. Freshwater Ecosystems Streams and Rivers • Even though most streams are shallow, it is difficult for most photosynthetic organisms to accumulate nutrients necessary for growth. – Most clear streams are not very productive. – Most debris is input from terrestrial sources. • Periphyton is the collection of algae, animals and fungi attached to rocks and other objects on the bottom.
  • 69. Freshwater Ecosystems Streams and Rivers • Swamps are wetlands containing trees able to live in environments that are permanently flooded, or flooded most of the year. • Marshes are wetlands dominated by grasses and reeds. • Many swamps and marshes are successional states that eventually become totally terrestrial communities.
  • 70. Freshwater Ecosystems Human impact: • Most freshwater ecosystems have been heavily affected by human activity. • Any activity that takes place on land ultimately affects freshwater because of runoff from the land. • Agricultural runoff, sewage, sediment, and trash all find their way into streams and lakes.
  • 71. Summary Ecosystems change as one kind of organism replaces another in a process called succession. The climax community is a relatively stable stage. Major regional terrestrial climax communities are called biomes. Primary determiners of the kinds of biomes that develop are temperature and yearly rainfall distribution.
  • 72. Summary Major biomes are desert, grassland, savanna, Mediterranean shrublands, tropical dry forest, tropical rainforest, temperate deciduous forest, taiga, and tundra. Aquatic ecosystems can be divided into marine (saltwater) and freshwater ecosystems. The shore substrate determines the mixture of organisms that can live there. Lakes have a structure similar to that of the ocean, but with different species.

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