Changes in Ecosystems: Ecological Succession

Transcription

1 Changes in Ecosystems: Ecological Succession

2 Introduction to Succession Imagine that Union Grove High School has been abandoned. There is no one to mow the grass, clean the hallways, or maintain the buildings. Draw the UGHS football field as it is today and as you predict it will look after the number of years listed below. Include a list of the plant and animal species that you predict will inhabit this area at each Present: 1 year 10 year 50 years 100 years

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4 Standard SEV2. Obtain, evaluate, and communicate information to construct explanations of stability and change in Earth s ecosystems. c. Construct an argument to predict changes in biomass, biodiversity, and complexity within ecosystems, in terms of ecological succession.

5 Learning Targets. I can SEV2d - SK5: Define biodiversity SEV2c - LK1: Define biomass SEV2c - LR1: Compare and contrast primary and secondary succession SEV2d - LP1: Construct an argument to predict changes in biomass, biodiversity, and complexity within ecosystems, in terms of ecological succession.

6 What is Ecological Succession? Natural, gradual changes in the types of species that live in an area Can be primary or secondary The gradual replacement of one plant community by another through natural processes over time

7 Primary Succession Begins in a place without any soil:»sides of volcanoes»landslides»glacier retreat First, lichens that do not need soil to survive grow on rocks Next, mosses grow to hold newly made soil Known as PIONEER SPECIES

8 Pioneer Species Lichens break down rock to form soil. Low, growing moss plants trap moisture and prevent soil erosion

9 Primary Succession Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

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11 Primary Succession Simple plants like mosses and ferns can grow in the new soil

12 Primary Succession The simple plants die, adding more organic material (nutrients to the soil) The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

13 Primary Succession These plants die, and they add more nutrients to the soil Shrubs and trees can survive now

14 Primary Succession Insects, small birds, and mammals have begun to move into the area What was once bare rock, now supports a variety of life

15 Primary Succession 6/5/03 M-DCC / PCB 2340C 15

16 Secondary Succession Begins in a place that already has soil and was once the home of living organisms (disturbance removes biomass) Occurs faster and has different pioneer species than primary succession Example: after forest fires

17 What is the Role of Disturbance in Succession? A disturbance is a discrete event in time that disrupts an ecosystem or community. Natural disturbances = fires, hurricanes, tornadoes, droughts, and floods. Anthropogenic disturbances = deforestation, overgrazing, and plowing. Disturbances create openings for opportunistic species to colonize areas and change the community structure of an area.

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20 Climax or mature Community A stable group of plants and animals that is the end result of the succession process Does not always mean big trees Grasses in prairies Cacti in deserts

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22 HOW DO ECOSYSTEMS RESPOND TO CHANGE? A change in structure ensures a change in function and species composition (i.e. change in biodiversity) Gradual change During succession, some species colonize and their populations become more numerous, whereas other species populations decline and even disappear.

23 Is Succession Predictable? General patterns of succession are predictable. Research indicates there is no ecological plan leading to ecological balance or equilibrium. can be highly variable, chaotic, and unpredictable. We do know there will be changes to structure, function, and species composition that will continue to change over time. The Earth s ecosystems are dynamic and resilient. Research shows that ecosystems with high diversity in primary producers are the most resilient ecosystems.

24 Page 76: Primary vs secondary succession Venn diagram Rebuilding of an ecosystem Most common form of succession Begins with pioneer plants (lichens) Begins with grasses Slowest form of succession Can occur in any ecosystem Can be the result of a catastrophic event Soil already in place Fastest form of succession Least common form of succession Soil must be created Generally predictable Greater biodiversity Greater biomass