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Changes in Ecosystems: Ecological Succession Definition: • 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 Flood Fire Hurricanes Tornadoes Human activity Rock Slides http://www.atmo.ttu.edu/Hill%20City%20Tornado%20Enhanced.jp g http://serc.carleton.edu/images/research_education/nativelan ds/nezperce/logging.jpg http://www.eo.ucar.edu/kids/dangerwx/images/storm_surge.jpeg • • • • • • http://www.wildlandfire.com/pics/wall/wildfire_elkbath.jpg What are some common disturbances that can lead to changes? http://www.eos.ubc.ca/research/landslides/landslides_files/image019.jpg http://www.weathersafety.ohio.gov/images/aerial-flood06_350.jpg Primary Succession • Begins in a place without any soil – Sides of volcanoes – Landslides – Flooding • Starts with the arrival of living things such as lichens that do not need soil to survive • Called PIONEER SPECIES http://botit.botany.wisc.edu http://www.saguaro-juniper.com/ Lichens • Do not require soil. • Colorful, flaky patches. • Composed of two species, a fungi and an algae. • The algae photosynthesize and the fungi absorbs nutrients from rocks and holds water. • Over time, they break down the rock. • As the rocks breaks apart, water freezes and thaws on the cracks, which breaks up the rocks further. • When the lichens die, they accumulate in the cracks. • Then mosses begin to grow and die, leading to the creation of fertile soil. • Fertile soil is made up of the broken rocks, decayed organisms, water, and air. 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 http://www.life.uiuc.edu Primary Succession • Simple plants like mosses and ferns can grow in the new soil http://www.uncw.edu http://uisstc.georgetow n.edu Primary Succession • The simple plants die, adding more organic material • The soil layer thickens, and grasses, wildflowers, and other plants begin to take over http://www.cwrl.utexas.edu Primary Succession • These plants die, and they add more nutrients to the soil • Shrubs and tress can survive now http://www.rowan.edu Primary Succession • Insects, small birds, and mammals have begun to move in • What was once bare rock now supports a variety of life http://p2-raw.greenpeace.org Secondary Succession • Begins in a place that already has soil and was once the home of living organisms • Occurs faster and has different pioneer species than primary succession • Example: after forest fires http://www.geo.arizona.edu http://www.ux1.eiu.edu http://www.agen.ufl.edu Climax 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