Ecological Succession Both the biotic or living and the abiotic or non- living components of an ecosystem change over time. • Will this landscape of rocks remain this way forever? The answer is, “NO!” • Over the years, one kind of community is replaced by another kind of community until eventually, a stable community develops. • The gradual change in a community is known as succession. Two Types of Succession • Primary Succession: The process of creating life in an area where no life or soil previously existed. • Secondary Succession: The process of rerebuilding a previously existing community after being destroyed by some disaster like fire. Soil exists. Primary succession • The development of an ecosystem in an area that has never had a community living within it occurs by a process called PRIMARY SUCCESSION. • An example of an area in which a community has never lived before, would be a new lava or rock from a volcano that makes a new island. Primary Succession • Begins in a place without any soil – Sides of volcanoes – Receding Glaciers • Starts with the arrival of living things such as lichens that do not need soil to survive. • Called PIONEER SPECIES • Lichen is a classic Pioneer species Pioneer Organisms • Primary succession on land begins in an area where there are no living things and no soil. • The first plants or plant-like organisms that arrive are called pioneer organisms. • They can grow on bare rock without soil eventually breaking it up and helping soil to form. These include lichens and algae. Modification of the environment • 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 Creation of New Soil • Creation of soil allows plants to grow. Primary Succession • Simple plants like mosses and ferns can grow in the new soil Primary Succession • The simple plants die, adding more organic material. • The soil layer thickens, and grasses, wildflowers, and other plants begin to take over. • Then These plants die, and they add more nutrients to the soil. • Shrubs and tress can now survive now. Primary Succession • Insects, small birds, and mammals have begun to move in. • What was once bare rock now supports a variety of life. How does the change of the plants determine the types of animals in the community? • Since plants are the basic source of food for a community, the types of plants that are present determine the animals that live there and eat those plants. Thus, as the plant populations change, so too do the animal populations. Pictures of Succession • One sequence of plant succession in New Jersey might be lichens----then----grasses--shrubs----conifers (pine trees)---deciduous forests(beech and maple trees). Climax Community • Succession ends with the development of a climax community. Here, the plants and animals exist in balance with each other and the environment. For example, in New Jersey a hemlock-beech-maple forest is a climax community. Animals that reside here include, chipmunks, deer, bear, turkeys, rabbits, squirrels, fox, birds, to name a few! Typical New Jersey State forest Animals in a hemlock, beech, maple forest Animals found in a TYPICAL New Jersey State forest Climax communities are stable • The climax community will exist indefinitely without further change, unless something catastrophic occurs. A volcanic eruption or a forest fire, will alter and possibly destroy the climax community. Then, ecological succession begins again and after many years, a new climax community will develop. 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 Secondary succession • SECONDARY SUCCESSION begins in habitats where communities were entirely or partially destroyed by some kind of damaging event. • When an existing community has been cleared by a disturbance such as a fire, tornado, etc...and the soil remains intact, the area begins to return to its natural community. Because these habitats previously supported life, secondary succession, unlike primary succession, begins on substrates that already bear soil. In addition, the soil contains a native seed bank. • Since the soil is already in place, secondary succession can take place five to ten times faster than primary succession. Why Does Ecological Succession Occur? • Organisms alter their environment • Organisms become less suitable for environment • New organisms better adapted to changes in the environment come in and out compete original organisms A Summary of Changes That occur During Succession • Pioneer species colonize a bare or disturbed site. Soil building. • Changes in the physical environment occur (e.g., light, moisture). • New species of plants displace existing plants because their seedlings are better able to become established in the changed environment. • Newly arriving species alter the physical conditions, often in ways that enable other species to become established. • Animals come in with or after the plants they need to survive. • Eventually a climax community that is more or less stable will become established and have the ability to reproduce itself. • Disturbances will start the process of succession again. Does Ecological Succession Ever Stop? • No • Do Humans Affect Ecological Succession?