Imagine a forest that has been destroyed by a forest fire. All the plants Pioneer species in secondary succession are small, fast growing plants and animals that lived there are gone. But the burned-up forest will not that make many seeds. Next, taller plants and shrubs shade out, or grow remain lifeless forever. Plants and animals will return to the area in a around and above, the pioneers. Then, tree seedlings appear. Over time, a process called ecological succession. mature community returns. This process may take hundreds of years.

Succession is gradual change in the structure and makeup of an Succession can happen even in mature or climax communities. For ecological community over time. This can happen in an area where a example, when a tree falls in a mature forest, sunlight may again be able to disturbance destroyed an existing ecosystem. It can also happen in an area reach the forest floor, which would allow new growth to begin. In this case, of new land where an ecosystem has never existed before. As succession succession would begin with new smaller plants. Communities are always progresses, new populations of organisms replace previous populations. changing and growing.

Primary succession occurs where no ecosystem has existed before. It is a Examples of ecological succession: very slow process because it begins on bare rock. A glacier that retreats leaves behind no soil. Lava from a volcanic eruption hardens into bare rock. Example A - A dirt field is plowed and left over the summer. Over the Primary succession begins with soil formation. summer, weeds start to grow on the field. After the weeds grow, small shrubs begin to take root. After a few years, trees begin to grow in the field. The first stage of succession involves pioneer species. In primary succession, pioneer plants are those that can grow without soil, such as Example B – An old wheat field has been left alone by the farmer that once lichens. Lichens begin breaking down a rock. Seasonal cycles of freezing planted the field. After a while, grasses move into the field and begin to and thawing form cracks in the rock. The dead remains of lichens and dust take over. Next, flowering plants, such as wildflowers begin to grow. Later, fall into the cracks. Mosses may being to grow. When mosses and lichens small shrubs begin to grow in the old wheat field. Finally, a few years later, die, they form parts of soil. Slowly, enough soil forms for small shrubs to native trees begin to grow in the field. grow. The roots of the shrubs break up more rock and more soil forms. Example C - A sandy beach along the coast starts to have some small plants Larger plants are able to grow. Eventually, a mature community exists that have rapidly spreading roots. The plants take root and begin to grow. where once there was only a bare rock. This brings in more fertile soil production and other shrubs begin to grow in Primary succession has been recorded at Glacier Bay, Alaska, as a glacier the area. After a few years, trees begin to take root where there once was has retreated. At the edge of the glacier there is ground-up rock called just a sandy beach. glacial till. Farther away is till covered with lichens. Back even farther, Example D - A volcano erupted along a mountain side. After the eruption, small shrubs and tree seedlings are growing. Where the glacier was long the ground was basically just rock. Lichens and mosses began to grow on ago, there is now a mature forest. the rock and began to break down the rock to form soil. Small grasses begin When disturbances destroy an existing habitat, secondary succession to take root and start to grow also. Smaller shrubs come next. Small may occur. This disturbance could be a forest fire or volcanic eruption. The burrowing animals moved in to disturb the soil even more as larger plants plants and animals are gone, but the soil remains. Secondary succession start to grow. After several years, trees take root and grow where there begins on existing soil. once was only rock.