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Write in your notes: I can distinguish between primary & secondary
succession.
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Ecological Succession
https://www.youtube.com/watch?v=V49IovRSJDs
Ecological Succession refers to the gradual process of change that occurs over time in the communities of organisms that inhabit an area. During the process of ecological succession, species of plants and animals are replaced by new species to form a different ecosystem.
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Primary ecological succession occurs when new organisms begin to inhabit an area that previously was devoid of all life. No soil is present.
Initially, this area consisted of bare rock. As particles of dust blew in over a period of years, enough dirt accumulated for small organisms like lichens and mosses to grow. As these organisms die, a thicker layer of soil starts to build up allowing larger producers to grow.
Causes of Primary Succession: lava flow, glacier retreat, or landslide
A glacier has scraped away allsoil and living things.
A volcanic eruption can wipe out an area.
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As the glaciers began retreating during the last ice age, the areas they had covered were scoured clear of any life. It took thousands of years for forested communities to develop in areas that were once covered by ancient glaciers.
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New lakes formed from melting glaciers were also void of life. Over time, rivers and wind erosion carried sediments and nutrients to these lakes which allowed life to take root.
New Zealand: Succession Due to Lava
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Nine years after Mount Saint Helens erupted and covered miles in every direction with volcanic ash and mud, primary succession had not taken place.
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Thirty years after the eruption, the thick, well-developed forest ecosystem had not returned. But as can be seen here, life is returning slowly.
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Secondary Ecological Succession is succession that does not start from “scratch.” Areas that are cleared to be used for agricultural purposes of that have been deforested still usually have good soil and lots of smaller plants or at least seeds still in the area. HOWEVER, the community of plants and animals that populate the ecosystem may not be the same ones that were there before.
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In temperate regions, if the original forest was a hardwood forest, then it may take over 100 years before that area returns to being a hardwood forest. Trees like pine grow much faster, so the first forest that develops will be a pine forest (soft wood) rather than hardwood.
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The fast-growing, opportunists that quickly begin to repopulate a cleared area are known as “pioneer” species. Once succession has essentially ended, the final community of plants and animals is known as the climax community.
FIRE SUCCESSION: Fire Disturbance and Year Two
Developing or disturbed ecosystems are not stable. They will go through stages of ecological succession.
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If you were to have arrived to Richmond Hill in the early 1700’s you would have noticed that most of the area was hardwood forest. One hundred years later, much of the area would have be cleared for farming. In the early 1900’s, much of Richmond Hill’s swampy areas were drained so they too could be converted to farmland. Some of these old farms were abandoned and are now forested again. https://www.youtube.com/watch?v=dhYArqKVF9Q
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Over many hundreds or even thousands of years, succession can be so complete that a pond can be reduced in size or even convert into forest. This frequently begins as a result of the process of eutrophication.
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Eutrophication is the build-up of major blooms of cyanobacteria, algae, and aquatic plants in a body of water that results from run-off that is high in nitrogen and phosphorous. Sources of this run-off include agricultural areas (animal waste and fertilizers), residential areas, and sewage treatment plants.
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Eutrophication does occur naturally, but usually takes much longer. As the amount of organic matter in an area increases, more decomposed organic nutrients end up in the water. This is a natural fertilizer that promotes the growth of producers. http://www.youtube.com/watch?v=rzE6BNNLew0
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1. Describe the process of eutrophication. Eutrophication is the rapid growth of producers in a body of water resulting from run-off high in nitrogen and phosphorous.
2. What sources of run-off are most likely to result in eutrophication?Run-off from agricultural areas (fertilizer or animal waste), residential areas (lawn fertilizer), or sewage treatment plants.
3. If the source of the run-off continues to discharge into a body of water, particularly small ponds or streams, how might that affect the community of organisms living in or near the pond?The pond could eventually fill in completely and transform into a meadow and later into forest. This would result in a radical shift in the types of organisms.
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4. This map shows the extent of glacial coverage in North America during the last ice age (15,000 years ago.) According to this map, which area of the United States must have undergone primary succession as the glaciers retreated?Northeastern, U.S., area around the Great Lakes, states bordering Canada.
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