Succession as progressive change in an ecological community. Primary vs. secondary succession. The idea of a climax community.
Key points
Succession is a series of progressive changes in the composition of an ecological community over time.
In primary succession, newly exposed or newly formed rock is colonized by living things for the first time.
In secondary succession, an area previously occupied by living things is disturbed—disrupted—then recolonized following the disturbance.
Introduction
Have you ever looked at a landscape with a complex, diverse community of plants and animals—such as a forest—and wondered how it came to be? Once upon a time, that land must have been empty rock, yet today, it supports a rich ecological community consisting of populations of different species that live together and interact with one another. Odds are, that didn't happen overnight!
Ecologists have a strong interest in understanding how communities form and change over time. In fact, they have spent a lot of time observing how complex communities, like forests, arise from empty land or bare rock. They study, for example, sites where volcanic eruptions, glacier retreats, or wildfires have taken place, clearing land or exposing rock.
In studying these sites over time, ecologists have seen gradual processes of change in ecological communities. In many cases, a community arising in a disturbed area goes through a series of shifts in composition, often over the course of many years. This series of changes is called ecological succession.
Succession
Ecological succession is a series of progressive changes in the species that make up a community over time. Ecologists usually identify two types of succession, which differ in their starting points:
In primary succession, newly exposed or newly formed rock is colonized by living things for the first time.
In secondary succession, an area that was previously occupied by living things is disturbed, then re-colonized following the disturbance.
Succession often involves a progression from communities with lower species diversity—which may be less stable—to communities with higher species diversity—which may be more stable
Primary succession and pioneer species
Primary succession occurs when new land is formed or bare rock is exposed, providing a habitat that can be colonized for the first time.
For example, primary succession may take place following the eruption of volcanoes, such as those on the Big Island of Hawaii. As lava flows into the ocean, new rock is formed. On the Big Island, approximately 32 acres of land are added each year. What happens to this land during primary succession?
First, weathering and other natural forces break down the substrate, rock, enough for the establishment of certain hearty plants and lichens with few soil requirements, known as pioneer species, see image below. These species help to further break down the mineral-rich lava into soil where other, less hardy species can grow and eventually replace the pioneer species. In addition, as these early species grow and die, they add to an ever-growing layer of decomposing organic material and contribute to soil formation.
Photograph of succulent plants colonizing lava during primary succession on Maui.
This process repeats multiple times during succession. At each stage, new species move into an area, often due to changes to the environment made by the preceding species, and may replace their predecessors. At some point, the community may reach a relatively stable state and stop changing in composition. However, it's unclear if there is always—or even usually—a stable endpoint to succession, as we'll discuss later in the article.
Secondary succession
In secondary succession, a previously occupied area is re-colonized following a disturbance that kills much or all of its community.
A classic example of secondary succession occurs in oak and hickory forests cleared by wildfire. Wildfires will burn most vegetation and kill animals unable to flee the area. Their nutrients, however, are returned to the ground in the form of ash. Since a disturbed area already has nutrient-rich soil, it can be recolonized much more quickly than the bare rock of primary succession.
Before a fire, the vegetation of an oak and hickory forest would have been dominated by tall trees. Their height would have helped them acquire solar energy, while also shading the ground and other low-lying species. After the fire, however, these trees do not spring right back up. Instead, the first plants to grow back are usually annual plants—plants that live a single year—followed within a few years by quickly growing and spreading grasses. The early colonizers can be classified as pioneer species, as they are in primary succession.
A diagram showing succession in a forrest. There are 7 images in the diagram. The first image is a flame. The second image is shows only soil. The third image shows the beginning of new vegetation. The remaining images show an increase in new vegetation including shrubs and trees. The final image shows a forrest.
Over many years, due at least in part to changes in the environment caused by the growth of grasses and other species, shrubs will emerge, followed by small pine, oak, and hickory trees. Eventually, barring further disturbances, the oak and hickory trees will become dominant and form a dense canopy, returning the community to its original state—its pre-fire composition. This process of succession takes about 150 years.
The path and endpoint of succession
The early ecologists who first studied succession thought of it as a predictable process in which a community always went through the same series of stages. They also thought that the end result of succession was a stable, unchanging final state called a climax community, largely determined by an area's climate. For instance, in the example above, the mature oak and hickory forest would be the climax community.
Today, the idea of a set path for succession and a stable climax community have been called into question. Rather than taking a predetermined path, it appears that succession can follow different routes depending on the specifics of the situation.
Attribution
This article is a modified derivative of the following articles:
"Community ecology," by Robert Bear and David Rintoul, CC BY 4.0. Download the original article for free at http://cnx.org/contents/db89c8f8-a27c-4685-ad2a-19d11a2a7e2e@24.18
"Succession in communities - Advanced" by Douglas Wilkin and Jean Brainerd, CK-12 Foundation, CC BY-NC 3.0
The modified article is licensed under a CC BY-NC-SA 4.0 license.
Works cited
- G. Tyler Miller and Scott E. Spoolman, "How Do Communities and Ecosystems Respond to Changing Environmental Conditions?" in Essentials of Ecology, 5th ed. (Belmont: Cengage Learning, 2009), 118.
References
"Climax Community." Wikipedia. Last modified March 27, 2016. https://en.wikipedia.org/wiki/Climax_community.
"Disturbance (Ecology)." Wikipedia. Last modified March 27, 2016. https://en.wikipedia.org/wiki/Disturbance_(ecology).
"Ecological Succession." Wikipedia. Last modified May 31, 2016. https://en.wikipedia.org/wiki/Ecological_succession.
Marietta College Department of Biology and Environmental Science. "Succession." Biomes of the World. Last modified October 14, 2013. http://w3.marietta.edu/~biol/biomes/succession.htm.
Miller, G. Tyler and Scott E. Spoolman. "How Do Communities and Ecosystems Respond to Changing Environmental Conditions?" in Essentials of Ecology, 115-119. 5th ed. Belmont: Cengage Learning, 2009.
"Pioneer Species." Wikipedia. Last modified May 21, 2016. https://en.wikipedia.org/wiki/Pioneer_species.
Purves, William K., David E. Sadava, Gordon H. Orians, and H. Craig Heller. "Disturbance and Community Structure." In Life: The Science of Biology, 1063-1065. 7th ed. Sunderland: Sinauer Associates, 2003.
Reece, Jane B., Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, and Robert B. Jackson. "Disturbance Influences Species Diversity and Composition." In Campbell Biology, 1222-1225. 10th ed. San Francisco: Pearson, 2011.
Log in mukonyole5 7 years agoPosted 7 years ago. Direct link to mukonyole5's post “What are some of the stag...” What are some of the stages that occur during primary succession ? • (8 votes) Kartikeya Sharma 6 years agoPosted 6 years ago. Direct link to Kartikeya Sharma's post “This is an example of hyd...” This is an example of hydrarch primary succession (i.e. succession in a wet area): Source: https://farm9.staticflickr.com/8109/8599159947_97e409f201_o.jpg (6 votes) Taran 7 years agoPosted 7 years ago. Direct link to Taran's post “why does only one or two ...” why does only one or two tree species dominate the environment of a forest? • (3 votes) Ivana - Science trainee 4 years agoPosted 4 years ago. Direct link to Ivana - Science trainee's post “Maybe because it relies o...” Maybe because it relies on the competition. It is really hard to have many dominating figures or leaders, right? Imagine working in a workplace where out of 15 employees, 7 are bosses. Is that even possible?! :D (3 votes) zmc0002 6 years agoPosted 6 years ago. Direct link to zmc0002's post “Why don't we see pioneer ...” Why don't we see pioneer species dominating for long periods of time if there are not continued disturbances? • (2 votes) Maffews 6 years agoPosted 6 years ago. Direct link to Maffews's post “As the pioneer species al...” As the pioneer species alters the environment, it makes it more suitable for other organisms to colonise. When they colonise the environment it is changed again which further makes the environment more suitable to a wider range of organisms, increasing biodiversity. It gets to the point that the environment is altered so much it is no longer able/suitable to support the pioneer species; as other more adapted species outcompete it for resources. (5 votes) anna.t.alexander 5 years agoPosted 5 years ago. Direct link to anna.t.alexander's post “What is the difference be...” What is the difference between evolution and succession? • (1 vote) tyersome 5 years agoPosted 5 years ago. Direct link to tyersome's post “Evolution involves change...” Evolution involves changes in allele frequencies within a species.§ Succession involves changes in species frequencies within an ecosystem. Does that help? §Note: I'm simplifying a bit for clarity so these aren't perfectly correct definitions (e.g. I should say population rather than species and "ecological community" rather than ecosystem). (6 votes) villalobosalan 4 years agoPosted 4 years ago. Direct link to villalobosalan's post “When soil first forms ove...” When soil first forms over bare rock, what is it made of? • (3 votes) zenafadhil2005 2 years agoPosted 2 years ago. Direct link to zenafadhil2005's post “idk but its nutrients fro...” idk but its nutrients from lichens breaking down the rocks (2 votes) 133408 serinity 5 years agoPosted 5 years ago. Direct link to 133408 serinity's post “what is an ecosystem with...” what is an ecosystem with diverse species • (3 votes) Ivana - Science trainee 4 years agoPosted 4 years ago. Direct link to Ivana - Science trainee's post “Ecosystem which has as mo...” Ecosystem which has as most possible diverse species with different niches - from water organisms (take bog) to the nearby meadow and eventually trees. (2 votes) daniel millan 6 years agoPosted 6 years ago. Direct link to daniel millan's post “So moss and lichens grow ...” So moss and lichens grow on rocks and break own the rocks to become soil? • (3 votes) smartinez80 7 years agoPosted 7 years ago. Direct link to smartinez80's post “what is primary successio...” what is primary succession ? • (2 votes) bart0241 7 years agoPosted 7 years ago. Direct link to bart0241's post “Primary succession is the...” Primary succession is the process by which a new environment begins to emerge without soil, after a disturbance (fires, earthquakes, etc..) (2 votes) Kwabena Yeboah 7 years agoPosted 7 years ago. Direct link to Kwabena Yeboah's post “What are the processes of...” What are the processes of soil formation • (1 vote) Riky M 7 years agoPosted 7 years ago. Direct link to Riky M's post “Soil formation takes plac...” Soil formation takes place during primary succession - which is when plants colonise bare ground for the first time. The first species of plant that colonises the rock is usually lichen. They are able to survive extreme conditions. While the lichen is present, they capture dust and other small particles present in the air. They then combine these together to form something soil like, however, it so thin that you are unlikely to see it. It is also completely devoid of any nutrients or minerals for any plants to make use of. This is taken care of by the weathering of rock - it gets broken down into smaller and smaller particles which allows the lichen to incorporate them into the 'soil'. Once the lichen dies, it adds humus (organic matter) to the 'soil'. This allows the mineral and nutrient content to be much higher than the just the mixture of dust and other small particles. This process is repeated several thousand times before mosses and herbaceous plants are able to take root. Once these decompose, they too add humus and nutrients to the soil. They make the soil deeper and thus allow more complex and larger plants to take root. As you can see, it a very long and drawn out process! (4 votes) Ronali Fernando 5 years agoPosted 5 years ago. Direct link to Ronali Fernando's post “What does plagioclimax me...” What does plagioclimax mean in primary succession? • (2 votes) Ivana - Science trainee 4 years agoPosted 4 years ago. Direct link to Ivana - Science trainee's post “Human effect destroyed th...” Human effect destroyed the community and prevented from further development. It means that primary succession just started to develop but there is no possibility to persist and survive because of human influence. (2 votes)Want to join the conversation?
Stages:
1. Phytoplankton stage
2. Submerged plant stage
3. Submerged free floating plant stage
4. Reed-swamp stage
5. Marsh-meadow stage
6. Scrub stage
7. (climax) Forest
And predation.
Ground species, birds, different types of vegetation etc.
