Succession
Introduction
Over time, the composition of plant species in an area will change, a pattern known as succession. Succession is a cyclical process, but it starts with a disturbance. A disturbance is any event, whether natural or human-caused, that kills organisms or alters their spatial arrangement in an ecosystem.
After a disturbance, the ground is often left exposed, and various species compete for available resources during regrowth. A plant’s survivability depends on its characteristics and how well it can tolerate the current environment.
Succession typically occurs in three stages, ultimately resulting in a climax community—a stable state where the environment can sustain species at all growth stages. The climax community will persist until another disturbance restarts the cycle.
Image: Navigating Through Rocky Land" by Mike Goren is licensed under CC BY 2.0.
Disturbances and the Necessity of Fire
Common natural disturbances include:
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Forest fires
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Floods
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Droughts
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Extreme weather events
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Disease outbreaks
Human-caused disturbances, such as mowing, logging, clear-cutting, introducing invasive species, and damming, are also common. While disturbances might seem destructive, they are not always harmful. Many ecosystems rely on natural or controlled fires to redistribute nutrients into the soil, promoting healthier regrowth. Controlled burns mimic natural wildfires and are often prescribed by management organizations to prevent the buildup of fuel (dead plant material) on the forest floor, which can lead to more severe wildfires.
However, fire suppression has been a contentious issue. Some argue that preventing fires can lead to more intense future fires due to the accumulation of fuel, while others believe that prescribed fires interrupt natural processes. This debate has led many lawmakers to suppress all fires, which may negatively impact ecosystems that depend on fire as part of their natural cycle.
Image: "Willard Fire: using wildfire to benefit the forest" by Coconino NF Photography is licensed under CC BY-SA 2.0.
Two Different Kinds of Succession
Not all succession starts the same way. When a disturbance is extreme—like a volcanic eruption or glacier retreat—it leaves behind newly exposed rocks with no soil. This is called primary succession. Lichens, mosses, and fungi are among the first organisms to colonize this new land. Over time, as these pioneers decompose, they create soil, allowing more plant species to establish.
If the disturbance is less severe and the soil remains intact (such as after a fire or clear-cutting), the process is known as secondary succession. This allows plants to regrow faster since soil nutrients are already present.
Pioneer Stage
Pioneer plants are the first to colonize a disturbed area. These species, such as lichens, mosses, grasses, and wildflowers, reproduce and grow quickly, requiring minimal soil nutrients. They are shade-intolerant and thrive in open, sunny areas. Pioneer habitats, like fields and prairies, are susceptible to invasive species, so management is crucial to ensure native species dominate.
At ONSC, our meadow is kept in the pioneer stage by frequent mowing, providing habitat for pollinators, insects, rodents, and animals like the Eastern wild turkey.
Image: "Fungi and lichens on a stump" by Sylvia Duckworth is licensed under CC BY-SA 2.0
Shrub Stage
As biodiversity increases, shrubs and small trees begin to grow, introduced by seeds dispersed by animals. Common shrub stage species in the Ozarks include greenbriar, blackberry, sassafras, elderberry, and coral berry or buckbrush. Pioneer trees such as Eastern red cedar and shortleaf pine also thrive in this stage.
You can find shrub-stage habitats at the edges of meadows or surrounding young forests at ONSC, providing forage and shelter for animals like white-tailed deer.
Image: "Trees & Shrubs - Laurustinus - Viburnum tinus" by Mick E. Talbot is licensed under CC BY 2.0
Young Forest
As the area grows undisturbed, sun-loving trees like Eastern red cedars and shortleaf pines become dominant. Seedlings of more shade-tolerant bushes and trees, such as Carolina buckthorn, spicebush, oaks and hickories, begin to grow in the shaded understory. These forests provide habitat for various animals like squirrels, owls, raccoons, and turtles.
Image: "Cedar Swamp Forest" by wackybadger is licensed under CC BY-SA 2.0
Mature Forest
In the mature forest stage, shade-tolerant trees like oaks and hickories replace the pioneer trees. The forest floor is rich with acorns and hickory nuts, supporting animals like black bears, gray squirrels, and white-tailed deer. Although this is often referred to as the climax community, the forest will continue to evolve. Without disturbances, species like maples—even more shade-tolerant than oaks and hickories—may take over, leading to an ecological regression. Managed disturbances are often necessary to maintain the balance in climax communities.
Image: "Dead Old Growth" by k_hargrav is licensed under CC BY 2.0
Resource Competition
Plants compete for light, water, nutrients, and soil space, shaping which species dominate certain areas. The varied sun exposure and soil types in the Ozarks mean you can often observe different stages of succession within the same general area.
Some habitats, like glades, are climax communities that resemble the pioneer stage due to the rocky soil and open slopes. These areas support unique species like the Texas brown tarantula and pygmy rattlesnake. Without management, such as removing invading Eastern red cedars, glades would transition into forests, losing their unique biodiversity.
Image: Wildcat Glade c Missouri Department of Conservation
Links to More Information
Disturbances and Fire
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Forest Service Research: Disturbances and Fire
Learn about how fire and other disturbances play a role in forest ecosystems. -
USDA Forest Service: Ecological Disturbances and Fire Suppression
A detailed report on fire suppression and its effects on forests. -
Fire Suppression Threats
Overview of how fire suppression can harm ecosystems that rely on natural fires. -
Berkeley Study on Wildfire Management
Explore research findings on wildfire management versus suppression.
Ecological Succession
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University of Chicago: Ecological Succession Explained
A broad overview of ecological succession in various ecosystems. -
University of Missouri: Early Successional Vegetation
Learn more about early successional vegetation and its importance in wildlife habitats.
Local and Regional Resources
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Arkansas Natural Heritage Commission
Information on rare plants and animals, and science-based conservation efforts in Arkansas. -
Eastern Red Cedar Information
Explore the characteristics and management of Eastern red cedar forests.