Ecological succession is an important concept to ecology that describes how ecosystems change. It states that in a given area, communities replace each other in a predictable manner. Succession can be set off by a natural disaster or disturbance such as a forest fire, landslide, or human logging that leaves a habitat unoccupied by plants or animals. A series of species will then colonize the area in a predictable sequence. Perhaps the best way to understand ecological succession is to find a few examples of it.
Sand Dunes Become Woodlands with Ecological Succession
The Offwell Woodland & Wildlife Trust in the U.K. explains how sand dunes in temperate zones can become woodlands in their article “Coastal Sand Dunes: An Example of Primary Succession”. On a flat beach, flotsam washes ashore and plants growing inland cause sand to pile up as the wind blows across the beach. Small plants such as Sand Couch-grass and later on Marram grass stabilize the dune with their root systems, causing sand to stay in place. Nutrients from animal droppings and from decaying grass make an environment suitable for lichens and mosses to grow. Further decaying vegetation creates a sandy soil suitable for scrub such as hawthorn. Eventually trees will find the soil suitable for growing in and the dune will become woodland. This process can occur over hundreds of years.
Ecological Succession Means Ponds Become Grassland
The Missouri Botanical Garden explains in their 2002 webpage “Pond Succession” how ponds eventually become forests or grassland. First, a geological event occurs that creates a hole which fills with water and thus becomes a pond. As the pond develops seeds are flown in by the wind or brought in by birds and animals. Plants begin to grow on the pond’s bottom. Over hundreds of years, generations of plants die. Their decaying matter raises the floor of the pond. As the pond floor becomes level with the ground around it, the area becomes a marsh. Over time the marsh is filled with dirt and debris. It becomes suitable for trees to grow in and becomes a swamp. The swamp dries out and becomes a grassland or forest. The whole process takes hundreds of years.
Ecological Succession Leading to Forests
Duke University describes on their web page “Forest Environment >> Forest Succession” how abandoned farmland eventually became the Duke Forest. This farmland was overworked so that its soils no longer had the nutrients necessary to create healthy crops. After the farmland was abandoned, horseweed and crabgrass began to grow, followed by asters and larger plant species. After three years of abandonment, grass scrub began to take over followed by a few pine trees. From the 19th to 30th year after abandonment the land was a pine forest. The pine forest matured and began to transition to a hardwood forest around year 70. After a hundred years of abandonment what was once farmland had become an oak-hickory forest. Such succession can also occur after forest fires and other disturbances.
Ecological Succession Involves Many Different Species
Although these examples tend to focus on the plant life in succession, it is important to remember that ecological succession involves many different species. New plants attract new animals and new species will interact with each other different. The study of species interaction and the development of communities is an important part of ecology.
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