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Plant Succession: Definition & Overview

Instructor: Amanda Robb

Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.

In this lesson, we'll look at the process of primary and secondary plant succession. We'll provide an overview of the different stages during succession and the order in which different types of species appear.

What Is Succession?

Picture buying an empty lot. Nothing has been built yet at all, but there's a lot of potential. After laying down the concrete foundation, the workers are able to construct the scaffolding of the house, put up walls and eventually lay down the floors. The building has to occur in a specific way so one structure can support the next. You couldn't start with a couch on your empty lot!

As it turns out, ecosystems work the same way in a process called succession. Succession is the sequence of organism colonization in an ecosystem that has previously been destroyed. Succession starts with an empty area, either pure rock, or a forest destroyed by a fire or clear cutting. Small plants take hold and a specific sequence of growth occurs, eventually resulting in a mature ecosystem again. Like our house, you can't start with the most complex plants. You have to lay a foundation that can support the other layers.

Primary Succession

Picture a barren volcano in Hawaii. Lava has streamed down over the lush landscape for thousands of years, leaving smooth, black rock behind. However, life can still take hold here through primary succession, which starts in a barren environment. Primary succession usually takes a long time, since the ecosystem has to start from scratch.

Primary succession starts from barren rock
primary succession

Secondary Succession

Secondary succession is like primary succession fast forwarded. It doesn't start from a barren location, but rather an ecosystem that has been through a natural or man-made disaster, such as a fire, clear-cutting, or a flood. The soil and seeds present aren't destroyed, so species that appear much later in primary succession, like shrubs and trees appear rapidly. Secondary succession skips the early stages where rock needs to be broken down into soil.

Secondary succession starts with existing plants
boreal forest

Species Colonization

Now, let's look at the different types of species that grow, starting with the first species to appear in primary succession.

Pioneer Species

Picture a barren rock quarry. Humans have destroyed all forms of life, digging up valuable minerals in the area. Surely this disaster of an ecosystem couldn't support life. Well, think again because some plants will persevere. These species are called pioneer species, and they take hold even on empty rock to make a life when wind or animals bring seeds into the area.

Pioneer species are generally low laying plants with simple structures, such as lichen, moss and even some types of fungi. These plants change the structure of the rock, breaking it down into smaller pieces and eventually into soil for other plants to take hold.

Lichen and moss are the first species to take hold
lichen

Grasses

Now that those pioneer species have created soil, grass can take hold. The grasses continue to change the soil, adding more nutrients. The grasses reproduce and bring with them bugs, small birds and mammals. These animals continue to help the grass reproduce, shaping the environment into a grassland. Secondary succession starts here and proceeds through the next steps much more rapidly than primary succession.

Shrubs

So, we have some grasses and lichen. We're still pretty far away from the beautiful forests that occurred before the ecosystem was destroyed. We need some larger plants to take hold with the nutrients the grass provides. The first to come in are shrubs that love the hot, baking sun present in the grassland. The shrubs bring new animals that bring more seeds and continue to change the ecosystem.

Young Forest

Young forests are next in succession and contain large amounts of young trees, called saplings. As the new ecosystem grows it becomes vertically stratified. Different species live at different heights, each needing different amount of light and catering to different species. As trees take hold, shade on the forest floor increases. Grasses and shrubs that are shade-intolerant will die out, with shade-lovers taking their place. This also affects the animal population in the forest. New animals that primarily live in trees and prefer the canopy begin to appear.

Sapling regrowth in secondary succession
young forest

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