Where does primary ecological succession typically begin?

• A. After a flood with existing soil
• B. In an area cleared by a wildfire
• C. In lifeless areas with no soil, such as after a lava flow
• D. In a mature forest with established soil

Answer: (C)

Primary ecological succession starts in places where there is no soil and the environment is bare, like freshly solidified lava flows. When rock first becomes exposed, there are no nutrients or seeds in soil to support a plant community, so hardy organisms such as lichens and some mosses move in first. They can survive on the rock, begin to break it down, and add organic material as they grow and die. That initial buildup of soil is what allows other plants to establish, and over time the ecosystem becomes more complex with grasses, shrubs, and then trees.

This is different from scenarios where soil already exists. After a flood, a wildfire, or in a previously forested area that’s been cleared, soil remains and seeds or roots can sprout more quickly, so those cases are secondary succession. A mature forest with established soil isn’t starting from scratch either. So the lifeless, soil-free setting—such as after a lava flow—is where primary succession typically begins.