What is the primary distinction between primary and secondary succession?

The primary distinction between primary and secondary succession is indeed the nature of the ground being colonized. Primary succession occurs in environments that are completely devoid of life and soil, such as after a volcanic eruption or glacial retreat. In these scenarios, organisms must establish themselves from bare rock or other inorganic surfaces, leading to soil formation over time.

In contrast, secondary succession takes place in areas where a disturbance has cleared an existing community but left the soil intact, such as after forest fires, floods, or human activities like farming. Because soil and some organisms still remain in the environment, secondary succession typically progresses more quickly and may follow a different trajectory compared to primary succession.

This distinction underscores the importance of the initial conditions present in an ecosystem, dramatically influencing the types of organisms that can establish and the subsequent community structure.

The other factors listed, such as the type of organisms, speed of the process, and age of the environment, can vary and are not definitive characteristics that set the two types of succession apart. For instance, while secondary succession often proceeds more rapidly, both types can eventually lead to similar climax communities given enough time.