Primary succession occurs in an area without any initial vegetation. Secondary succession occurs in an area with initial vegetation. Primary succession is initiated either due to a biological factor or an external agent. An external factor initiates secondary succession.

Secondary succession. n., [ˈsɛkənˌdɛɹi səkˈsɛʃ.ən] Definition: re-establishment of organisms following an ecological disturbance.

The first step in Primary Succession is Nudation. During this step, the ecosystem is cleared by either a natural occurrence or manmade disturbance. All that is left after this event is barren rock. Examples of natural occurrence would be a volcano eruption, landslide, or glaciers melting.

Answer and Explanation: Because the substrate already exists, secondary succession usually happens faster than primary succession. There is no soil in primary succession thus, it must form. This process takes a more extended period because pioneer species must invade the area, die, and soil formed due to this cycle.

In primary succession, newly exposed or newly formed rock is colonized by living things for the first time. In secondary succession, an area that was previously occupied by living things is disturbed, then re-colonized following the disturbance.

Model 2 – Secondary Succession After 3–5 years grasses and low-growing shrubs have colonized the land. After 20 years small trees form young woodland. 50–100 years after the setback event, mature oak woodland is restored. Established climax community.

There are two major types of ecological succession: primary succession and secondary succession.