The answer would be SOIL.
Primary succession refers to the ecological succession that occurs in a new land where life has not yet existed. It takes place after a lava flow cools and hardens into a new land, or when a glacier recedes and exposes new land. Because the land that results from these processes is totally new land, the soil must first be produced. On the other hand, secondary succession happens in a formerly inhabited area that was disturbed. The disturbance could be a fire, flood, or human action such as farming. Secondary succession is faster because the soil is already in place. In this case, the pioneer species are plants such as grasses, birch trees, and fireweed. Organic matter from the pioneer species improves the soil. This lets other plants move into the area.