Primary succession is one of two types of ecological succession an biological succession of plant life, and occurs in an environment in which new substrate, devoid of vegetation and usually lacking soil, is deposited (for example a lava flow). (The other type of succession, (ecology)|habitat]], creating conditions nearer the optimum for vascular plant growth; pedogenesis or the formation of soil is the most important process. These pioneer plants are then dominated and often replaced by plants better adapted to less austere conditions, these plants include vascular plants like grasses and some shrubs that are able to live in thin soils that are often mineral based. A good example of primary succession takes place after a volcano has erupted. The barren land is first colonized by pioneer plants which pave the way for later, less hardy plants, such as hardwood trees, by facilitating pedogenesis, especially through the biotic acceleration of weathering and the addition of organic debris to the surface regolith.