As a result, salt marsh has extended 800 meters seawards during the last century, while valley woodland has kept pace by invading the landward limit of the marshland. Autogenic succession - is a succession where both the plant community and environment change, and this change is caused by the activities of the plants over time. Mt. St. Helens after the last volcanic eruption. Progressive succession - is a succession where the community becomes complex and contains more species and biomass over time. Retrogressive succession - is a succession where the community becomes simplistic and contains fewer species and less biomass over time.
Some retrogressive successions are allogenic in nature.
For example, the introduction of grazing animals result in degenerated rangeland. Table 7i-1 describes some of the plant, community, and ecosystem attributes that change with succession. The essential feature of facilitation succession , in contrast with either the tolerance or inhibition models, is that changes in the abiotic environment are imposed by the developing plant community . Thus, the entry and growth of the later species depends on earlier species preparing the ground. The tolerance model suggests that a predictable sequence is produced because different species have different strategies for exploiting resources .