During ecological succession:

Ecological succession involves a gradual and fairly predictable change in the species composition of a given area, i.e., the numbers and types of animals. The establishment of a new biotic community is very slow in its primary phase. 

The first set of species or community that develops in a bare area in ecological succession is the pioneer community. Pioneer species facilitate succession. The final steady stable self-sustaining community in an ecological succession that lead to a community that is in near equilibrium with the environment and is called climax community.