The pioneer species on a bare rock are usually lichen, mosses and annual grass stage, and blue-green algae. In primary succession rocks, lichens are able to secrete acids to dissolve rocks, helping in weathering and soil formation. It paves way to some very small plants like bryophytes, which are able to take hold in the small amount of soil. They are, with time, succeeded by bigger plants.
Several hard and light demanding trees grow in the area occupied by shrubs. Slowly environment becomes more moist and shadier so that plants of climax community can spread in this area. The type of climax community that will ultimately get established are shrubs and trees,