On a bare rocky area the following  steps are bound to occur. The first organisms to inhabit the area would be lichens. Lichen are the only organism that can subsist on bare rocks, lichens break up the rock surface which enables dust and humus particles to accumulate in crevices. This provides a foothold for mosses and later ferns and grasses which cause further breakdown of rock and build-up of humus. Small shrubs take root followed by trees which can thrive on relatively poor soil e.g conifers move in, later more exacting deciduous species come in.
At each stage a dominant species can be recognised, this influences the environment in such a way as to make it suitable for another species and this replaces the former as the dominant species etc. Eventually, a climax community is established and no further influx of new species. Climax community would not after the environment in a manner injurious to itself. It remain balanced and self-perpetuating; major environmental changes may after the climax, such alteration might revert it to a more primitive stage