Succession is a phenomenon in which older communities are replaced by advanced and newer communities
Primary succession is the one in which succession occurs at newer area where none of the community previously evolved
Secondary succession is the one in which the substrate has already been prepared by the older communities so that the newer community which will arrive grow faster that is why secondary succession has faster pace
Glacial retreats leave behind nothing but bare rock as they retreat from an area, leaving barren land from which primary succession can occur which enables scientist to study plant succession
