A floristic unit which is characterized by diagnostic species that occur in all strata (overstory and understory) of the vegetation, which may be aggregated into floristic alliances. The diagnostic species used to determine both the Alliance and Association are primarily the dominant species. When data indicate that additional diagnostic species (including differential, indicator, or character species) provide a better characterization of ecological patterns, they are used in addition to the dominant species to classify these floristic units. Source less