The terms phytophysiognomy and formation were proposed practically at the same time. The term biome, proposed later, only added the element fauna to the phytophysiognomic and climatic uniformity of the formation concept. Several conceptual modifications have been presented by a number of authors along time, adding other environmental factors to the original concept of biome, as soil for example. Walter proposed an essentially ecological concept, considering biome as an area of uniform environment, belonging to a zonobiome, which is defined by the climatic zone where it is found. This concept takes into consideration other important ecological factors, as altitude and soil, which then constitute orobiomes and pedobiomes. Another factor to be considered is natural fire (pyrobiomes). Biome and morphoclimatic and phytogeographical domain are not synonyms, since the latter does not necessarily have a uniform environment. The tropical savanna biome is a complex of phytophysiognomies, a complex of formations, which represents a gradient of ecologically related biomes, reason enough to consider this complex as a biological unit.
formation; biome; zonobiome; domain; savanna
