The biome known as caatinga (from the Tupi word meaning 'white forest') or caatingas in northeastern Brazil has its origin possibly long after the splitting of the South American and African continents as a result of geological, edaphic, and climaticinteractions, with its floristic composition and physiognomy attained through periods of decreasing rainfall and prevailing irregular pluviometric regime, and its xerophytic identity derived along the Tertiary-Quaternary. This biome, characteristically unique in the world, occupies an area of 844,453 km2, which corresponds to roughly 10% of the Brazilian territory (IBGE 2004), extending along undulated pediplanes of erosive origin that exposed the Brazilian Precambrian crystalline bedrock (Cole 1960; Andrade and Lins 1965) and formed numerous exorheic ephemeral water courses (Ab'Saber 1974), which drain in a radial pattern to the north, east, and south, due to the presence of a mountain range in the center of the biome (Sampaio 1995).
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