Item

Abstract

Cerrado is a seasonal savanna type covering 20% of the Brazilian territory, however in large areas its vegetation has been replaced by agriculture. The high plains of the Central Brazilian Shield are incised by a large number of stream valleys. In spite of their small individual size, the extension of the stream valleys is estimated to 5% of the total Cerrado area. Apart from their geographical occurrence, Cerrado streams are characterized by extremely low conductivity, weak buffering capacity and variable pH values which are a consequence of the ion poverty of the soils. The hydrographs show very stable patterns during the dry season and frequently recurring flashfloods during the rainy season. The biota of Cerrado streams reveal a range of characteristics such as a reduced proportion of shredding invertebrates, large numbers of predators, and high resistance and resilience to spates. Species traits of aquatic insects include adaptations such as small body size, polivoltine life cycles and the synchronous occurrence of different larval stages. These features make them interesting objects for the development and testing of new stream concepts. On the other hand, the biota and habitat structures are highly sensitive to inputs of inorganic sediments from erosion gullies which threaten literally all Cerrado streams in the agricultural landscapes of Mato Grosso