Soil resources and plant communities of the central Brazilian cerrado and their development

Cerrado is the natural vegetation of the poorer soils in central Brazil and covers approximately 23% of the land area of the country. It has a marked seasonal climate and posseses a large characteristic flora of fire-resistant plants including about 800 species of trees and large shrubs. The soils are acidic with low CEC and high levels of Al saturation. They are well drained and the majority are Oxisols (ferrallitic soils). The vegetation ranges from treeless grasslands to closed xeromorphic forests. Attempts have been made to correlate increased density of the woody vegetation with gradients in soil nutrients but the relationship is complex. Two floristically different types of cerrad$\tilde {a}$o (closed savanna woodland) are associated with mesotrophic and dystrophic soils respectively. Fire is also an important factor in influencing the density of woody vegetation. A distinct commununity of cerrado trees and shrubs occurs in areas where the water table is periodically high. Aluminium is an important factor in cerrado soils and frequently occurs at levels toxic to cultivated plants. On the other hand, the native species are adapted to high Al levels and a number are Al accumulators. Much of the cerrado area is now cultivated. The strategy has been to neutralize the effects of soil acidity and build up soil fertility, mainly by adding P and Ca. Extensive areas have also been turned over to cattle pasture and pine or eucalypt plantations. A plea is made for greater conservation of cerrado areas since, at present, only a small fraction of this vegetation lies within protected reserves.