The Water Economy of the Vegetation of the `Campos Cerrados' in Southern Brazil

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Abstract
Campos Cerrados of savanna-like aspect cover extensive areas of central and southern Brazil. They are characterized by small trees (5-8 m.) with contorted stems. The depth of the soil is very great, and the water table occurs at 17-18 m. Drought during the rainless period affects only the upper 2-2.5 m. The behavior of the vegetation depends on whether the roots reach the always-humid part of the soil or not. The first is the case of the majority of the small trees and shrubs; they often retain their leaves during the dry season. Saturation deficit of the leaves remains low, and the stomatal mechanism usually reacts slowly. They have no xerophytic character. The shallow-rooted vegetation includes grasses (e.g., Echinolaena inflexa) which wilt during the dry season, and summer-green plants which survive the dry season only in the form of subterranean bulbs or great root- or stem-formations such as the "Xylopodia" of Cochlospermum. Stomatal reactions are more rapid than those of deep-rooted plants. The abundance of water in the soil of Emas and the fact that in undisturbed areas under similar conditions there are hygrophytic forests lead to the conclusion that the Cerrado is not the natural vegetation of the region, but a fire disclimax.