Geomophology, soils and vegetation differentiation in a tropical rain forest environment in Suriname

Abstract

A landscape model of a tropical rain forest environment is described. The main events of the geomorphological evolution of the study area since the late Tertiary comprise the development of a planation surface during the Miocene followed by deposition of Pliocene continental Upper Coesewijne sediments and subsequent dissection during Quaternary times. Parent material and geomorphology led to the development of Entisols and Ultisols. The occurrence of various subgroups of these orders is closely related to the distribution of the main vegetation formation types, mesophytic semideciduous forest. Xeromorphic forrnations like walaba forest and savanna forest, and mixed mesophytic and walaba forest. Differences in chemical properties of four respresentative soils which are all very poor, appear to be small and it is suggested that they cannot be regarded as main causes of the vegetation differentiation in the study area. Differences in soil physical properties are more pronounced resulting in distinct variations of soil water retention characteristics. Under the given climatic conditions a comparison is made of the water balance of the representative soils. Results suggest that the mean monthly plant-available soil moisture is a major variable in vegetation differentiation. whereas the length of the edaphically dry period is of lesser importance. In relation to the implementation of the Kabalebo storage lakes project these findings imply the necessity for research into the risks of savannisation and increased sediment production.