Soils from the Amazonia

Abstract

The Ecuadorian Amazonia is the part of the great Amazonia Basin, which borders with the Andes mountain range at the sector with more volcanic past. These landscapes extend from the Andes adjacent areas to the political border with Peru and Colombia to the east and northeast, respectively. This is a unique region which has been shaped by the arrangement of the geological structures and the climatic change that the region has suffered over geological times. The Amazonian reliefs are characterized by a gradual decrease in altitude from west to east resembling a set of stairs generating two characteristic landscapes: (a) Sub-Andean reliefs, which include corridors, mountain ranges and flanks; and (b) Peri-Andean Amazonia with Peri-Andean hills, and Piedmont and Fluvial Environments. In the Sub-Andean reliefs, the steep slopes range from 3000 to 600 m o.s.l., while the Peri-Andean reliefs are located at attitudes lower than 600 m o.s.l. Soils from the northern Sub-Andean reliefs are derived from volcanic ash, while at the south, without volcanic ash cover, old rocks have developed acid, reddish brown, light textured soils with high Al content. More than two-thirds of the Peri-Andean Amazonia has acid, heavy textured, highly leached, red, well-drained soils developed from tertiary sediments, while the northeast section developed over quaternary sediments covered by volcanic ash developed Andisols. The areas with fluvial influence have poorly drained, silty clay, greyey soils.