Distribution of Soils in the Landscape of the Distrito Federal, Brazil.
Marilusa P. C. Lacerda and Inara O. Barbosa. Univ of Brasilia, Campus Darcy Ribeiro, Brasilia, Brazil
Distrito Federal (DF), in Brazil, is presenting fast development with modifications in the use of their lands and, consequently, generating environmental problems. It becomes, then, necessary a actual evaluation of their natural resources, mainly soils. Correlation studies among soils, relief and origin material (geomorpho-geopedology) they can be used in the generation of models of distribution of soils in the landscapes. These models can be used in the elaboration of preliminary maps of soils of an area, contributing in the traditional activities of pedologic mapping. This work assessed to establish a model of distribution of soils of a representative portion of DF, through studies of the correlations geomorpho-geopedologic. The area of the study is located in the portion N-NW of DF, delimited by the coordinates 47o52'39"e 47o52'30" W and 15o45'00" and 15o30'00” S, totaling an area of 742,76 Km2. Initially, the available secondary informations of Distrito Federal on the natural resources were otained. Later, were carried out field activities to accomplish the establishment of the correlations geomorpho-geopedologic. The work was based in the interpretation of the Geomorphological Surfaces of Distrito Federal and Geological Domains in the study area and their relationships with the classes of soils, described to proceed: Surfaces Geomorphological, according to Novaes Pinto (1997, 1994): Surface 1 - Flat regions, with altitudes varying between 1.300 and 1.150 m, Surface 2 - Regions of intermediate dissection, with altitudes varying from 1.000 to 1.150 m and Surface 3 - Regions of hidrographic dissection, with forms of undulated relief, with altitudes among 1.000 to 750m; Geological Domains, described by Silva and Campos (1998): - Domain 1 - MPp - Sequence sedimentary Paranoá (Mesoproterozoic-Neoproterozoic): MPpac: Shale carbonated Facies, MPpr4: Loamy Metarhythmite Facies, MPpq3: Quartzite Facies, MPpr3: Sandy Metarhythmite Facies, MPpa: Slate Facies, MPps: Metassiltite Facies and MPpq2: Quartzite microconglomeratic Facies; and Domain 2 - MPc - Sequence sedimentary Canastra (Mesoproterozoic): MPcf: Phyllites and sericites and chlorite-schists, MPccx: Calc-schists Facies and MPcmx: Mica-schists Facies.The model geomorpho-geopedolic established is summarized to proceed: - Geomorphological Surfaces 1, 2 and 3, slope of 0-10%, Geological Domains MPp: Oxic Rhodustox + Oxic Plinthustox; - Geomorphological Surfaces 1 and 2, slope of 0-10%, Geological Domains MP(MPq3): Typic Troppsamment; - Geomorphological Surface 3, slope of 0-10%, Geological Domains MPc, MPp: Oxic Rhodustox + Oxic Cambustox; - Geomorphological Surface 3, slope of 0-10%, Geological Domains MPc: Oxic Rhodustox; - Geomorphological Surfaces 1, 2 and 3, slope from 10 to 45%: Typic Haplustept; - Geomorphological Surfaces 1 and 2, slope > 45%: Typic Haplustept + Typic Haplustent + Typic Tropsaprent + Rocks; - Geomorphological Surface 3, slope of 10-24%, Geological Domains MPp (MPpac), MPc (MPcf, MPccx and limestone lenses): Tropic Rhodustult + Tropic Haplustult + Ferric Haplustult + Mollic Eutrferralf + Tropic Mollrendent + Typic Haplustept; - Geomorphological Surface 3, slope of 24-45%, Geological Domains MPp (MPpac), MPc (MPcf, MPccx and limestone lenses): Typic Haplustept + Tropic Mollrendent; - Geomorphological Surface 3, slope > 45%, Geological Domains MPp (MPpac), MPc (MPcf, MPccx and limestone lenses): Typic Haplustept + Tropic Mollrendent + Typic Haplustent + Typic Tropsaprent + Rocks. The generated model was checked in field activities and corroborated in evaluations of representative profiles of the main classes of soils, which they were described, analyzed and classified. It was shown representative of the distribution of the soils in the landscape of Distrito Federal, supplying data for pedologic mapping in scale of detail of the area.