Potentiality of The Topographic Position Index in The Predictive Pedological Mapping in a Capricornio-PR River Subbasin

Abstract

The soils of the northwest of the state of Paraná have a high intensity of erosive processes due to its physical-natural characteristics, and these processes initiate in the Ultisols, located in the lower thirds of the slope and evolve reassembling towards the Oxisols. Digital Soil Mapping (DSM) can assist the detailing of existing pedological maps, because the topographic attributes extracted from the Digital Terrain Model (DTM) can predict soil classes. The attribute Topographic Position Index (TPI) compartmentalizes the slope in portions of lower thirds, closer to the bottom of valleys, and the upper thirds, near the water partings. Applied in the sub-basin of the Capricórnio River, this index showed great representativeness in the distribution of the studied soils. By cross-tabulation, the TPI was combined with the topographic attribute slope allowing to define three groups: Oxisols, in the upper and middle thirds of the slopes, with gentle slopes; Ultisols, in the lower thirds, of steeper slopes; and the third, which is a transition between both groups. By the DSM, the distribution of the Ultisols in the basin was 14,7 % of the total area. Oxisols extended in most of the basin, with 76,1 %. The portions with transitional soils occupied 9,2 %. The importance of DSM is highlighted, since it can detail more precisely maps less detailed.