Soil-relief relation in alisol-arenosol pedological system in the northeast region of the state of Paraná: Case of amaporã

Abstract

The genesis of soils is related to landscape factors, the variation in our morphological characteristics is directly linked to different formation processes. Relief is a pedogenesis conditioning factor, dating back to the idea that diversity of forms influences the formation and spatial configuration of soils. In the Brazilian System of Soil Classification (SiBCS), sandy-textured soils have a suborder that encompasses them, being classified as Neossolos order level and Quartzarênicos (RQ) suborder level. The RQs represent about 8% of the national territory and are distributed practically in all states of Brazil, their occurrence is mainly associated with the geological substrate, as in the case of northwestern Paraná, the Caiuá group sand stones, recurring the existence of sandy soils located in valley bottoms. Thus, this paper aims to describe and illustrate the architecture of the horizons as well as the granulometry variation of the soil along two topossequences, located in Amaporã, northwestern Paraná. The Pedological Coverage Structural Analysis method was applied through two topossequences (T1 and T2), which allowed to verify the lateral distribution of the soils from the top to the valley through hand auger explorations at a depth of 120 cm. For each sample exploration were collected at depths of 0-5, 20, 50, 90 and 120 cm that were later analyzed for their particle size. The studied topossequences present a pedological system composed of two soil classes Alissols and Arenosols. Alisols occupy the entire upper and middle portion of the slopes while Arenosols occupy the valleys. The particle size variations indicated that there is a decrease in the smaller fractions, mainly clay, as the valley settles down. There is also a gradual transition in the color of the soil from red in the upstream to yellow and whitish portions near the valley. The Alisol - Arenosol Pedological System was interpreted as the final stage of the pedogenetic evolution for the study region, a product of subsurface eluviation processes, which export all fine-grained material and promote a consequent relative accumulation of sand to the valley bottoms.