Sistema Latossolo-Planossolo: autodesenvolvimento pedológico e evolução da paisagem.

Abstract

Typical landscapes of the Brazilian semiarid region are characterized by predominantly flat relief and shallow eutrophic soils. However, exceptional landscapes were also observed, featuring thick soils in the transitional zone between flat and dissected reliefs in regions of crystalline rocks. In this context, we emphasize the importance of investigating the lower course of the Gavião River (southeast Bahia), where the presence of Latossolos on the Sertaneja Surface remains poorly understood. Our objective was to analyze the pedogeomorphological evolution of the lower course of the Gavião River watershed. We adopted a multi‐scale approach encompassing geological–geomorphological analysis, examining relief compartments, and focusing on slopes and soil profiles, which were detailed at the micromorphological level. We conducted field surveys and laboratory soil analyses (physical, chemical, X-ray diffractometry, and micromorphology) to investigate the relationship between the soils and the landscape. The results revealed a toposequence in which Latossolos transform into Planossolos. We observed that the latossolic cover developed in situ and was being degraded by processes of extreme desiccation and argilluviation, resulting in soil compaction and a loss of fine material due to the formation of a hydromorphic alteration front, culminating in the genesis of Neossolos. The predominance of coarse fragments in Neossolos reflects the removal of fine material by gleization. In contrast, Planossolos are formed by argilluviation, ferrólise, bissialitization, and reprecipitation of 2:1 minerals. Subsequent analyses indicated an evolutionary panorama marked by an arenaceous organization of latossolic covers, clay accumulation on lower slopes, a concentration of coarse fragments in the lowest portions of the relief, and terrain leveling initiated by relief modification and the lowering of water accumulation sectors. In this scenario, we observed a marked increase in soil erodibility, exacerbated by the degradation of Caatinga vegetation cover. In summary, we conclude that pedogeomorphological processes act in an integrated manner, configuring a complex system of soil and slope transformation that alters regional landforms over time. Such transitional landscapes require special attention as they are susceptible to environmental degradation and necessitate conservation strategies adapted to their evolutionary patterns to avoid exacerbating erosive and desertification processes.