Paisagens e solos do Pantanal do Salobra– MS

Abstract

The present study aims to identify the geoenvironments of the floodplain of the Salobra River and to characterize the physical, chemical, mineralogical, and morphological properties of the soils formed in this region, derived from carbonate materials of the Corumbá Group, transported by the river from its headwaters in the Bodoquena Plateau. The study area comprises the lower course of the Salobra River sub-basin, located within the geomorphological unit of the Northern Bodoquena Depression, referred to in this study as the Salobra Pantanal. Ten soil profiles were described and sampled, and five geoenvironments were identified, organized into two landscape compartments: (1) slightly flood-prone areas, represented by continuous and fragmented units, including terraces and forested mounds (capões); and (2) highly flood-prone areas, represented by bays, corixos (secondary channels), and the depositional plain of the Salobra River. Most soils exhibit dark surface horizons and subsurface horizons with grayish tones. Soil pH in H₂O ranged from 6.28 to 8.84 (mean 8.06), indicating predominantly neutral to alkaline reactions. Physical analysis revealed a predominance of clay in the slightly flood-prone geoenvironments, although high clay contents were also observed in seasonally flooded areas, with variations in sand and silt proportions. A notable feature is the presence of gastropod shell fragments, especially in soils from the lower-lying areas. Calcium carbonate equivalent showed high concentrations, reaching up to 900 g/kg in certain horizons. The results highlight the strong influence of the carbonate rocks of the Corumbá Group on the genesis of soils in the Salobra River floodplain, controlling their morphology, chemical composition, and mineralogy. Total oxide contents revealed the predominance of SiO₂, Al₂O₃, and Fe₂O₃, as well as significant variations in CaO among geoenvironments, evidencing the contrast between silicate and carbonate components and the strong control exerted by the parent material on the mineralogical organization of the soils. These characteristics, together with fluvial dynamics, confer specificity to the landscape and have direct implications for understanding pedogenesis.