Influence of vegetation type on silicon content in different subtropical soils

Abstract Soil weathering is the term that describes soil genesis, and its good visual indicators are natural vegetation cover and soil morphology. However, do the same soil types under different vegetation covers affect the degree of soil weathering? Our objective was to study two contrasting soil types under natural vegetation to discuss the degree of weathering, considering their morphology, silicon (Si) content, and fine mineralogy assemblage. Soil samples were collected in nearby Brazilian regions with Ferralsol and Regosol soils, as well as native forest and grassland areas. Soil profile, mineralogy, and chemical composition (total and available ions) were described. Both soils presented the following minerals: mica/illite, kaolinite, quartz, and cristobalite. Available Si content ranged from 6.31 to 8.76 mg kg −1 , and it was higher in Ferralsol than in Regosol soils but did not show dependency on the vegetation type. The total SiO 2 content ranged from 283.5 to 341.4 g kg −1 . The Ki index was higher in the A horizons (2.77) of Ferralsols than in Regosols. The silt/clay ratio content discriminated soil types more accurately. Although vegetation types, mineralogy effects, and Si availability were weak as factors of soil evolution under native conditions, these findings do not end the discussion about the impact of vegetation cover on soil weathering. Further studies on different soil classes are recommended, including assessments of Si content in plant tissues, to elucidate the link of vegetation and mineralogy to chemical availability. Core Ideas The impact of vegetation on the degree of soil weathering is still poorly understood. The studied soils share similar mineralogical characteristics, regardless of their degree of weathering and morphology. Vegetation type does not influence the concentration of available silicon in the studied soils. Plain Language Summary Soil vegetation cover is a factor agent for soil development and evolution (weathering). The study objective was to take contrast soil types under two natural vegetation types to discuss soil weathering aspects. Concerning soil morphology, silicon concentrations, and mineralogical composition, vegetation types played a limited role in soil evolution under native conditions.