The current weather conditions indicate a substitution of grassland by forest vegetation in the Campos de Cima da Serra in Rio Grande do Sul, Brazil. This change in vegetation changes the contents of soil organic matter and soil moisture. This study aimed to evaluate the pedogenetic iron oxides in an Oxisol under native forest and grassland and its relationship with soil total organic carbon content and soil specific surface area. Replacing grassland with native forest resulted in an accumulation of soil organic carbon and possibly influenced dissolutive processes of crystalline iron oxides types and neoformation of metastable types of low crystallinity. In native forest soil, the increase of total organic carbon increased the soil specific surface area, masking the positive effect of iron oxides on this physical characteristic.
dissolution; organic matter; magnetic susceptibility
