Soils Developed on Geomorphic Surfaces in the Mountain Region of the State of Rio de Janeiro

ABSTRACT: The evaluation of soils in representative landscapes constitutes an opportunity to evaluate spatial distribution, discuss formation processes, and apply this knowledge to land use and management. In this sense, from the perspective of an environmentally diversified region, the aim of the present study is to evaluate the occurrence and understand the formation of soils in different geomorphic surfaces of a landscape from a mountain region in the state of Rio de Janeiro. The study was developed in the Pito Aceso microbasin in the municipality of Bom Jardim, composed of narrow valleys and a rugged mountain domain, with elevation between 640 and 1,270 m. In a representative landscape, the geomorphic surfaces were obtained from the slope segments and flow lines. On the geomorphic surfaces, soil profiles were described by their morphological properties, collected, and analyzed to describe the chemical and physical properties of each horizon. Geomorphological aspects and possible variations of the parent material directly affected pedogenesis and led to distinct soil classes in the landscape. Variation in the geomorphic surfaces directs the processes for soil formation under current conditions, as well as the preservation of polygenetic soils. Soils of lower development and with greater participation of the exchangeable cations were identified at the summit (talus deposit) (Neossolo Litólico and Cambissolo Húmico) and toeslope (colluvial-alluvial) (Neossolo Flúvico), whereas more developed soils with lower nutrient content occur in the concave (Argissolos Vermelho and Amarelo) and convex (Latossolo Amarelo) backslope, except for the Argissolo Vermelho-Amarelo in the shoulder, which had high exchangeable cations contents.