GENESIS AND CLASSIFICATION OF SOILS OVER FOREST AND PASTURE IN A TOPOSEQUENCE, IN SOUTHERN AMAZONIA

The state of Rondonia has several soil classes, many of which have been subjected to conversion from forest to pasture by the use of fire, causing irreversible damage. Thus, studies are needed to assess changes in soil attributes, as a way to provide information that minimizes the impacts generated. Thus, the objective was to characterize, classify and evaluate the fragility of soils when used as pastures in a toposequence in the district of Uniao Bandeirantes, Porto Velho, Rondonia, Brazil. In the field, a toposequence was selected, where the profiles corresponding to each environment were selected based on the relief position, vegetation patterns (forest and pasture), pedological characteristics and parent material. In each environment, trenches were opened, which were morphologically characterized and samples were collected for physical-chemical analysis of the soil in the laboratory. The soils were classified according to the criteria established by the Brazilian Soil Classification System and by the World Reference Base for Soil Resources. Additionally, multivariate statistics were performed. In profiles P1 to P5, a monochromatic pattern was observed between the horizons. Soil profiles showed textural classes ranging from clayey loam to very clayey. Along the toposequence, two orders of soils, Latossolos and Plintossolos, were observed, which showed differences in the lower categorical levels. In the superficial horizons, modifications were observed in the attributes of granulometry, soil density, exchangeable bases and acidity components. By the multivariate analysis for the diagnostic horizons, three distinct groups were formed: Latossolos Amarelos, Plintossolos Petricos and Latossolos Vermelhos.

Automated summary

This study characterized, classified and evaluated the fragility of soils used as pastures in a specific area in Rondonia, Brazil. The researchers observed changes in soil attributes and categorized the soils based on different criteria. The results indicate significant differences in soil characteristics among forest and pasture areas.