Physical attributes and organic carbon in soils under natural and anthropogenic environments in the South Amazon region

The transformation of natural Amazonian environments into production systems, mainly related to agriculture and livestock, is considered the most frequent anthropic activity in the region, which can cause significant changes in physical attributes and soil organic carbon. On the other hand, the proper development of the plants depends basically on the quality of the soil, which is directly related to its attributes. Thus, the objective of this study was to evaluate the physical attributes and organic carbon of the soil in natural environments and in anthropic uses located in the southern region of Amazonas. Samples were collected at four spots in three depths (0.00–0.05 m, 0.05–0.10 m, 0.10–0.20 m), totalling 108 samples. The organic carbon has a positive correlation with silt, geometric mean diameter, weighted mean diameter and aggregates > 2 mm, and negative with soil and clay density. The environments with native forest 1, pasture and agroforestry are characterized by higher values of organic carbon, silt, geometric mean diameter, weighted average diameter and aggregates > 2 mm, while native forest 3, native forest 4 and açaí are characterized by higher values of clay and aggregates clay and aggregates between 2–1 mm and < 1 mm.