Impact of ecological stages on the soil microbiota and soil abiotic factors in tropical and subtropical Brazilian regions.

Our aim was to test if ecological stages may influence the arbuscular mycorrhizal fungi (AMF), nematodes, and the soil chemical properties in agroforestry systems (AF), unassisted forest restoration (UFR), and natural ecosystem (Ne) located in the Brazilian Tropical and Subtropical regions. We collected soil samples to determine AMF, nematodes, soil pH, P, and soil organic carbon (SOC). AMF and nematode richness in the AF and Ne were similar in the tropical region.

Spatial variability of chemical indicators of Amazon agricultural soils through geomultivariate statistics, Brazil.

This work focuses on evaluating the spatial variability of chemical attributes of soils under different agricultural use and native forest, indicating which are the possible indicator attributes of changes in environmental, through the use and management of the soil. The study was carried out in the southern region of the Amazonas state, in an Argissolo Vermelho-Amarelo (Ultisol). Sampling grids were established measuring: 90 m × 70 m with regular soil collection spacing of 10 m for the guarana and forest areas; 90 m × 56 m spaced at 10 m × 8 m for annatto area; and 54 m × 42 m with spacing between points of 6 m for the cupuaçu area, totaling 80 sampling points in each area, with soil samples collected at depths of 0.

Soil chemical attributes in areas under conversion from forest to pasture in southern Brazilian Amazon.

The south of the Brazilian Amazon is one of the largest cattle-producing regions in Brazil, however, most of the pastures are in low fertility soils. Thus, cattle breeders compensate for the low production of pastures, increasing the size of the areas, generating more deforestation and burning. These practices increase the chemical degradation process of Amazonian soils, making them increasingly infertile when improperly managed.

Physical soil attributes in areas under forest/pasture conversion in northern Rondônia, Brazil.

The main cause of physical degradation in pasture areas is overgrazing, and when combined with poorly productive soils, it causes the loss of millions of hectares of agricultural soils a year. Thus, work is needed to indicate which physical attributes are most sensitive to degradation, generating information so that soil management can be proposed, with a view to economic, social, and environmental aspects. Therefore, the objective of the work was to evaluate the impacts caused on the physical attributes of the soil, in forests converted to pastures in northern Rondônia, Brazil.

Pedoenvironmental indicators of soil in Western Amazonia, Brazil.

This study aimed to ascertain what soil attributes may be an indicator of natural and anthropic pedogenic changes in top grassland (TG), low grassland (LG), ecotone zone (EZ), and forest (F) in Western Amazonia. Twenty samples of the diagnostic horizons were collected from the studied pedoenvironments: TG (A 0.0-14 and Bi 0.

Natural concentrations and reference values of heavy metals in sedimentary soils in the Brazilian Amazon.

The soils of the Brazilian Amazon exhibit large geochemical diversity reflecting the different soil formation processes in an area covering 49% of the Brazilian territory. Soil contamination by heavy metals is one of the threats to the sustainability of this Biome but establishing quality reference values (QRVs) for the region is a challenging owing to the immense territorial area of the Amazon. This study aimed to determine the natural background of heavy metals in soils from the southwestern Brazilian Amazon in order to propose QRVs for Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, and Zn for alluvial sedimentary soils.