Mudanças nas frações da matéria orgânica do solo em diferentes sistemas de uso da terra no sul da Amazônia, Brasil

Abstract

Soil organic matter (SOM) is essential for the provision and maintenance of ecosystem services, and land use change associated with inadequate soil management are the main factors responsible for the decline of SOM. Thus, the objective was to assess the vulnerability of soil organic matter fractions to land use change in the southern Amazon, Brazil. The research was conducted in the municipality of Humaitá, southern region of Amazonas, Brazil. Four land use systems were selected: natural forest, açaí palm, pasture, and cassava plantation. In each land use system, eight sampling points were randomly determined, and soil samples were collected from the layers of 0-5 cm, 5-10 cm, 10-20 cm, and 20-40 cm depth. The C levels were quantified and after granulometric fractionation, the levels of particulate carbon (COP) and mineral carbon (COM), the carbon stock index (IEC), lability (L), lability index (LI), and carbon management index were determined. (IMC). The forest and pasture land use systems showed the highest COP levels (9.64 g kg-1) and (10.71 g kg-1), respectively, in the first layer. Furthermore, the highest levels of SOM were recorded for the cassava land use system (12.10 g kg-1) in the first layer. At the surface, the pasture and forest land use systems showed greater lability of SOM at 1.32 and 1.17, respectively. And the açai palm and cassava systems had the lowest carbon management indices. The change in land use in the southern Amazon modifies the COP and COM, as well as the lability of SOM and the carbon management index.