Lithic soils in the semi-arid region of Brazil: edaphic characterization and susceptibility to erosion

Soils (Leptosols or Epileptic Regosols) with lithic contact at a depth of 50 cm occupy almost 20% of the Brazilian semi-arid region. These lithic soils are susceptible to erosion due to faster saturation of water-holding capacity during rainfall, which accelerates the beginning of runoff. However, erosion traits of lithic soils in the semi-arid region of Brazil are less studied. The aim of this study was to characterize the soil and landscape attributes in areas with Neossolos Litolicos (Entisols) in the Caatinga biome to identify region of high susceptibility to erosion. Results showed that the soils were characterized by a sandy texture, soil structure with poor development and low content of organic carbon. These attributes increase susceptibility to erosion and reduce water storage capacity, especially in the states of Ceara and Sergipe. In these states, the content of rock fragments in the soil reaches 790 g/kg. High contents of silt and fine sand, high silt/clay ratio, predominance of Leptosols and strong rainfall erosivity were observed in Piaui and northwestern Ceara. A very high degree of water erosion was observed in the states of Pernambuco and Paraiba. Despite the low degree of erosion observed in the state of Bahia, it is highly susceptible to erosion due to the predominance of very shallow soils, rugged relief and high values of rainfall erosivity. Lower vulnerability was observed in the state of Alagoas because of its more smoothed relief, greater effective soil depth, thicker A horizon of soil and lower rainfall erosivity. In general, the characteristics that intensify the susceptibility to erosion in the Caatinga biome are those soil structures with poor development or without aggregation, low contents of organic carbon, high contents of silt and fine sand, high values of silt/clay ratio and rugged relief in some regions. This study collected information contributing to a better characterization of soils with lithic contact in the semi-arid region of Brazil. In addition, regions with a higher susceptibility to erosion were identified, revealing insights that could help develop strategies for environmental risk mitigation.

Automated summary

Soils with lithic contact at a depth of 50 cm occupy a significant portion of the Brazilian semi-arid region and are susceptible to erosion. This study aimed to characterize these soils and identify areas at high risk of erosion. Results showed that the sandy soils with poor soil structure and low organic carbon content were more vulnerable to erosion, especially in the states of Ceara and Sergipe. Regions with high contents of silt and fine sand, high silt/clay ratio, predominance of Leptosols and strong rainfall erosivity were observed in Piaui and northwestern Ceara. The states of Pernambuco and Paraiba showed a very high degree of water erosion. Bahia had a lower degree of erosion but was highly susceptible due to shallow soils, rugged relief and high rainfall erosivity. Alagoas had lower vulnerability due to its smoother relief, greater effective soil depth, thicker A horizon of soil and lower rainfall erosivity. In general, the characteristics that intensify the susceptibility to erosion in the Caatinga biome include poor soil structure, low organic carbon content, high silt and fine sand content, high silt/clay ratio and rugged relief in some regions.