Carbonate-affected soils and desertification in the middle course of the salitre river basin, bahia

Abstract

Desertifi cation in the Brazilian semiarid is associated with advanced land degradation levels, with the deterioration of soils and native vegetation (dry forest, locally named Caatingas). Soil exposure increases the risk of desertifi cation. This study analyzed the relationship between carbonate-aff ected soils and possible desertifi cation in the Salitre River basin's medium course, dry semiarid of Bahia state, in two relief compartments, called carbonate plateau and valley bottom depression. Remote sensing techniques were used for temporal delimitation of soil exposure, comparing the 1950 and 2019 years. The distribution of pedological coverage on a slope was analyzed to measure the soil morphological organization, which were also analyzed in the laboratory from their physical and chemical (with emphasis on the equivalent calcium carbonate) properties. The results showed a greater vegetation cover and more developed and stable soils in the carbonate plateau. In the valley bottom depression, 70% of exposed soil (growing in the last decades) occur under very unstable morphogenetic conditions, with strong removal of solum and on highly friable materials, of high alkalinity and levels of equivalent calcium carbonate that exceed 500 g kg-1. These conditions make it diffi cult to recover the caatingas in the depression area, revealing persistent and evolutionary soil exposure, suggesting a high risk of desertifi cation.