Temporal variation in soil organic carbon stocks under different land-use and land-cover conditions in a semi-arid region

Land-use and land-cover changes, combined with the variation in water availability may disrupt the balance between organic matter inputs and outputs in seasonally dry forests, potentially leading to reductions in soil organic carbon (SOC) stocks. However, how such temporal dynamics manifest across areas with different disturbance intensities remains poorly understood. Therefore, this study investigated temporal variation in SOC stocks across Caatinga areas under different land-use conditions in the Brazilian semi-arid region. We evaluated three areas with distinct vegetation cover: (i) preserved Caatinga; (ii) regenerating area; and (iii) deforested area. Soil samples for the determination of SOC stocks were collected at two depths (0–15 cm and 15–30 cm), along with undisturbed soil samples for the determination of bulk density. Microclimatic conditions were monitored using a micrometeorological station installed in the Caatinga area. Additionally, soil samples were collected during four distinct periods defined according to local water availability: the rainy-to-dry transition, dry period, dry-to-rainy transition, and rainy period. Our results indicated significant differences in SOC stocks among land-use conditions and across sampling periods. The preserved Caatinga (15.95 Mg ha −1 ) and the regenerating area (25.87 Mg ha −1 ) exhibited the highest SOC stocks, whereas the deforested area (8.62 Mg ha −1 ) showed substantially lower values. Temporal fluctuations in SOC stocks were observed across all areas but were more pronounced in the deforested area, which demonstrated greater sensitivity to microclimatic conditions associated with water availability. When the soil depths were analyzed separately, no significant differences in SOC stocks were observed between the evaluated layers. Principal component analysis indicated that land use influenced soil physical and chemical properties, with the deforested area showing higher bulk density and lower clay and organic carbon contents. We conclude that SOC stocks in the Caatinga ecosystems are more strongly influenced by land use history than by temporal variation in water availability, underscoring the critical role of native vegetation conservation and restoration in maintaining soil quality and ecosystem services in semi-arid environments. Therefore, sustainable land use management practices, combined with conservation and restoration efforts, are essential to mitigate SOC losses and promote the recovery of SOC stocks in Caatinga regions.