Climatic seasonality as a driver of soil carbon stability and soil quality in tropical semiarid regions

Soil management practices and seasonal climatic oscillations act as primary drivers of soil quality in tropical ecosystems. This study assessed the effects of seasonal variability on soil properties and integrated soil quality indices across different land-use systems and native Caatinga vegetation. Six bimonthly soil samplings were conducted under: i) two native dry forests (NF 1 and NF 2 ); ii) tillage with fire (TWF); iii) tillage without fire (TIL); iv) high-stocked pasture (PHS); and v) low-stocked pasture (PLS). Soil quality indices (SQI) integrate physical, chemical, and biological properties to represent key ecosystem functions, including microbial activity, resistance to degradation, and climate regulation. Higher levels of total organic carbon (TOC) and protected organic carbon (Prot-C), exchangeable Ca 2+ and Mg 2+ , soil flocculation degree, and enzyme activities were observed during the dry season. Native forests exhibited the highest SQI, followed by TIL and PLS. TOC (∼45 Mg ha −1 ) and Prot-C (∼43 Mg ha −1 ) stocks promoted greater carbon stabilization in the dry season, with a half-life of 196 days. SQI components increased by 83%, 29%, 303%, and 92% for general SQI, microbial activity, resistance to degradation, and climate regulation, respectively. Dry-season soil quality enhancement was driven by organic carbon, increased microbial biomass, and clay-mediated protection mechanisms, even under fire and intensive grazing. These results indicate that soil management in semiarid regions must prioritize the maintenance of organic carbon pools and soil structural stability, particularly by reducing physical-chemical disturbance during the rainy season, when the risk of carbon losses and soil degradation is highest. • Soil physical and chemical quality increases in the dry season across land uses. • Seasonal dryness enhances microbial efficiency, supporting soil quality. • Higher soil carbon stocks and protected carbon pools occur during the dry season. • Caatinga dry forests and low-intensity management sustain higher soil quality. • Seasonally adapted strategies reduce carbon losses and sustain services.