Modeling Soil Organic Carbon Dynamics Across Land Uses in Tropical Andean Ecosystems

Soil organic carbon (SOC) plays a crucial role in climate change mitigation by regulating atmospheric CO2 and maintaining ecosystem balance; however, its stability is influenced by land use in anthropized areas such as the tropical Andes. This study aimed to develop a dynamic compartmental model based on ordinary differential equations to simulate carbon fluxes among litter, humus, and microbial biomass under four different land uses in the Las Piedras River basin (Popayán, Colombia): riparian forest (RF), ecological restoration (ER), natural regeneration (NR), and livestock (LS). The model was calibrated using field data on soil physicochemical and biological properties, as well as carbon inputs and outputs. The results showed clear differences in SOC dynamics between land uses: RF exhibited the highest SOC stocks (148.7 Mg ha⁻¹) and microbial biomass, while LS showed the lowest values and the largest deviation from the model due to compaction and low residue input. The humus fraction remained the most stable pool (K₂ ≈ 10⁻⁴ month⁻¹), confirming its recalcitrant nature. Overall, the model accurately reproduced SOC behavior (MAE = 0.01–0.30 Mg ha⁻¹) and provides a useful framework for understanding carbon stabilization mechanisms and guiding adaptive soil management to enhance carbon sequestration in mountain ecosystems.