Soil CO₂ Flux and CO₂ Concentration in Depositional Soils Characterized by Layered Structures

This study simulating depositional profiles established three types of layered structures with different thicknesses of fine-grained and coarse-grained layers (L1: 1 cm fine-grained layer and 9 cm coarse-grained layer; L3: 3 cm fine-grained layer and 7 cm coarse-grained layer; L5: 5 cm fine-grained layer and 5 cm coarse-grained layer), with homogeneous soil without layered structure as the control (NL). Surface CO₂ flux and soil CO₂ concentrations in the upper and lower sections of the depositional soil profiles were measured continuously over a two-week period to examine the influence of layered structure on surface CO₂ flux. The results indicated that when the fine-grained layer thickness was 1 cm, surface CO₂ flux from this layered structure increased significantly compared to homogeneous soil, whereas when the fine-grained layer thickness was 3 cm and 5 cm, surface CO₂ flux decreased significantly compared to homogeneous soil. The responses of soil CO₂ concentrations in the upper and lower layers to layered structures were opposite to those of surface soil CO₂ flux.