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.

本研究通过模拟沉积剖面，构建了三类细颗粒层与粗颗粒层厚度配比各异的层状结构：L1组为1cm细颗粒层搭配9cm粗颗粒层，L3组为3cm细颗粒层搭配7cm粗颗粒层，L5组为5cm细颗粒层搭配5cm粗颗粒层；并以无层状结构的均质土壤作为对照组（NL）。本研究在为期两周的周期内连续监测了地表CO₂通量，以及沉积剖面上下层的土壤CO₂浓度，以探究层状结构对地表CO₂通量的影响。结果表明：当细颗粒层厚度为1cm时，该层状结构对应的地表CO₂通量较均质土壤显著升高；而当细颗粒层厚度为3cm与5cm时，地表CO₂通量则较均质土壤显著降低。剖面上下层土壤CO₂浓度对层状结构的响应趋势，与地表CO₂通量的响应趋势恰好相反。