It depends of water balance. If the water dreanage is good, you have less CO2 emission from the litter (it dryes quicly) and more from the soil (aerobic conditions). But if the deanage is bad and the litter remains wet, you have more CO2 emission from the litter (ir remains wet more time) and less from the soil, because usually the soil is water logged and turns to anaerobic conditions. So, you should measure your system very carefully!

Thank you for your answer