Effects of Drying-Rewetting Frequency on Vertical and Lateral Loss of Soil Organic Carbon in a Tidal Salt Marsh

Tidal salt marshes, as blue carbon ecosystems, play a critical role in mitigation of global climate change since their large soil organic carbon (SOC) pool. Drying-rewetting cycles induced by periodic tides have profound influence on soil carbon cycling in tidal salt marshes. However, the magnitude and mechaanism of the effects of drying-rewetting frequency on SOC loss in tidal salt marshes is still uncertain. Here, we conducted a mesocosm experiment to identify how drying-rewetting frequency changes alter the vertical (CO2 and CH4) and lateral (dissolved organic carbon) carbon losses of soils in a tidal salt marsh in the Yellow River Delta (YRD). We found that increasing soil moisture inhibited CO2 emission but stimulated CH4 emission in a tidal salt marsh. Soil dissolved organic carbon (DOC) was produced in the drying phase and rewetting lead to the loss of DOC. Soil moisture and salinity change induced by drying-rewetting cycles were the critical factors controlling vertical organic carbon loss in a tidal salt marsh. DOC had significant effects on CO2 emissions. Changes of tidal action and drying-rewetting cycle induced by global change can affect the pathway of carbon loss in a tidal salt marsh.