Effect of tidal hydrology on soil anaerobic CO2 production of freshwater marsh in the Yellow River estuary wetland, China

Tidal hydrology has an important effect on anaerobic carbon decomposition in estuary wetlands. However, it remains unclear how soil anaerobic CO2 production responds to change in tidal hydrology. We differentiated anaerobic CO2 production of freshwater marsh soil exposed to different tidal hydrology in the Yellow River estuary wetland. For this purpose, soil cores of a freshwater marsh with no-tidal hydrology were translocated to and cultured in the three tidal salt marshes with different tidal hydrology, respectively. Over 16-month culture, change in tidal hydrology significantly affected properties and anaerobic CO2 production of freshwater marsh soil. Exposure to tidal hydrology had increased pH and electrical conductivity (EC) of freshwater marsh soil, while decreased organic carbon (TOC), dissolved organic carbon (DOC) and C:N ratios. Anaerobic CO2 production of freshwater marsh soil showed a significantly reduction after exposed to different tidal hydrology conditions, with the corresponding mean decreasing from 2.53 μgC·g−1·d−1 under the no-tidal hydrology to 1.09–2.10 μgC·g−1·d−1 under the different tidal hydrology. Soil anaerobic CO2 production were negatively correlated with pH and EC, and positively correlated with TOC, DOC and C:N ratios, with a total 92.6% explanation of soil properties for the change in anaerobic CO2 production. The results suggest that soil anaerobic CO2 production of freshwater marsh soil might be inhibited when exposed to seawater intrusion due to the rise of salt and the decrease of substrate quality.