Effects of water and salinity on soil labile organic carbon in estuarine wetlands of the Yellow River Delta, China

Changes in labile organic carbon in wetland soils as indicators of soil quality and climate change have received many attention worldwide. Soil samples were collected in 2012 and 2013 in estuarine wetlands with different groundwater tables in the Yellow River Delta, and soil salinity, water content (WC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC) were determined to investigate the effects of water and salinity on labile organic carbon in wetland soils. Our results showed that the response of labile organic carbon to salt and water conditions varied varied in soil samples with different groundwater tables. The MBC in soils with low groundwater tables (LW) was the lowest when soil WC was 25% and then exhibited an increase with increasing WC. The DOC in LW soils has increased and MBC and DOC contents in soils with middle groundwater tables (MW) and high groundwater tables (HW) has decreased with increasing WC. MBC in three wetlands presented a "decreasing before increasing" tendency with increasing salinity, whereas DOC showed an "increasing before decreasing" tendency. Soil microbial biomass and soil fertility in estuarine wetlands with salinity between 1.8 and 2.0 ppt were relatively high, which was conducive to plant growth. The findings of this study provide a better understanding of the relationships between soil labile organic carbon and water and salt conditions as also deliver basic data for carbon sequestration and blue carbon management in estuarine wetlands. (C) 2019 Published by Elsevier B.V. on behalf of European Regional Centre for Ecohydrology of the Polish Academy of Sciences.