Microbial necromass carbon in estuarine tidal wetlands of China: Influencing factors and environmental implication

Microbial necromass is an important component of the stable soil organic carbon (SOC) pool. However, little is known about the spatial and seasonal patterns of soil microbial necromass and their influencing environmental factors in estuarine tidal wetlands. In the present study, amino sugars (ASs) as biomarkers of microbial necromass were investigated along the estuarine tidal wetlands of China. Microbial necromass carbon (C) contents were in the range of 1.2-6.7 mg g^-1 (3.6 ± 2.2 mg g^-1, n = 41) and 0.5-4.4 mg g^-1 (2.3 ± 1.5 mg g^-1, n = 41), which accounted for 17.3-66.5 % (44.8 % ± 16.8 %) and 8.9-45.0 % (31.0 % ± 13.7 %) of the SOC pool in the dry (March to April) and wet (August to September) seasons, respectively. At all sampling sites, fungal necromass C predominated over bacterial necromass C as a component of microbial necromass C. Compared to bacterial necromass C, fungal necromass C showed a stronger connection with ferrous oxides (Fe²⁺) and total Fe concentrations. Both fungal and bacterial necromass C contents revealed large spatial heterogeneity and declined in the estuarine tidal wetlands with the increase in latitude. Statistical analyses showed that the increases in salinity and pH in the estuarine tidal wetlands suppressed the accumulation of soil microbial necromass C.