[Effects of litter decomposition on contents and three-dimensional fluorescence spectroscopy characteristics of soil labile organic carbon in coastal wetlands of Jiaozhou Bay, China].

Litter of Suaeda glauca, Phragmites australis, and Spartina alterniflora from coastal wetland of Jiaozhou Bay was decomposed in a laboratory experiment. The contents of soil labile organic carbon including dissolved organic carbon (DOC) and microbial biomass carbon (MBC) were determined, with the spectra characteristics of which being investigated by three-dimensional fluorescence spectroscopy. The results showed that the contents of soil labile organic carbon during litter decomposition increased first, then decreased, and finally tended to be stable. Different litter types and adding ways had different effects on soil labile organic carbon. The contents of soil DOC and MBC decreased in the order of Suaeda glauca, Spartina alterniflora and Phragmites australis. Soil mixed with bulk leaf litter had more soil labile organic carbon than surface mulch. The number and position of fluorescence peak, and fluorescence intensity changed during litter decomposition. No tyrosine-like peaks appeared in the soil with litter addition. Many factors drove litter decomposition, with microbial decomposition being the dominant factor and litter nature as the essential factor. Litter decomposition could improve the content of soil active organic carbon and enhance the stability of soil carbon pool. Litter decomposition changed the structure and chemical composition of soil DOC, which improved its ability of migration and transformation in soil. Moreover, this process enhanced its biodegradability and microbial bioavailability, promoted the production of endogenous DOC by microorganisms, and consequently stimulated carbon cycling of wetland soil.