The Effect Of Litter Decomposition On Soil Active Organic Carbon In The Coastal Wetland Of Jiaozhou Bay

The special hydrological oxygen supply conditions and biological structure of coastal wetlands have regulatory functions on the storage,release and morphological transformation of soil labile organic carbon,and litter decomposition process,as the main source of soil labile organic carbon,has far-reaching effects on the carbon cycle of coastal wetlands.In this paper,the coastal wetland of Jiaozhou Bay was taken as the research area,and the soils of four research plots(bare beach,reed wetland,Alternanthera alterniflora wetland and Suaeda alterniflora wetland)were selected as the experimental soil in Dagu estuary and Yanghe estuary.The litter of three typical vegetation types,namely namely reed,S.salsa and S.alterniflora,was selected as the research object.Simulating the decomposition process of litter by laboratory culture experiment.The content of soil active organic carbon(DOC,MBC)and the ratio of soil active organic carbon to total organic carbon(DOC/TOC,microbial entropy)and the soil enzyme activity were measured.Three-dimensional fluorescence spectroscopy was used to analyze the DOC spectral characteristics during simulated litter decomposition,and to explore the source,composition and structural characteristics of soil DOC of Jiaozhou Bay,so as to elucidate the intrinsic mechanism of the effect of litter decomposition on soil active organic carbon and reveal the environmental performance of soil active organic carbon in Jiaozhou Bay wetland.It provides a scientific basis for further study of soil carbon cycle in wetland ecosystem.The main findings were provided as follows:(1)the contents of soil labile organic carbon of litter decomposition increased first,then decreased,and finally tended to be stable.The blank treatment did not change much.Litter input can promote the soil active organic carbon content.The soil carbon pool become more and more stable,which was resulted from the decomposition of soil microbes,the litter nature as the essential factor and the combined effects of multiple factors.(2)Litter types and adding ways haddifferent effects on soil labile organic carbon,and the contents of soil DOC and MBCdecreased in the order ofS.glauca,S.alterniflora and Phragmitesaustralis.In addition,soil mixed with bulk leaf litter had moresoil labile organic carbonthan surface mulch.The microbial decomposition is the main influencing factor.Correlation analysis showed that the content of DOC and MBC were the same,and soluble organic carbon was an important carbon and energy source for soil microbes.(3)The change of soil sucrase activity was consistent with the trend of soil active organic carbon content.Litter decomposition and soil enzyme activities promote each other.Litter properties affect soil enzyme activity.Enzyme activity affects soil active organic carbon dynamics and promotes soil metabolic processes together with soil microorganisms to maintain soil ecological environment.(4)Spectral analysis showed that this process enhanced its biodegradability and microbial bioavailability,promoted the production of endogenous DOC by microorganisms,and thus speeded up carbon cycle of wetland soil.The decomposition process of litter enhanced its biodegradability and microbial bioavailability,promoted the production of endogenous DOC by microorganisms,and thus accelerate carbon cycle of wetland soil.