Responses of Contents and Structure of DOM to Spartina alterniflora Invasion in Yanghe Estuary Wetland of Jiaozhou Bay, China

Abstract

This paper aimed to explore the effects of Spartina alterniflora invasion on the contents and structure of soil dissolved organic matter (DOM, including dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphorus (DOP), and dissolved organic sulphur (DOS)) in the Yanghe estuary, by the aid of ultraviolet-visible spectrum, three-dimensional fluorescence spectrum, and Fourier transform infrared spectroscopy. Soil samples were collected at 0–60 cm depths in different invasion years (0, 1, 5, and 8). The results showed that the DOC increased gradually with the increase of invasion time of S.alterniflora; whereas the contents of DON and DOP decreased. In the vertical section, all the DOM showed a decreasing trend with the increase of the soil profile except the DOC content in SAF-5 and SAF-8 plots (The SAF-5 and SAF-8 represent for the invasion time of 5 years and 8 years). The spectral analysis showed that the macromolecules of DOM increased after the invasion. The molecular weight and number of molecules of DOM changed after invasion. The changes were mainly concentrated in refractory macromolecules. S.alterniflora had a significant effect on the number of structural units and functional groups of soil DOM. The intensity of functional group peaks became stronger, and aromatic, aliphatic, and carbohydrate substances increased. In addition, the quantity and quality of soil DOM input by S.alternifolia strongly affect the complexity of DOM chemical structure. With the increase of invasion time, the degree of humification increases and the structure of DOM tends to be more complex. The findings of this study indicate that the invasion of S.alternifolia would enhance DOM owing to greater amount of biomass.

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