Soluble and Spectral Characteristics of DOM in Leaching Solution from Leaves and Litter-fall of Pinus massoniana and Dicranopteris dichotoma

Abstract:

In order to understand the soluble and spectral characteristics of dissolved organic matter (DOM) in leaching solution of 37-year-old Pinus massoniana plantation in Sanming, Fujian Province, subtropical China, the soluble and special characteristics of DOM from fresh leaves and litter-fall in L and F layers from Pinus massoniana (PIM) and Dicranopteris dichotoma (DID) were studied. The results showed that the DOM content, including dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP), increased with fluctuation along leaching time from 3 to 24 hours. DOC content of fresh leaves of DID was significantly higher than that in PIM (P<0.01), while DON and DOP are lower. The special ultraviolet-visible absorption (SUVA) and humification index (HIX) of DOM in F layer litter of both species was significantly higher than that in fresh leaves and L layer litter, it indicated that F layer litter contained more aromatic substances and high humification degree. Synchronous fluorescence peak showed DOM contained protein-like and fulvic acid-like fiuorophore. The six kinds of samples showed five IR absorption bands in common, with the strongest absorption in all cases arising from stretching vibration of H-bonding hydroxyl groups. The infrared absorption differences between three kinds of samples in the same stand supported that the conjugated systems grown larger from the fresh leaves to L layer litter to F layer litter. Overall, the chemical structures of DOM are more complex in more decomposed samples, and the PIM contains more DON and DOP than DID. On the one hand, it provide more nutrients for microorganisms, on the other hand, it increase the difficulty of the decomposition of the substrate.

Key words:Pinus massoniana;Dicranopteris dichotoma;Leaf;Litter-fall;DOM;Spectral characteristics