关键词: 郁闭度, 大型土壤动物, 马尾松人工林, 功能类群

Abstract: Concentration, composition and vertical distribution of dissolved organic matter (DOM) were investigated in sediment porewater from the north part of Dianchi Lake by UVvisible and fluorescence spectroscopy, and its main source and potential environmental effect were also revealed. DOC concentration was highest in the uppermost layer, with a sharp decrease within the sediment depth of 4-10 cm, and then increased. The ratios of α253/α203 and E3/E4 ranged from 0.03 to 0.22 and 5.3 to 8.8 respectively, which implied that the DOM in sediment porewater had relatively low humification and aromaticity with the predominance of small molecular weight fulvic acid. Humiclike peaks A and C were two dominant fluorophores in threedimensional fluorescence spectroscopy, whereas proteinlike fluorescence peaks B and D were observed only in the overlying water and top 2 cm porewater. Fluorescenee index (f₄₅₀/f₅₀₀) of DOM in sediment porewater varied from 1.8 to 2.0, indicating the majority nature of endogenous aquatic organisms. The results suggested that the geochemical characteristics of DOM in sediment porewater were related to lake eutrophication and regional cyanobacterial blooms in Dianchi Lake, and more attention should be paid to its potential effect on water environment.

Key words: soil macrofauna, canopy density, Pinus massoniana plantation, functional groups