Abstract: A field litterbag experiment using four dominant types of foliar litters (Cinnamomum longepaniculatum, Pinus massoniana, Quercus acutissima and Cryptomeria fortune) in the Sichuan Basin was conducted at two subtropical forests from November 2013 to October 2014. Airdrying foliar litters were placed in nylon litterbags (20 cm × 20 cm in size, 10 g per litterbag) with mesh sizes of 0.04 mm on the bottom and 0.04 mm (to exclude soil fauna) or 3.00 mm (to permit soil fauna in) on the top. Samples were harvested in different phenophases (litter falling, budding, expanding, maturing and senescing periods) and were used to determine the concentrations of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) in these foliar litters. After one year of decomposition, the DOC concentrations in the four foliar litters tended to decrease, whereas TDN concentrations tended to increase. Compared with the no soil fauna treatment, the DOC concentrations in foliar litters significantly decreased but the TDN concentrations significantly increased in the treatment with soil fauna, and the decrease of DOC concentration and the increase of TDN concentration were more obvious in the C. longepaniculatum and C. fortune litter, respectively. The effects of soil fauna on DOC and TDN concentrations were stronger in the leaf senescing and leaf falling periods, respectively. These results indicated that soil fauna significantly affects the decomposition of dissolved carbon and nitrogen in foliar litter, supporting the phenomenon of nitrogen sequestration during litter decomposition. Furthermore, the decomposed nitrogen in foliar litter promoted by soil fauna during the growing season is favorable for the requirement of nutrients for plant growth.

Key words: fluorescence spectra, dissolved organic matter, aromatic index, humification index., forest regeneration