Abstract: [Objective] In order to promote the soil fauna ecological study and provide the scientific management basis for the protection of forests in Changbai Mountains, the decomposition rate and nutrient release of Abies nephrolepis litter and the effect of soil fauna were studied in the coniferous forests of Changbai Mountains.[Method] Two kinds of litterbags with different mesh sizes of, 1 mm and 0.01 mm, were used to examine the needle litter decomposition rate and nutrient release of the dominant tree species (A. nephrolepis) and the effect of soil fauna on the processes in the coniferous forests of northern slope of Changbai Mountains. Soil fauna in the litterbags were separated from litter by hand picking and Tullgren funnel methods. The TOC content in litter was determined using the FeSO₄ titrimetric method. TN and TP contents were determined by an automated analyzer (WESTCO, Smartchem140, USA). Repeated-measures ANOVA were carried out to evaluate the effects of habitat, mesh size and their interactions on the decomposition rate and the contents of TOC, TN, and TP. Pearson's correlation coefficients were conducted to examine the relationship between the group number, individual of soil fauna and the decomposition rate and the contents of TOC, TN, and TP. Redundancy analysis (RDA) was performed to evaluate the relationships between soil fauna and the decomposition rate and the contents of TOC, TN, TP.[Result] After a year of field incubation, the decomposition rates in the 1 mm litterbags were significant higher than that in 0.01 mm litterbags in two habitats (P<0.05). The decomposition rates in two kinds of litterbags varied seasonally, and the decomposition rates in the summer and autumn were higher than those in winter and spring. Litter decomposition rate in the bright coniferous forest was higher than that in the dark coniferous forest at the end of experiment. The TN and TP relative contents (g·kg^-1) in litter rose in both mesh sizes litterbags. The TN and TP contents in the dark coniferous forest were higher than those in the bright coniferous forest, especially the TP relative content in the 1 mm litterbags (P<0.05). The TOC relative content (g·kg^-1) in the 1 mm litterbags in the bright coniferous forest was lower than that in the dark coniferous forest, while there was a opposite tendency in the 0.01 litterbags. The relative contents of TP in the 1 mm litterbags were significantly lower than those in the 0.01 mm litterbags (P=0.001), but no significant differences of the relative contents of TN and TOC were found between the two mesh sizes litterbags. A total of 905 individuals, belonging to 21 groups, were found in 1 mm litterbags in the dark coniferous forest during the incubation period. There were 19 groups, 1 227 individuals captured in the bright coniferous forest in the 1 mm litterbags. The main soil fauna, which participated in the litter decomposition, were Isotomidae, Oribatida, Pseudachorutidae, Hypogastruridae, Actinedida, Gamasida, Enchytraeidae and Tomoceridae. The decomposition rate had a significant positive correlation with individual, group number and main soil fauna, while the TOC, TN, and TP absolute contents (g) were significantly negatively correlated with individual, group number and main soil fauna. The analysis above showed that habitat impacted on the decomposition rate significantly, and had certain effect on the nutrient content.[Conclusion] Soil fauna played an obvious role in promoting the litter decomposition and the release of TOC, TN, and TP.

Key words: soil fauna, Abies nephrolepis, litter decomposition, nutrient release, coniferous forests, Changbai Mountains