Abstract: By using line transect method, an investigation was conducted on the floor litter and soil arthropod community in a mid mountain wet evergreen broad-leaved forest, a mossy dwarf forest, and a Populus bonatii forest in Ailao Mountain of Yunnan in April (dry and hot season), June (rainy season), and December (dry and cold season), 2005. In both dry and rainy seasons, the existing floor litter mass,  C storage, and C/N ratio in the three forests all increased in the order of mossy dwarf forest > P. bonatii forest > evergreen broad-leaved forest, but the N storage had less difference. In the floor litter layer of the forests, Acari and Collembola were the dominant groups of soil arthropod community, while Diptera larvae, Coleoptera, ants, and Homoptera were the common groups. The Sorenson coefficients of soil arthropod community in the three forests were extremely great. No significant differences were observed in the soil arthropod density (ind·m^-2)  in the floor litter layer among the three forests, but the relative density (ind·g^-1) of soil arthropods was higher in the evergreen broad-leaved forest and P.bonatii forest than in the mossy dwarf forest. In the three forests, the density of soil arthropods was significantly higher in dry season than in rainy season, but the Shannon diversity index had less difference. There were significant positive correlations between the existing floor litter mass and the individual density (ind·m^-2) and dominant groups of soil arthropod communities in dry and hot season (April), but negative correlations between the existing floor litter mass and the relative density (ind·g^-1) of soil arthropod communities and Acari in dry and cold season (December). The individual densities of Collembola and Coleoptera also had positive correlations with the N storage of the existing floor litter mass in the three forests. It was considered that the floor litter and the development of soil arthropod community in the litter layer of the subtropical forests in Ailao Mountain had a close relation with the vegetation structure of the forests, and the individual density and the diversity of the soil arthropod community were controlled by the floor litter, whereas the environmental factors such as temperature and moisture in the forests also had obvious effects on the seasonal dynamics of the individual density of the soil arthropods.

Key words: litter, soil arthropod, biodiversity, subtropical forest, Ailao Mountain