Abstract: We chose the aerially seeded Pinus massoniana plantations to study the relationships between the composition and diversity of understory vegetation and environmental factors using the redundancy analysis (RDA) and variation partitioning methods. Our results showed that: (1) A total of 54 understory species belonging to 29 families and 36 genera were recorded, and the importance values ofGlochidion puberumand Dicranopteris linearis were the highest in shrub and herb layers, respectively. Significant effects of average diameter at breast height (DBH), altitude and canopy density on species composition in shrub layer, and extremely significant effects of soil thickness on species composition in herb layer were found (P<0.01) using the forward selection and Monte Carlo analysis. (2) Nine factors selected by using Monte Carlo permutation test explained together 70.9% of species diversity variation, and average DBH, canopy density, soil thickness, available nitrogen and slope position were the important factors determining species diversity in understory vegetation. The biotic, abiotic factors and their interaction respectively explained 34.8%, 7.5% and 20.5% of the total variation in species diversity in understory vegetation, which indicated that biotic factors and their interactions with abiotic factors were the main factors affecting the species diversity in understory vegetation.

Key words: soil nutrient, vegetation restoration., soil respiration, microbial biomass, soil aggregate