Abstract: Plant species diversity, soil properties and their interactions of Masson pine (Pinus massoniana) plantations with different stand ages in the upper reaches of the Yangtze River were investigated in this study. The results showed that: (1) There were more lightrequiring plants in the 3-year-old Masson pine forest, while the stand canopy density and the abundance of shading plants increased along with increasing the stand age. (2) The species richness index was highest in the midstage Masson pine plantations, and then dropped slightly but higher than that in the young stands. Both of the Simpson and Shannon indexes of shrubs and herbs showed a fluctuation in the early stage, declined in the mid-stage, and then increased in the later stage. (3) Soil organic matter, total nitrogen and total phosphorus contents increased significantly along with the stand age. (4) There were significant correlations between plant species diversity and soil factors such as soil pH, soil water content and total phosphorus content. The results suggested that soil physicochemical properties affected the species regeneration and succession, meanwhile, the community succession led to changes in soil water and nutrient contents, providing facilitative conditions for survival, colonization and growth of more species.

Key words: carbon storage, biomass, Tamarix chinensis, coastal wetland