Abstract: This paper studied the characteristics of the natural understory vegetation in the artificial masson pine forest replanted after Chinese fir cut for 13 years. The results indicated that there were 100 species of understory vegetation, including 74 species of shrub or small arbor,accounting for 74.0% of the total species,belonging to 41 faculties and 63 categories,and 26 herbs belonging to 14 faculties and 23 categories.The tropical and subtropical elements were dominant in the vegetation,while the temperate ones were scare.The species diversity and richness were decreased after masson pine regenerated from Chinese fir.The analysis of important value showed that the main species of shrub or small arbor were Tinomiscium tonkinensis,Mycetia longiflora,Evodia lepta,Paederia scandens,Mussaenda pubuscens,Actinodaphne pilosa and Quercus glauca,and those of herb were Cyrtococcum patens,Blechnum orientale,Dicranopteris dichotoma,Adiantum flabellulatum,Adiantum edgeworthii and Pteris semipinnata.The biomass of the vegetation in different slope positions was decreased in order of upside>downside>middle part.There was a significantly positive correlation between the niche breath and the important value of main woody population.The important values of woody populations were higher than those of the others,and their niche breadths were also larger,which meant that they were more adaptable to the habitat.The niche overlaps of six population counterparts Tinomiscium tonkinensis-Mycetia longiflora,Tinomiscium tonkinensis-Evodia lepta, Mussaenda pubuscens-Maesa japonica,Quercus glauca-Aphananthe aspera,Actinodaphne pilosa-Saraca chinensis and Evodia lepta-Quercus glaucathese were very large,which could offer information for the restoration and reconstruction in selecting natural vegetation.The large niche overlaps of major woody population counterparts suggested their similar utilization of natural resources.

Key words: Pinus elliottii, Mixed stand, Soil nutrient, Microorganism, Enzyme activity