Abstract:Based on the vegetation survey on a secondary evergreen broad-leaf forest atSanjiaoshan, Conghua, near Guangzhou, the natural distribution characteristics,environmental condition, floristic composition and community characteristics of China'sendemic species Manglietia pachyphylla Chang and its conservation strategies were studied in June, 1997. The results indicated that Manglietia pachyphylla was naturally distributed inthe secondary evergreen broad-leaf forest at altitudes from 650 to 1 000 metres in a narrow zone．There were 132 species of vascular plant in 89 genera of 57 families in plots of 1 200 m2. The diversity index and evenness of the tree and shrub species in the community were 5.45 and 84.39％，respectively，which were similar to those of other evergreen broad-leaf forest in the neighboring regions， but lower than those in tropical rain forest in Hainan. The floristic composition of the community showed a transitional characteristics of tropical and subtropical elements．The community was termed as Syzygium buxifolium + Daphniphyllum subverticillatum + Manglietia pachyphylla Community．It can be vertically divided into three layers，tree (with 2 sublayers)，shrub，and grass layers．There were many species in the tree layer and shrub layer， but few species in the grass layer．The dominant species of Magnoliaceae in tree layer were found to be Manglietia pachyphytta and Michelia maudiae. The mesophanerophytes and microphanerophytes made up high percentage，and the megaphanerophytes，Hemicryptophytes and therophytes were not found in the species life form spectrum of the community．The mesophyll also made up high percentage in leaf-size class spectrum of the community．The distribution pattern of magnoliaccous plants were measured by variance／means ratio．and the result indicated that most of the dominant species were clumped in distribution，Manglietia pachyphylla and Michelia skinnerana were clumped，and Michelia maudiae was random．Analysis on structure of magnoliaceous populations indicated that Michelia maudiae and Michetia skinnriana were at the stable stage，but Mangtietia pachyphylla expressed a decline tendency．Therefore，Manglietia pachyphylla is an endalagered species which must be preserved through in situ and ex situ conservation，and the preservation strategies should be centred on in, situ conservation.
