Abstract: In order to rtveal the structure,type and characters of the ecosystem in southwestern upland of Snow Peak Mountain,structures and composing characters of 26 typical flora were studied.The results showed that there were 759 species,405 genus,162 family plants in this area,which were mostly distributed in the tropical and subtropical zone.The flora had obvious characters of transition.The most broad related are unnom Guizhou and Gui Zhun areas.The relationship to central China,southern China and eastern China is also close.For life forms,the most is the phanerophytes.Meso phanerophytes and micro phanerophytes are main composing plant of arbor synusia in the area.In synusia structure,except for the warm shrubs,frost flora all have arbor synusia,shrub synusia,herbage synusia and lichen synusia.The evergreen broad leaved meso phanerophytessynusia dominates the arbor layer .Moreover,they form the edificator synusia of the community.The 26 florae were divided into 7 vegetation types which belong to four successional stage of forest florae, respectively.These florae have the value of protecting the original forest structure and function and for studing the natural forest recovery. Main species of plants include Machius chienkweiensis,Castanopsis eyrei,Liquidambar formosana,and Cyclobalanopsis glauca in to the arbor layer and Maesa insignis,Loropetalum chinense,and Rhododendron cavaleriei in the shrub layer.

Key words: Umbilical orange, Phosphorus deficiency, Strong light stress, Photoinhibition, Chlorophyll fluorescence, Dissipation mechanism of energy