| The southern part of Gaoligongshan Nature Reserve straddles Longyang and Tengchong Districts of Baoshan City, lying between 24°56′~26°09′North Latitude and 98°34′~98°50′East Longitude, with the highest latitute—Nanzhaigongfang 3150m. Its total area is 124459 hm2. Mid-montane humit evergreen broadleaved forests (MHBF) is the largest and best reserved type of vegetation, occupying the 2300~2800m above sea level. Base on the investigation of respectively 6 plots (totally 6000 m2) on eastern and western slope, this study compared floristic composition, community characteristics and species diversity of MHBF between eastern and western slope in southern Gaoligong Mountains. The results showed:(1) Vascular plants in MHBF of eastern slope belong to 71families, 117 genera, 192 species, in west slope that was 76 families, 125 genera, 215 species. Western slope contained more abundant species than eastern slope. In species component, both eastern and western slope were mainly consisted by Dicotyledoneae. The coefficients of similarity in family, genus and species between the two slopes were respectively 72.48%, 63.37% and 45.21%, which indicated that the two slopes included many common families and genera, while there was relatively bigger difference and diversity in species composition.(2) Endemic to China, East Asia and tropical Asia type were the common floristic composition of two slopes. The analysis on proportion of tropical and temperate elements in family, genus and species levels (family: eastern slope 1:0.71, western slope 1:0.52; genus: eastern slope 1:1, western slope 1:0.94; species: eastern slope 0.15:1, western slope 0.24:1) indicated that the MBHF on both slope occupied the transition area from tropical to temperate zone. The altitudinal pattern of floristic composition suggested that, with the elevation increased, the tropical elements gradually reduced, while the temperate and Chinese endemic elements ascended. These results revealed that the two slope had a common genesis and evolution process of flora.(3) The MHBF in both slope could be divided into 2 formations(Form. Lithocarpus hancei and Form. Lithocarpus variolosus), 8 associations. The Ass. Myrsine semiserrata-Lithocarpus hancei and Ass.Illicium simonsii-Lithocarpus variolosus were the common association of two slopes. All these indicated the abundant diversity of community types of two slopes.(4) In species composition, the two slopes had common dominant family (Fagaceae), genera (Lithocarpus) and species (Lithocarpus hancei and Lithocarpus variolosus). Mainly endemic species to eastern slope contained species of Ericaceae, Theaceae and Fagaceae. Endemic species to western slope were belonged to Lauraceae. In shrub layer, the common dominant genus was Fargesia of Gramineae. Mainly endemic species to eastern slope included species of Ericaceae, to western slope that were Gramineae and Caprifoliaceae. In herb layer, the chiefly common dominant families were Compositae, Cyperaceae and Liliaceae. Endemic species to eastern slope was pteridophyta, to western slope were Urticaceae, Primulaceae and Polygonaceae. In interlayer species, eastern slope was dominant by epiphytes and vines; western slope was dominabt by vines. The coefficient of similarity in tree layer was lowest and highest in interlayer species.For life form, both slopes were dominated by meso-phanerophytes and micro-phanerophytes, which corresponded with the life from characteristic of subtropical evergreen broad-leaved forests. For leaf charcters, both slope were dominant by papery leaf, microphyll leaf, simple leaf, not entire leaf and acuminate leaf. it inflected the characteristic of mid-subtropical evergreen broad-leaved forests.(5) The community diversity of western slope was higher than that of eastern slope and the species distribution on western slope was evener. The species abundance of tree layer and interlayer of eastern slope were higher, while species of two layers on western slope were evener. For shrub layer and herb layer, western slope was more abundant and evener than that of eastern slope.The species diversity on eastern slope decreased first and than increased along altitude. The maximum value appeared at 2300m, and then reached its minimum value at 2600m. On western slope, the species diversity increased first and than decreased along altitude. The maximum value occurred at 2500m and minimum value occurred at 2600m. In tree layer, the species diversity of both slopes rose first and then descended. The maximum value of eastern slope appeared at 2700m and on eastern slope appeared at 2500m. In shrub layer, the species diversity of both slopes descended first and then rose. The maximum value of eastern slopes occurred at 2300m, the western slope between 2500~2600m. In herb layer, the two slopes had the same pattern, both appeared two maximum values respectively in high and low altitude, and had negative relation with coverage of tree layer and shrub layer. The diversity of interlayer species decreased with the altitude increased. The maximum value of both slope appeared at 2300m.Whittaker index and Routkedge index ofβdiversity decreased first and than increased along altitude gradient, with two maximum values appearing at low and high altitude. The minimum value exited at the middle altitude zone. Jaccarad index and Routkedge index rose first and then descended along altitude gradient. The maximum values occurred at middle-high altitude, which was the distrubution scope of Form. Lithocarpus variolosus. The minimum value occurred twice respectively at low and high altitude. These results suggested that low and high altitude zone located at the transition region of communities, the habitat condition was worse and impacted by human activities. As the result, the common species of communities were few, the similarity was low, so the Whittaker and Routkedge index were relatively lager. At the middle high altitude area, better hydrothermal condition and less human impact lead to more common species, larger similarity and smaller Whittaker and Routkedge index.
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