FLORISTIC DIVERSITY AND COOCCURRENCES IN A SUBTROPICAL BROAD-LEAVED FOREST AND 2 CONTRASTING REGROWTH STANDS IN CENTRAL-WEST YUNNAN PROVINCE, CHINA

Many of the natural forested ecosystems that still remain in mainland China are being cleared with potentially detrimental effects on woody plant species diversity on both local and regional scales. The most ex tensive stand of subtropical broad-leaved forest remaining in China is located in Yunnan Province. In an effort to document the influence of human-induced disturbance on Yunnan's woody flora, floristic inventor ies were conducted in a stand of primary forest and in regrowth stands located in its interior and along its outer margin in the Xujiaba Nat ure Sanctuary in the Ailao Mountain Range. Of particular interest was the location of the disturbance relative to the primary forest source area. A total of 134 woody plant species representing 74 genera and 43 families were recorded. The floristics of the two regrowth stands wer e significantly different from each other, with < 10% of their respect ive floras comprised of co-occurring species. The interior regrowth st and had a higher number of co-occurring species with the primary fores t; however, > 40% were still non-co-occurring. The principal families represented in the primary forest and the interior regrowth stand were Aquifoliaceae, Berberidaceae, Fagaceae, Lauraceae, Rosaceae, Smilacac eae, Symplocaceae, Theaceae, and Vacciniaceae. The three dominant spec ies with relative importance values ranging from > 5% to 18% in both t he primary forest and the interior regrowth stand were Castanopsis wat tii, Lithocarpus jingdongensis, and Symplocos sumuntia. The edge regro wth stands had the lowest species diversity and were dominated by the native pine Pinus yunnanensis, with a relative importance of 24%. The principal families represented in the edge regrowth stand were Betulac eae, Ericaceae, Fagaceae, Myricaceae, Pinaceae, and Theaceae. Only the Fagaceae and Theaceae were well-represented in all three stands. The results of the study document the low species diversity in post-cuttin g regrowth on the margins of the primary forest as compared with post- cutting regrowth in the forest interior.