A STUDY OF THEVEGETATION ANDFLORISTIC AFFINITYOF THE LIMESTONEFORESTS IN SOUTHERNAND SOUTHWESTERNCHINA'Xu Zhaoran2ABSTRACT Four thousand two hundred eighty-seven specific and infraspecific taxa in 1213 genera and 195 families of vascularplants are reported from the forests occurring on limestone outcrops in southern and southwestern China; the majorityare from the provinces of Guangxi, Guizhou, and Yunnan. Data of natural conditions in the explored area, includinggeology, geography, meteorology, soil sciences, and vegetation, are presented. The flora is treated in 14 distributiontypes, for example, tropical elements total 69.1% of the flora, northern temperate 9.9%, East Asian 9.9%, and endemiesof China 4.7%. Some genera, such as Camellia. Eurya, Hydrangea, Rhododendron, and Symplocos, are poorly repre-sented in the limestone forests, while Chirita, Excentrodendron, Paraboea, Platycarya, and some other genera areendemic or very abundant in this kind of vegetation. About one-third of the species are endemic or dominant speciesin the limestone vegetation. Characterized by calciphiles, a "limestone flora" is a valid floristic category distinct fromnon-limestone floras, especially an acid-soil flora in the saine region. The flora of southern and southwestern China iswell known for its richness in endemism and bio-diversity (Wu, 1980), but the forests occurring onthe limestone outcrops in the same region, knownas limestone forests, are much less known in theliterature. Wu (1980) reported some studies on theplant communities occurring on the limestone sub-strates in China, but no comprehensive surveys ofthe vegetation and flora of the limestone forests forthe entire southern and southwestern portion ofChina were available before the present study be-gan. The current study was carried out from 1982 un-til 1987 as partial fulfillment of my master's anddoctoral degrees at Sun Yatsen University in China,and it continued until recently with funding supportfrom the World Wide Fund for Nature Internationaland the Smithsonian Institution. Data sunmmnarizedin this paper mostly were collected on my expedi-tions rmade from 1982 to recent years (Table 1).which resulted in about 8500 plant collections fromforests occurring on limestone substrates, as wellas a number of samples of rock and soil, and otherdata. A checklist of vascular plant species fromChinese limestone forests based on my collectionsand the literature was compiled (Xu, 1993). The floristic analysis reported here is based onthe published checklist (Xu, 1993). Although mysurveys focused on the provinces of Guangxi,Guizhou, and Yunnan, the study results are repre-sentative of Chinese limestone forests becausethese three provinces contain typical Chinese karstlandscapes (Fig. 1). Limestone species are considered for this studyto be those that occur on limestone substrates butmay also occur on non-limestone substrates; lime-stone endemic species are those that occur exclu-sively on limestone substrates.HABITAT CONDITIONS China possesses the largest limestone area in theworld, with pure carbonate substrates covering anarea of 283,000 km2 (Fig. 1). The majority of lime-stone outcrops related to this study lie on the slopefrom the Guangxi Basin to the Yungui Plateau, i.e.,southwestern Guangxi, southern Guizhou, andsoutheastern Yunnan (Fig. 1, upper left corner), ' I am grateful to Chang Hungta for his inspiring suggestion that 1 pursue this subject in my graduate studies, andto colleagues who directly or indirectly helped improve the current paper. World Wide Fund for Nature Internationaland the Smithsonian Institution provided additional funding support. 2 Department of Biology, Zhongshan University, Guangzhou 510275, P. R. China. Present Address: Department ofBiological Sciences, The University of Alabama, Tuscaloosa, Alabama 35487, U.S.A.ANN. MISSOURI BOT. GARDI. 82: 570-580. 1995.