| Karst region in Southwest China is one of the biodiversity distributing centers in China. Focus on Maolan karst forest nature reserve in Guizhou province and Nongla in Mashan County, Guangxi Province, the study presents contrast on characteristics of element geochemistry, resident flora and species diversity in three kind of karst environments where bedrocks are made up of pure limestone, pure dolomite and impure carbonate rock. The dissertation contains five parts that covers summarization, geochemistry features in different karst environments, species diversity in different karst geochemistry backgrounds, constituent characteristics of flora in different karst geochemistry backgrounds, conclusions and discusses. Main points are as follows: 1.Investigations were performed using typical plot method in the two pre-mentioned areas in the condition that conform to altitude, gradient and sloping directions and so forth while merely differ from lithologies. Biodiversity is valued using several kinds of indices such as Patrick and Gleason species richness index, Simpson and Shannon-Wiener diversity index, Pielou and Alatalo evenness index, Jaccard and Sφransen coefficient of community similarity. The comparative results showed that①the community richness, species diversity indices and evenness of tree layer and shrub layer shared the same order of pure limestone region > pure dolomite region >impure carbonate rock region amongst the three different bedrock types, while in herb layer the order changed into pure dolomite region > pure limestone region > impure carbonate rock region. The community diversity in Nongla was higher than that of in Maolan, but differed from different community layers: the former was higher in tree layer, while reversed in shrub layer and herb layer. ②The diversity in different layers of communities in Maolan was in the following order: tree layer > Shrub layer > herb layer, but in Nongla, tree layer fell into the last.③the species diversity was dissimilar in different slope directions in karst peaks. Generally, species diversity and richness was the highest on south slopes besides herb layer, in limestone region. In dolomite region, it was more complicated: the highest diversity of tree layer, shrub layer and herb layer were respectively on east, south and north slopes. ④The coefficient of similarity was considerable low between all plots. It was greater between plots among the same type of lithology than those between them. Plot area has little influence on the coefficient. Species turnover rate was quite high among the plots, and was higher in dolomite region than that in limestone. 2. Maolan karst region riches in special family, genes and species, which shows a order of pure limestone region > pure dolomite region > impure carbonate rock region . There is 15 families distributing in each kind of lithology, with 7 of which in both pure limestone and pure dolomite region, and only one family is found in impure carbonate stone region.38, 35 and 12 genus was found only in pure limestone, pure dolomite and impure carbonate rock regions, respectively. 254 species can only be spotted in one type of lithology region, account for 73.84 percent of the gross species, 105 in limestone region,110 in pure dolomite region while 29 in impure carbonate region. 3. Element geochemistry characteristic of rock, soil and epikarst spring water collected in various plots were analyzed.①Contents of silicon, aluminium and iron in pure limestone region are 10 times more than those in pure dolomite region in Maolan. ②pH of soil in pure limestone regions fluctuates from 7.53 to 7.69, slight tendency to alkalescence; soil in pure dolomite region shows neutrality inclination to weak acidity with variation pH of 6.1-6.9. Higher concentration of calcium and magnesium exists in soil in limestone region. Contents of soil microelements in pure dolomite region are generally higher, i.e., content of manganese, zinc and cobalt is 1-2 times more than those in limestone region. ③Higher concentration of ions of calcium and iron exists in epikarst spring in pure limestone regions than that in impure ones, while magnesium ion is more in the latter.
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