Study on biogeographical divisions of China
On the basis of comprehensive natural factors (including altitude, landform, climate, vegetation, water system, farm belt, and so on), we first divide China's territory into 124 basic units by applying GIS techniques. Then 171 species of mammals and 509 of plants are selected for analysis on the basis of taxa with many representative species, wide distributions across China or thought to reveal biogeographic divisions in less well known parts of the country. We collected distribution data of these species through the China Species Information System, and utilized the GIS technique to identify in which of the 124 units each species has been recorded. The resulting data matrix was then arranged into dendrograms, aggregating the units at various levels on the basis of the mammal and plant distributions by application of similarity cluster analysis using both the Sørensen comparability index formula, and the Ward method to calculate correlation matrices. Finally, we summarize the different distribution characteristics of the aggregated units and their reasons of the two categories from these cluster dendrograms, and reach some important conclusions on the biogeographical regionalization of China. This research adopts a study method of starting from minimal basic units and then aggregating up to higher-level divisions, which is a new methodological attempt in the biogeographic division research field within China. By this method, the division boundaries can be determined by the cluster results of species distribution comparability rather than the limited species and ecology knowledge of an individual researcher as has been done in the past. This makes the resulting classification more objective and broader based. This method is also applicable to other biological taxa.