The Systematic Classification And Floristic Geography Of Herbaceous Plants Of Saxifragaceae In Gansu Province

The systematic classification and floristic geography of Saxifragaceae in GansuProvince were studied in this thesis. The all species of the family Saxifragaceae weretried to recognize in Gansu province based on herbarium examinations of more thanthree thousand specimens from five herbaria(abbreviated as PE、WUK、NWTC、HNWP、GAUF), literatures and additional filed work, they had also contributed toreveal the main morphological characters and their evolution studies. Based on thematerials of systematic classification and geographic distribution, the moderngeographic distribution patterns (distribution types) of all species and genera in thisregion were classified and taken into statistical analysis. Used similarity coefficientanalysis to compare with adjacent regions to display the geographical distributionfeatures, floristic elements, the relationship of floristic similarity and the floristicorigin of the family Saxifragaceae in Gansu. The results were summarized as follows:1.8genera and62species (include60species and4varieties) of the familySaxifragaceae were recognized in Gansu province; Morphological description,localities, habitats and specimens cite were given in detail and systematic key to thegenera and species had been made.2. Saxifraga stellariifolia Franch.、Saxifraga mengtzeana Engl. et Irmsch.、Saxifraga cernua Linn.、Saxifraga nanella Engl.、and Saxifraga confertifolia Engl. etIrmsch.of the Saxifragaceae were recognized as new records species distributed inGansu province.3. According to different areal divisions, the geographic distribution ranges of thefamily in Gansu were divided into8regions: among the mountains area in theMiddle-upper reaches of Bailong River and the mountains area in northern-middlereaches of Longxi Loess Plateau was seemed to be the centre of the distributiondensity and the species diversity of Saxifragaceae in Gansu province. And they are inthe fringe of present geographical distribution of Saxifragaceae.4. It was single in distribution types of the family Saxifragaceae in Gansu；and the temperate distribution elements of the flora of Saxifragaceae in Gansu wereabsolutely dominant.5. There were higher floristic similarity of genera and species between Gansuand Shanxi, Qinghai as well as Sichuan, but the similarity coefficient betweenXinjiang, Inner Mongolia as well as Ningxia was lower; the more far from this centerthe more poor in species of the family Saxifragaceae.6. Lastly, it can be regarded that the western regions of China was quite possiblethe location of its origin. The principal reasons of the floristic development and theirareal division of the family in Gansu may be summed up in the migration anddifferentiation of the species. They were also assumed that western region of Chinawas the mainly migratory way for the family to the North.