The Systematic Classification And Floristic Geography Of Orchids In Gansu Province

The systematic classification and floristic geography of orchids in Gansu Province were studied in this thesis. All the species of orchids were recognized in Gansu province based on herbarium examinations of more than four thousand specimens from five herbarias (abbreviated as PE, WUK, LZU, NWTC, GAUF), literatures and additional filed work, they had also contributed to reveal the main morphological characters and their evolution studies. Based on the materials of systematic classification and geographic distribution, the modern geographic distribution patterns(distribution types) of all the species and genera in this region were classified and taken into statistical analysis,and were used similarity coefficient analysis to compare with adjacent regions to display the geographical distribution features, floristic elements, the relationship of floristic similarity and the floristic origin of the family orchid in Gansu. The results were summarized as follows:1. 41 genera and 95 species and 3 varieties of the family orchids were recognized in Gansu province;Morphological description,localities, habitats, specimens cite were given in detail and were the systematic key to the genera and species had been made.2. Nothodoritis Z. H. Tsi was recognized as a newly recorded genus in Gansu. The genus Nothodoritis Z. H.Tsi, as the endemic to China pattern genera, was distributed from Tianmu Mountain in Zhejiang province to Kangxian country in Gansu province.And Orchis cyclochila (Franch.et Sav.)Maxim., Epipactis helleborine (L.) Crantz var.tangutica (Schlechter) S.C.Chen & G.Zhu.and Calanthe brevicornu Lindl., Nothodoritis zhejiangensis Z.H.Tsi were recognized as new records in geographical distribution from Gansu Province.3. The areal-types of genera of this orchid flora could be divided into 9 types and 5 subtypes. Among them, the temperate flora type was the richest one, accounting for 73.17% of the total genera. 4. It was abundance in species and diversity in forms of the family orchids in Gansu,with 6 genera terrestrial, 30 epiphytic and 5 saprophytic genera, among them, epiphytic genera were the richest, and the temperate distributed elements of the flora of orchids in Gansu were absolutely dominant. The endemic to China species were obvious.5. According to different areal divisions,the geographic distribution ranges of the family in Gansu were divided into 8 regions: among the mountains area in the Middle-upper reaches of Bailong River and the mountains area in southern Qinling was seemed to be the centre of the distribution density and the species diversity of orchids in Gansu province .6. There were higher floristic similarity of genera and species between Gansu and Shaanxi, Sichuan, but the similarity coefficient between Qinghai,Xinjiang, Yunnan, Tibet, Inner Mongolia as well as Ningxia was lower. All above indicated that the Hengduan Mountains region was the distribution center of orchids, the farther from this center, the poorer species of the family orchids there were.7. The orchid flora in Gansu province was closely linked with Hengduan Mountain Region, it is the important fringe of the northern extension of Hengduan Mountain Region; The orchid flora in Gansu province was mainly to the temperate nature, which had the common area of nature and origin with Hengduan Mountain Region, it was the continuation and development of latter.