Study On The Liverworts Of Bailongjiang Valley In Gansu Province, NW China

Bailongjiang Valley, located between 101°40′- 105°20′E, 32°21′- 34°20′N, covers an area of 31 800 km2 in the southern of Gansu province, which is formed by Diebu County, Dangchang County, Zhouqu County, Wudu County and Wen County. Bailongjiang Valley, the richest region of vegetation in Gansu province, is situated in the transitional climatic belt between north subtropical and warm temperate zone. As the geography and environment of this valley are very complex, the geographical elements of vegetation flora are extremely various. Although it is abundant in bryophyte resource, species of bryophyte in this area are known poorly. Therefore, the research of liverworts of Bailongjiang Valley will supply new and important information for the bryoflora of the valley and even Gansu province.3000 specimens of bryophyte were collected in the outdoor investigation of Bailongjiang Valley between 2007 and 2008. Based on the indoor identification of about 500 specimens of liverworts and analysis of related references, 97 species (including subspecies and varieties and so on) in 33 genera of 18 families were identified. Among them, 75 species, 25 genera and 12 families are newly recorded in Bailongjiang Valley. 62 species, 14 genera and 4 families are new to Gansu province and 29 species and 4 genera are reported for the first time in the Northwest China. One endangered liverwort and two East Asiatic endemic genera, which are Ascidiota blepharophylla Mass., Macvicaria Nichols. and Ascidiota Mass., were found in this valley.The species, genera and families of liverworts in Bailongjiang Valley account for 85.7 %, 86.8 %, 87.4 % of the whole species, genera and families of liverworts in Gansu province respectively. Judging from the data offered above, we can conclude that Bailongjiang Valley, especially downriver of this valley (accounting for more than 80% of species of Bailongjiang Valley), is the main distribution and key region of liverworts in Gansu province.The liverwort flora of Bailongjiang Valley is divided into 11 geographical elements. Temperate element is dominant, accounting for 42.31% and the next comes East-Asia element, accounting for 34%. Endemic to china element accounts for 9.28% as well as Tropical element . It is suggested from the above analysis that Temperate element and East-Asia element make up the majority of the liverwort flora of Bailongjiang Valley. It also has a high level endemism and has a related relationship with the liverworts flora of subtropical area.The liverwort flora of Foping Nature Reserve, Northwest Sichuan, Qilian Mountain, Helan Mountain, Xinjiang are selected to compare with Bailongjiang Valley's. Considering comparison of the liverwort species abundance in 6 areas, liverworts of Bailongjiang Valley and Foping Nature Reserve are abundant and that of Qilian Mountain and Helan Mountain are poor. Judging form cluster analysis and similarity coefficient of species and genera, Bailongjiang Valley holds the closest relationship with Foping Nature Reserve followed by Northwest Sichuan, Xinjiang and Qilian Mountain, and holds the farthest with Helan Mountain.Considering the relationship between Bailongjiang Valley and other 5 areas and the characteristics of bryological regions of China, we may come to the preliminary conclusion that Bailongjiang Valley belongs to Central China region.