THE FLORISTIC STRUCTURE OF EAST XIZANG REGION
1984, 3 (2):
East Xizang region belongs to Sino-Himalayan forest sukingdom of Horaltic Kindom.(Fig.1).The species of wild spermatophytes in this region amount to 2318 (Tab, 1),constituting 44.79% of the total number in Xizang.32.66% of them, e.g.757 species are the endemics to China, among which 49% (371 species) are distributed only in South Hengduan Mountains, such as Abies ern-estil, A.forrestii, Larix potaninii,Picea brachytula var.complanata, P.liki-angesis var.hirtella, Pinus densata, They are dominats of subalpine coniferous forest in East Xizang.There are 425 endemic species to Xizang, e.g.18.33% of the total number.Among them 340 species represent the region's endemics, including 50 species of Compositae, 21 of Rosaceae, 20 of Gramineae, 16 of Papaveraceae and so on.Altogether 1182 species are attained including the endemics of Xizang and of the 0 her parts of China, that is, 50.99% of the total number of species.From this percentage we may see that flora in East Xizang is a young and quite flourishing species-endemism.The elements of East Asian distribution pattern occupy an important place in the flora of East Xizang and consist of 753 species, constituting 31.7% of the total number.Among them 311 species belong to East Himalayas and 195 to the whole Himalayas.There are a lot of common alpine Plants Himalayas, such as Cassippe selaginoides.Diplarche multiflora, Saxifraga (22 species), Rholdod-endron (20), Primula (24), Gentiana (10), Pedicularis (16).It appears that the flora of East Xizang region, asapart of Sino-Himalayan forest flora of Horaltic Kingdom, is closely related to East Asiatic flora.The so-called relationship between East Xizang flora and Mediterranean-Central Asian flora is really next' to nothing.East Xizang region is subdivided into 2 subregions:A.Hengduan Mountains subregion with 64 endemic species of 37 genera of 21 families, including monotypic genus Salweenia of the primitive tribe Soph-oreae in Leguminosae.It was very probably a member of Gondwanaland flora which hed survived after finding a refuge in the midstream valleys of Nujiang River (Salween) and Lancang River (Mekong)B.Bomi-Gyaca subregion with 276 endemic species of 90 genera of 30 families includes Quercus tungmainsis, Brassiopsis Karmalaica, Agapetes praeclara, Aconitum (12 species), Corydalis (14), Pedicularis (14) and so on.The monotypic genus Parapteropyrum tibeticum is found in this sudregion and appears to be the definite Tethysian element during the drawing back of Tethys sea.
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