Floristic Study of Vascular Plants in Typical Plant Communities in the Middle and Upper Reaches of the Yarlung Zangbo River

[Objective] Species composition and flora of vascular plants in the middle and upper reaches of the Yarlung Zangbo River were analyzed,to provide scientific basis for the estimation and protection of plant diversity,construction of ecological security shelter for the Tibetan Plateau.[Methods] In the middle and upper reaches of the Yarlung Zangbo River,quadrat (line transect) method was applied to investigate the phytocoenoses in sample plots,and relative literature was used to analyze the floristic composition and floristic element of vascular plants in the middle and upper reaches of the Yarlung Zangbo River.[Results]① There are 96 species (including subspecies and variations),69 genera of 35 vascular plant families,accounting for 16.83%,5.48%,1.66% and 11.63%,2.02%,0.31% of total vascular plant families,genera and species in Tibet and China.② There are 24 monotypic-genus families,accounting for 68.57% of the total family number in the local area;22 monotypic-species families,accounting for 62.86% of the total family number in the local area.Local flora shows the characteristics of ancient relict,such as Euphorbiaceae,Rubiaceae,Liliaceae and Ranunculaceae,they are all ancient primitive groups of the third flora and the fourth flora.③ Local vascular plant genera fall into 10 areal types and 8 variations.④ Temperate elements are much more than tropical elements,R/T is 0.19,indicating that vascular plants have typical temperate nature and residual tropical nature.There are only a few endemic genera,but more endemic species to the local area,and these species are closely related,of which there are some transitional species,indicating that local flora is too young to experience more differentiation and specialization.⑤ There are 24 Chinese endemic species,accounting for 25% of total number of species in the local area;among which there are 12 endemic species to Tibet,accounting for 50% of endemic species to China,12.5% of total number of species in the local area.Four key wild plant species are included in the second batch of national key protection.[Conclusions]① There are scarce plant groups in the local area.② Among the obvious advantages,single-genus (species) families possess the absolute advantage,and the flora has ancient origins.③ The local flora has diversified distribution types,and the complicated geographical elements.④ Temperate species possess obvious advantages,and the flora is young.⑤ Rich unique and rare species have high species diversity protection and research value.

[Objective] Species composition and flora of vascular plants in the middle and upper reaches of the Yarlung Zangbo River were analyzed, to provide scientific basis for the estimation and protection of plant diversity, construction of ecological security shelter for the Tibetan Plateau.[Methods] In the middle and upper reaches of the Yarlung Zangbo River, quadrat(line transect) method was applied to investigate the phytocoenoses in sample plots, and relative literature was used to analyze the floristic composition and floristic element of vascular plants in the middle and upper reaches of the Yarlung Zangbo River.[Results](1) There are 96 species(including subspecies and variations), 69 genera of 35 vascular plant families, accounting for 16.83%, 5.48%,1.66% and 11.63%, 2.02%, 0.31% of total vascular plant families, genera and species in Tibet and China.(2) There are 24 monotypic-genus families, accounting for 68.57% of the total family number in the local area; 22 monotypic-species families, accounting for 62.86% of the total family number in the local area.Local flora shows the characteristics of ancient relict, such as Euphorbiaceae, Rubiaceae, Liliaceae and Ranunculaceae, they are all ancient primitive groups of the third flora and the fourth flora.(3) Local vascular plant genera fall into 10 areal types and 8 variations.(4) Temperate elements are much more than tropical elements, R/T is 0.19, indicating that vascular plants have typical temperate nature and residual tropical nature.There are only a few endemic genera, but more endemic species to the local area, and these species are closely related, of which there are some transitional species, indicating that local flora is too young to experience more differentiation and specialization.(5) There are 24 Chinese endemic species, accounting for 25% of total number of species in the local area; among which there are 12 endemic species to Tibet, accounting for 50% of endemic species to China, 12.5% of total number of species in the local area.Four key wild plant species are included in the second batch of national key protection.[Conclusions](1) There are scarce plant groups in the local area.(2) Among the obvious advantages, single-genus(species) families possess the absolute advantage, and the flora has ancient origins.(3) The local flora has diversified distribution types, and the complicated geographical elements.(4) Temperate species possess obvious advantages, and the flora is young.(5) Rich unique and rare species have high species diversity protection and research value.