Study On The Flora Of Seed Plants In The Mongolian Plateau

Mongolian plateau located in the Arid and Semi-arid Areas in Asia hinterland, and the flora in this region was a representative in the world flora. The floristic composition, geographical elements, life form, water ecotype, origin and evolution, floristic regionalization and rare and endangered plants of seed plants in Mongolian plateau, based on vegetation investigation and document data,were studied according to applying some botany and geobotany principle disciplines. The results as follows:(1) The seed plants were relatively indigent. 4280 species plants (ingcluding the subspecies, varieties and forms), belonging to 761 genus and 115 families, distributed in Mongolian plateau regions naturally. Among them, there were 32 gymnosperm species and 4248 angiosperm specie s, belonging to 8 genus and 3 families, 753 genus and 112 families separately.(2) The geographical components of the flora were diverse. The mono-specific family, oligo-specific family, mono-specific genera and oligo-specific genera were the main source of flora complexity and species diversity, which distributed widely in Mongolian plateau. The dominance of the multi-specific family, multi-specific genus, mid-specific genera and oligo-specific genera were evident in the number of species. In many cases, mid-specific family, plum-specific family and plum-specific genera have significant influence to the structure of flora and vegetable composition, though they are not dominant species of local plant community and the representative components.(3) The flora in this region, which consisted of complicated geographic element, interconnected and interpenetrated with other flora broadly. The transition of the flora was obvious to a certain extent. Temperate element took the predominated position and owned the typically North Temperate character.(4) This flora was a part of the Holarctic region. According to the geobotanical principle and the basic characteristics of physiognomy flora of Mongolian plateau region, it could be divided into four sub-kingdoms, five regions, nine provinces and thirty districts.(5) According to the ordination of R/T (tropic genera/ temperate generra) of nine provinces, we found the ratio of R/T descended with increasing of latitude and an apparent rule on latitude zonation of floristic variation was expressed. The similar result was obtained through the calculations of shared genera and generic similarity index between nine floras. The results, from cluster analysis on the floristic spectrum, indecated that the closest similarity occurred between External Baikal province and Khangai Mountain forest grassland province. The similarity between Altai Mountain grassland province and North Gobi desert grassland province took the second place.(6) In 761 seed plants genera of Mongolian plateau, 10 endemic genera and 255 special species were included, which was 1.46% of the total genera (not include world distribution) and 5.95% of the total number of species, respectively.(7) Herbage was dominant in life styles in Mongolian plateau. Families, genera and specie, which include herbaceous plants, account for 80.9% of the seed plants families, 85.4% of genera and 85.1% of species in this region resperctively.(8) In water ecotypes, the mesophytes and the xerophils were primary, accounting for 64.6% and 26.8% resperctively.(9) More rare and endangered plants distributed on the Mongolian plateau. The qualitative and quantitative principles were adopted to determine the threatened status of the rare and endangered plants in Mongolian plateau according to the study on the plants geographic distribution, population and ecological environment. Three categories were determined, namely Endangered, Vulnerable and Rare plant. The protected priority was divided into three classes, and the number of the protected plants in first class was 4, the second class was 33 and the third class was 68 in Mongolian plateau regions.(10) Mongolian plateau was not only the main distribution area for zonal vegetation of the Eurasian continent, especially for grassland vegetation, but also one of important parts in the world flora.(11) Both palaeo-elements and neo-elements can co-exist in this region, but the neo-elements were dominant. Most of the elements of this flora oringined from coastwise and traces of Tethys, but some of them formed in the desert environment, some of them, such as East-Asia and Temperate elements, others elected and differentiated in idiographic environment, transferred from other floras.