| Yuanjiang Nature Reserve (YNR) is the first Dry-Hot vellay Nature Reserve with an area 46666.67 hectare. It is located in the midsouthern of Yunnan Province, and is located in the valley between Yunnan plateau and Ailao Mountain. It is extending from 23°18′~23°55′N and 101°39′~102°22′E. The landscape of Yuanjiang county is belong to Middle Mountain Heavy Cutting types, the mountain is basically in the mountains north-south, the Yuanjiang River divide it into two branches. The county town living in the central and surrounding hills,the mountains radiate out in all the directions order to form the downfaulted rift valley. This Nature Reserve includes six parts that are East Coast of Yuanjiang, Nanxi, Zhangba-Wangxiangtai, Molang, Xintian and Gancha."Foehn effect"Which is resulted by the obstruct of Ailao Mountain and Wuliang Mountain, result in the hot-dry climate in the vellay and come forth the sight of Savana. In the higher mountain, temperature is lower and the rainfall is crescent, come forth the subtropical climate. The vegetation is gradual change.The main types of forest in YNR are Karst mountain valleys of southeastern Yunnan monsoon evergreen broad-leaved forest area (ⅡAi-2) in Southern plateau subtropical monsoon evergreen broad-leaved forest zone (ⅡA), it is belonging to inferior area of Semi-humid evergreen broad-leaved forest in west China (ⅣB). This area are not big in Yunnan province, but its natural environment and vegetation character are special and its flora is obviously different from Yunnan Plateau.On the basis of large investigation, collection and identification of specimen, reference of literatures, this paper discusses the floristic structure, character and adscription of flora, and analyses the flora in different level of family, genus and species. Based on the statistics, the analysis results as follows, (1) 188 families, 835 genera and 2080 species of wild seed plants are recorded in the YNR, and of these families, genera and species, there are 3 families, 4 genera and 8 species in Gymnospermae, 185 families, 831 genera and 2072 species in Angiospermae. So the floristic is abundant. (2) The geographical ingredient of flora is multiplex and its connection is comprehensive. Of the total 15 distributing types of statistics, there are 10, 14 and 14 types in family, genus and species level. (3) The flora has evident transitional character from tropics to subtropics zone, and shows an obvious tropical zone character. Contrast between tropical and temperate ingredients of family, genus and species are 2.63:1,2.69:1,1.94:1. The analysis of Floristic equilibrium point show that there is no Floristic equilibrium point in this area until the highest mountain. (4) Tropical Asia, East Asia and Endemics of China ingredients are the three origins of the flora. The amount and percentage of each type are as follows: 148 genera (17.72%) and 846 species (41.03%); 62 genera(7.43%) and 255 species (12.37%);6 genera (0.72%) and 647 species (31.38%). (5) The flora of YNR belongs to Sino-Himalaya of East Asia. The statistics of the generic areal-types shows that there are 62 genera of East Asia, and the percentage between the subtypes of Sino-Himalaya and Sino-Japan is 27: 9. (6) There are abundant endemic in YNR. There are 5 families of East Asia in the NZNR, which are Tetracentraceae Dipentodontaceae, Actinidiaceae, Aucubaceae, Helwingiaceae. This statistics indicates that the YNR is part of East Asia'and has consistency in geological history with East Asia and also makes know that this area has close correlation with East Asia. There are 6 genera and 902 species endemics of the China and this indicates the important position of the YNR in Yunnan and even in China. Even though there are relatively little endemics genera in this area, but the existence of more endemics species of China, especially there are 24 endemic species only in this area, which is in the dry and hot climate have to adapt to it after theirs genera had been distributed in this area. In addition, according to records in the Flora of Yunnan and the Flora of China, there are 10 species who distributed only in Yuanjiang in China, that fully shown that the special nature of the area's climate. (7) There are 10 new distributions in Yunnan at this investigation, belonging to 6 families and 9 genera. More of these species are herb or shrub which distributed in the mountain valley, reflecting the flora of the area of the rich. Plenty of new distributions indicated the flora is abundance in this area. In addition, it also shows the investigations of plant and vegetation is few in this area. So the YNR has very important value on plant diversity investigation and conservation in Yunnan, even in China.In this paper, the approach of statistics and analasis has done some improvements and try on the basis of the generally method used to do in China. such as the scope of famlilies in angiosperm is defined according to"polyphyletic-polychronic-polytopic"(8-Classes System), the endemics of China composition is classified two basic components as tropical and temperate, so that reflect their character of the flora in the study area more accurately and effectively...
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