- Flora of the Research Forest in Yen Tu, Quang Ninh. - The vascular flora of the Research Forest in Yen Tu, Quang Ninh was assessed between 2005 and 2006. - In the area under review, 721 species belonging to 425 genera and 154 families were identified. - When the flora of the area is analysed by Raunkiaer’s life form system, the results are as follows: phanerophytes 596 (82.7. - and unknown 16 (2.2%) species, respectively.. - Keywords: Vascular plant, Flora, Yen Tu, Quang Ninh Research Forest.. - This research was carried out to determine the flora of the Research Forest in Yen Tu, Quang Ninh. - The vegetation of the area has been extensively destroyed by anthropogenic effects and, therefore, plants try to survive under unsuitable conditions. - The Research Area is located within the borders of the North by Son Dong district (Bac Giang province), in the East by Vang Danh village, in the West by Trang Luong, Dong Trieu district, and in South by Dong Thi, Uong Bi district (Quang Ninh province). - Yen Tu, Quang Ninh Research Forest is covered two mainly mountain chains toward to North from 660m peak to 908m peak and two junior mountain chains toward North-South.. - Altitude in the study area ranges from 50m Nam Mau plain to 1068m Yen Tu peak. - The study area consist three mainly stream systems as Vang Tan, Giai Oan and Bai Dau.. - The geological structure of the research area mostly consists of aged calcareous rocks, paleo- allvium and sand gravel. - There are 4 large soil groups in the study area as follows:. - cultivated soil in Nam Mau plain, due to the climate, topography and differences in the main substance.. - The typical climate of the region is clearly two seasons. - It characterized by hot, humidity and rainy summer which starts from May to October, meanwhile cool and dry winter which starts from November to April of the next year.. - The temperature decreases gradually and the rain increases towards the upper parts of the mountains. - The research material consists of some 2015 plant specimens collected from the research area. - Subsequently, the Flora of Vietnam [1-4] and the other related floras [5-9] and monographs [10-12] were used in the identification of the specimens.. - Moreover, some of the specimens were compared with the type specimens which have been keeping at the Herbarium of Forest University and National University of Hanoi (HNU) during the study period between 2005 and 2006. - The most of the plant specimens are kept at the Herbarium of University Forest and other are kept at the Herbarium of National University of Hanoi (HNU). - As a result of the identification of the plant specimens, 154 families, 425 genera, and 721 species were determined. - Nine of the 721 species belonging to the Lycopodiophyta and 34 are Polypodiophyta and the other 678 belonging to the spermaphyte plant. - The dispersion of the plant taxa belonging to Angiospermae that were defined in the study area according to the large taxonomical groups is shown in Table 2. - The Dicotyledonae group are contained by of species of genus and of family, meanwhile the Monocotyledonae are included by of species of genus and of family, respectively in the study area.. - Number of families Number of genera Number of species Divisions. - The distribution of the species according to the class of Angiospermae Number of families Number of genera Number of species Class. - As can be seen from Table 3, with of the species are phanerophytes are chamaephytes are cryptophytes are hemicryptophytes are therophytes, and 16 (2.2%) are unknown, respectively. - Although the average rainfall per year is 1785mm, most of the rain falls in August, September and November. - The family Euphorbiaceae is the largest in the study area with 52 (7.2%) species. - The Euphorbiaceae are the largest family here, because they are one of the largest families in Vietnam. - The Asteraceae family is the second largest family in this area, partly because they are the largest family in the world as well as in Vietnam and partly because of the large number of wild chrysanthenum plants growing in cultivated areas.. - The 10 largest families according to number of species in this study and the studies mentioned above are compared in Table 4.. - The order of the largest families varies only slightly between studies. - In the studies of the Yen Tu area, the Acanthaceae, Cyperaceae, Orchidaceae, and Apocynaceae families are not listed as one of the 10 largest families although they are one the 10 largest in Vietnam as a whole. - Meanwhile, the family Euphorbiaceae is the largest family in the studies carried out in Yen Tu, Cat Ba and Huu Lung areas and is one the 10 largest in Vietnam as a whole. - The family Asteraceae is the 2 nd largest family in the studies carried out in Yen Tu and Huu Lung and is the 6 th largest in Cat Ba. - In contrast, in the studies of the Yen Tu, Huu Lung and Cat Ba areas, the family Moraceae is listed as one of the 10 largest families although is not one of the 10 largest in Vietnam as a whole. - The Moraceae family is 3rd in the list from the Yen Tu, Cat Ba, and 5 th in the list from Huu Lung area. - Although this appears to be a significant divergence from the general distribution of Vietnam flora, the family Moraceae is, in fact, one of the 10 largest families in East-North region of Vietnam. - As the same Caesalpiniaceae, Fagaceae, and Verbenaceae occupied 8 th , 9 th , 10 th , in Yen Tu area, respectively. - But they are not listed one of the 10 largest in Vietnam as a whole. - It could be explained by differences in the habitats of the study area. - in the lists is occupied by Rubiaceae, Lauraceae, Fabaceae and Poaceae families. - This result was expected because they are one of the 10 largest families in Vietnam as a whole.. - The genera containing the highest number of species in this study and the other studies are listed in Table 5. - The 10 genera containing the highest number of species vary significantly.. - However, each list includes contains between 4 and 8 of the 10 genera containing the highest number of species. - The genera Blumea DC., Desmodium Desv., Calamus L., Smilax L., Polygonum L., Elaeocarpus L., Sauropus Blume, Mallotus Lour., which are not among the 10 largest genera, are also included in the lists. - The genus Calamus L., Cinnamomum Schaeff., Smilax L., occupy 6 th , 8 th , 10 th position in Yen Tu, respectively, but it is not listed as one of the 10 largest genera in the studies compared. - This discrepancy can be explained by differences in the habitats of the study areas.. - They are one of 10 largest genera in Vietnam, but they are not occupied in other compared. - This discrepancy also can be explained by differences in the habitats of the study areas.. - The richest genera in the studies compared. - The research area is a designated protection area and is located in one of the centres of plant diversity in Northern Vietnam. - The author wishes to thank the Manage Board of the Yen Tu, Quang Ninh Research Forest for help during our sample collecting. - Flora of China