Floristic Investigation of Shirin Darreh Dam Watershed Area Located in the North West of Bojnourd, North Khorassan Province

Shirin Darreh water shed area is located in Irano-Touranian region and devided in plain and Mountain parts. A part of Hyrcanian province is located in west of area. Water shed of Shirin Darreh river is located in the 37-38 , 38 of the north latitude and 56-58 , 55 of the east longitude, southern slopes of Hezar Masjed mountains, north west of Khorassan province.The mean of altitude of area is 1481 m and amount of rainfall is 270 mm. The climate of region is cold-semidry. Floristic analysis of area showed that here were 45 families, 185 genera and 275 plant species. The biggest plant family of the region is Compositae with 54 species. Leguminosae (34 sp.), Graminae (28 sp.) are in the next order and there are some monotype families like Valerianaceae, Cistaceae, Podophyllaceae. The life form percentage of plants are as follows: Th 35.30%, Hem 28%, Cr 7.30%, Ch 6.20% and Ph 3%. The phytogeographycal distribution of this region are as follows: IT 41.82%, IT-ES 13.46%, IT-M 12.75%, ES 4.8%, Cosm 1.46%, Endm 1.46% and Med 1.1%.