Introduction of trees and shrubs in Zanjan county in the northwest of Iran

Zanjan county has 6763 km2 area, the altitude of 1663 m.a.s.l. Mean annual precipitation and temperature is 297.6 mm and 11°C, respectively. From a topographical point of view, Zanjan is a mountainous area where fertile plains have been formed due to Tode composition of Rivers, such as Ghezel-Ozan and Zanjanrood. The appropriateness of ecological conditions is the cause of favorable vegetation diversity. A floristic study of plant species in each region is an effective way of understanding the capacities and conservation of the hereditary reserves of ecological systems. In order to identify the tree and shrub species, life forms, and chorology, samples were collected using conventional methods of floristic studies during years 2016-2017. Totally, 100 species belonging to 72 genera and 35 plant families were identified using the necessary references, of which1 species belonged to monocotyledons,10 species to gymnosperms, and 89 species to dicotyledons. Based on species richness, the most important families included: Rosaceae (26species), Oleaceae (8species), Moraceae and Salicaceae (6 species), Fabaceae (5species), and Cupressaceae (4species), as well as Cerasus and Prunuseach with 4 species and Berberis,Crataegus, Morus, Populus, and Salix with 3 species, were the largest genera of plants. According to Raunkiaer system of classification, the dominant life forms in this region are Mesophanerophytes (37%) followed by Microphanerophytes (33%), Nanophanerophytes (21%), and Megaphanerophytes (9%) respectively. Vegetative elements of Irano-Turanian are of the most important chorological groups in the region based on Zohary s method and Amygdaluslycioides Spach is an endemic plant of Iran.