محمد محمودی - Research Assistant Prof., Botany Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), P.O. Box ۱۳۱۸۵-۱۱۶, Tehran, Iran
فرخ قهرمانی نژاد - Prof., Department of Plant Sciences, Faculty of Biological Sciences, Kharazmi University, Tehran ۱۵۷۱۹-۱۴۹۱۱, Iran
علی اصغر معصومی - Research Prof., Botany Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), P.O. Box ۱۳۱۸۵-۱۱۶, Tehran, Iran

The present study, was aimed to investigate flora and phytogeography of the Damirli mountains, located in Zanjan province in northwestern of Iran. In this area, the total amount of ۸۰۹ taxa of vascular plant belonging to ۶۹ families and ۳۳۳ genera are introduced. Hemicryptophytes with ۳۹۹ species are ranked first in life forms. Therophytes, chamaephytes, phanerophytes with ۱۹۴, ۱۹۹, and ۱۹ species are ranked next, respectively. The patterns of altitudinal distribution of the species were not similar and ۱۰ different patterns were recognized. This study revealed that, as the altitude increases, the species richness decreases and along ca ۱۶۰۰ meters, elevational gradient is almost reduced to half. Sixty-nine percent of the flora of the region belongs to Irano-Turanian region and Euro-Siberian/Irano-Turanian/Mediterranea, Irano-Turanian/ Mediterranean, and Euro-Siberian/Irano-Turanian species have considerable share in flora of the studied region (۹%, ۷%, and ۶%, respectively). Five percent of the flora of the region belong to the pluriregional species and ۲.۳% belong to cosmopolitan or subcosmopolitan. In lower places, the flora of the area is influenced by Mediterranean region, western and central parts of Irano-Turanian, and even Saharo-Sindian region. As the altitude rises, the floristic composition of the region is changed, and the species of the western parts of the Irano-Turanian region and cosmopolitan species as well as pluriregional dominate. In the Damirli region, ۱۲۱ taxa of Iranian endemic plants exist among which ۱۱ species are endemic and eight others are subendemic to Zanjan province. The present study, therefore, revealed that, there is a meaningful relationship between altitude and the endemism so that, as the altitude increases for ۱۰۰ meters, there is a ۳.۸% increase in the amount of endemism. 

Biodiversity, Endemism, Flora, phytogeography, Species richness, vegetation