THE FLORISTIC COMPOSITION, BIOLOGICAL SPECTRUM AND CHOROTYPES OF VEGETATION IN THE WATERSHED OF KORDAN REGION, WEST ALBORZ PROVINCE, IRAN

Floristic studies are one of the most effective methods for managing and Protection of biological reserves of vegetation, and it plays an important role in controlling erosion and rehabilitating destroyed areas. Destructive conditions have caused the reduction of valuable plant species in the flora of the region. Therefore, the aim of this research was to investigate the floristic composition, geographical distribution, biological spectrum and and identifying endemic species in the Kordan watershed in the Kurdish watershed in Alborz province of Iran. The flora of the region was studied by field trip between 2019 and 2021 in different plant phenological stages. In total, 151 species of flora belonging to 28 families and 115 genera were surveyed and identified in several field trips during the study period from 201 to 2021. Based on the number of species, Asteraceae (35 species and 24 genera), Poaceae (17 species and 13 genera), and Lamiaceae (15 species and 13 genera) were the most important families. The largest genera were Astragalus, Centaurea, Bromus, Salsola, Cirsium and Alyssum. In this study, the life-form spectra were classified on the basis of Raunkiaer's system. Then, the 𝜒2 test was used to compare the biological spectrum with Raunkiaer's normal spectrum and with those in other floristic studies conducted in the near the study area.  The results showed that the life-form spectrum in the present study w::as char::acteristic of a cold dry and mountainous climate region with hot and dry summer and relatively cold winter and dominated by hemicryptophytes (46% of the recorded species), followed by therophytes (32% of the recorded species). Findings also indicated that the effects of climate, and human activities such as overgrazing caused a reduction in phanerophytes from around 46 to 5%, increases in therophytes from about 13 to 32% and hemicryptophytes from 26 to 46% in comparison with Raunkiaer's normal spectrum. It can be concluded that hemicryptophytes and phanerophytes usually comprise the highest and lowest percentages of life forms in studies conducted in the Irano-Turanian growth zone.