A Contribution To Flora, Life Form and Chorology of Plants in Noor and Sisangan Lowland Forests

Lowland hyrcanian (caspian) areas possess a number of important remnant patches of deciduous euro-siberian forests distributed sparsely in the three iranian provinces, guilan, mazandaran and golestan. noor and sisangan are two large patches of such lowland forests classified as “natural forest parks” in the context of “iranian natural resources”. in spite of a few local studies, broad knowledge upon the flora and vegetation of these areas are lacking. a total of 225 species belonging to 175 genera and 77 plant families were collected from the studied areas. the largest families in terms of species richness, were poaceae (28 spp.), asteraceae (18 spp.) and rosaceae (9 spp.), respectively. the genera with the largest number of species were carex (6 spp.), veronica (5 spp.) and euphorbia, polygonum, solanum (each with 4 spp.), respectively. in the assessment of life form spectrum, the dominant life forms were therophytes (30.2%), followed by the geophytes (27.1%), hemicryptophytes (20.9%) and phanerophytes (18.2%). the flora was mostly composed of pluriregional elements with 60 taxa (27.3%), followed by euro-siberian/irano-turanian/mediterranean elements with 43 taxa (19.5%). life form spectra and chorotype percentages were discussed for each study area separately. according to sørensen’s (1948) similarity index, there was a remarkable similarity between two forest areas. noor and sisangan forests were highly threatened ecosystems in case of species loss and changing natural communities due to occurrence of anthropogenic and over-grazing effects.