Phytosociological survey of Noor and Sisangan lowland Hyrcanian forests Mazandaran province

The northern forests of Iran are Tertiary relicts and large parts of its lowlands have been destroyed due to human interference. However، only some small patches of these forests have remained yet which deserve a high value of conservation policies. Noor and Sisangan forests in Mazandaran lowlands were investigated with a phytosociological approach. The phytosociological data were collected from 55 relevés and classified using modified TWINSPAN in the JUICE software. Four vegetation unites were described: Celtis australis-Buxus hyrcana، Fraxinus excelsior subsp. coriariifolia-Cardamine tenera، Populus caspica-Alnus subcordata and Parrotia persica-Carpinus betulus. Exhaustive investigation of all diagnostic species of described communities in the Hyrcanian forest، clarified the connectivity of the studied vegetation unites with two major alliances، Parrotio-Carpinion and Alnion subcordatae. Obviously، the final decision on the syntaxonomical situation of the associations would be impossible without more a comprehensive investigation on the whole Hyrcanian area.