Classification of the Hyrcanian forest vegetation, northern Iran

Prepared by Hamid Gholizadeh, Alireza Naqinezhad & Milan Chytrý

Hyrcanian relict forests of Northern Iran, Javaherdasht area of Gilan province. Photo: Hamid Gholizadeh

The Hyrcanian forests, unlike the arid and semiarid landscape throughout most of Iran, is one of the remnants of ancient natural deciduous forests which form a vegetation belt in the southern shores of the Caspian Sea. The belt is located in the northern slopes of Alborz Mountains in northern Iran, covers four Iranian provinces and is 800 km long (from W to E), 20–110 km wide (from N to S) and has a surface area of 1.84 million hectares. This unique forest massif was designated as a World Heritage site of UNESCO in 2019. Presence of endemic Arcto-Tertiary floristic elements, such as Gleditsia caspia, Parrotia persica, Pterocarya fraxinifolia and Zelkova carpinifolia, identifies the Hyrcanian forests as a unique relict ecosystem preserving the phylogenetic heritage of the late Tertiary. Forest flora and vegetation in this ecoregion are related to the Euro-Siberian phytogeographical region, being exceptional to the Middle East, but the upper-montane belt (approximately above 2000 m a.s.l.) is affected by Irano-Turanian phytogeographical elements.

Location of the Hyrcanian forest, as a green arc along the Caspian Sea, N. Iran. The main figure is from http://earth.imagico.de, the inset figure is Fig. 1 from the main paper.

A database of almost 1600 vegetation plots including ca. 800 vascular plant taxa was established using recent vegetation data collected in the last 15 years by the first two authors and those compiled from all available literature since 1959. The database covers the whole geographic range of the Hyrcanian forests at altitudes ranging from -22 to 2850 m a.s.l. We analysed 21 different plant communities occurring in the whole ecoregion using a new method of “expert system”. These plant communities vary from west to east (longitudinal gradient) and north to south (elevation gradient) and strongly depend on climatic as well as topographic features.

Oriental beech (Fagus orientalis) communities in Kordkoy montane belt of Golestan province (ca. 1200 m a.s.l.). Photo: Alireza Naqinezhad

This is a plain language summary for the paper of Gholizadeh et al. published in the Applied Vegetation Science (https://doi.org/10.1111/avsc.12469).