Flora and vegetation of rocky outcrops/cliffs near the Hyrcanian forest timberline, Mazandaran mountains, Northern Iran

18 April 2017

Naqinezhad, Alireza; Esmailpoor, Ali

Rocky outcrops and cliffs of Iran particularly those occurring in timberlines and forest/steppe ecotones of the Hyrcanian area are considered as among the most important and fragile ecosystems due to their role in harboring many Iranian endemic/sub-endemic and rare plant species. As a representative of such ecosystems, one of the last remnants and relatively undisturbed timberline and ecotone area of the Central Hyrcanian area, Northern Iran was selected for a phytogeographical floristic and vegetation analyses. Flora and vegetation of rocky outcrops and crevices ranging altitudinally from 2500 to 3000 m a.s.l. was surveyed in the framework of 40 relevés of 25 m2 surface area. A total of 215 vascular plants belonging to 55 families and 150 genera were determined in different vegetation types. Hemicrytophytes (55.8 %) were the dominant life form and Euro-Siberian/Irano-Turanian biregional plants (28.2%) were the most common chorotype in the study rocks. Phytogeographical analysis indicated that Euro-Siberian elements (including Hyrcanian endemics) precede other uniregional chorotypes in the timberline and upper-mountain parts of the Central Hyrcanian area. The Caucasus, an important biodiversity hotspot close to Iran, had considerable common taxa with Irano-Turanian floristic regions. Five vegetation types were identified using modified TWINSPAN and subsequently shown on the indirect gradient analysis applying both species-related (species richness, life form and phytogeographical elements) and topographic/bedrocks features of the studied relevés. Vegetation of the area is affected mainly by altitude, heat index and northness on the first axis and slope inclination as well as bedrock features on the second axis of the gradient analysis. The information on flora, vegetation and phytogeographical distribution of plants described here will serve as the basis for further conservation in the Tertiary relict Hyrcanian forests.