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

Due to their numerous endemic/sub‐endemic and rare plant species, rocky outcrops and cliffs, particularly those occurring at the timberline and forest/steppe ecotones of the Hyrcanian area, are considered as among the most important and fragile ecosystems in Iran. As a representative of such ecosystems, one of the last remnants of relatively undisturbed timberline and ecotone areas of the central Hyrcanian region was selected for phytogeographical, floristic and vegetation analyses. The flora and vegetation of rocky outcrops and crevices at altitudes of 2500–3000 m a.s.l. was surveyed by 40 relevés of 25 m 2 surface area. A total of 215 vascular plants belonging to 55 families and 150 genera were identified in the 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 at the study sites. A 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, has a considerable number of taxa in common with the Irano–Turanian floristic regions. Five vegetation types were identified using a modified TWINSPAN procedure and subsequently analysed by indirect gradient analysis applying both species‐related (species richness, life form and phytogeographical elements) and topographic/bedrocks features of the studied relevés. The analysis revealed that the vegetation of the area is mainly affected by altitude, heat index, northness, slope inclination and bedrock features.