Vegetation Patterns of the Irano-Turanian Steppe along a 3,000 m Altitudinal Gradient in the Alborz Mountains of Northern Iran

摘要: The Irano-Turanian floristic region is a major center of endemism in the Holarctic Eurasia. Alborz Mountains northern Iran are complex and heterogeneous environmental system with rich water resources great habitat diversity. We have investigated steppe plant communities along an altitudinal gradient ranging from approximately 1,000 m a.s.l. semi-desert steppes near Tehran to height 3,966 at summit Mount Tochal. Our two-way indicator species analysis 1,069 vegetation samples resulted classification five zones: (1) Artemisia Tehran, (2) Stipa grassland alluvial undulating hills north west (3) submontane zone, (4) subalpine cushion formation zone (5) alpine meadow subnival Annuals ephemerals decline as altitude increases almost disappear zone. Past human impacts ancient Persian civilization traditional pastoral economy affected physiognomy communities; thorny dwarf shrubs now dominate treeless region. Lower competition for space, different phenology presence edaphic hydrological layers associated anthropogenic reasons entanglement arid- semi-arid steppe. phytogeography changes omni-Irano-Turanian Saharo-Sindian transgressive lower altitudes more limited range western local endemics higher altitudes.