Phytosociological and ecological study of the high alpine vegetation of Tuchal Mountains (Central Alborz, Iran)

The present paper deals with the phytosociology and ecology of the high alpine zone of Tuchal Mts. (Central Alborz). On the basis of 185 phytosociological releves, the vegetation of high alpine snow-beds, fellfields and xerophytic habitats of Tuchal Mts. is analysed. By means of phytosociological classification and ordination (Detrended Correspondence Analysis), the plant communities and environmental factors governing the variance in vegetation are described and discussed. The studied plant communities are arranged in two provisional orders, four alliances (Taraxaco brevirostris-Polygonion serpyllacei, Astragalion iodotropidis, Cousinion multilobae and Acantholimion demawendici) and 13 associations (Polygonetum serpyllacei, Ranunculetum crymophili, Trifolietum radicosi, Astragaletum iodotropidis, Galio decumbentis-Thymetum pubescentis, Vicietum ciceroideae, Rumicetum elbursensis, Bufonio kotschyanae-Cousinietum multilobae prov., Hordeo violacei-Cousinietum multilobae prov., Astragalo chrysanthi-Cousinietum multilobae prov., Oxytropido persicae-Cousinictum multilobae, Acantholimetum demawendici and Jurinelletum frigidae). The communities of these habitats strongly depend upon the duration of snow-cover. Edaphic and hydrological quality of micro-sites is more important for the species composition and vegetation mosaic than the regional climatic gradient. About 90% of the species of the study area are Irano-Turanian elements. All syntaxa are further characterized by life form spectra. Flowering phenology of seven associations was studied according to the snowmelt gradient.