Autecology of Stipa hohenackerianaTrin & Rupr in TehranProvince

Stipa hohenackeriana Trin & Rupr is a perennial plant of the gramineae family. This species covers a wide range of habitats in Tehran province. The habitat characteristics of this species including topography, climate, vegetation type, soil, associated species, plant phenology and root system were investigated. The results showed that these habitats were located in altitudes of 880 to 2400 m above sea level. The average rainfall in the habitats was 150 mm to 378 mm. The annual average temperature, annual minimum temperature and annual maximum temperature were 15.5 to 24.4°C, -2 to 12°C and 32 to 42 °C, respectively. This plant was observed in a range of shallow to very deep soils at slopes of more than 0.5 percent. Soil acidity measurement showed levels of 8.1 to of 8.71 and the electrical conductivity of the soil were 0.19 to 0.98 ds/m. In most habitats, this species has emerged as the dominant. Average canopy cover, density and frequency were 8.43%, 9050 plants / ha and 90%, respectively. The ratio of root to shoot weight was 0.226. This plant has a highly branched root system. Phenology of the species in different habitats showed that the growth started from mid-March to mid April. Production stage of pods was in late May. Flowering was from late May to late June. Seed production occured from late May to late July. According to regional climatic conditions, the seeds were matured. From early September to early October the plant was in summer dormancy. This study showed that chemical compounds of crude protein and crude fat were maximum at early growth stage but gradually decreased in the coming stages.