Investigation on the phenology of Stipa barbata in steppe and semi-steppe rangelands of Iran

Rangelands are composed of a variety of plant species whose different phenological stages are largely influenced by climatic factors. Therefore, considering the fluctuations of climatic conditions, each species is ready to be grazed in a particular time of growth period and also grazing should be stopped in a particular time. In this research, the phenological stages of Stipa barbata were investigated in five sites of semi steppe and three sites of steppe vegetative regions during 2007-2010. After determining the geographical characteristics of each site, 10 plants were selected and the growth stages including germination, vegetative growth, flowering, seed maturity, and dormancy period were recorded in 15-day and 7-day periods during growth stage and reproductive stage, respectively during four years. Also, meteorological data including daily tempreture, and monthly rainfall were collected from the nearest synoptic station. According to the results, the phenological stages of the studied species were more affected by GDD and rainfall index during the growing season. GDD (Growth Degree Days) in each phenological stage was almost identical from year to year with little difference. It is also not much difference among the studied sites.