Knowledge of the process of change in vegetal biomass in perennial plant species is indispensable in a sound of range management. Research area is of rangeland of Til village from Shabestar distract with distance is 25 Kilometers from it. This area is semi arid area and this land covered with natural range land grasses. Root and shoot in these species were sampled in one stage from late Mar late to late Aug. roots of plants stable soils on slope and provide resistance against the forces that improve slope instability. The aim of this work was to assess which biomass quantitative is associated with differential productivity of A.Longistylum(S&G) Species. In the research Alyssum longistylum biomass was been studied in under –ground plant biomass in soil studying of area with measure dept of roots and height of stems, vegetal sample was collected form studying area with random plot 1m*m statistical plant during one the vegetative season in this research. Results of this research showed plant average root dept is about 6.75 cm, average stem height is about 6.63 cm and average under ground of plant biomass is about 0.10 gr/m2 and average over ground of plant biomass is about 0.60 gr/m2.
