The most appropriate level of utilization for Bromus tomentellus at Karsanak rangelands in Chaharmahal & Bakhtiari

Appropriate use of rangelands, creates vegetation stability, prevents degradation and improves their suitability  conditio. Determination of allowable level of vegetation utilization of the species could lead to plan for the proper distribution of livestock on rangeland. To measure the level of use, a 0.5 ha exclosure was established in Karsanak site before the start of the growing season in 2007 and 40 individual Plants of Bromus tomentellus were selected randomly inside of the exclosure in order to determine the effect of different harvesting intensities (simulated grazing) on forage and seed production. Clipped treatments included 0, 25, 50 and 75 percent of annual growth. There were 10 replications in the plan. Clipping continued for 4 years in three months of grazing season. Vigor and freshness, mortality, plant maximum height, forage and seed production were observed and measured during the 4 years. Data were analyzed in a split plot design in time with SAS software. The results of forage production of Bromus tomentellus showed that the effect of years is statistically significant at 1%. And the interaction of the year and different intensities of harvest, is not significant at the 5%. Lowest forage production has happened in 2007 harvesting at 25% and its highest in 2009 in control treatment. The results of seed production showed that the And the interaction of the year and different intensities of harvest is statistically significant at 1% But their interaction was not significant at the 5% error level. Due to environmental changes affecting of this species, it can be concluded that about 50 percent of annual yield removal is safe for persistence and health of Bromus tomentellus in Karsanak and other areas with similar climate and soil conditions in drought years but the harvest of up to 75 percent in normal years apparently does not harm the plant.