Effect of different grazing intensities on nutrient allocation and quantitative characteristics of specie Bromus tomentellus Boiss (Case study: North East of Delfan County)

In order to investigate the effect of different intensities on the quality and quantity of forage in the Bromus tomentellus Boiss species, mountain ranges in the northeastern part of the Delfan city were selected. Three zones with different grazing intensities were selected including the grazing area (reference), medium grazing (key) and heavy grazing (critical). In each region, sampling of surface coatings was done in a systematic randomized way in 30 plots 1*1 square meter during three transects with a length of 100 meters. Vegetation characteristics such as canopy cover and density were calculated and then the production per unit area was calculated by cutting and weighing method. The aerial parts of B. tomentellus, in each treatment, were used to harvest 60 plant aerial parts and transferred to the laboratory. In the laboratory, the samples were dried in the oven at 65 °C and milled and chemical decomposition was performed on them. Analysis of variance and Tukey test were used for comparison of means. The results showed that the percentage of crude protein, potassium, phosphorus, calcium, digestible dry matter and metabolic energy, density, crown cover, and production of the species studied were significant in the areas of grazing, medium grazing and heavy grazing (P <0.01). In both heavy and medium grazing treatments, the protein decreased by 28% and 8%, respectively. Also, potassium, phosphorus, calcium, digestible dry matter and metabolic energy in two treatments under the grazing have a significant decrease compared to the exclosure area. The amount of production, density and canopy in the key area (17, 16 and 31 percent, respectively) and the critical area (42, 69 and 68 percent respectively) are lower than the reference area. The result of this study showed that heavy and medium grazing would reduce the quality and quantity of B. tomentellus species.