effects of different harvesting intensity on production, strength and vitality of bromus tomentellus (case study: majid abad qorveh rangelands, kurdistan)

to study the effect of different harvesting intensity on forage production of bromus tomentellus was considered of majid abad qorveh. treatments included four harvested intensity 25, 50 and 75 percent and control (no harvest).data were analyzed based on splitplot over time during four years(1386-1389) using sas and irristat software. the results showed that the main effect of year, different harvesting intensity and interactions effect of different harvesting intensity and years are significant on forage production and vitality of bromus tomentellus. comparing the harvesting intensity of 50 and 25 percent indicated no significant difference between them. the highest intensity of production is harvest intensity of 25 percent with 390 mm perecipition in 1389 and the lowest harvest intensity is 50 and 75 percent with170 mm perecipition in 1387. regarding to ammi analysis, the first interaction principal component(ipc1) had a significant effect and express a 93/6 percent of the interaction of the sum of squares. the first main component biplot interaction showed that the 25 percent treatments had a highest average production and stability is relatively good, control treatment had a lowest stability and 75 percent treatment had a highest stability. according to the results, to preserve the production and vitality of bromus tomentellus the harvesting intensity of 25 percent is recommended.