Effects of defoliation intensity and continuous grazing on basal area, canopy cover and height of two species of Bromus tomentellus and Ferula haussknechtii in Saral Rangelands of Kurdistan Province, Iran

In most Iranian rangelands, continuous grazing begins with melting snow and continues until the beginning of snow. This study was conducted to evaluate the effects of continuous grazing system on a number of morphological attributes of Bromus tomentellus and Ferula haussknechtii during 2010-2011 in Saral Rangelands of Kurdistan Province. The 30-year exclosure was selected as control area inside the Saral Research Station. In different growth stages, the morphological attributes including the shortest and longest basal area diameter, theshortest and longest canopy diameter, and the height of 10 plants were measured. The annual yield of 30 plants of each species in each year was clipped and weighed to determine forage consumption intensity. All data were subjected to statistical analysis in a completely randomized design using combined analysis. Mean comparisons were performed using Duncan’s Multiple Range Test. Continuous grazing caused to the increase of basal area diameter and canopy diameter of B. tomentellus significantly; however, the height varied in two studied treatments, depending on the year. The three studied morphological attributes of F. haussknekhtii were affected drastically by continuous grazing. In this species, basal area diameter was more affected by the conditions of the year. In both species, ungrazed plants used seasonable rainfall more efficiently as compared to the grazed plants.