in this study the effect of month, place and different years on the preferencevalue of bromus tomentellus in semi-steppe region was studied. the preferencevalue of the bromus tomentellus was studied in two years and four months in three sites as cheshme anjir (fars), badamstan (zanjan) firuzkuh (tehran). to determine the preferencevalue of species the two methods of as preference index and timi...