Investigation of different harvesting simulation treatments on production and vitality of Bromus tomentellus (Case study: Gharabagh rangelands, West Azarbayjan)

Rangelands are the largest of the earth''s natural resources that the use of them with proper management can be affordable in terms of economic and agricultural. Due to the successful results of cultivation of some grasses including Bromus tomentellus in Gharabagh of West Azerbaidjan، the determination of allowable use for Bromus tomentellus can be useful in conservation and proper utilization of the mentioned species as well as ensuring its survival. Treatments in each block were four grazing intensities of 25، 50، and 75% and control (no harvest). In each treatment، 10 individuals of species were considered as replications. Data were analyzed in a split plot in time for four years (2007-2010) by SAS & IRRISTAT software. Results showed that the effect of year، different harvesting intensities and interactions between year and different harvesting intensities on forage production and vitality of Bromus tomentellus was significant at 1% level of probability. No significant difference was found between control treatment and grazing intensity of 25 percent as well as 25 and 50 percent. With increasing harvesting intensity to 50 and 75 percent، average rate of production decreased significantly compared to control. Average production and vitality showed a downward trend during 2007-2010 due to the severe reduction of average production and vitality at 75% harvesting intensity. Other treatments including control، 25، and 50 percent، showed almost similar trend during the four years. Based on AMMI analysis، first interaction principle component (IPC1) was significant at 1% level of probability and explained 99. 19% of interaction sum of squares. According to the biplot of first interaction principle component and average production، the least production and stability was obtained at 75% harvesting intensity while maximum stability was recorded for 50% harvesting intensity. According to the results، a harvesting intensity of 50% is recommended for Bromus tomentellus in the region so that health and vitality of this species is preserved during the harvesting years.