Pubescent wheatgrass (Agropyron trichophorum (Link) Richt.) is growing in semiarid regions of Iran at altitude of 500 to 2000 m. Among different grasses growing in Iran, A. trichophorum is relatively resistant to grazing and defoliation as compared to other species of Agropyron genus which are dominant in the most summer rangelands. In Emam Gholi protected summer rangelands, Ghochan, Khorasan province, Iran, A. trichophorum as a dominant grass was selected for our study, and was subjected to a series of defoliation treatments. Forty eight quadrates of 0.5 m2 were established in two macro-plots and subjected to one, two, three, and four weekly interval clipping started in May 6, 2016 in vegetative stage and other treatments of once clipping started in May 6, May 19, June 3, and a control treatment was clipped only once in July 15. Floral stalks of A. trichophorum were counted before clipping. Then, quadrates were clipped to the ground surface, air dried and weighed for different treatments. Using ANOVA, the responses to frequent clipping showed that there were no significant differences in daily, current, primary, and total production of A. trichophorum (p>0.05) which may be due to the reservation of carbohydrate in roots and base of this grass after 15 years of protection. Low slope of sigmoid curve for weight of clipped plants also confirmed the resistibility of this species to defoliation, but as the frequency of clippings were increased, the number of floral stalks was decreased showing an exponential model (p<0.0). To find the allowable use of A. trichophorum, further years of research will be required to evaluate the responses to defoliation in different locations. تفاصيل المقالة

One of the most important issues in rangeland management is the estimation of carrying capacity. To estimate range production, we need to use a large number of sample plots to clip plants in a sampling scheme; therefore, due to vast area of rangelandsand time and cost limitations, direct estimation of rangeland production by sampling plots is almost impossible. Since there is a strong relationship between climatic factors and rangeland production, using indirect estimation methods of rangeland production is important. The relationship between production samples and climatic factors can be easily predicted. Present study was conducted in five locations of Spandol, Zarchak, Torogh, Aselme, and Dash, Iran in 2013. In this research, the relationships between forage production and three climate parameters including precipitation, temperature, and precipitation to temperature ratio (P/T) were investigated. For each parameter, 33 variables (periods) were considered. Stepwise regression analysis was used to select the most effective periods of precipitation and temperature. The relationship between production and March to April precipitation and November to December temperature was positive but with October to March temperature, it was negative. The relationship between production and P/T was negative in May to June and positive in January to March. In general, simultaneous of rainfall and temperature had effective roles in increasing dry matter production of grasslands in the studied areas. تفاصيل المقالة