effects of time and frequency of clipping on production and regrowth of agropyron trichophorum (link) richtin emam gholi summer rangelands, ghochan, iran

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 ofagropyrongenus which are dominant in the most summer rangelands. in emam gholi protected summer rangelands, ghochan, khorasan province, iran, a. trichophorumas a dominant grass was selected for our study, and was subjected to a series of defoliation treatments. forty eight quadrates of 0.5 m^2were 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. trichophorumwere 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.