Evaluating of utilization gradient of Artemisia sieberi Besser. around watering points using group regression (Case study: Chahe-Nou rangeland, Damghan)

Determining of utilization factor is one of the most important factors which used to evaluation of equality between livestock and rangeland. Water points are one of the effective factors that effect on the grazing distribution in rangelands. While some factors such as slope، height and soil factors have no limitation، distance from watering points is limited the use of forages. In this research، the percentage of use factor of Artemisia sieberi Besser was calculated around watering points using ocular estimate method. The aptest regression equations were determined for each of watering points. Before grazing of livestock، 10 pair plots of 4m2 were established with pegs. The dry weights of forage at 10 plots were calculated randomly. After grazing، the factor of use in the other 10 plots was estimated and the real utilization of them was calculated by clipping and weighting method. The estimated and real data were used to calculate of regression equation. And the estimated data modified with it. In this stage، after grazing، two transects of 1. 7 km were established around each of watering points randomly. In each of 100 m of one transect، the utilization rate of A. si. was estimated by establishing of a plot of 4 m2. All of the estimated data were modified by regression equation that calculated in previous stage. The regression coefficients of two equations were compared each other using group regression method. And final regression equation was calculated. The results show that the utilization factor of A. si، and distance from watering point have a high correlation each other (R-sq = 85%). As well as، with increasing of distance from watering point، the utilization factor decreases.