Comparing 3 methods of forage estimation in summer rangelands (Case study: Sar-Aliabad rangelands of Golestan province)

To find an accurate and rapid method of estimating herbage standing crop, clipping and weighing, double sampling, and comparative yield methods were compared in two vegetation types of grasslands and one cushion shrubland in Sar-Aliabad summer rangelands of Golestan province. In representative stands of each vegetation type, eighty 1-m2 plots were clipped and weighed. In double sampling method, 16 plots were estimated and clipped. In comparative yield method, standard (reference) plots were used as the highest yield belonged to the reference plot 5 and the lowest yield belonged to the reference plot 1. A high correlation was found between estimated and clipped plot in double sampling method. There was also high correlation between reference plots and their weights, so estimation of double sampling and ranks of comparative yield method were corrected by using regression equations. There were no significant differences among 3 methods, but time consumption of double sampling was better than the other methods. So, because of extensive application of double sampling method in grasslands and shrublands and its high accuracy and precision this method of yield estimation is recommended for the study area.