Middle-East Journal of Scientific Research 21 (9): 1520-1525, 2014 ISSN 1990-9233 © IDOSI Publications, 2014 DOI: 10.5829/idosi.mejsr.2014.21.09.21702 Corresponding Author: Mahmood Ehsanzadeh Fard, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran. 1520 Predication of Biomass of Three Perennial Range Grasses Using Dimensional Analysis Mahmood Ehsanzadeh Fard and Gholam Ali Heshmati Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran Abstract: Biomass of key range plants is one of the most commonly measured attributes in range inventory programs that is a base for most range management decisions. This study was done to estimate biomass of three grasses (Agropyron cristatum, Bromus tomentellus and Stipa barbata) using dimension analysis. So plant biomass was measured through harvesting method. Plants height, basal diameter and canopy diameter were recorded in the field as dimensional parameters. Pearson correlation coefficients were used to assess relationships of dimensional variables with biomass. The variables were then evaluated for predicting biomass by using best subset and stepwise regression approaches. Results showed that there was significant relation between biomass and dimensional parameters. The results clearly showed that dimensional analysis is an appropriate method for estimation grasses biomass. So we can say that the dimensional parameters are good predictors of biomass and all parameters are not the same in terms of explanatory power. In this study plant height was the best predicator of the biomass in single species models and multispecies model. Basal diameter added medium predictive value when height was already in the model. Only in multispecies model, canopy diameter remained in the model and its explanatory power was relatively acceptable. Key words: Biomass Agropyron cristatum Bromus tomentellus Stipa barbata Regression Dimensional analysis INTRODUCTION Biomass is one of the most commonly measured Proper rangeland management has always been regarded as the most important indicator of ecological and centered on exact documentation of all the existing management processes in the vegetation. Biomass resource status within a management unit, so that provides a valuable tool to make short-term stocking rate collected information can be used to develop high quality adjustments according to the amount of forage reserves short and long-term land use plans; and eventually and residual biomass [3]. play a positive role in improving the country livestock Biomass refers to the weight of plant material within industry [1]. Grazing by animals, both domestic livestock a given area. Other general terms, such as 'yield' or and wildlife, remains a primary land use on rangelands. 'production', are sometimes used interchangeably with Therefore, many rangeland inventory and monitoring biomass. Production term most of the time reflects current programs must focus on obtaining information that can be year's growth and includes all green organs of stem, interpreted to ensure productive and sustainable forage flowering branches, flowers, seeds and fruits. consumption within the management unit. So one of the The production measurement methods have main factors that should be concerned in range been developed since the early 19 century but much management, is stocking rate. Stocking rate is a more efforts and studies have been devoted to fundamental component of rangeland management developing methods to estimate production. So some decision in terms of rangeland vegetation, domestic new techniques were developed or traditional livestock, wildlife and economic responses [1] because it ones were adjusted somehow. It is obvious that is an important management tool that connects standing techniques with high accuracy and precision are crop and utilization level that key species can tolerate [2]. acceptable. attributes in range management programs. So biomass is th