Estimation of biomass and utilization of three perennial range grasses in Saudi Arabia

Most range management decisions are based on quantitative measurements of production and utilization of key range plant species. A study was conducted to estimate biomass production and utilization of three perennial grasses using dimension analysis and height–weight profiles. Plant height, basal diameter and canopy diameter were highly correlated with biomass ofLasiurus sindicus. Plant biomass ofPennisetum divisumandStipagrostis drariiwas correlated to basal and canopy diameters. The three variables were evaluated for predicting biomass of the three grass species using best subset regression approach. From a practical point of view, basal and canopy diameters would be good predictors ofL. sindicusandS. drariibiomass. ForP. divisum, all three dimension measurements are needed for satisfactory results. Height–weight profiles were developed for each species to assess utilization based on estimation of percentage of height removed in relation to percentage weight removed. Although good correlation was found between height and weight, it is likely that light grazing will be underestimated. However, this would not limit the use of height–weight profiles as defoliation thresholds are never approached under long-term light grazing.