Using allometric equations for determining the biomass of saxaul (Halloxylon ammodenderon C.A.May)

This research was conducted in Yazd- Ardakan plain to determine biomass of Saxaul shrubs. Twenty shrubs were selected randomly for cutting down. Standing attributes include diameter at root collar (DRC), height, stems number and crown diameters were measured. Stem and leaves were separated and weighted and some samples were taken to determine dry/wet weight ratio. Above-ground biomass of the shrubs was calculated according to dry/wet weight ratio. Linear regression analysis was conducted for predicting biomass of the shrubs. Results indicated that there was strong correlation between above-ground biomass and diameter at root collar. The best models were detected for trunk dry weight- DRC (R2=0.82), Above-ground biomass- DRC (R2=0.84) and branch dry weight-crown area (R2=0.75). Models based on crown diameter and height were significant and could predict 60 to 70 presents of variations in biomass. Finally, it can be concluded that diameter at root collar is the best predictor of biomass in saxaul plantations. Also age-specific equations provide better predictions of biomass with lower error, provided that sample size is sufficient.