Effect of Spacing on the Biomass Production and Allocation in Conocarpus erectus L. Trees Grown in Riyadh, Saudi Arabia

The main objectives of this study were to investigate the effect of different spacing levels on the biomass production and allocation in Conocarpus erectus trees grown in the arid environments of Saudi Arabia and to develop allometric equations for predicting the total above-ground biomass of these trees as well the biomass of each tree component (main stem, branches and foliage). Seedlings were planted at three different spacing (0.7, 1.4 and 2.1m). After three years, the main stem dry biomass was 2.0, 3.26 and 5.56 kg tree-1 while branches biomass was 1.28, 5.05 and 8.16 kg tree-1 and foliage biomass was 1.29, 3.62 and 7.18 kg tree-1 for spacing 0.7, 1.4 and 2.1m, respectively. The total tree biomass was 4.57, 11.93 and 20.80 kg tree-1 for the same spacing, respectively. Total biomass yield for tree components was calculated per hectare and the highest yield was produced from the close spacing (0.7m) which gave 40.8, 26.1 and 26.3 ton ha-1 for stem, branches and foliage, respectively. The effect of spacing on the relative distribution of the biomass components in the individual trees was also studied. The best biomass prediction equations were developed based on the combined tree parameters of square diameter at ground level multiplied by total tree height (D2H) and the space area occupied by each tree (S)