Carbon Storage by Utility-Compatible Trees

Urban trees can favorably affect factors underlying global warming by storing carbon and by reducing energy needed for cooling and heating buildings. To estimate the amount of carbon stored by smaller types of urban trees, excluding leaves and roots, standardized measurements were taken to determine wood density, wood volume, and dry weight of selected samples of Amelanchier, Malus, Pyrus calleryana, and Syringa reticulata cultivars. Wood density as defined by specific weight ranged from 0.53 to 0.64 g/cm3 for all genera. Densities at two upper trunk positions were significantly different from those at the base. The wood density of Syringa reticulata was significantly less than the other genera. Regression analyses of wood weight based on height and diameter of trees up to 12 cm (4.7 in.) dbh indicated a linear relationship in Amelanchier, but curvilinear (not linear) equations explained more of the variation in Malus and Pyrus. Smaller trees, those 2.3 to 4.9 cm dbh, typically stored between 2.1 and 2.3 kg of carbon in trunks and branches; trees between 5.0 and 7.9 cm stored between 8.4 and 15.1 kg, and trees larger than 8.0 cm up to 11.7 cm stored between 24.5 and 37.5 kg of carbon. The narrow-crowned Pyrus calleryana 'Capital' stored considerably lower amounts of carbon than the other Pyrus calleryana cultivars. These estimates may be increased by 22% to add carbon stored in roots, according to other studies.