The overlooked carbon loss due to decayed wood in urban trees

•The distribution pattern and extent of decay documented in this study was species-dependant and can be aggravated by arboticultural practices.•Decayed wood is not correlated with tree vitality in U. procera and may occur even in visually healthy standing trees within the genera.•The standing volume of U. procera trees with DBH≥40cm needs to be discounted by a factor of 13% due to internal decayed wood regardless of the species vitality index.•Calculations of stored carbon by urban trees may need to be discounted by a species-decay factor rather than a standard factor that account only for differences in biomass yield between natural and urban trees.