Five years after the creation of the plots the biggest ailanthus in the rural test site measured about five feet tall.The city site boasted a 20-footer.

• 制成这几块试验点五年后，在乡村试验点的最大臭椿树只有大约五英尺高，而在城市试验点的臭椿树却已长到了20英尺高。