A comparative study of air pollution tolerance capabilities of four tree species in Xi'an city, China

Due to the different responses to air pollutants, plants could be used as the bio-monitors to estimate the air pollution. The air pollution tolerance index, calculated by ascorbic acid content, relative water content, leaf extract pH and total leaf chlorophyll content, is a very important tool to select the sensitive species as bio-indicator of air pollution. In the present study, the air pollution tolerance indexes of four evergreen tree species collected from different polluted areas in Xi'an city were evaluated to determine the sensitivity degrees of trees to air pollutants and their performance in urban areas. Moreover, the anticipated performance index was calculated by combining the air pollution tolerance index values with some relevant socioeconomic and biological characteristics. The results showed that the highest air pollution tolerance indexes were Cedrus deodara and Sabina chinensis, and it was determined that the species with very good performance was Cedrus deodara. On the other hand, the species with the most sensitive and poor performance were Ligustrum lucidum and Euonymus japonicas. All the results exhibited that Ligustrum lucidum and Euonymus japonicas could be effectively used as bio-indicators of air pollution, and Cedrus deodara was the appropriate tree species for green belt development in Xi'an, China.