Carbon sequestration and foliar dust retention by woody plants in the greenbelts along two major Taiwan highways

Anthropogenic emissions of greenhouse gases and particulate matter have caused continued environmental concerns at both local and global scales. Greenbelts along highways have been implemented to aid in the uptake of emissions along transport sectors. The present study evaluated the capabilities of carbon sequestration and foliar dust retention in 88 woody tree species, and 1520 individuals in the greenbelts along Taiwan National Highways no. 1 and no. 3. More than 2.2 and 1.7 million average annual vehicle passages were respectively recorded for the two highways. Among species, Bischofia javanica, Acacia confusa, Swietenia macrophylla and Alstonia scholaris exhibited optimal carbon sequestration capabilities in trunks and branches, with respective carbon storage levels of 175, 105, 23.8 and 15 kg per plant. Results showed a respective estimated 19.9 and 12.3 thousand tons of carbon sequestrated by trunks and branches in greenbelts of Highways no. 1 and no. 3, respectively. The foliar dust retention capabilities of Ac. confusa and Casuarina equisetifolia were the highest in the two greenbelts, with respective foliar dust retentions of 564.9 and 60.3 g per plant. The leaves in the two greenbelts retained an estimated 47.9 and 17.3 t of foliar dust for Highways no. 1 and no. 3, respectively. The present study demonstrated that woody plant species in greenbelts exhibit a substantial contribution to carbon sequestration and foliar dust retention for two heavily used highways in Taiwan.