Urban Main Roadside Plantation Enhances Species Richness, Diversity and Carbon Storage than Sub roadside Plantation: An Empirical Study in Dhaka City

While the ecological role of urban main roadside (MR) plantation is well-documented, the contribution of sub roadside (SR) plantation remains unclear. Using both purposive and random sampling methods, we investigated species richness, diversity and above-below ground biomass carbon (AGC and BGC) storage of the MR and SR plantations in northern and southern parts of Dhaka urban city. We found that species richness is comparatively lower in SR than MR in Dhaka north (MR: 4.70 ± 0.24, SR: 3.51 ± 0.14), Dhaka south (MR: 4.45 ± 0.24, SR: 4.20 ± 0.32) and north + south (MR: 4.55 ± 0.17, SR: 3.85 ± 0.18) sites respectively. We also found that MR of the Dhaka north city showed higher mean AGC storage than SR (MR: 63.78 ± 11.33 Mg ha ^− 1 , SR: 40.16 ± 5.03 Mg ha ^− 1 ), however the result is opposite in case of Dhaka south (MR: 80.99 ± 7.50 Mg ha ^− 1 , SR: 103.58 ± 7.65 Mg ha ^− 1 ). When combined north + south roadside together, maximum AGC was found in MR (73.62 ± 7.99, Mg ha ^− 1 ) than SR (71.87 ± 8.39 Mg ha ^− 1 ). Similar trend was observed in term of BGC and total biomass carbon (TC) where SR showed less carbon storage potentiality than MR. Significant positive (all, P <  0.05) relationships were observed among AGC, BGC and TC storage in response to species richness both MR and SR across sites with few exceptions in case of species diversity. Our study suggested that SR are contributing fewer ecosystem functions than MR of Dhaka urban mega city thus enhancement of SR plantation along with MR is strongly suggested to maintain sustainable urban ecosystem function.