Abstract
The ever-increasing vehicle counts have resulted in a significant increase in air pollution impacting human and natural ecosystems including trees, and physical properties. Roadside plantations often act as a first defense line against the vehicular emissions to mitigate the impacts of pollutants. However, they are themselves vulnerable to these pollutants with varying levels of tolerance capacity. This demands a scientific investigation to assess the role of roadside plantation for better management and planning for urban sprawl where selected trees could be grown to mitigate the impacts of harmful pollutants. The present study assesses the impacts of vehicular emissions on the adaptation and mitigation potential of two important roadside tree species i.e. Grevillea robusta and Mangifera indica planted along roadsides in the capital city of Uttarakhand. Uttarakhand is one of the Indian Western Himalayan State and its capital city is situated on the foothills of Himalaya. The adaptation and mitigation potential were evaluated by studying the response of pollutants on the functional traits which drive the physiology of the trees. The CO2 assimilation rate, transpiration rate, stomatal conductance, water use efficiency (WUE), air pollution tolerance index (APTI), copper and proline accumulation, dust removal efficiency (DRE), leaf thickness and cooling created by plantation were studied to evaluate the response of trees exposed to roadside traffics. To compare the influence of pollutants, traits of trees grown in a control site with few or absence of vehicular movement were compared with the roadside trees. The control site represented part of a reserve forest where human interference is controlled and human-induced activities are prohibited. The vehicular frequency was found to modulate tree characteristics. The tree characteristics representing WUE, APTI, proline and copper accumulation, leaf thickness, cooling impact, and DRE were enhanced significantly, while the decreased CO2 assimilation rate was observed near roadside trees compared to the control site. We found both of the species to perform well to be used as one of the potential species for roadside and urban greening. However, there is a need to assess the potential of other species in reference to the present study.
Highlights
IntroductionThe advent of technology has blessed us with a lot of inventions over the years and one of them was ‘the automobile’
Assessing adaptation and mitigation potential of roadside trees under the influence of vehicular emissions compared to Forest Research Institute (FRI) where the vehicular movement was least (Figs 2a and 6)
Gs of G. robusta revealed less reduction (~21%) than M. indica at the roadside, which represented diminution at the roadside (0.64±0.01 mol H2O m-2 s-1) when comparison made with FRI (0.81±0.01 mol H2O m-2 s-1)
Summary
The advent of technology has blessed us with a lot of inventions over the years and one of them was ‘the automobile’. The past 40 years have witnessed a tremendous increase in the number of vehicles as a result of the growing human population and developments have driven demands. This has resulted in the creation and expansion of roads adding to the soil, water, air, and noise pollution. Vehicular emission has been noticed to be one of the most concerns of urban air pollution. Different trees have varying levels of combating capacity distinguished with their adaptation and mitigation potential This raises the question “Which are the most efficient trees appropriate to combat urban air pollution in an effective and efficient way?”. The roadside plantations are expected to combat air pollution
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